On Tue, 10 May 2022 at 22:29, Douglas Anderson dianders@chromium.org wrote:

While working on the DP AUX bus code I found a few small things that should be fixed. Namely the non-devm version of of_dp_aux_populate_ep_devices() was missing an export. There was also an extra blank line in a kerneldoc and a kerneldoc that incorrectly documented a return value. Fix these.

Fixes: aeb33699fc2c ("drm: Introduce the DP AUX bus") Signed-off-by: Douglas Anderson dianders@chromium.org

Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org

---

None of these seem critical, so my plan is to land this in drm-misc-next and not drm-misc-fixes. This will avoid merge conflicts with future patches.

Changes in v3:

• Patch ("drm/dp: Export symbol / kerneldoc fixes...") split for v3.

drivers/gpu/drm/display/drm_dp_aux_bus.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_aux_bus.c b/drivers/gpu/drm/display/drm_dp_aux_bus.c index dccf3e2ea323..552f949cff59 100644 --- a/drivers/gpu/drm/display/drm_dp_aux_bus.c +++ b/drivers/gpu/drm/display/drm_dp_aux_bus.c @@ -66,7 +66,6 @@ static int dp_aux_ep_probe(struct device *dev)

• @dev: The device to remove.
• Calls through to the endpoint driver remove.

• */

static void dp_aux_ep_remove(struct device *dev) { @@ -120,8 +119,6 @@ ATTRIBUTE_GROUPS(dp_aux_ep_dev); /**

• dp_aux_ep_dev_release() - Free memory for the dp_aux_ep device
• @dev: The device to free.

• • Return: 0 if no error or negative error code.
  */

static void dp_aux_ep_dev_release(struct device *dev) { @@ -256,6 +253,7 @@ int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux)

    return 0;

} +EXPORT_SYMBOL_GPL(of_dp_aux_populate_ep_devices);

static void of_dp_aux_depopulate_ep_devices_void(void *data) { -- 2.36.0.550.gb090851708-goog

On 10/05/2022 22:29, Douglas Anderson wrote:

While working on the DP AUX bus code I found a few small things that should be fixed. Namely the non-devm version of of_dp_aux_populate_ep_devices() was missing an export. There was also an extra blank line in a kerneldoc and a kerneldoc that incorrectly documented a return value. Fix these.

Fixes: aeb33699fc2c ("drm: Introduce the DP AUX bus") Signed-off-by: Douglas Anderson dianders@chromium.org

Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org

---

None of these seem critical, so my plan is to land this in drm-misc-next and not drm-misc-fixes. This will avoid merge conflicts with future patches.

Changes in v3:

• Patch ("drm/dp: Export symbol / kerneldoc fixes...") split for v3.

  drivers/gpu/drm/display/drm_dp_aux_bus.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_aux_bus.c b/drivers/gpu/drm/display/drm_dp_aux_bus.c index dccf3e2ea323..552f949cff59 100644 --- a/drivers/gpu/drm/display/drm_dp_aux_bus.c +++ b/drivers/gpu/drm/display/drm_dp_aux_bus.c @@ -66,7 +66,6 @@ static int dp_aux_ep_probe(struct device *dev)

• @dev: The device to remove.
• Calls through to the endpoint driver remove.

• */ static void dp_aux_ep_remove(struct device *dev) {

@@ -120,8 +119,6 @@ ATTRIBUTE_GROUPS(dp_aux_ep_dev); /**

• dp_aux_ep_dev_release() - Free memory for the dp_aux_ep device
• @dev: The device to free.

• • Return: 0 if no error or negative error code.
  */ static void dp_aux_ep_dev_release(struct device *dev) {

@@ -256,6 +253,7 @@ int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux)

return 0; } +EXPORT_SYMBOL_GPL(of_dp_aux_populate_ep_devices);

static void of_dp_aux_depopulate_ep_devices_void(void *data) {

On 10/05/2022 22:29, Douglas Anderson wrote:

As talked about in this patch in the kerneldoc of of_dp_aux_populate_ep_device() and also in the past in commit a1e3667a9835 ("drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev"), it can be difficult for eDP controller drivers to know when the panel has finished probing when they're using of_dp_aux_populate_ep_devices().

The ti-sn65dsi86 driver managed to solve this because it was already broken up into a bunch of sub-drivers. That means we could solve the problem there by adding a new sub-driver to get the panel. We could use the traditional -EPROBE_DEFER retry mechansim to handle the case where the panel hadn't probed yet.

In parade-ps8640 we didn't really solve this. The code just expects the panel to be ready right away. While reviewing the code originally I had managed to convince myself it was fine to just expect the panel right away, but additional testing has shown that not to be the case. We could fix parade-ps8640 like we did ti-sn65dsi86 but it's pretty cumbersome (since we're not already broken into multiple drivers) and requires a bunch of boilerplate code.

After discussion [1] it seems like the best solution for most people is:

• Accept that there's always at most one device that will probe as a result of the DP AUX bus (it may have sub-devices, but there will be one device _directly_ probed).
• When that device finishes probing, we can just have a call back.

This patch implements that idea. We'll now take a callback as an argument to the populate function. To make this easier to land in pieces, we'll make wrappers for the old functions. The functions with the new name (which make it clear that we only have one child) will take the callback and the functions with the old name will temporarily wrap.

[1] https://lore.kernel.org/r/CAD=FV=Ur3afHhsXe7a3baWEnD=MFKFeKRbhFU+bt3P67G0MVz...

Signed-off-by: Douglas Anderson dianders@chromium.org

Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org

---

Changes in v3:

• Don't call done_probing() if there are no children; return -ENODEV.
• Split out EXPORT_SYMBOL and kerneldoc fixes to its own patch.
• Used Dmitry's proposed name: of_dp_aux_populate_bus()

Changes in v2:

• Change to assume exactly one device.

• Have a probe callback instead of an extra sub device.

  drivers/gpu/drm/display/drm_dp_aux_bus.c | 209 +++++++++++++++-------- include/drm/display/drm_dp_aux_bus.h | 34 +++- 2 files changed, 168 insertions(+), 75 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_aux_bus.c b/drivers/gpu/drm/display/drm_dp_aux_bus.c index 552f949cff59..f5741b45ca07 100644 --- a/drivers/gpu/drm/display/drm_dp_aux_bus.c +++ b/drivers/gpu/drm/display/drm_dp_aux_bus.c @@ -3,10 +3,10 @@

• Copyright 2021 Google Inc.
• The DP AUX bus is used for devices that are connected over a DisplayPort

• • AUX bus. The devices on the far side of the bus are referred to as
• • endpoints in this code.

• • AUX bus. The device on the far side of the bus is referred to as an
• • endpoint in this code.

• • Commonly there is only one device connected to the DP AUX bus: a panel.

• • There is only one device connected to the DP AUX bus: an eDP panel.
  • Though historically panels (even DP panels) have been modeled as simple
  • platform devices, putting them under the DP AUX bus allows the panel driver
  • to perform transactions on that bus.

@@ -22,6 +22,11 @@ #include <drm/display/drm_dp_aux_bus.h> #include <drm/display/drm_dp_helper.h>

+struct dp_aux_ep_device_with_data {

• struct dp_aux_ep_device aux_ep;
• int (*done_probing)(struct drm_dp_aux *aux);

+};

• /**
  • dp_aux_ep_match() - The match function for the dp_aux_bus.
  • @dev: The device to match.

@@ -48,6 +53,8 @@ static int dp_aux_ep_probe(struct device *dev) { struct dp_aux_ep_driver *aux_ep_drv = to_dp_aux_ep_drv(dev->driver); struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev);

• struct dp_aux_ep_device_with_data *aux_ep_with_data =

• container_of(aux_ep, struct dp_aux_ep_device_with_data, aux_ep);
  

  int ret;

  ret = dev_pm_domain_attach(dev, true);

@@ -56,7 +63,32 @@ static int dp_aux_ep_probe(struct device *dev)

ret = aux_ep_drv->probe(aux_ep); if (ret)

• dev_pm_domain_detach(dev, true);
  

• goto err_attached;
  

• if (aux_ep_with_data->done_probing) {

• ret = aux_ep_with_data->done_probing(aux_ep->aux);
  

• if (ret) {
  

• 	/*
  

• 	 * The done_probing() callback should not return
  

• 	 * -EPROBE_DEFER to us. If it does, we treat it as an
  

• 	 * error. Passing it on as-is would cause the _panel_
  

• 	 * to defer.
  

• 	 */
  

• 	if (ret == -EPROBE_DEFER) {
  

• 		dev_err(dev,
  

• 			"DP AUX done_probing() can't defer\n");
  

• 		ret = -EINVAL;
  

• 	}
  

• 	goto err_probed;
  

• }
  

• }
• return 0;

+err_probed:

• if (aux_ep_drv->remove)

• aux_ep_drv->remove(aux_ep);
  

+err_attached:

• dev_pm_domain_detach(dev, true);

  return ret; }

@@ -122,7 +154,11 @@ ATTRIBUTE_GROUPS(dp_aux_ep_dev); */ static void dp_aux_ep_dev_release(struct device *dev) {

• kfree(to_dp_aux_ep_dev(dev));

• struct dp_aux_ep_device *aux_ep = to_dp_aux_ep_dev(dev);

• struct dp_aux_ep_device_with_data *aux_ep_with_data =

• container_of(aux_ep, struct dp_aux_ep_device_with_data, aux_ep);
  

• kfree(aux_ep_with_data); }

  static struct device_type dp_aux_device_type_type = {

@@ -136,12 +172,14 @@ static struct device_type dp_aux_device_type_type = {

• @dev: The device to destroy.
• @data: Not used

• • This is just used as a callback by of_dp_aux_depopulate_ep_devices() and

• • This is just used as a callback by of_dp_aux_depopulate_bus() and
  • is called for _all_ of the child devices of the device providing the AUX bus.
  • We'll only act on those that are of type "dp_aux_bus_type".

• • This function is effectively an inverse of what's in the loop
• • in of_dp_aux_populate_ep_devices().

• • This function is effectively an inverse of what's in
• • of_dp_aux_populate_bus(). NOTE: since we only populate one child
• • then it's expected that only one device will match all the "if" tests in
• • this function and get to the device_unregister().
  • Return: 0 if no error or negative error code.
  */

@@ -164,123 +202,150 @@ static int of_dp_aux_ep_destroy(struct device *dev, void *data) }

/**

• • of_dp_aux_depopulate_ep_devices() - Undo of_dp_aux_populate_ep_devices
• • @aux: The AUX channel whose devices we want to depopulate

• • of_dp_aux_depopulate_bus() - Undo of_dp_aux_populate_bus
• • @aux: The AUX channel whose device we want to depopulate

• • This will destroy all devices that were created
• • by of_dp_aux_populate_ep_devices().

• • This will destroy the device that was created
• • by of_dp_aux_populate_bus().
  */

-void of_dp_aux_depopulate_ep_devices(struct drm_dp_aux *aux) +void of_dp_aux_depopulate_bus(struct drm_dp_aux *aux) { device_for_each_child_reverse(aux->dev, NULL, of_dp_aux_ep_destroy); } -EXPORT_SYMBOL_GPL(of_dp_aux_depopulate_ep_devices); +EXPORT_SYMBOL_GPL(of_dp_aux_depopulate_bus);

/**

• • of_dp_aux_populate_ep_devices() - Populate the endpoint devices on the DP AUX
• • @aux: The AUX channel whose devices we want to populate. It is required that

• • of_dp_aux_populate_bus() - Populate the endpoint device on the DP AUX
• • @aux: The AUX channel whose device we want to populate. It is required that

  •   drm_dp_aux_init() has already been called for this AUX channel.
    

• • @done_probing: Callback functions to call after EP device finishes probing.

• •            Will not be called if there are no EP devices and this
    

• •            function will return -ENODEV.
    

• • This will populate all the devices under the "aux-bus" node of the device
• • providing the AUX channel (AKA aux->dev).

• • This will populate the device (expected to be an eDP panel) under the
• • "aux-bus" node of the device providing the AUX channel (AKA aux->dev).
  • When this function finishes, it is _possible_ (but not guaranteed) that

• • our sub-devices will have finished probing. It should be noted that if our
• • sub-devices return -EPROBE_DEFER that we will not return any error codes
• • ourselves but our sub-devices will _not_ have actually probed successfully
• • yet. There may be other cases (maybe added in the future?) where sub-devices
• • won't have been probed yet when this function returns, so it's best not to
• • rely on that.

• • our sub-device will have finished probing. It should be noted that if our
• • sub-device returns -EPROBE_DEFER or is probing asynchronously for some
• • reason that we will not return any error codes ourselves but our
• • sub-device will _not_ have actually probed successfully yet.
• • In many cases it's important for the caller of this function to be notified
• • when our sub device finishes probing. Our sub device is expected to be an
• • eDP panel and the caller is expected to be an eDP controller. The eDP
• • controller needs to be able to get a reference to the panel when it finishes
• • probing. For this reason the caller can pass in a function pointer that
• • will be called when our sub-device finishes probing.
  • If this function succeeds you should later make sure you call

• • of_dp_aux_depopulate_ep_devices() to undo it, or just use the devm version

• • of_dp_aux_depopulate_bus() to undo it, or just use the devm version
  • of this function.

• • Return: 0 if no error or negative error code.

• • Return: 0 if no error or negative error code; returns -ENODEV if there are

• •     no children. The done_probing() function won't be called in that
    

• •     case.
    

  */

-int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux) +int of_dp_aux_populate_bus(struct drm_dp_aux *aux,

• 	   int (*done_probing)(struct drm_dp_aux *aux))
  

  {

• struct device_node *bus, *np;

• struct device_node *bus = NULL, *np = NULL; struct dp_aux_ep_device *aux_ep;

• struct dp_aux_ep_device_with_data *aux_ep_with_data; int ret;

  /* drm_dp_aux_init() should have been called already; warn if not */ WARN_ON_ONCE(!aux->ddc.algo);

  if (!aux->dev->of_node)

• return 0;
  

• return -ENODEV;
  

  bus = of_get_child_by_name(aux->dev->of_node, "aux-bus"); if (!bus)

• return 0;
  

• return -ENODEV;
  
  

• for_each_available_child_of_node(bus, np) {

• if (of_node_test_and_set_flag(np, OF_POPULATED))
  

• 	continue;
  

• np = of_get_next_available_child(bus, NULL);
• of_node_put(bus);
• if (!np)

• return -ENODEV;
  
  

• aux_ep = kzalloc(sizeof(*aux_ep), GFP_KERNEL);
  

• if (!aux_ep)
  

• 	continue;
  

• aux_ep->aux = aux;
  

• if (of_node_test_and_set_flag(np, OF_POPULATED)) {

• dev_err(aux->dev, "DP AUX EP device already populated\n");
  

• ret = -EINVAL;
  

• goto err_did_get_np;
  

• }

• aux_ep->dev.parent = aux->dev;
  

• aux_ep->dev.bus = &dp_aux_bus_type;
  

• aux_ep->dev.type = &dp_aux_device_type_type;
  

• aux_ep->dev.of_node = of_node_get(np);
  

• dev_set_name(&aux_ep->dev, "aux-%s", dev_name(aux->dev));
  

• aux_ep_with_data = kzalloc(sizeof(*aux_ep_with_data), GFP_KERNEL);
• if (!aux_ep_with_data) {

• ret = -ENOMEM;
  

• goto err_did_set_populated;
  

• }

• ret = device_register(&aux_ep->dev);
  

• if (ret) {
  

• 	dev_err(aux->dev, "Failed to create AUX EP for %pOF: %d\n", np, ret);
  

• 	of_node_clear_flag(np, OF_POPULATED);
  

• 	of_node_put(np);
  

• aux_ep_with_data->done_probing = done_probing;

• 	/*
  

• 	 * As per docs of device_register(), call this instead
  

• 	 * of kfree() directly for error cases.
  

• 	 */
  

• 	put_device(&aux_ep->dev);
  

• aux_ep = &aux_ep_with_data->aux_ep;
• aux_ep->aux = aux;
• aux_ep->dev.parent = aux->dev;
• aux_ep->dev.bus = &dp_aux_bus_type;
• aux_ep->dev.type = &dp_aux_device_type_type;
• aux_ep->dev.of_node = of_node_get(np);
• dev_set_name(&aux_ep->dev, "aux-%s", dev_name(aux->dev));

• 	/*
  

• 	 * Following in the footsteps of of_i2c_register_devices(),
  

• 	 * we won't fail the whole function here--we'll just
  

• 	 * continue registering any other devices we find.
  

• 	 */
  

• }
  

• }

• ret = device_register(&aux_ep->dev);
• if (ret) {

• dev_err(aux->dev, "Failed to create AUX EP for %pOF: %d\n", np, ret);
  
  

• of_node_put(bus);

• /*
  

•  * As per docs of device_register(), call this instead
  

•  * of kfree() directly for error cases.
  

•  */
  

• put_device(&aux_ep->dev);
  

• goto err_did_set_populated;
  

• }

  return 0;

+err_did_set_populated:

• of_node_clear_flag(np, OF_POPULATED);

+err_did_get_np:

• of_node_put(np);
• return ret; }

-EXPORT_SYMBOL_GPL(of_dp_aux_populate_ep_devices); +EXPORT_SYMBOL_GPL(of_dp_aux_populate_bus);

-static void of_dp_aux_depopulate_ep_devices_void(void *data) +static void of_dp_aux_depopulate_bus_void(void *data) {

• of_dp_aux_depopulate_ep_devices(data);

• of_dp_aux_depopulate_bus(data); }

  /**

• • devm_of_dp_aux_populate_ep_devices() - devm wrapper for of_dp_aux_populate_ep_devices()
• • @aux: The AUX channel whose devices we want to populate

• • devm_of_dp_aux_populate_bus() - devm wrapper for of_dp_aux_populate_bus()
• • @aux: The AUX channel whose device we want to populate
• • @done_probing: Callback functions to call after EP device finishes probing.

• •            Will not be called if there are no EP devices and this
    

• •            function will return -ENODEV.
    

  • Handles freeing w/ devm on the device "aux->dev".

• • Return: 0 if no error or negative error code.

• • Return: 0 if no error or negative error code; returns -ENODEV if there are

• •     no children. The done_probing() function won't be called in that
    

• •     case.
    

  */

-int devm_of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux) +int devm_of_dp_aux_populate_bus(struct drm_dp_aux *aux,

• 		int (*done_probing)(struct drm_dp_aux *aux))
  

  { int ret;

• ret = of_dp_aux_populate_ep_devices(aux);

• ret = of_dp_aux_populate_bus(aux, done_probing); if (ret) return ret;

  return devm_add_action_or_reset(aux->dev,

• 			of_dp_aux_depopulate_ep_devices_void,
  

• 			aux);
  

• 			of_dp_aux_depopulate_bus_void, aux);
  

  }

-EXPORT_SYMBOL_GPL(devm_of_dp_aux_populate_ep_devices); +EXPORT_SYMBOL_GPL(devm_of_dp_aux_populate_bus);

int __dp_aux_dp_driver_register(struct dp_aux_ep_driver *drv, struct module *owner) { diff --git a/include/drm/display/drm_dp_aux_bus.h b/include/drm/display/drm_dp_aux_bus.h index 4f19b20b1dd6..8a0a486383c5 100644 --- a/include/drm/display/drm_dp_aux_bus.h +++ b/include/drm/display/drm_dp_aux_bus.h @@ -44,9 +44,37 @@ static inline struct dp_aux_ep_driver *to_dp_aux_ep_drv(struct device_driver *dr return container_of(drv, struct dp_aux_ep_driver, driver); }

-int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux); -void of_dp_aux_depopulate_ep_devices(struct drm_dp_aux *aux); -int devm_of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux); +int of_dp_aux_populate_bus(struct drm_dp_aux *aux,

• 	   int (*done_probing)(struct drm_dp_aux *aux));
  

+void of_dp_aux_depopulate_bus(struct drm_dp_aux *aux); +int devm_of_dp_aux_populate_bus(struct drm_dp_aux *aux,

• 		int (*done_probing)(struct drm_dp_aux *aux));
  

+/* Deprecated versions of the above functions. To be removed when no callers. */ +static inline int of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux) +{

• int ret;
• ret = of_dp_aux_populate_bus(aux, NULL);
• /* New API returns -ENODEV for no child case; adapt to old assumption */
• return (ret != -ENODEV) ? ret : 0;

+}

+static inline int devm_of_dp_aux_populate_ep_devices(struct drm_dp_aux *aux) +{

• int ret;
• ret = devm_of_dp_aux_populate_bus(aux, NULL);
• /* New API returns -ENODEV for no child case; adapt to old assumption */
• return (ret != -ENODEV) ? ret : 0;

+}

+static inline void of_dp_aux_depopulate_ep_devices(struct drm_dp_aux *aux) +{

• of_dp_aux_depopulate_bus(aux);

+}

#define dp_aux_dp_driver_register(aux_ep_drv) \ __dp_aux_dp_driver_register(aux_ep_drv, THIS_MODULE)

On Tue, 10 May 2022 at 22:30, Douglas Anderson dianders@chromium.org wrote:

This adds a devm managed version of drm_bridge_add(). Like other "devm" function listed in drm_bridge.h, this function takes an explicit "dev" to use for the lifetime management. A few notes:

• In general we have a "struct device" for bridges that makes a good candidate for where the lifetime matches exactly what we want.
• The "bridge->dev->dev" device appears to be the encoder device. That's not the right device to use for lifetime management.

Suggested-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Signed-off-by: Douglas Anderson dianders@chromium.org

Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org

---

Changes in v3:

• Patch ("drm/bridge: Add devm_drm_bridge_add()") new for v3.

drivers/gpu/drm/drm_bridge.c | 23 +++++++++++++++++++++++ include/drm/drm_bridge.h | 1 + 2 files changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index c96847fc0ebc..e275b4ca344b 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -170,6 +170,29 @@ void drm_bridge_add(struct drm_bridge *bridge) } EXPORT_SYMBOL(drm_bridge_add);

+static void drm_bridge_remove_void(void *bridge) +{

•   drm_bridge_remove(bridge);
  

+}

+/**

• • devm_drm_bridge_add - devm managed version of drm_bridge_add()
• • @dev: device to tie the bridge lifetime to
• • @bridge: bridge control structure
• • This is the managed version of drm_bridge_add() which automatically
• • calls drm_bridge_remove() when @dev is unbound.
• • Return: 0 if no error or negative error code.
• */

+int devm_drm_bridge_add(struct device *dev, struct drm_bridge *bridge) +{

•   drm_bridge_add(bridge);
  

•   return devm_add_action_or_reset(dev, drm_bridge_remove_void, bridge);
  

+} +EXPORT_SYMBOL(devm_drm_bridge_add);

/**

• drm_bridge_remove - remove the given bridge from the global bridge list

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index f27b4060faa2..42aec8612f37 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -796,6 +796,7 @@ drm_priv_to_bridge(struct drm_private_obj *priv) }

void drm_bridge_add(struct drm_bridge *bridge); +int devm_drm_bridge_add(struct device *dev, struct drm_bridge *bridge); void drm_bridge_remove(struct drm_bridge *bridge); int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge, struct drm_bridge *previous, -- 2.36.0.550.gb090851708-goog

-- With best wishes Dmitry

On 10/05/2022 22:29, Douglas Anderson wrote:

While it works, for the most part, to assume that the panel has finished probing when devm_of_dp_aux_populate_ep_devices() returns, it's a bit fragile. This is talked about at length in commit a1e3667a9835 ("drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev").

When reviewing the ps8640 code, I managed to convince myself that it was OK not to worry about it there and that maybe it wasn't really _that_ fragile. However, it turns out that it really is. Simply hardcoding panel_edp_probe() to return -EPROBE_DEFER was enough to put the boot process into an infinite loop. I believe this manages to trip the same issues that we used to trip with the main MSM code where something about our actions trigger Linux to re-probe previously deferred devices right away and each time we try again we re-trigger Linux to re-probe.

Let's fix this using the callback introduced in the patch ("drm/dp: Callbacks to make it easier for drivers to use DP AUX bus properly"). When using the new callback, we have to be a little careful. The probe_done() callback is no longer always called in the context of our probe routine. That means we can't rely on being able to return -EPROBE_DEFER from it. We re-jigger the order of things a bit to account for that.

With this change, the device still boots (though obviously the panel doesn't come up) if I force panel-edp to always return -EPROBE_DEFER. If I fake it and make the panel probe exactly once it also works.

Signed-off-by: Douglas Anderson dianders@chromium.org

Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org

---

Changes in v3:

• Adapt to v3 changes in aux bus.
• Use devm_drm_bridge_add() to simplify.

Changes in v2:

• Rewrote atop new method introduced by patch #1.

  drivers/gpu/drm/bridge/parade-ps8640.c | 74 ++++++++++++++++---------- 1 file changed, 46 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index e2467e58b5b7..ff4227f6d800 100644 --- a/drivers/gpu/drm/bridge/parade-ps8640.c +++ b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -537,7 +537,7 @@ static const struct drm_bridge_funcs ps8640_bridge_funcs = { .pre_enable = ps8640_pre_enable, };

-static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridge) +static int ps8640_bridge_get_dsi_resources(struct device *dev, struct ps8640 *ps_bridge) { struct device_node *in_ep, *dsi_node; struct mipi_dsi_device *dsi; @@ -576,13 +576,40 @@ static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridg dsi->format = MIPI_DSI_FMT_RGB888; dsi->lanes = NUM_MIPI_LANES;

• return devm_mipi_dsi_attach(dev, dsi);

• return 0;

+}

+static int ps8640_bridge_link_panel(struct drm_dp_aux *aux) +{

• struct ps8640 *ps_bridge = aux_to_ps8640(aux);

• struct device *dev = aux->dev;

• struct device_node *np = dev->of_node;

• int ret;

• /*

• * NOTE about returning -EPROBE_DEFER from this function: if we
  

• * return an error (most relevant to -EPROBE_DEFER) it will only
  

• * be passed out to ps8640_probe() if it called this directly (AKA the
  

• * panel isn't under the "aux-bus" node). That should be fine because
  

• * if the panel is under "aux-bus" it's guaranteed to have probed by
  

• * the time this function has been called.
  

• */
  

• /* port@1 is ps8640 output port */

• ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0);

• if (IS_ERR(ps_bridge->panel_bridge))

• return PTR_ERR(ps_bridge->panel_bridge);
  

• ret = devm_drm_bridge_add(dev, &ps_bridge->bridge);

• if (ret)

• return ret;
  

• return devm_mipi_dsi_attach(dev, ps_bridge->dsi); }

  static int ps8640_probe(struct i2c_client *client) { struct device *dev = &client->dev;

• struct device_node *np = dev->of_node; struct ps8640 *ps_bridge; int ret; u32 i;

@@ -623,6 +650,14 @@ static int ps8640_probe(struct i2c_client *client) if (!ps8640_of_panel_on_aux_bus(&client->dev)) ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID;

• /*

• * Get MIPI DSI resources early. These can return -EPROBE_DEFER so
  

• * we want to get them out of the way sooner.
  

• */
  

• ret = ps8640_bridge_get_dsi_resources(&client->dev, ps_bridge);

• if (ret)

• return ret;
  

• ps_bridge->page[PAGE0_DP_CNTL] = client;

  ps_bridge->regmap[PAGE0_DP_CNTL] = devm_regmap_init_i2c(client, ps8640_regmap_config);

@@ -665,35 +700,19 @@ static int ps8640_probe(struct i2c_client *client) if (ret) return ret;

• devm_of_dp_aux_populate_ep_devices(&ps_bridge->aux);

• ret = devm_of_dp_aux_populate_bus(&ps_bridge->aux, ps8640_bridge_link_panel);

• /* port@1 is ps8640 output port */
• ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0);
• if (IS_ERR(ps_bridge->panel_bridge))

• return PTR_ERR(ps_bridge->panel_bridge);
  

• drm_bridge_add(&ps_bridge->bridge);
• ret = ps8640_bridge_host_attach(dev, ps_bridge);
• if (ret)

• goto err_bridge_remove;
  

• return 0;

• /*

• * If devm_of_dp_aux_populate_bus() returns -ENODEV then it's up to
  

• * usa to call ps8640_bridge_link_panel() directly. NOTE: in this case
  

• * the function is allowed to -EPROBE_DEFER.
  

• */
  

• if (ret == -ENODEV)

• return ps8640_bridge_link_panel(&ps_bridge->aux);
  
  

-err_bridge_remove:

• drm_bridge_remove(&ps_bridge->bridge); return ret; }

-static int ps8640_remove(struct i2c_client *client) -{

• struct ps8640 *ps_bridge = i2c_get_clientdata(client);
• drm_bridge_remove(&ps_bridge->bridge);
• return 0;

-}

• static const struct of_device_id ps8640_match[] = { { .compatible = "parade,ps8640" }, { }

@@ -702,7 +721,6 @@ MODULE_DEVICE_TABLE(of, ps8640_match);

static struct i2c_driver ps8640_driver = { .probe_new = ps8640_probe,

• .remove = ps8640_remove, .driver = { .name = "ps8640", .of_match_table = ps8640_match,