When reprobing an MST topology during resume, we have to account for the fact that while we were suspended it's possible that mstbs may have been removed from any ports in the topology. Since iterating downwards in the topology requires that we hold &mgr->lock, destroying MSTBs from this context would result in attempting to lock &mgr->lock a second time and deadlocking.

So, fix this by first moving destruction of MSTBs into destroy_connector_work, then rename destroy_connector_work and friends to reflect that they now destroy both ports and mstbs.

Note that even though this means that MSTBs will still be accessible for a short period of time between their removal from the topology and delayed destruction, we are still protected against referencing a MSTB with a refcount of 0 since we use kref_get_unless_zero() in most places.

Changes since v1: * s/destroy_connector_list/destroy_port_list/ s/connector_destroy_lock/delayed_destroy_lock/ s/connector_destroy_work/delayed_destroy_work/ s/drm_dp_finish_destroy_branch_device/drm_dp_delayed_destroy_mstb/ s/drm_dp_finish_destroy_port/drm_dp_delayed_destroy_port/ - danvet * Use two loops in drm_dp_delayed_destroy_work() - danvet * Better explain why we need to do this - danvet * Use cancel_work_sync() instead of flush_work() - flush_work() doesn't account for work requeing

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel@ffwll.ch Signed-off-by: Lyude Paul lyude@redhat.com Reviewed-by: Sean Paul sean@poorly.run --- drivers/gpu/drm/drm_dp_mst_topology.c | 164 +++++++++++++++++--------- include/drm/drm_dp_mst_helper.h | 26 ++-- 2 files changed, 128 insertions(+), 62 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 9cccc5e63309..66ff226d8c86 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1398,34 +1398,17 @@ static void drm_dp_destroy_mst_branch_device(struct kref *kref) struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, topology_kref); struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; - bool wake_tx = false;

- mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { - list_del(&port->next); - drm_dp_mst_topology_put_port(port); - } - mutex_unlock(&mgr->lock); - - /* drop any tx slots msg */ - mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; - wake_tx = true; - } - mutex_unlock(&mstb->mgr->qlock); + INIT_LIST_HEAD(&mstb->destroy_next);

- if (wake_tx) - wake_up_all(&mstb->mgr->tx_waitq); - - drm_dp_mst_put_mstb_malloc(mstb); + /* + * This can get called under mgr->mutex, so we need to perform the + * actual destruction of the mstb in another worker + */ + mutex_lock(&mgr->delayed_destroy_lock); + list_add(&mstb->destroy_next, &mgr->destroy_branch_device_list); + mutex_unlock(&mgr->delayed_destroy_lock); + schedule_work(&mgr->delayed_destroy_work); }

/** @@ -1540,10 +1523,10 @@ static void drm_dp_destroy_port(struct kref *kref) * we might be holding the mode_config.mutex * from an EDID retrieval */

- mutex_lock(&mgr->destroy_connector_lock); - list_add(&port->next, &mgr->destroy_connector_list); - mutex_unlock(&mgr->destroy_connector_lock); - schedule_work(&mgr->destroy_connector_work); + mutex_lock(&mgr->delayed_destroy_lock); + list_add(&port->next, &mgr->destroy_port_list); + mutex_unlock(&mgr->delayed_destroy_lock); + schedule_work(&mgr->delayed_destroy_work); return; } /* no need to clean up vcpi @@ -3085,7 +3068,7 @@ void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr) DP_MST_EN | DP_UPSTREAM_IS_SRC); mutex_unlock(&mgr->lock); flush_work(&mgr->work); - flush_work(&mgr->destroy_connector_work); + flush_work(&mgr->delayed_destroy_work); } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_suspend);

@@ -3995,34 +3978,104 @@ static void drm_dp_tx_work(struct work_struct *work) mutex_unlock(&mgr->qlock); }

-static void drm_dp_destroy_connector_work(struct work_struct *work) +static inline void +drm_dp_delayed_destroy_port(struct drm_dp_mst_port *port) { - struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, destroy_connector_work); - struct drm_dp_mst_port *port; - bool send_hotplug = false; + port->mgr->cbs->destroy_connector(port->mgr, port->connector); + + drm_dp_port_teardown_pdt(port, port->pdt); + port->pdt = DP_PEER_DEVICE_NONE; + + drm_dp_mst_put_port_malloc(port); +} + +static inline void +drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) +{ + struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; + struct drm_dp_mst_port *port, *tmp; + bool wake_tx = false; + + mutex_lock(&mgr->lock); + list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_del(&port->next); + drm_dp_mst_topology_put_port(port); + } + mutex_unlock(&mgr->lock); + + /* drop any tx slots msg */ + mutex_lock(&mstb->mgr->qlock); + if (mstb->tx_slots[0]) { + mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + mstb->tx_slots[0] = NULL; + wake_tx = true; + } + if (mstb->tx_slots[1]) { + mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + mstb->tx_slots[1] = NULL; + wake_tx = true; + } + mutex_unlock(&mstb->mgr->qlock); + + if (wake_tx) + wake_up_all(&mstb->mgr->tx_waitq); + + drm_dp_mst_put_mstb_malloc(mstb); +} + +static void drm_dp_delayed_destroy_work(struct work_struct *work) +{ + struct drm_dp_mst_topology_mgr *mgr = + container_of(work, struct drm_dp_mst_topology_mgr, + delayed_destroy_work); + bool send_hotplug = false, go_again; + /* * Not a regular list traverse as we have to drop the destroy - * connector lock before destroying the connector, to avoid AB->BA + * connector lock before destroying the mstb/port, to avoid AB->BA * ordering between this lock and the config mutex. */ - for (;;) { - mutex_lock(&mgr->destroy_connector_lock); - port = list_first_entry_or_null(&mgr->destroy_connector_list, struct drm_dp_mst_port, next); - if (!port) { - mutex_unlock(&mgr->destroy_connector_lock); - break; + do { + go_again = false; + + for (;;) { + struct drm_dp_mst_branch *mstb; + + mutex_lock(&mgr->delayed_destroy_lock); + mstb = list_first_entry_or_null(&mgr->destroy_branch_device_list, + struct drm_dp_mst_branch, + destroy_next); + if (mstb) + list_del(&mstb->destroy_next); + mutex_unlock(&mgr->delayed_destroy_lock); + + if (!mstb) + break; + + drm_dp_delayed_destroy_mstb(mstb); + go_again = true; } - list_del(&port->next); - mutex_unlock(&mgr->destroy_connector_lock);

- mgr->cbs->destroy_connector(mgr, port->connector); + for (;;) { + struct drm_dp_mst_port *port;

- drm_dp_port_teardown_pdt(port, port->pdt); - port->pdt = DP_PEER_DEVICE_NONE; + mutex_lock(&mgr->delayed_destroy_lock); + port = list_first_entry_or_null(&mgr->destroy_port_list, + struct drm_dp_mst_port, + next); + if (port) + list_del(&port->next); + mutex_unlock(&mgr->delayed_destroy_lock); + + if (!port) + break; + + drm_dp_delayed_destroy_port(port); + send_hotplug = true; + go_again = true; + } + } while (go_again);

- drm_dp_mst_put_port_malloc(port); - send_hotplug = true; - } if (send_hotplug) drm_kms_helper_hotplug_event(mgr->dev); } @@ -4209,12 +4262,13 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, mutex_init(&mgr->lock); mutex_init(&mgr->qlock); mutex_init(&mgr->payload_lock); - mutex_init(&mgr->destroy_connector_lock); + mutex_init(&mgr->delayed_destroy_lock); INIT_LIST_HEAD(&mgr->tx_msg_downq); - INIT_LIST_HEAD(&mgr->destroy_connector_list); + INIT_LIST_HEAD(&mgr->destroy_port_list); + INIT_LIST_HEAD(&mgr->destroy_branch_device_list); INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work); INIT_WORK(&mgr->tx_work, drm_dp_tx_work); - INIT_WORK(&mgr->destroy_connector_work, drm_dp_destroy_connector_work); + INIT_WORK(&mgr->delayed_destroy_work, drm_dp_delayed_destroy_work); init_waitqueue_head(&mgr->tx_waitq); mgr->dev = dev; mgr->aux = aux; @@ -4255,7 +4309,7 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr) { drm_dp_mst_topology_mgr_set_mst(mgr, false); flush_work(&mgr->work); - flush_work(&mgr->destroy_connector_work); + cancel_work_sync(&mgr->delayed_destroy_work); mutex_lock(&mgr->payload_lock); kfree(mgr->payloads); mgr->payloads = NULL; @@ -4267,7 +4321,7 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr) drm_atomic_private_obj_fini(&mgr->base); mgr->funcs = NULL;

- mutex_destroy(&mgr->destroy_connector_lock); + mutex_destroy(&mgr->delayed_destroy_lock); mutex_destroy(&mgr->payload_lock); mutex_destroy(&mgr->qlock); mutex_destroy(&mgr->lock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 4a25e0577ae0..b2160c366fb7 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -143,6 +143,12 @@ struct drm_dp_mst_branch { */ struct kref malloc_kref;

+ /** + * @destroy_next: linked-list entry used by + * drm_dp_delayed_destroy_work() + */ + struct list_head destroy_next; + u8 rad[8]; u8 lct; int num_ports; @@ -571,18 +577,24 @@ struct drm_dp_mst_topology_mgr { struct work_struct tx_work;

/** - * @destroy_connector_list: List of to be destroyed connectors. + * @destroy_port_list: List of to be destroyed connectors. + */ + struct list_head destroy_port_list; + /** + * @destroy_branch_device_list: List of to be destroyed branch + * devices. */ - struct list_head destroy_connector_list; + struct list_head destroy_branch_device_list; /** - * @destroy_connector_lock: Protects @connector_list. + * @delayed_destroy_lock: Protects @destroy_port_list and + * @destroy_branch_device_list. */ - struct mutex destroy_connector_lock; + struct mutex delayed_destroy_lock; /** - * @destroy_connector_work: Work item to destroy connectors. Needed to - * avoid locking inversion. + * @delayed_destroy_work: Work item to destroy MST port and branch + * devices, needed to avoid locking inversion. */ - struct work_struct destroy_connector_work; + struct work_struct delayed_destroy_work; };

int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,

Since we're going to be implementing suspend/resume reprobing very soon, we need to make sure we are extra careful to ensure that our locking actually protects the topology state where we expect it to. Turns out this isn't the case with drm_dp_port_setup_pdt() and drm_dp_port_teardown_pdt(), both of which change port->mstb without grabbing &mgr->lock.

Additionally, since most callers of these functions are just using it to teardown the port's previous PDT and setup a new one we can simplify things a bit and combine drm_dp_port_setup_pdt() and drm_dp_port_teardown_pdt() into a single function: drm_dp_port_set_pdt(). This function also handles actually ensuring that we grab the correct locks when we need to modify port->mstb.

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Lyude Paul lyude@redhat.com Reviewed-by: Sean Paul sean@poorly.run --- drivers/gpu/drm/drm_dp_mst_topology.c | 181 +++++++++++++++----------- include/drm/drm_dp_mst_helper.h | 6 +- 2 files changed, 110 insertions(+), 77 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 204d0c832c65..3f16c0cb094b 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1486,24 +1486,6 @@ drm_dp_mst_topology_put_mstb(struct drm_dp_mst_branch *mstb) kref_put(&mstb->topology_kref, drm_dp_destroy_mst_branch_device); }

-static void drm_dp_port_teardown_pdt(struct drm_dp_mst_port *port, int old_pdt) -{ - struct drm_dp_mst_branch *mstb; - - switch (old_pdt) { - case DP_PEER_DEVICE_DP_LEGACY_CONV: - case DP_PEER_DEVICE_SST_SINK: - /* remove i2c over sideband */ - drm_dp_mst_unregister_i2c_bus(&port->aux); - break; - case DP_PEER_DEVICE_MST_BRANCHING: - mstb = port->mstb; - port->mstb = NULL; - drm_dp_mst_topology_put_mstb(mstb); - break; - } -} - static void drm_dp_destroy_port(struct kref *kref) { struct drm_dp_mst_port *port = @@ -1713,38 +1695,79 @@ static u8 drm_dp_calculate_rad(struct drm_dp_mst_port *port, return parent_lct + 1; }

-/* - * return sends link address for new mstb - */ -static bool drm_dp_port_setup_pdt(struct drm_dp_mst_port *port) +static int drm_dp_port_set_pdt(struct drm_dp_mst_port *port, u8 new_pdt) { - int ret; - u8 rad[6], lct; - bool send_link = false; + struct drm_dp_mst_topology_mgr *mgr = port->mgr; + struct drm_dp_mst_branch *mstb; + u8 rad[8], lct; + int ret = 0; + + if (port->pdt == new_pdt) + return 0; + + /* Teardown the old pdt, if there is one */ + switch (port->pdt) { + case DP_PEER_DEVICE_DP_LEGACY_CONV: + case DP_PEER_DEVICE_SST_SINK: + /* + * If the new PDT would also have an i2c bus, don't bother + * with reregistering it + */ + if (new_pdt == DP_PEER_DEVICE_DP_LEGACY_CONV || + new_pdt == DP_PEER_DEVICE_SST_SINK) { + port->pdt = new_pdt; + return 0; + } + + /* remove i2c over sideband */ + drm_dp_mst_unregister_i2c_bus(&port->aux); + break; + case DP_PEER_DEVICE_MST_BRANCHING: + mutex_lock(&mgr->lock); + drm_dp_mst_topology_put_mstb(port->mstb); + port->mstb = NULL; + mutex_unlock(&mgr->lock); + break; + } + + port->pdt = new_pdt; switch (port->pdt) { case DP_PEER_DEVICE_DP_LEGACY_CONV: case DP_PEER_DEVICE_SST_SINK: /* add i2c over sideband */ ret = drm_dp_mst_register_i2c_bus(&port->aux); break; + case DP_PEER_DEVICE_MST_BRANCHING: lct = drm_dp_calculate_rad(port, rad); + mstb = drm_dp_add_mst_branch_device(lct, rad); + if (!mstb) { + ret = -ENOMEM; + DRM_ERROR("Failed to create MSTB for port %p", port); + goto out; + }

- port->mstb = drm_dp_add_mst_branch_device(lct, rad); - if (port->mstb) { - port->mstb->mgr = port->mgr; - port->mstb->port_parent = port; - /* - * Make sure this port's memory allocation stays - * around until its child MSTB releases it - */ - drm_dp_mst_get_port_malloc(port); + mutex_lock(&mgr->lock); + port->mstb = mstb; + mstb->mgr = port->mgr; + mstb->port_parent = port;

- send_link = true; - } + /* + * Make sure this port's memory allocation stays + * around until its child MSTB releases it + */ + drm_dp_mst_get_port_malloc(port); + mutex_unlock(&mgr->lock); + + /* And make sure we send a link address for this */ + ret = 1; break; } - return send_link; + +out: + if (ret < 0) + port->pdt = DP_PEER_DEVICE_NONE; + return ret; }

/** @@ -1881,10 +1904,9 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, struct drm_device *dev, struct drm_dp_link_addr_reply_port *port_msg) { + struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; struct drm_dp_mst_port *port; - bool ret; bool created = false; - int old_pdt = 0; int old_ddps = 0;

port = drm_dp_get_port(mstb, port_msg->port_number); @@ -1896,7 +1918,7 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, kref_init(&port->malloc_kref); port->parent = mstb; port->port_num = port_msg->port_number; - port->mgr = mstb->mgr; + port->mgr = mgr; port->aux.name = "DPMST"; port->aux.dev = dev->dev; port->aux.is_remote = true; @@ -1909,11 +1931,9 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,

created = true; } else { - old_pdt = port->pdt; old_ddps = port->ddps; }

- port->pdt = port_msg->peer_device_type; port->input = port_msg->input_port; port->mcs = port_msg->mcs; port->ddps = port_msg->ddps; @@ -1925,29 +1945,33 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, /* manage mstb port lists with mgr lock - take a reference for this list */ if (created) { - mutex_lock(&mstb->mgr->lock); + mutex_lock(&mgr->lock); drm_dp_mst_topology_get_port(port); list_add(&port->next, &mstb->ports); - mutex_unlock(&mstb->mgr->lock); + mutex_unlock(&mgr->lock); }

if (old_ddps != port->ddps) { if (port->ddps) { if (!port->input) { - drm_dp_send_enum_path_resources(mstb->mgr, - mstb, port); + drm_dp_send_enum_path_resources(mgr, mstb, + port); } } else { port->available_pbn = 0; } }

- if (old_pdt != port->pdt && !port->input) { - drm_dp_port_teardown_pdt(port, old_pdt); - - ret = drm_dp_port_setup_pdt(port); - if (ret == true) - drm_dp_send_link_address(mstb->mgr, port->mstb); + if (!port->input) { + int ret = drm_dp_port_set_pdt(port, + port_msg->peer_device_type); + if (ret == 1) { + drm_dp_send_link_address(mgr, port->mstb); + } else if (ret < 0) { + DRM_ERROR("Failed to change PDT on port %p: %d\n", + port, ret); + goto fail; + } }

if (created && !port->input) { @@ -1955,18 +1979,11 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,

build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath)); - port->connector = (*mstb->mgr->cbs->add_connector)(mstb->mgr, - port, - proppath); - if (!port->connector) { - /* remove it from the port list */ - mutex_lock(&mstb->mgr->lock); - list_del(&port->next); - mutex_unlock(&mstb->mgr->lock); - /* drop port list reference */ - drm_dp_mst_topology_put_port(port); - goto out; - } + port->connector = (*mgr->cbs->add_connector)(mgr, port, + proppath); + if (!port->connector) + goto fail; + if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV || port->pdt == DP_PEER_DEVICE_SST_SINK) && port->port_num >= DP_MST_LOGICAL_PORT_0) { @@ -1974,12 +1991,24 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, &port->aux.ddc); drm_connector_set_tile_property(port->connector); } - (*mstb->mgr->cbs->register_connector)(port->connector); + + (*mgr->cbs->register_connector)(port->connector); }

-out: /* put reference to this port */ drm_dp_mst_topology_put_port(port); + return; + +fail: + /* Remove it from the port list */ + mutex_lock(&mgr->lock); + list_del(&port->next); + mutex_unlock(&mgr->lock); + + /* Drop the port list reference */ + drm_dp_mst_topology_put_port(port); + /* And now drop our reference */ + drm_dp_mst_topology_put_port(port); }

static void @@ -1987,16 +2016,14 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, struct drm_dp_connection_status_notify *conn_stat) { struct drm_dp_mst_port *port; - int old_pdt; int old_ddps; bool dowork = false; + port = drm_dp_get_port(mstb, conn_stat->port_number); if (!port) return;

old_ddps = port->ddps; - old_pdt = port->pdt; - port->pdt = conn_stat->peer_device_type; port->mcs = conn_stat->message_capability_status; port->ldps = conn_stat->legacy_device_plug_status; port->ddps = conn_stat->displayport_device_plug_status; @@ -2008,11 +2035,17 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, port->available_pbn = 0; } } - if (old_pdt != port->pdt && !port->input) { - drm_dp_port_teardown_pdt(port, old_pdt);

- if (drm_dp_port_setup_pdt(port)) + if (!port->input) { + int ret = drm_dp_port_set_pdt(port, + conn_stat->peer_device_type); + if (ret == 1) { dowork = true; + } else if (ret < 0) { + DRM_ERROR("Failed to change PDT for port %p: %d\n", + port, ret); + dowork = false; + } }

drm_dp_mst_topology_put_port(port); @@ -3975,9 +4008,7 @@ drm_dp_delayed_destroy_port(struct drm_dp_mst_port *port) if (port->connector) port->mgr->cbs->destroy_connector(port->mgr, port->connector);

- drm_dp_port_teardown_pdt(port, port->pdt); - port->pdt = DP_PEER_DEVICE_NONE; - + drm_dp_port_set_pdt(port, DP_PEER_DEVICE_NONE); drm_dp_mst_put_port_malloc(port); }

diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index b2160c366fb7..8ba2a01324bb 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -55,8 +55,10 @@ struct drm_dp_vcpi { * @num_sdp_stream_sinks: Number of stream sinks * @available_pbn: Available bandwidth for this port. * @next: link to next port on this branch device - * @mstb: branch device attach below this port - * @aux: i2c aux transport to talk to device connected to this port. + * @mstb: branch device on this port, protected by + * &drm_dp_mst_topology_mgr.lock + * @aux: i2c aux transport to talk to device connected to this port, protected + * by &drm_dp_mst_topology_mgr.lock * @parent: branch device parent of this port * @vcpi: Virtual Channel Payload info for this port. * @connector: DRM connector this port is connected to.

Currently, MST lacks locking in a lot of places that really should have some sort of locking. Hotplugging and link address code paths are some of the offenders here, as there is actually nothing preventing us from running a link address probe while at the same time handling a connection status update request - something that's likely always been possible but never seen in the wild because hotplugging has been broken for ages now (with the exception of amdgpu, for reasons I don't think are worth digging into very far).

Note: I'm going to start using the term "in-memory topology layout" here to refer to drm_dp_mst_port->mstb and drm_dp_mst_branch->ports.

Locking in these places is a little tougher then it looks though. Generally we protect anything having to do with the in-memory topology layout under &mgr->lock. But this becomes nearly impossible to do from the context of link address probes due to the fact that &mgr->lock is usually grabbed under random various modesetting locks, meaning that there's no way we can just invert the &mgr->lock order and keep it locked throughout the whole process of updating the topology.

Luckily there are only two workers which can modify the in-memory topology layout: drm_dp_mst_up_req_work() and drm_dp_mst_link_probe_work(), meaning as long as we prevent these two workers from traveling the topology layout in parallel with the intent of updating it we don't need to worry about grabbing &mgr->lock in these workers for reads. We only need to grab &mgr->lock in these workers for writes, so that readers outside these two workers are still protected from the topology layout changing beneath them.

So, add the new &mgr->probe_lock and use it in both drm_dp_mst_link_probe_work() and drm_dp_mst_up_req_work(). Additionally, add some more detailed explanations for how this locking is intended to work to drm_dp_mst_port->mstb and drm_dp_mst_branch->ports.

Signed-off-by: Lyude Paul lyude@redhat.com Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Sean Paul sean@poorly.run --- drivers/gpu/drm/drm_dp_mst_topology.c | 28 ++++++++++++++--------- include/drm/drm_dp_mst_helper.h | 32 +++++++++++++++++++++++---- 2 files changed, 46 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 08c316a727df..11d842f0bff5 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2147,37 +2147,40 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_port *port; - struct drm_dp_mst_branch *mstb_child; + if (!mstb->link_address_sent) drm_dp_send_link_address(mgr, mstb);

list_for_each_entry(port, &mstb->ports, next) { - if (port->input) - continue; + struct drm_dp_mst_branch *mstb_child = NULL;

- if (!port->ddps) + if (port->input || !port->ddps) continue;

if (!port->available_pbn) drm_dp_send_enum_path_resources(mgr, mstb, port);

- if (port->mstb) { + if (port->mstb) mstb_child = drm_dp_mst_topology_get_mstb_validated( mgr, port->mstb); - if (mstb_child) { - drm_dp_check_and_send_link_address(mgr, mstb_child); - drm_dp_mst_topology_put_mstb(mstb_child); - } + + if (mstb_child) { + drm_dp_check_and_send_link_address(mgr, mstb_child); + drm_dp_mst_topology_put_mstb(mstb_child); } } }

static void drm_dp_mst_link_probe_work(struct work_struct *work) { - struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, work); + struct drm_dp_mst_topology_mgr *mgr = + container_of(work, struct drm_dp_mst_topology_mgr, work); + struct drm_device *dev = mgr->dev; struct drm_dp_mst_branch *mstb; int ret;

+ mutex_lock(&mgr->probe_lock); + mutex_lock(&mgr->lock); mstb = mgr->mst_primary; if (mstb) { @@ -2190,6 +2193,7 @@ static void drm_dp_mst_link_probe_work(struct work_struct *work) drm_dp_check_and_send_link_address(mgr, mstb); drm_dp_mst_topology_put_mstb(mstb); } + mutex_unlock(&mgr->probe_lock); }

static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr, @@ -3313,6 +3317,7 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) up_req_work); struct drm_dp_pending_up_req *up_req;

+ mutex_lock(&mgr->probe_lock); while (true) { mutex_lock(&mgr->up_req_lock); up_req = list_first_entry_or_null(&mgr->up_req_list, @@ -3328,6 +3333,7 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) drm_dp_mst_process_up_req(mgr, up_req); kfree(up_req); } + mutex_unlock(&mgr->probe_lock); }

static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) @@ -4349,6 +4355,7 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, mutex_init(&mgr->payload_lock); mutex_init(&mgr->delayed_destroy_lock); mutex_init(&mgr->up_req_lock); + mutex_init(&mgr->probe_lock); INIT_LIST_HEAD(&mgr->tx_msg_downq); INIT_LIST_HEAD(&mgr->destroy_port_list); INIT_LIST_HEAD(&mgr->destroy_branch_device_list); @@ -4414,6 +4421,7 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr) mutex_destroy(&mgr->qlock); mutex_destroy(&mgr->lock); mutex_destroy(&mgr->up_req_lock); + mutex_destroy(&mgr->probe_lock); } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);

diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 7d80c38ee00e..bccb5514e0ef 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -55,8 +55,6 @@ struct drm_dp_vcpi { * @num_sdp_stream_sinks: Number of stream sinks * @available_pbn: Available bandwidth for this port. * @next: link to next port on this branch device - * @mstb: branch device on this port, protected by - * &drm_dp_mst_topology_mgr.lock * @aux: i2c aux transport to talk to device connected to this port, protected * by &drm_dp_mst_topology_mgr.lock * @parent: branch device parent of this port @@ -92,7 +90,17 @@ struct drm_dp_mst_port { u8 num_sdp_stream_sinks; uint16_t available_pbn; struct list_head next; - struct drm_dp_mst_branch *mstb; /* pointer to an mstb if this port has one */ + /** + * @mstb: the branch device connected to this port, if there is one. + * This should be considered protected for reading by + * &drm_dp_mst_topology_mgr.lock. There are two exceptions to this: + * &drm_dp_mst_topology_mgr.up_req_work and + * &drm_dp_mst_topology_mgr.work, which do not grab + * &drm_dp_mst_topology_mgr.lock during reads but are the only + * updaters of this list and are protected from writing concurrently + * by &drm_dp_mst_topology_mgr.probe_lock. + */ + struct drm_dp_mst_branch *mstb; struct drm_dp_aux aux; /* i2c bus for this port? */ struct drm_dp_mst_branch *parent;

@@ -118,7 +126,6 @@ struct drm_dp_mst_port { * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. * @msg_slots: one bit per transmitted msg slot. - * @ports: linked list of ports on this branch. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. * @tx_slots: transmission slots for this device. @@ -156,6 +163,16 @@ struct drm_dp_mst_branch { int num_ports;

int msg_slots; + /** + * @ports: the list of ports on this branch device. This should be + * considered protected for reading by &drm_dp_mst_topology_mgr.lock. + * There are two exceptions to this: + * &drm_dp_mst_topology_mgr.up_req_work and + * &drm_dp_mst_topology_mgr.work, which do not grab + * &drm_dp_mst_topology_mgr.lock during reads but are the only + * updaters of this list and are protected from updating the list + * concurrently by @drm_dp_mst_topology_mgr.probe_lock + */ struct list_head ports;

/* list of tx ops queue for this port */ @@ -502,6 +519,13 @@ struct drm_dp_mst_topology_mgr { */ struct mutex lock;

+ /** + * @probe_lock: Prevents @work and @up_req_work, the only writers of + * &drm_dp_mst_port.mstb and &drm_dp_mst_branch.ports, from racing + * while they update the topology. + */ + struct mutex probe_lock; + /** * @mst_state: If this manager is enabled for an MST capable port. False * if no MST sink/branch devices is connected.

This is a complicated one. Essentially, there's currently a problem in the MST core that hasn't really caused any issues that we're aware of (emphasis on "that we're aware of"): locking.

When we go through and probe the link addresses and path resources in a topology, we hold no locks when updating ports with said information. The members I'm referring to in particular are:

- ldps - ddps - mcs - pdt - dpcd_rev - num_sdp_streams - num_sdp_stream_sinks - available_pbn - input - connector

Now that we're handling UP requests asynchronously and will be using some of the struct members mentioned above in atomic modesetting in the future for features such as PBN validation, this is going to become a lot more important. As well, the next few commits that prepare us for and introduce suspend/resume reprobing will also need clear locking in order to prevent from additional racing hilarities that we never could have hit in the past.

So, let's solve this issue by using &mgr->base.lock, the modesetting lock which currently only protects &mgr->base.state. This works perfectly because it allows us to avoid blocking connection_mutex unnecessarily, and we can grab this in connector detection paths since it's a ww mutex. We start by having drm_dp_mst_handle_up_req() hold this when updating ports. For drm_dp_mst_handle_link_address_port() things are a bit more complicated. As I've learned the hard way, we can grab &mgr->lock.base for everything except for port->connector. See, our normal driver probing paths end up generating this rather obvious lockdep chain:

&drm->mode_config.mutex -> crtc_ww_class_mutex/crtc_ww_class_acquire -> &connector->mutex

However, sysfs grabs &drm->mode_config.mutex in order to protect itself from connector state changing under it. Because this entails grabbing kn->count, e.g. the lock that the kernel provides for protecting sysfs contexts, we end up grabbing kn->count followed by &drm->mode_config.mutex. This ends up creating an extremely rude chain:

&kn->count -> &drm->mode_config.mutex -> crtc_ww_class_mutex/crtc_ww_class_acquire -> &connector->mutex

I mean, look at that thing! It's just evil!!! This gross thing ends up making any calls to drm_connector_register()/drm_connector_unregister() impossible when holding any kind of modesetting lock. This is annoying because ideally, we always want to ensure that drm_dp_mst_port->connector never changes when doing an atomic commit or check that would affect the atomic topology state so that it can reliably and easily be used from future DRM DP MST helpers to assist with tasks such as scanning through the current VCPI allocations and adding connectors which need to have their allocations updated in response to a bandwidth change or the like.

Being able to hold &mgr->base.lock throughout the entire link probe process would have been _great_, since we could prevent userspace from ever seeing any states in-between individual port changes and as a result likely end up with a much faster probe and more consistent results from said probes. But without some rework of how we handle connector probing in sysfs it's not at all currently possible. In the future, maybe we can try using the sysfs locks to protect updates to connector probing state and fix this mess.

So for now, to protect everything other than port->connector under &mgr->base.lock and ensure that we still have the guarantee that atomic check/commit contexts will never see port->connector change we use a silly trick. See: port->connector only needs to change in order to ensure that input ports (see the MST spec) never have a ghost connector associated with them. But, there's nothing stopping us from simply throwing the entire port out and creating a new one in order to maintain that requirement while still keeping port->connector consistent across the lifetime of the port in atomic check/commit contexts. For all intended purposes this works fine, as we validate ports in any contexts we care about before using them and as such will end up reporting the connector as disconnected until it's port's destruction finalizes. So, we just do that in cases where we detect port->input has transitioned from true->false. We don't need to worry about the other direction, since a port without a connector isn't visible to userspace and as such doesn't need to be protected by &mgr->base.lock until we finish registering a connector for it.

For updating members of drm_dp_mst_port other than port->connector, we simply grab &mgr->base.lock in drm_dp_mst_link_probe_work() for already registered ports, update said members and drop the lock before potentially registering a connector and probing the link address of it's children.

Finally, we modify drm_dp_mst_detect_port() to take a modesetting lock acquisition context in order to acquire &mgr->base.lock under &connection_mutex and convert all it's users over to using the .detect_ctx probe hooks.

With that, we finally have well defined locking.

Changes since v4: * Get rid of port->mutex, stop using connection_mutex and just use our own modesetting lock - mgr->base.lock. Also, add a probe_lock that comes before this patch. * Just throw out ports that get changed from an output to an input, and replace them with new ports. This lets us ensure that modesetting contexts never see port->connector go from having a connector to being NULL. * Write an extremely detailed explanation of what problems this is trying to fix, since there's a _lot_ of context here and I honestly forgot some of it myself a couple times. * Don't grab mgr->lock when reading port->mstb in drm_dp_mst_handle_link_address_port(). It's not needed.

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Sean Paul sean@poorly.run Signed-off-by: Lyude Paul lyude@redhat.com --- .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 28 +-- drivers/gpu/drm/drm_dp_mst_topology.c | 230 ++++++++++++------ drivers/gpu/drm/i915/display/intel_dp_mst.c | 28 ++- drivers/gpu/drm/nouveau/dispnv50/disp.c | 32 +-- drivers/gpu/drm/radeon/radeon_dp_mst.c | 24 +- include/drm/drm_dp_mst_helper.h | 38 ++- 6 files changed, 240 insertions(+), 140 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c index 5ec14efd4d8c..f8214acf70b3 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c @@ -123,21 +123,6 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux, return result; }

-static enum drm_connector_status -dm_dp_mst_detect(struct drm_connector *connector, bool force) -{ - struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector); - struct amdgpu_dm_connector *master = aconnector->mst_port; - - enum drm_connector_status status = - drm_dp_mst_detect_port( - connector, - &master->mst_mgr, - aconnector->port); - - return status; -} - static void dm_dp_mst_connector_destroy(struct drm_connector *connector) { @@ -177,7 +162,6 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector) }

static const struct drm_connector_funcs dm_dp_mst_connector_funcs = { - .detect = dm_dp_mst_detect, .fill_modes = drm_helper_probe_single_connector_modes, .destroy = dm_dp_mst_connector_destroy, .reset = amdgpu_dm_connector_funcs_reset, @@ -252,10 +236,22 @@ static struct drm_encoder *dm_mst_best_encoder(struct drm_connector *connector) return &amdgpu_dm_connector->mst_encoder->base; }

+static int +dm_dp_mst_detect(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, bool force) +{ + struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector); + struct amdgpu_dm_connector *master = aconnector->mst_port; + + return drm_dp_mst_detect_port(connector, ctx, &master->mst_mgr, + aconnector->port); +} + static const struct drm_connector_helper_funcs dm_dp_mst_connector_helper_funcs = { .get_modes = dm_dp_mst_get_modes, .mode_valid = amdgpu_dm_connector_mode_valid, .best_encoder = dm_mst_best_encoder, + .detect_ctx = dm_dp_mst_detect, };

static void amdgpu_dm_encoder_destroy(struct drm_encoder *encoder) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 11d842f0bff5..7bf4db91ff90 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1905,6 +1905,78 @@ void drm_dp_mst_connector_early_unregister(struct drm_connector *connector, } EXPORT_SYMBOL(drm_dp_mst_connector_early_unregister);

+static void +drm_dp_mst_port_add_connector(struct drm_dp_mst_branch *mstb, + struct drm_dp_mst_port *port) +{ + struct drm_dp_mst_topology_mgr *mgr = port->mgr; + char proppath[255]; + int ret; + + build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath)); + port->connector = mgr->cbs->add_connector(mgr, port, proppath); + if (!port->connector) { + ret = -ENOMEM; + goto error; + } + + if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV || + port->pdt == DP_PEER_DEVICE_SST_SINK) && + port->port_num >= DP_MST_LOGICAL_PORT_0) { + port->cached_edid = drm_get_edid(port->connector, + &port->aux.ddc); + drm_connector_set_tile_property(port->connector); + } + + mgr->cbs->register_connector(port->connector); + return; + +error: + DRM_ERROR("Failed to create connector for port %p: %d\n", port, ret); +} + +/* + * Drop a topology reference, and unlink the port from the in-memory topology + * layout + */ +static void +drm_dp_mst_topology_unlink_port(struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_port *port) +{ + mutex_lock(&mgr->lock); + list_del(&port->next); + mutex_unlock(&mgr->lock); + drm_dp_mst_topology_put_port(port); +} + +static struct drm_dp_mst_port * +drm_dp_mst_add_port(struct drm_device *dev, + struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_branch *mstb, u8 port_number) +{ + struct drm_dp_mst_port *port = kzalloc(sizeof(*port), GFP_KERNEL); + + if (!port) + return NULL; + + kref_init(&port->topology_kref); + kref_init(&port->malloc_kref); + port->parent = mstb; + port->port_num = port_number; + port->mgr = mgr; + port->aux.name = "DPMST"; + port->aux.dev = dev->dev; + port->aux.is_remote = true; + + /* + * Make sure the memory allocation for our parent branch stays + * around until our own memory allocation is released + */ + drm_dp_mst_get_mstb_malloc(mstb); + + return port; +} + static void drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, struct drm_device *dev, @@ -1912,35 +1984,40 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; struct drm_dp_mst_port *port; - bool created = false; - int old_ddps = 0; + int old_ddps = 0, ret; + u8 new_pdt = DP_PEER_DEVICE_NONE; + bool created = false, send_link_addr = false;

port = drm_dp_get_port(mstb, port_msg->port_number); if (!port) { - port = kzalloc(sizeof(*port), GFP_KERNEL); + port = drm_dp_mst_add_port(dev, mgr, mstb, + port_msg->port_number); if (!port) return; - kref_init(&port->topology_kref); - kref_init(&port->malloc_kref); - port->parent = mstb; - port->port_num = port_msg->port_number; - port->mgr = mgr; - port->aux.name = "DPMST"; - port->aux.dev = dev->dev; - port->aux.is_remote = true; - - /* - * Make sure the memory allocation for our parent branch stays - * around until our own memory allocation is released + created = true; + } else if (port_msg->input_port && !port->input && port->connector) { + /* Destroying the connector is impossible in this context, so + * replace the port with a new one */ - drm_dp_mst_get_mstb_malloc(mstb); + drm_dp_mst_topology_unlink_port(mgr, port); + drm_dp_mst_topology_put_port(port);

+ port = drm_dp_mst_add_port(dev, mgr, mstb, + port_msg->port_number); + if (!port) + return; created = true; } else { + /* Locking is only needed when the port has a connector + * exposed to userspace + */ + drm_modeset_lock(&mgr->base.lock, NULL); old_ddps = port->ddps; }

port->input = port_msg->input_port; + if (!port->input) + new_pdt = port_msg->peer_device_type; port->mcs = port_msg->mcs; port->ddps = port_msg->ddps; port->ldps = port_msg->legacy_device_plug_status; @@ -1968,59 +2045,39 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb, } }

- if (!port->input) { - int ret = drm_dp_port_set_pdt(port, - port_msg->peer_device_type); - if (ret == 1) { - drm_dp_send_link_address(mgr, port->mstb); - } else if (ret < 0) { - DRM_ERROR("Failed to change PDT on port %p: %d\n", - port, ret); - goto fail; - } + ret = drm_dp_port_set_pdt(port, new_pdt); + if (ret == 1) { + send_link_addr = true; + } else if (ret < 0) { + DRM_ERROR("Failed to change PDT on port %p: %d\n", + port, ret); + goto fail; }

- if (created && !port->input) { - char proppath[255]; - - build_mst_prop_path(mstb, port->port_num, proppath, - sizeof(proppath)); - port->connector = (*mgr->cbs->add_connector)(mgr, port, - proppath); - if (!port->connector) - goto fail; - - if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV || - port->pdt == DP_PEER_DEVICE_SST_SINK) && - port->port_num >= DP_MST_LOGICAL_PORT_0) { - port->cached_edid = drm_get_edid(port->connector, - &port->aux.ddc); - drm_connector_set_tile_property(port->connector); - } + if (!created) + drm_modeset_unlock(&mgr->base.lock); + else if (!port->connector && !port->input) + drm_dp_mst_port_add_connector(mstb, port);

- (*mgr->cbs->register_connector)(port->connector); - } + if (send_link_addr && port->mstb) + drm_dp_send_link_address(mgr, port->mstb);

/* put reference to this port */ drm_dp_mst_topology_put_port(port); return;

fail: - /* Remove it from the port list */ - mutex_lock(&mgr->lock); - list_del(&port->next); - mutex_unlock(&mgr->lock); - - /* Drop the port list reference */ - drm_dp_mst_topology_put_port(port); - /* And now drop our reference */ + drm_dp_mst_topology_unlink_port(mgr, port); drm_dp_mst_topology_put_port(port); + if (!created) + drm_modeset_unlock(&mgr->base.lock); }

static void drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, struct drm_dp_connection_status_notify *conn_stat) { + struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; struct drm_dp_mst_port *port; int old_ddps; bool dowork = false; @@ -2029,6 +2086,10 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, if (!port) return;

+ /* Locking is only needed if the port's exposed to userspace */ + if (port->connector) + drm_modeset_lock(&mgr->base.lock, NULL); + old_ddps = port->ddps; port->mcs = conn_stat->message_capability_status; port->ldps = conn_stat->legacy_device_plug_status; @@ -2054,10 +2115,12 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, } }

+ if (port->connector) + drm_modeset_unlock(&mgr->base.lock); + drm_dp_mst_topology_put_port(port); if (dowork) queue_work(system_long_wq, &mstb->mgr->work); - }

static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_topology_mgr *mgr, @@ -2157,8 +2220,11 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m if (port->input || !port->ddps) continue;

- if (!port->available_pbn) + if (!port->available_pbn) { + drm_modeset_lock(&mgr->base.lock, NULL); drm_dp_send_enum_path_resources(mgr, mstb, port); + drm_modeset_unlock(&mgr->base.lock); + }

if (port->mstb) mstb_child = drm_dp_mst_topology_get_mstb_validated( @@ -2189,11 +2255,16 @@ static void drm_dp_mst_link_probe_work(struct work_struct *work) mstb = NULL; } mutex_unlock(&mgr->lock); - if (mstb) { - drm_dp_check_and_send_link_address(mgr, mstb); - drm_dp_mst_topology_put_mstb(mstb); + if (!mstb) { + mutex_unlock(&mgr->probe_lock); + return; } + + drm_dp_check_and_send_link_address(mgr, mstb); + drm_dp_mst_topology_put_mstb(mstb); + mutex_unlock(&mgr->probe_lock); + drm_kms_helper_hotplug_event(dev); }

static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr, @@ -2478,8 +2549,6 @@ static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_handle_link_address_port(mstb, mgr->dev, &reply->ports[i]);

- drm_kms_helper_hotplug_event(mgr->dev); - out: if (ret <= 0) mstb->link_address_sent = false; @@ -3274,13 +3343,14 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; }

-static inline void +static inline bool drm_dp_mst_process_up_req(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_pending_up_req *up_req) { struct drm_dp_mst_branch *mstb = NULL; struct drm_dp_sideband_msg_req_body *msg = &up_req->msg; struct drm_dp_sideband_msg_hdr *hdr = &up_req->hdr; + bool hotplug = false;

if (hdr->broadcast) { const u8 *guid = NULL; @@ -3298,16 +3368,17 @@ drm_dp_mst_process_up_req(struct drm_dp_mst_topology_mgr *mgr, if (!mstb) { DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", hdr->lct); - return; + return false; }

/* TODO: Add missing handler for DP_RESOURCE_STATUS_NOTIFY events */ if (msg->req_type == DP_CONNECTION_STATUS_NOTIFY) { drm_dp_mst_handle_conn_stat(mstb, &msg->u.conn_stat); - drm_kms_helper_hotplug_event(mgr->dev); + hotplug = true; }

drm_dp_mst_topology_put_mstb(mstb); + return hotplug; }

static void drm_dp_mst_up_req_work(struct work_struct *work) @@ -3316,6 +3387,7 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) container_of(work, struct drm_dp_mst_topology_mgr, up_req_work); struct drm_dp_pending_up_req *up_req; + bool send_hotplug = false;

mutex_lock(&mgr->probe_lock); while (true) { @@ -3330,10 +3402,13 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) if (!up_req) break;

- drm_dp_mst_process_up_req(mgr, up_req); + send_hotplug |= drm_dp_mst_process_up_req(mgr, up_req); kfree(up_req); } mutex_unlock(&mgr->probe_lock); + + if (send_hotplug) + drm_kms_helper_hotplug_event(mgr->dev); }

static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) @@ -3441,22 +3516,31 @@ EXPORT_SYMBOL(drm_dp_mst_hpd_irq); /** * drm_dp_mst_detect_port() - get connection status for an MST port * @connector: DRM connector for this port + * @ctx: The acquisition context to use for grabbing locks * @mgr: manager for this port - * @port: unverified pointer to a port + * @port: pointer to a port * - * This returns the current connection state for a port. It validates the - * port pointer still exists so the caller doesn't require a reference + * This returns the current connection state for a port. */ -enum drm_connector_status drm_dp_mst_detect_port(struct drm_connector *connector, - struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port) +int +drm_dp_mst_detect_port(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, + struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_port *port) { - enum drm_connector_status status = connector_status_disconnected; + int ret;

/* we need to search for the port in the mgr in case it's gone */ port = drm_dp_mst_topology_get_port_validated(mgr, port); if (!port) return connector_status_disconnected;

+ ret = drm_modeset_lock(&mgr->base.lock, ctx); + if (ret) + goto out; + + ret = connector_status_disconnected; + if (!port->ddps) goto out;

@@ -3466,7 +3550,7 @@ enum drm_connector_status drm_dp_mst_detect_port(struct drm_connector *connector break;

case DP_PEER_DEVICE_SST_SINK: - status = connector_status_connected; + ret = connector_status_connected; /* for logical ports - cache the EDID */ if (port->port_num >= 8 && !port->cached_edid) { port->cached_edid = drm_get_edid(connector, &port->aux.ddc); @@ -3474,12 +3558,12 @@ enum drm_connector_status drm_dp_mst_detect_port(struct drm_connector *connector break; case DP_PEER_DEVICE_DP_LEGACY_CONV: if (port->ldps) - status = connector_status_connected; + ret = connector_status_connected; break; } out: drm_dp_mst_topology_put_port(port); - return status; + return ret; } EXPORT_SYMBOL(drm_dp_mst_detect_port);

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c index bbcab27644dc..a9962846a503 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c @@ -391,20 +391,7 @@ static int intel_dp_mst_get_ddc_modes(struct drm_connector *connector) return ret; }

-static enum drm_connector_status -intel_dp_mst_detect(struct drm_connector *connector, bool force) -{ - struct intel_connector *intel_connector = to_intel_connector(connector); - struct intel_dp *intel_dp = intel_connector->mst_port; - - if (drm_connector_is_unregistered(connector)) - return connector_status_disconnected; - return drm_dp_mst_detect_port(connector, &intel_dp->mst_mgr, - intel_connector->port); -} - static const struct drm_connector_funcs intel_dp_mst_connector_funcs = { - .detect = intel_dp_mst_detect, .fill_modes = drm_helper_probe_single_connector_modes, .atomic_get_property = intel_digital_connector_atomic_get_property, .atomic_set_property = intel_digital_connector_atomic_set_property, @@ -465,11 +452,26 @@ static struct drm_encoder *intel_mst_atomic_best_encoder(struct drm_connector *c return &intel_dp->mst_encoders[crtc->pipe]->base.base; }

+static int +intel_dp_mst_detect(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, bool force) +{ + struct intel_connector *intel_connector = to_intel_connector(connector); + struct intel_dp *intel_dp = intel_connector->mst_port; + + if (drm_connector_is_unregistered(connector)) + return connector_status_disconnected; + + return drm_dp_mst_detect_port(connector, ctx, &intel_dp->mst_mgr, + intel_connector->port); +} + static const struct drm_connector_helper_funcs intel_dp_mst_connector_helper_funcs = { .get_modes = intel_dp_mst_get_modes, .mode_valid = intel_dp_mst_mode_valid, .atomic_best_encoder = intel_mst_atomic_best_encoder, .atomic_check = intel_dp_mst_atomic_check, + .detect_ctx = intel_dp_mst_detect, };

static void intel_dp_mst_encoder_destroy(struct drm_encoder *encoder) diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c index a13924ae1992..a9d6aa110cfd 100644 --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c @@ -986,20 +986,11 @@ nv50_mstc_atomic_check(struct drm_connector *connector, return drm_dp_atomic_release_vcpi_slots(state, mgr, mstc->port); }

-static const struct drm_connector_helper_funcs -nv50_mstc_help = { - .get_modes = nv50_mstc_get_modes, - .mode_valid = nv50_mstc_mode_valid, - .best_encoder = nv50_mstc_best_encoder, - .atomic_best_encoder = nv50_mstc_atomic_best_encoder, - .atomic_check = nv50_mstc_atomic_check, -}; - -static enum drm_connector_status -nv50_mstc_detect(struct drm_connector *connector, bool force) +static int +nv50_mstc_detect(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, bool force) { struct nv50_mstc *mstc = nv50_mstc(connector); - enum drm_connector_status conn_status; int ret;

if (drm_connector_is_unregistered(connector)) @@ -1009,14 +1000,24 @@ nv50_mstc_detect(struct drm_connector *connector, bool force) if (ret < 0 && ret != -EACCES) return connector_status_disconnected;

- conn_status = drm_dp_mst_detect_port(connector, mstc->port->mgr, - mstc->port); + ret = drm_dp_mst_detect_port(connector, ctx, mstc->port->mgr, + mstc->port);

pm_runtime_mark_last_busy(connector->dev->dev); pm_runtime_put_autosuspend(connector->dev->dev); - return conn_status; + return ret; }

+static const struct drm_connector_helper_funcs +nv50_mstc_help = { + .get_modes = nv50_mstc_get_modes, + .mode_valid = nv50_mstc_mode_valid, + .best_encoder = nv50_mstc_best_encoder, + .atomic_best_encoder = nv50_mstc_atomic_best_encoder, + .atomic_check = nv50_mstc_atomic_check, + .detect_ctx = nv50_mstc_detect, +}; + static void nv50_mstc_destroy(struct drm_connector *connector) { @@ -1031,7 +1032,6 @@ nv50_mstc_destroy(struct drm_connector *connector) static const struct drm_connector_funcs nv50_mstc = { .reset = nouveau_conn_reset, - .detect = nv50_mstc_detect, .fill_modes = drm_helper_probe_single_connector_modes, .destroy = nv50_mstc_destroy, .atomic_duplicate_state = nouveau_conn_atomic_duplicate_state, diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c b/drivers/gpu/drm/radeon/radeon_dp_mst.c index 2994f07fbad9..ee28f5b3785e 100644 --- a/drivers/gpu/drm/radeon/radeon_dp_mst.c +++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c @@ -233,21 +233,26 @@ drm_encoder *radeon_mst_best_encoder(struct drm_connector *connector) return &radeon_connector->mst_encoder->base; }

+static int +radeon_dp_mst_detect(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, + bool force) +{ + struct radeon_connector *radeon_connector = + to_radeon_connector(connector); + struct radeon_connector *master = radeon_connector->mst_port; + + return drm_dp_mst_detect_port(connector, ctx, &master->mst_mgr, + radeon_connector->port); +} + static const struct drm_connector_helper_funcs radeon_dp_mst_connector_helper_funcs = { .get_modes = radeon_dp_mst_get_modes, .mode_valid = radeon_dp_mst_mode_valid, .best_encoder = radeon_mst_best_encoder, + .detect_ctx = radeon_dp_mst_detect, };

-static enum drm_connector_status -radeon_dp_mst_detect(struct drm_connector *connector, bool force) -{ - struct radeon_connector *radeon_connector = to_radeon_connector(connector); - struct radeon_connector *master = radeon_connector->mst_port; - - return drm_dp_mst_detect_port(connector, &master->mst_mgr, radeon_connector->port); -} - static void radeon_dp_mst_connector_destroy(struct drm_connector *connector) { @@ -262,7 +267,6 @@ radeon_dp_mst_connector_destroy(struct drm_connector *connector)

static const struct drm_connector_funcs radeon_dp_mst_connector_funcs = { .dpms = drm_helper_connector_dpms, - .detect = radeon_dp_mst_detect, .fill_modes = drm_helper_probe_single_connector_modes, .destroy = radeon_dp_mst_connector_destroy, }; diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index bccb5514e0ef..fd142db42cb0 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -45,21 +45,31 @@ struct drm_dp_vcpi { /** * struct drm_dp_mst_port - MST port * @port_num: port number - * @input: if this port is an input port. - * @mcs: message capability status - DP 1.2 spec. - * @ddps: DisplayPort Device Plug Status - DP 1.2 - * @pdt: Peer Device Type - * @ldps: Legacy Device Plug Status - * @dpcd_rev: DPCD revision of device on this port - * @num_sdp_streams: Number of simultaneous streams - * @num_sdp_stream_sinks: Number of stream sinks - * @available_pbn: Available bandwidth for this port. + * @input: if this port is an input port. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @mcs: message capability status - DP 1.2 spec. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @ddps: DisplayPort Device Plug Status - DP 1.2. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @pdt: Peer Device Type. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @ldps: Legacy Device Plug Status. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @dpcd_rev: DPCD revision of device on this port. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @num_sdp_streams: Number of simultaneous streams. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @num_sdp_stream_sinks: Number of stream sinks. Protected by + * &drm_dp_mst_topology_mgr.base.lock. + * @available_pbn: Available bandwidth for this port. Protected by + * &drm_dp_mst_topology_mgr.base.lock. * @next: link to next port on this branch device * @aux: i2c aux transport to talk to device connected to this port, protected - * by &drm_dp_mst_topology_mgr.lock + * by &drm_dp_mst_topology_mgr.base.lock. * @parent: branch device parent of this port * @vcpi: Virtual Channel Payload info for this port. - * @connector: DRM connector this port is connected to. + * @connector: DRM connector this port is connected to. Protected by + * &drm_dp_mst_topology_mgr.base.lock. * @mgr: topology manager this port lives under. * * This structure represents an MST port endpoint on a device somewhere @@ -653,7 +663,11 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled);

-enum drm_connector_status drm_dp_mst_detect_port(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port); +int +drm_dp_mst_detect_port(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, + struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_port *port);

bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);

This probably hasn't caused any problems up until now since it's probably nearly impossible to encounter this in the wild, however if we were to receive a connection status notification from the MST hub after resume while we're in the middle of reprobing the link addresses for a topology then there's a much larger chance that a port could have changed from being an output port to input port (or vice versa). If we forget to update this bit of information, we'll potentially ignore a valid PDT change on a downstream port because we think it's an input port.

So, make sure we read the input_port field in connection status notifications in drm_dp_mst_handle_conn_stat() to prevent this from happening once we've implemented suspend/resume reprobing.

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Lyude Paul lyude@redhat.com Reviewed-by: Sean Paul sean@poorly.run --- drivers/gpu/drm/drm_dp_mst_topology.c | 52 +++++++++++++++++++-------- 1 file changed, 38 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 7bf4db91ff90..c8e218b902ae 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2079,18 +2079,40 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; struct drm_dp_mst_port *port; - int old_ddps; - bool dowork = false; + int old_ddps, ret; + u8 new_pdt; + bool dowork = false, create_connector = false;

port = drm_dp_get_port(mstb, conn_stat->port_number); if (!port) return;

- /* Locking is only needed if the port's exposed to userspace */ - if (port->connector) + if (port->connector) { + if (!port->input && conn_stat->input_port) { + /* + * We can't remove a connector from an already exposed + * port, so just throw the port out and make sure we + * reprobe the link address of it's parent MSTB + */ + drm_dp_mst_topology_unlink_port(mgr, port); + mstb->link_address_sent = false; + dowork = true; + goto out; + } + + /* + * Locking is only needed if the port's exposed to userspace + */ drm_modeset_lock(&mgr->base.lock, NULL); + } else if (port->input && !conn_stat->input_port) { + create_connector = true; + /* Reprobe link address so we get num_sdp_streams */ + mstb->link_address_sent = false; + dowork = true; + }

old_ddps = port->ddps; + port->input = conn_stat->input_port; port->mcs = conn_stat->message_capability_status; port->ldps = conn_stat->legacy_device_plug_status; port->ddps = conn_stat->displayport_device_plug_status; @@ -2103,21 +2125,23 @@ drm_dp_mst_handle_conn_stat(struct drm_dp_mst_branch *mstb, } }

- if (!port->input) { - int ret = drm_dp_port_set_pdt(port, - conn_stat->peer_device_type); - if (ret == 1) { - dowork = true; - } else if (ret < 0) { - DRM_ERROR("Failed to change PDT for port %p: %d\n", - port, ret); - dowork = false; - } + new_pdt = port->input ? DP_PEER_DEVICE_NONE : conn_stat->peer_device_type; + + ret = drm_dp_port_set_pdt(port, new_pdt); + if (ret == 1) { + dowork = true; + } else if (ret < 0) { + DRM_ERROR("Failed to change PDT for port %p: %d\n", + port, ret); + dowork = false; }

if (port->connector) drm_modeset_unlock(&mgr->base.lock); + else if (create_connector) + drm_dp_mst_port_add_connector(mstb, port);

+out: drm_dp_mst_topology_put_port(port); if (dowork) queue_work(system_long_wq, &mstb->mgr->work);

Does what it says on the tin.

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Reviewed-by: Sean Paul sean@poorly.run Signed-off-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/drm_dp_mst_topology.c | 59 +++++++++++++-------------- 1 file changed, 29 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index c8e218b902ae..d486d15aa002 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3212,45 +3212,44 @@ EXPORT_SYMBOL(drm_dp_mst_topology_mgr_suspend); */ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr) { - int ret = 0; + int ret; + u8 guid[16];

mutex_lock(&mgr->lock); + if (!mgr->mst_primary) + goto out_fail;

- if (mgr->mst_primary) { - int sret; - u8 guid[16]; + ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, + DP_RECEIVER_CAP_SIZE); + if (ret != DP_RECEIVER_CAP_SIZE) { + DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n"); + goto out_fail; + }

- sret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE); - if (sret != DP_RECEIVER_CAP_SIZE) { - DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n"); - ret = -1; - goto out_unlock; - } + ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, + DP_MST_EN | + DP_UP_REQ_EN | + DP_UPSTREAM_IS_SRC); + if (ret < 0) { + DRM_DEBUG_KMS("mst write failed - undocked during suspend?\n"); + goto out_fail; + }

- ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, - DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC); - if (ret < 0) { - DRM_DEBUG_KMS("mst write failed - undocked during suspend?\n"); - ret = -1; - goto out_unlock; - } + /* Some hubs forget their guids after they resume */ + ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16); + if (ret != 16) { + DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n"); + goto out_fail; + } + drm_dp_check_mstb_guid(mgr->mst_primary, guid);

- /* Some hubs forget their guids after they resume */ - sret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16); - if (sret != 16) { - DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n"); - ret = -1; - goto out_unlock; - } - drm_dp_check_mstb_guid(mgr->mst_primary, guid); + mutex_unlock(&mgr->lock);

- ret = 0; - } else - ret = -1; + return 0;

-out_unlock: +out_fail: mutex_unlock(&mgr->lock); - return ret; + return -1; } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);

Currently, we enable hotplug detection only after we re-enable the display. However, this is too late if we're planning on sending sideband messages during the resume process - which we'll need to do in order to reprobe the topology on resume.

So, enable hotplug events before reinitializing the display.

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Sean Paul sean@poorly.run Signed-off-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/nouveau/nouveau_display.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c index 6f038511a03a..53f9bceaf17a 100644 --- a/drivers/gpu/drm/nouveau/nouveau_display.c +++ b/drivers/gpu/drm/nouveau/nouveau_display.c @@ -407,6 +407,17 @@ nouveau_display_init(struct drm_device *dev, bool resume, bool runtime) struct drm_connector_list_iter conn_iter; int ret;

+ /* + * Enable hotplug interrupts (done as early as possible, since we need + * them for MST) + */ + drm_connector_list_iter_begin(dev, &conn_iter); + nouveau_for_each_non_mst_connector_iter(connector, &conn_iter) { + struct nouveau_connector *conn = nouveau_connector(connector); + nvif_notify_get(&conn->hpd); + } + drm_connector_list_iter_end(&conn_iter); + ret = disp->init(dev, resume, runtime); if (ret) return ret; @@ -416,14 +427,6 @@ nouveau_display_init(struct drm_device *dev, bool resume, bool runtime) */ drm_kms_helper_poll_enable(dev);

- /* enable hotplug interrupts */ - drm_connector_list_iter_begin(dev, &conn_iter); - nouveau_for_each_non_mst_connector_iter(connector, &conn_iter) { - struct nouveau_connector *conn = nouveau_connector(connector); - nvif_notify_get(&conn->hpd); - } - drm_connector_list_iter_end(&conn_iter); - return ret; }

Since we're going to be reprobing the entire topology state on resume now using sideband transactions, we need to ensure that we actually have short HPD irqs enabled before calling drm_dp_mst_topology_mgr_resume(). So, do that.

Changes since v3: * Fix typo in comments

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Lyude Paul lyude@redhat.com Acked-by: Alex Deucher alexander.deucher@amd.com --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index 887bc1d5d9e2..8f67d301ad81 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -1186,15 +1186,15 @@ static int dm_resume(void *handle) /* program HPD filter */ dc_resume(dm->dc);

- /* On resume we need to rewrite the MSTM control bits to enamble MST*/ - s3_handle_mst(ddev, false); - /* * early enable HPD Rx IRQ, should be done before set mode as short * pulse interrupts are used for MST */ amdgpu_dm_irq_resume_early(adev);

+ /* On resume we need to rewrite the MSTM control bits to enable MST*/ + s3_handle_mst(ddev, false); + /* Do detection*/ drm_connector_list_iter_begin(ddev, &iter); drm_for_each_connector_iter(connector, &iter) {

For very subtle mistakes with topology refs, it can be rather difficult to trace them down with the debugging info that we already have. I had one such issue recently while trying to implement suspend/resume reprobing for MST, and ended up coming up with this.

Inspired by Chris Wilson's wakeref tracking for i915, this adds a very similar feature to the DP MST helpers, which allows for partial tracking of topology refs for both ports and branch devices. This is a lot less advanced then wakeref tracking: we merely keep a count of all of the spots where a topology ref has been grabbed or dropped, then dump out that history in chronological order when a port or branch device's topology refcount reaches 0. So far, I've found this incredibly useful for debugging topology refcount errors.

Since this has the potential to be somewhat slow and loud, we add an expert kernel config option to enable or disable this feature, CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS.

Changes since v1: * Don't forget to destroy topology_ref_history_lock Changes since v4: * Correct order of kref_put()/topology_ref_history_unlock - we can't unlock the history after kref_put() since the memory might have been freed by that point * Don't print message on allocation error failures, the kernel already does this for us

Cc: Juston Li juston.li@intel.com Cc: Imre Deak imre.deak@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Harry Wentland hwentlan@amd.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Reviewed-by: Sean Paul sean@poorly.run Signed-off-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/Kconfig | 14 ++ drivers/gpu/drm/drm_dp_mst_topology.c | 241 ++++++++++++++++++++++++-- include/drm/drm_dp_mst_helper.h | 45 +++++ 3 files changed, 290 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 36357a36a281..f3f5910743d4 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -93,6 +93,20 @@ config DRM_KMS_FB_HELPER help FBDEV helpers for KMS drivers.

+config DRM_DEBUG_DP_MST_TOPOLOGY_REFS + bool "Enable refcount backtrace history in the DP MST helpers" + select STACKDEPOT + depends on DRM_KMS_HELPER + depends on DEBUG_KERNEL + depends on EXPERT + help + Enables debug tracing for topology refs in DRM's DP MST helpers. A + history of each topology reference/dereference will be printed to the + kernel log once a port or branch device's topology refcount reaches 0. + + This has the potential to use a lot of memory and print some very + large kernel messages. If in doubt, say "N". + config DRM_FBDEV_EMULATION bool "Enable legacy fbdev support for your modesetting driver" depends on DRM diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 428160270482..cedfa281a22e 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -28,6 +28,13 @@ #include <linux/sched.h> #include <linux/seq_file.h>

+#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) +#include <linux/stackdepot.h> +#include <linux/sort.h> +#include <linux/timekeeping.h> +#include <linux/math64.h> +#endif + #include <drm/drm_atomic.h> #include <drm/drm_atomic_helper.h> #include <drm/drm_dp_mst_helper.h> @@ -1399,12 +1406,187 @@ drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port) } EXPORT_SYMBOL(drm_dp_mst_put_port_malloc);

+#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + +#define STACK_DEPTH 8 + +static noinline void +__topology_ref_save(struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_topology_ref_history *history, + enum drm_dp_mst_topology_ref_type type) +{ + struct drm_dp_mst_topology_ref_entry *entry = NULL; + depot_stack_handle_t backtrace; + ulong stack_entries[STACK_DEPTH]; + uint n; + int i; + + n = stack_trace_save(stack_entries, ARRAY_SIZE(stack_entries), 1); + backtrace = stack_depot_save(stack_entries, n, GFP_KERNEL); + if (!backtrace) + return; + + /* Try to find an existing entry for this backtrace */ + for (i = 0; i < history->len; i++) { + if (history->entries[i].backtrace == backtrace) { + entry = &history->entries[i]; + break; + } + } + + /* Otherwise add one */ + if (!entry) { + struct drm_dp_mst_topology_ref_entry *new; + int new_len = history->len + 1; + + new = krealloc(history->entries, sizeof(*new) * new_len, + GFP_KERNEL); + if (!new) + return; + + entry = &new[history->len]; + history->len = new_len; + history->entries = new; + + entry->backtrace = backtrace; + entry->type = type; + entry->count = 0; + } + entry->count++; + entry->ts_nsec = ktime_get_ns(); + + return; +} + +static int +topology_ref_history_cmp(const void *a, const void *b) +{ + const struct drm_dp_mst_topology_ref_entry *entry_a = a, *entry_b = b; + + if (entry_a->ts_nsec > entry_b->ts_nsec) + return 1; + else if (entry_a->ts_nsec < entry_b->ts_nsec) + return -1; + else + return 0; +} + +static inline const char * +topology_ref_type_to_str(enum drm_dp_mst_topology_ref_type type) +{ + if (type == DRM_DP_MST_TOPOLOGY_REF_GET) + return "get"; + else + return "put"; +} + +static void +__dump_topology_ref_history(struct drm_dp_mst_topology_ref_history *history, + void *ptr, const char *type_str) +{ + struct drm_printer p = drm_debug_printer(DBG_PREFIX); + char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL); + int i; + + if (!buf) + return; + + if (!history->len) + goto out; + + /* First, sort the list so that it goes from oldest to newest + * reference entry + */ + sort(history->entries, history->len, sizeof(*history->entries), + topology_ref_history_cmp, NULL); + + drm_printf(&p, + "%s (%p/%px) topology count reached 0, dumping history:\n", + type_str, ptr, ptr); + + for (i = 0; i < history->len; i++) { + const struct drm_dp_mst_topology_ref_entry *entry = + &history->entries[i]; + ulong *entries; + uint nr_entries; + u64 ts_nsec = entry->ts_nsec; + u64 rem_nsec = do_div(ts_nsec, 1000000000); + + nr_entries = stack_depot_fetch(entry->backtrace, &entries); + stack_trace_snprint(buf, PAGE_SIZE, entries, nr_entries, 4); + + drm_printf(&p, " %d %ss (last at %5llu.%06llu):\n%s", + entry->count, + topology_ref_type_to_str(entry->type), + ts_nsec, rem_nsec / 1000, buf); + } + + /* Now free the history, since this is the only time we expose it */ + kfree(history->entries); +out: + kfree(buf); +} + +static __always_inline void +drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb) +{ + __dump_topology_ref_history(&mstb->topology_ref_history, mstb, + "MSTB"); +} + +static __always_inline void +drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) +{ + __dump_topology_ref_history(&port->topology_ref_history, port, + "Port"); +} + +static __always_inline void +save_mstb_topology_ref(struct drm_dp_mst_branch *mstb, + enum drm_dp_mst_topology_ref_type type) +{ + __topology_ref_save(mstb->mgr, &mstb->topology_ref_history, type); +} + +static __always_inline void +save_port_topology_ref(struct drm_dp_mst_port *port, + enum drm_dp_mst_topology_ref_type type) +{ + __topology_ref_save(port->mgr, &port->topology_ref_history, type); +} + +static inline void +topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr) +{ + mutex_lock(&mgr->topology_ref_history_lock); +} + +static inline void +topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr) +{ + mutex_unlock(&mgr->topology_ref_history_lock); +} +#else +static inline void +topology_ref_history_lock(struct drm_dp_mst_topology_mgr *mgr) {} +static inline void +topology_ref_history_unlock(struct drm_dp_mst_topology_mgr *mgr) {} +static inline void +drm_dp_mst_dump_mstb_topology_history(struct drm_dp_mst_branch *mstb) {} +static inline void +drm_dp_mst_dump_port_topology_history(struct drm_dp_mst_port *port) {} +#define save_mstb_topology_ref(mstb, type) +#define save_port_topology_ref(port, type) +#endif + static void drm_dp_destroy_mst_branch_device(struct kref *kref) { struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, topology_kref); struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;

+ drm_dp_mst_dump_mstb_topology_history(mstb); + INIT_LIST_HEAD(&mstb->destroy_next);

/* @@ -1442,11 +1624,17 @@ static void drm_dp_destroy_mst_branch_device(struct kref *kref) static int __must_check drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) { - int ret = kref_get_unless_zero(&mstb->topology_kref); + int ret;

- if (ret) - DRM_DEBUG("mstb %p (%d)\n", mstb, - kref_read(&mstb->topology_kref)); + topology_ref_history_lock(mstb->mgr); + ret = kref_get_unless_zero(&mstb->topology_kref); + if (ret) { + DRM_DEBUG("mstb %p (%d)\n", + mstb, kref_read(&mstb->topology_kref)); + save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET); + } + + topology_ref_history_unlock(mstb->mgr);

return ret; } @@ -1467,9 +1655,14 @@ drm_dp_mst_topology_try_get_mstb(struct drm_dp_mst_branch *mstb) */ static void drm_dp_mst_topology_get_mstb(struct drm_dp_mst_branch *mstb) { + topology_ref_history_lock(mstb->mgr); + + save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_GET); WARN_ON(kref_read(&mstb->topology_kref) == 0); kref_get(&mstb->topology_kref); DRM_DEBUG("mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref)); + + topology_ref_history_unlock(mstb->mgr); }

/** @@ -1487,8 +1680,13 @@ static void drm_dp_mst_topology_get_mstb(struct drm_dp_mst_branch *mstb) static void drm_dp_mst_topology_put_mstb(struct drm_dp_mst_branch *mstb) { + topology_ref_history_lock(mstb->mgr); + DRM_DEBUG("mstb %p (%d)\n", mstb, kref_read(&mstb->topology_kref) - 1); + save_mstb_topology_ref(mstb, DRM_DP_MST_TOPOLOGY_REF_PUT); + + topology_ref_history_unlock(mstb->mgr); kref_put(&mstb->topology_kref, drm_dp_destroy_mst_branch_device); }

@@ -1498,6 +1696,8 @@ static void drm_dp_destroy_port(struct kref *kref) container_of(kref, struct drm_dp_mst_port, topology_kref); struct drm_dp_mst_topology_mgr *mgr = port->mgr;

+ drm_dp_mst_dump_port_topology_history(port); + /* There's nothing that needs locking to destroy an input port yet */ if (port->input) { drm_dp_mst_put_port_malloc(port); @@ -1541,12 +1741,17 @@ static void drm_dp_destroy_port(struct kref *kref) static int __must_check drm_dp_mst_topology_try_get_port(struct drm_dp_mst_port *port) { - int ret = kref_get_unless_zero(&port->topology_kref); + int ret;

- if (ret) - DRM_DEBUG("port %p (%d)\n", port, - kref_read(&port->topology_kref)); + topology_ref_history_lock(port->mgr); + ret = kref_get_unless_zero(&port->topology_kref); + if (ret) { + DRM_DEBUG("port %p (%d)\n", + port, kref_read(&port->topology_kref)); + save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET); + }

+ topology_ref_history_unlock(port->mgr); return ret; }

@@ -1565,9 +1770,14 @@ drm_dp_mst_topology_try_get_port(struct drm_dp_mst_port *port) */ static void drm_dp_mst_topology_get_port(struct drm_dp_mst_port *port) { + topology_ref_history_lock(port->mgr); + WARN_ON(kref_read(&port->topology_kref) == 0); kref_get(&port->topology_kref); DRM_DEBUG("port %p (%d)\n", port, kref_read(&port->topology_kref)); + save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_GET); + + topology_ref_history_unlock(port->mgr); }

/** @@ -1583,8 +1793,13 @@ static void drm_dp_mst_topology_get_port(struct drm_dp_mst_port *port) */ static void drm_dp_mst_topology_put_port(struct drm_dp_mst_port *port) { - DRM_DEBUG("port %p (%d)\n", - port, kref_read(&port->topology_kref) - 1); + topology_ref_history_lock(port->mgr); + + DRM_DEBUG("port %p/%px (%d)\n", + port, port, kref_read(&port->topology_kref) - 1); + save_port_topology_ref(port, DRM_DP_MST_TOPOLOGY_REF_PUT); + + topology_ref_history_unlock(port->mgr); kref_put(&port->topology_kref, drm_dp_destroy_port); }

@@ -4577,6 +4792,9 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, mutex_init(&mgr->delayed_destroy_lock); mutex_init(&mgr->up_req_lock); mutex_init(&mgr->probe_lock); +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + mutex_init(&mgr->topology_ref_history_lock); +#endif INIT_LIST_HEAD(&mgr->tx_msg_downq); INIT_LIST_HEAD(&mgr->destroy_port_list); INIT_LIST_HEAD(&mgr->destroy_branch_device_list); @@ -4643,6 +4861,9 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr) mutex_destroy(&mgr->lock); mutex_destroy(&mgr->up_req_lock); mutex_destroy(&mgr->probe_lock); +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + mutex_destroy(&mgr->topology_ref_history_lock); +#endif } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);

diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 144027e27464..d5fc90b30487 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -26,6 +26,26 @@ #include <drm/drm_dp_helper.h> #include <drm/drm_atomic.h>

+#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) +#include <linux/stackdepot.h> +#include <linux/timekeeping.h> + +enum drm_dp_mst_topology_ref_type { + DRM_DP_MST_TOPOLOGY_REF_GET, + DRM_DP_MST_TOPOLOGY_REF_PUT, +}; + +struct drm_dp_mst_topology_ref_history { + struct drm_dp_mst_topology_ref_entry { + enum drm_dp_mst_topology_ref_type type; + int count; + ktime_t ts_nsec; + depot_stack_handle_t backtrace; + } *entries; + int len; +}; +#endif /* IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) */ + struct drm_dp_mst_branch;

/** @@ -89,6 +109,14 @@ struct drm_dp_mst_port { */ struct kref malloc_kref;

+#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + /** + * @topology_ref_history: A history of each topology + * reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS. + */ + struct drm_dp_mst_topology_ref_history topology_ref_history; +#endif + u8 port_num; bool input; bool mcs; @@ -162,6 +190,14 @@ struct drm_dp_mst_branch { */ struct kref malloc_kref;

+#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + /** + * @topology_ref_history: A history of each topology + * reference/dereference. See CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS. + */ + struct drm_dp_mst_topology_ref_history topology_ref_history; +#endif + /** * @destroy_next: linked-list entry used by * drm_dp_delayed_destroy_work() @@ -647,6 +683,15 @@ struct drm_dp_mst_topology_mgr { * transmissions. */ struct work_struct up_req_work; + +#if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) + /** + * @topology_ref_history_lock: protects + * &drm_dp_mst_port.topology_ref_history and + * &drm_dp_mst_branch.topology_ref_history. + */ + struct mutex topology_ref_history_lock; +#endif };

int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,