Some TypeC -> native DP adapters, at least the Club CAC-1557 adapter, incorrectly filter out HPD short pulses with a duration less than ~540 usec, leading to MST probe failures.
According to the DP alt mode specification adapters should forward short pulses with a duration greater than 250 usec. According to the DP specificatin DP sources should detect short pulses in the 500 usec -> 2 ms range. Based on this filtering out short pulses with a duration less than 540 usec is incorrect.
To make such adapters work add support for a driver polling on MST inerrupt flags, and wire this up in the i915 driver. The sink can clear an interrupt it raised after 110 ms if the source doesn't respond, so use a 50 ms poll period to avoid missing an interrupt. Polling of the MST interrupt flags is explicitly allowed by the DP specification.
This fixes MST probe failures I saw using this adapter and a DELL U2515H monitor.
Signed-off-by: Imre Deak imre.deak@intel.com --- drivers/gpu/drm/drm_dp_mst_topology.c | 18 +++++++++++++++--- drivers/gpu/drm/i915/display/intel_dp_mst.c | 15 +++++++++++++++ include/drm/drm_dp_mst_helper.h | 1 + 3 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 5bc72e800b85..d1bf340a95a8 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1178,11 +1178,23 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, struct drm_dp_sideband_msg_tx *txmsg) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; + unsigned long wait_expires = jiffies + msecs_to_jiffies(4000); int ret;
- ret = wait_event_timeout(mgr->tx_waitq, - check_txmsg_state(mgr, txmsg), - (4 * HZ)); + for (;;) { + ret = wait_event_timeout(mgr->tx_waitq, + check_txmsg_state(mgr, txmsg), + mgr->cbs->update_hpd_irq_state ? + msecs_to_jiffies(50) : + wait_expires); + + if (ret || !mgr->cbs->update_hpd_irq_state || + time_after(jiffies, wait_expires)) + break; + + mgr->cbs->update_hpd_irq_state(mgr); + } + mutex_lock(&mgr->qlock); if (ret > 0) { if (txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT) { diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c index d18b406f2a7d..1ff7d0096262 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c @@ -765,8 +765,23 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo return NULL; }
+static void +intel_dp_mst_update_hpd_irq_state(struct drm_dp_mst_topology_mgr *mgr) +{ + struct intel_dp *intel_dp = container_of(mgr, struct intel_dp, mst_mgr); + struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp); + struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev); + + spin_lock_irq(&i915->irq_lock); + i915->hotplug.short_port_mask |= BIT(dig_port->base.port); + spin_unlock_irq(&i915->irq_lock); + + queue_work(i915->hotplug.dp_wq, &i915->hotplug.dig_port_work); +} + static const struct drm_dp_mst_topology_cbs mst_cbs = { .add_connector = intel_dp_add_mst_connector, + .update_hpd_irq_state = intel_dp_mst_update_hpd_irq_state, };
static struct intel_dp_mst_encoder * diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 9e1ffcd7cb68..c902f4380200 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -475,6 +475,7 @@ struct drm_dp_mst_topology_mgr; struct drm_dp_mst_topology_cbs { /* create a connector for a port */ struct drm_connector *(*add_connector)(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, const char *path); + void (*update_hpd_irq_state)(struct drm_dp_mst_topology_mgr *mgr); };
#define DP_MAX_PAYLOAD (sizeof(unsigned long) * 8)