[PATCH v3 1/2] drm/probe_helper: Add drm_connector_helper_funcs.mode_valid_ctx

[PATCH v3 1/2] drm/probe_helper: Add drm_connector_helper_funcs.mode_valid_ctx

[Lyude Paul]

This is just an atomic version of mode_valid, which is intended to be
used for situations where a driver might need to check the atomic state
of objects other than the connector itself. One such example is with
MST, where the maximum possible bandwidth on a connector can change
dynamically irregardless of the display configuration.

Changes since v1:
* Use new drm logging functions
* Make some corrections in the mode_valid_ctx kdoc
* Return error codes or 0 from ->mode_valid_ctx() on fail, and store the
  drm_mode_status in an additional function parameter
Changes since v2:
* Don't accidentally assign ret to mode->status on success, or we'll
  squash legitimate mode validation results
* Don't forget to assign MODE_OK to status in drm_connector_mode_valid()
  if we have no callbacks
* Drop leftover hunk in drm_modes.h around enum drm_mode_status

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
---
 drivers/gpu/drm/drm_crtc_helper_internal.h |  7 +-
 drivers/gpu/drm/drm_probe_helper.c         | 94 ++++++++++++++--------
 include/drm/drm_modeset_helper_vtables.h   | 42 ++++++++++
 3 files changed, 109 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_helper_internal.h b/drivers/gpu/drm/drm_crtc_helper_internal.h
index f0a66ef47e5ad..25ce42e799952 100644
--- a/drivers/gpu/drm/drm_crtc_helper_internal.h
+++ b/drivers/gpu/drm/drm_crtc_helper_internal.h
@@ -73,8 +73,11 @@ enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
 					 const struct drm_display_mode *mode);
 enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
 					    const struct drm_display_mode *mode);
-enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
-					      struct drm_display_mode *mode);
+int
+drm_connector_mode_valid(struct drm_connector *connector,
+			 struct drm_display_mode *mode,
+			 struct drm_modeset_acquire_ctx *ctx,
+			 enum drm_mode_status *status);
 
 struct drm_encoder *
 drm_connector_get_single_encoder(struct drm_connector *connector);
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index e0ed58d291ed9..f7bd1d35aa805 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -86,17 +86,19 @@ drm_mode_validate_flag(const struct drm_display_mode *mode,
 	return MODE_OK;
 }
 
-static enum drm_mode_status
+static int
 drm_mode_validate_pipeline(struct drm_display_mode *mode,
-			    struct drm_connector *connector)
+			   struct drm_connector *connector,
+			   struct drm_modeset_acquire_ctx *ctx,
+			   enum drm_mode_status *status)
 {
 	struct drm_device *dev = connector->dev;
-	enum drm_mode_status ret = MODE_OK;
 	struct drm_encoder *encoder;
+	int ret;
 
 	/* Step 1: Validate against connector */
-	ret = drm_connector_mode_valid(connector, mode);
-	if (ret != MODE_OK)
+	ret = drm_connector_mode_valid(connector, mode, ctx, status);
+	if (ret || *status != MODE_OK)
 		return ret;
 
 	/* Step 2: Validate against encoders and crtcs */
@@ -104,8 +106,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
 		struct drm_bridge *bridge;
 		struct drm_crtc *crtc;
 
-		ret = drm_encoder_mode_valid(encoder, mode);
-		if (ret != MODE_OK) {
+		*status = drm_encoder_mode_valid(encoder, mode);
+		if (*status != MODE_OK) {
 			/* No point in continuing for crtc check as this encoder
 			 * will not accept the mode anyway. If all encoders
 			 * reject the mode then, at exit, ret will not be
@@ -114,10 +116,10 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
 		}
 
 		bridge = drm_bridge_chain_get_first_bridge(encoder);
-		ret = drm_bridge_chain_mode_valid(bridge,
-						  &connector->display_info,
-						  mode);
-		if (ret != MODE_OK) {
+		*status = drm_bridge_chain_mode_valid(bridge,
+						      &connector->display_info,
+						      mode);
+		if (*status != MODE_OK) {
 			/* There is also no point in continuing for crtc check
 			 * here. */
 			continue;
@@ -127,8 +129,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
 			if (!drm_encoder_crtc_ok(encoder, crtc))
 				continue;
 
-			ret = drm_crtc_mode_valid(crtc, mode);
-			if (ret == MODE_OK) {
+			*status = drm_crtc_mode_valid(crtc, mode);
+			if (*status == MODE_OK) {
 				/* If we get to this point there is at least
 				 * one combination of encoder+crtc that works
 				 * for this mode. Lets return now. */
@@ -198,16 +200,26 @@ enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
 	return encoder_funcs->mode_valid(encoder, mode);
 }
 
-enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
-					      struct drm_display_mode *mode)
+int
+drm_connector_mode_valid(struct drm_connector *connector,
+			 struct drm_display_mode *mode,
+			 struct drm_modeset_acquire_ctx *ctx,
+			 enum drm_mode_status *status)
 {
 	const struct drm_connector_helper_funcs *connector_funcs =
 		connector->helper_private;
 
-	if (!connector_funcs || !connector_funcs->mode_valid)
-		return MODE_OK;
+	if (!connector_funcs)
+		*status = MODE_OK;
+	else if (connector_funcs->mode_valid_ctx)
+		return connector_funcs->mode_valid_ctx(connector, mode, ctx,
+						       status);
+	else if (connector_funcs->mode_valid)
+		*status = connector_funcs->mode_valid(connector, mode);
+	else
+		*status = MODE_OK;
 
-	return connector_funcs->mode_valid(connector, mode);
+	return 0;
 }
 
 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
@@ -385,8 +397,9 @@ EXPORT_SYMBOL(drm_helper_probe_detect);
  *      (if specified)
  *    - drm_mode_validate_flag() checks the modes against basic connector
  *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
- *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
- *      driver and/or sink specific checks
+ *    - the optional &drm_connector_helper_funcs.mode_valid or
+ *      &drm_connector_helper_funcs.mode_valid_ctx helpers can perform driver
+ *      and/or sink specific checks
  *    - the optional &drm_crtc_helper_funcs.mode_valid,
  *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
  *      helpers can perform driver and/or source specific checks which are also
@@ -517,22 +530,39 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 		mode_flags |= DRM_MODE_FLAG_3D_MASK;
 
 	list_for_each_entry(mode, &connector->modes, head) {
-		if (mode->status == MODE_OK)
-			mode->status = drm_mode_validate_driver(dev, mode);
+		if (mode->status != MODE_OK)
+			continue;
 
-		if (mode->status == MODE_OK)
-			mode->status = drm_mode_validate_size(mode, maxX, maxY);
+		mode->status = drm_mode_validate_driver(dev, mode);
+		if (mode->status != MODE_OK)
+			continue;
 
-		if (mode->status == MODE_OK)
-			mode->status = drm_mode_validate_flag(mode, mode_flags);
+		mode->status = drm_mode_validate_size(mode, maxX, maxY);
+		if (mode->status != MODE_OK)
+			continue;
+
+		mode->status = drm_mode_validate_flag(mode, mode_flags);
+		if (mode->status != MODE_OK)
+			continue;
 
-		if (mode->status == MODE_OK)
-			mode->status = drm_mode_validate_pipeline(mode,
-								  connector);
+		ret = drm_mode_validate_pipeline(mode, connector, &ctx,
+						 &mode->status);
+		if (ret) {
+			drm_dbg_kms(dev,
+				    "drm_mode_validate_pipeline failed: %d\n",
+				    ret);
+
+			if (drm_WARN_ON_ONCE(dev, ret != -EDEADLK)) {
+				mode->status = MODE_ERROR;
+			} else {
+				drm_modeset_backoff(&ctx);
+				goto retry;
+			}
+		}
 
-		if (mode->status == MODE_OK)
-			mode->status = drm_mode_validate_ycbcr420(mode,
-								  connector);
+		if (mode->status != MODE_OK)
+			continue;
+		mode->status = drm_mode_validate_ycbcr420(mode, connector);
 	}
 
 prune:
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 421a30f084631..4efec30f8badc 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -968,6 +968,48 @@ struct drm_connector_helper_funcs {
 	 */
 	enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
 					   struct drm_display_mode *mode);
+
+	/**
+	 * @mode_valid_ctx:
+	 *
+	 * Callback to validate a mode for a connector, irrespective of the
+	 * specific display configuration.
+	 *
+	 * This callback is used by the probe helpers to filter the mode list
+	 * (which is usually derived from the EDID data block from the sink).
+	 * See e.g. drm_helper_probe_single_connector_modes().
+	 *
+	 * This function is optional, and is the atomic version of
+	 * &drm_connector_helper_funcs.mode_valid.
+	 *
+	 * To allow for accessing the atomic state of modesetting objects, the
+	 * helper libraries always call this with ctx set to a valid context,
+	 * and &drm_mode_config.connection_mutex will always be locked with
+	 * the ctx parameter set to @ctx. This allows for taking additional
+	 * locks as required.
+	 *
+	 * Even though additional locks may be acquired, this callback is
+	 * still expected not to take any constraints into account which would
+	 * be influenced by the currently set display state - such constraints
+	 * should be handled in the driver's atomic check. For example, if a
+	 * connector shares display bandwidth with other connectors then it
+	 * would be ok to validate the minimum bandwidth requirement of a mode
+	 * against the maximum possible bandwidth of the connector. But it
+	 * wouldn't be ok to take the current bandwidth usage of other
+	 * connectors into account, as this would change depending on the
+	 * display state.
+	 *
+	 * Returns:
+	 * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
+	 * the &enum drm_mode_status value to @status, or a negative error
+	 * code otherwise.
+	 *
+	 */
+	int (*mode_valid_ctx)(struct drm_connector *connector,
+			      struct drm_display_mode *mode,
+			      struct drm_modeset_acquire_ctx *ctx,
+			      enum drm_mode_status *status);
+
 	/**
 	 * @best_encoder:
 	 *
-- 
2.26.2

Re: [Intel-gfx] [PATCH v3 1/2] drm/probe_helper: Add drm_connector_helper_funcs.mode_valid_ctx

[Imre Deak]

On Fri, Jul 10, 2020 at 03:31:43PM -0400, Lyude Paul wrote:
> This is just an atomic version of mode_valid, which is intended to be
> used for situations where a driver might need to check the atomic state
> of objects other than the connector itself. One such example is with
> MST, where the maximum possible bandwidth on a connector can change
> dynamically irregardless of the display configuration.
> 
> Changes since v1:
> * Use new drm logging functions
> * Make some corrections in the mode_valid_ctx kdoc
> * Return error codes or 0 from ->mode_valid_ctx() on fail, and store the
>   drm_mode_status in an additional function parameter
> Changes since v2:
> * Don't accidentally assign ret to mode->status on success, or we'll
>   squash legitimate mode validation results
> * Don't forget to assign MODE_OK to status in drm_connector_mode_valid()
>   if we have no callbacks
> * Drop leftover hunk in drm_modes.h around enum drm_mode_status
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Lee Shawn C <shawn.c.lee@intel.com>

Some nits below, but looks good in either way:

Reviewed-and-tested-by: Imre Deak <imre.deak@intel.com>


> ---
>  drivers/gpu/drm/drm_crtc_helper_internal.h |  7 +-
>  drivers/gpu/drm/drm_probe_helper.c         | 94 ++++++++++++++--------
>  include/drm/drm_modeset_helper_vtables.h   | 42 ++++++++++
>  3 files changed, 109 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc_helper_internal.h b/drivers/gpu/drm/drm_crtc_helper_internal.h
> index f0a66ef47e5ad..25ce42e799952 100644
> --- a/drivers/gpu/drm/drm_crtc_helper_internal.h
> +++ b/drivers/gpu/drm/drm_crtc_helper_internal.h
> @@ -73,8 +73,11 @@ enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
>  					 const struct drm_display_mode *mode);
>  enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
>  					    const struct drm_display_mode *mode);
> -enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
> -					      struct drm_display_mode *mode);
> +int
> +drm_connector_mode_valid(struct drm_connector *connector,
> +			 struct drm_display_mode *mode,
> +			 struct drm_modeset_acquire_ctx *ctx,
> +			 enum drm_mode_status *status);
>  
>  struct drm_encoder *
>  drm_connector_get_single_encoder(struct drm_connector *connector);
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index e0ed58d291ed9..f7bd1d35aa805 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -86,17 +86,19 @@ drm_mode_validate_flag(const struct drm_display_mode *mode,
>  	return MODE_OK;
>  }
>  
> -static enum drm_mode_status
> +static int
>  drm_mode_validate_pipeline(struct drm_display_mode *mode,
> -			    struct drm_connector *connector)
> +			   struct drm_connector *connector,
> +			   struct drm_modeset_acquire_ctx *ctx,
> +			   enum drm_mode_status *status)
>  {
>  	struct drm_device *dev = connector->dev;
> -	enum drm_mode_status ret = MODE_OK;
>  	struct drm_encoder *encoder;
> +	int ret;
>  
>  	/* Step 1: Validate against connector */
> -	ret = drm_connector_mode_valid(connector, mode);
> -	if (ret != MODE_OK)
> +	ret = drm_connector_mode_valid(connector, mode, ctx, status);
> +	if (ret || *status != MODE_OK)
>  		return ret;

After this point ret is guaranteed to stay 0, so would be clearer to
just s/return ret/return 0/ later in this func.

>  
>  	/* Step 2: Validate against encoders and crtcs */
> @@ -104,8 +106,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
>  		struct drm_bridge *bridge;
>  		struct drm_crtc *crtc;
>  
> -		ret = drm_encoder_mode_valid(encoder, mode);
> -		if (ret != MODE_OK) {
> +		*status = drm_encoder_mode_valid(encoder, mode);
> +		if (*status != MODE_OK) {
>  			/* No point in continuing for crtc check as this encoder
>  			 * will not accept the mode anyway. If all encoders
>  			 * reject the mode then, at exit, ret will not be
> @@ -114,10 +116,10 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
>  		}
>  
>  		bridge = drm_bridge_chain_get_first_bridge(encoder);
> -		ret = drm_bridge_chain_mode_valid(bridge,
> -						  &connector->display_info,
> -						  mode);
> -		if (ret != MODE_OK) {
> +		*status = drm_bridge_chain_mode_valid(bridge,
> +						      &connector->display_info,
> +						      mode);
> +		if (*status != MODE_OK) {
>  			/* There is also no point in continuing for crtc check
>  			 * here. */
>  			continue;
> @@ -127,8 +129,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
>  			if (!drm_encoder_crtc_ok(encoder, crtc))
>  				continue;
>  
> -			ret = drm_crtc_mode_valid(crtc, mode);
> -			if (ret == MODE_OK) {
> +			*status = drm_crtc_mode_valid(crtc, mode);
> +			if (*status == MODE_OK) {
>  				/* If we get to this point there is at least
>  				 * one combination of encoder+crtc that works
>  				 * for this mode. Lets return now. */
> @@ -198,16 +200,26 @@ enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
>  	return encoder_funcs->mode_valid(encoder, mode);
>  }
>  
> -enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
> -					      struct drm_display_mode *mode)
> +int
> +drm_connector_mode_valid(struct drm_connector *connector,
> +			 struct drm_display_mode *mode,
> +			 struct drm_modeset_acquire_ctx *ctx,
> +			 enum drm_mode_status *status)
>  {
>  	const struct drm_connector_helper_funcs *connector_funcs =
>  		connector->helper_private;

would look a bit neater by
	int ret = 0;
and

>  
> -	if (!connector_funcs || !connector_funcs->mode_valid)
> -		return MODE_OK;
> +	if (!connector_funcs)
> +		*status = MODE_OK;
> +	else if (connector_funcs->mode_valid_ctx)
> +		return connector_funcs->mode_valid_ctx(connector, mode, ctx,
> +						       status);

		ret = ...
> +	else if (connector_funcs->mode_valid)
> +		*status = connector_funcs->mode_valid(connector, mode);
> +	else
> +		*status = MODE_OK;
>  
> -	return connector_funcs->mode_valid(connector, mode);
> +	return 0;

	return ret;

>  }
>  
>  #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
> @@ -385,8 +397,9 @@ EXPORT_SYMBOL(drm_helper_probe_detect);
>   *      (if specified)
>   *    - drm_mode_validate_flag() checks the modes against basic connector
>   *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
> - *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
> - *      driver and/or sink specific checks
> + *    - the optional &drm_connector_helper_funcs.mode_valid or
> + *      &drm_connector_helper_funcs.mode_valid_ctx helpers can perform driver
> + *      and/or sink specific checks
>   *    - the optional &drm_crtc_helper_funcs.mode_valid,
>   *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
>   *      helpers can perform driver and/or source specific checks which are also
> @@ -517,22 +530,39 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
>  		mode_flags |= DRM_MODE_FLAG_3D_MASK;
>  
>  	list_for_each_entry(mode, &connector->modes, head) {
> -		if (mode->status == MODE_OK)
> -			mode->status = drm_mode_validate_driver(dev, mode);
> +		if (mode->status != MODE_OK)
> +			continue;
>  
> -		if (mode->status == MODE_OK)
> -			mode->status = drm_mode_validate_size(mode, maxX, maxY);
> +		mode->status = drm_mode_validate_driver(dev, mode);
> +		if (mode->status != MODE_OK)
> +			continue;
>  
> -		if (mode->status == MODE_OK)
> -			mode->status = drm_mode_validate_flag(mode, mode_flags);
> +		mode->status = drm_mode_validate_size(mode, maxX, maxY);
> +		if (mode->status != MODE_OK)
> +			continue;
> +
> +		mode->status = drm_mode_validate_flag(mode, mode_flags);
> +		if (mode->status != MODE_OK)
> +			continue;
>  
> -		if (mode->status == MODE_OK)
> -			mode->status = drm_mode_validate_pipeline(mode,
> -								  connector);
> +		ret = drm_mode_validate_pipeline(mode, connector, &ctx,
> +						 &mode->status);
> +		if (ret) {
> +			drm_dbg_kms(dev,
> +				    "drm_mode_validate_pipeline failed: %d\n",
> +				    ret);
> +
> +			if (drm_WARN_ON_ONCE(dev, ret != -EDEADLK)) {
> +				mode->status = MODE_ERROR;
> +			} else {
> +				drm_modeset_backoff(&ctx);
> +				goto retry;
> +			}
> +		}
>  
> -		if (mode->status == MODE_OK)
> -			mode->status = drm_mode_validate_ycbcr420(mode,
> -								  connector);
> +		if (mode->status != MODE_OK)
> +			continue;
> +		mode->status = drm_mode_validate_ycbcr420(mode, connector);
>  	}
>  
>  prune:
> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> index 421a30f084631..4efec30f8badc 100644
> --- a/include/drm/drm_modeset_helper_vtables.h
> +++ b/include/drm/drm_modeset_helper_vtables.h
> @@ -968,6 +968,48 @@ struct drm_connector_helper_funcs {
>  	 */
>  	enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
>  					   struct drm_display_mode *mode);
> +
> +	/**
> +	 * @mode_valid_ctx:
> +	 *
> +	 * Callback to validate a mode for a connector, irrespective of the
> +	 * specific display configuration.
> +	 *
> +	 * This callback is used by the probe helpers to filter the mode list
> +	 * (which is usually derived from the EDID data block from the sink).
> +	 * See e.g. drm_helper_probe_single_connector_modes().
> +	 *
> +	 * This function is optional, and is the atomic version of
> +	 * &drm_connector_helper_funcs.mode_valid.
> +	 *
> +	 * To allow for accessing the atomic state of modesetting objects, the
> +	 * helper libraries always call this with ctx set to a valid context,
> +	 * and &drm_mode_config.connection_mutex will always be locked with
> +	 * the ctx parameter set to @ctx. This allows for taking additional
> +	 * locks as required.
> +	 *
> +	 * Even though additional locks may be acquired, this callback is
> +	 * still expected not to take any constraints into account which would
> +	 * be influenced by the currently set display state - such constraints
> +	 * should be handled in the driver's atomic check. For example, if a
> +	 * connector shares display bandwidth with other connectors then it
> +	 * would be ok to validate the minimum bandwidth requirement of a mode
> +	 * against the maximum possible bandwidth of the connector. But it
> +	 * wouldn't be ok to take the current bandwidth usage of other
> +	 * connectors into account, as this would change depending on the
> +	 * display state.
> +	 *
> +	 * Returns:
> +	 * 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
> +	 * the &enum drm_mode_status value to @status, or a negative error
> +	 * code otherwise.
> +	 *
> +	 */
> +	int (*mode_valid_ctx)(struct drm_connector *connector,
> +			      struct drm_display_mode *mode,
> +			      struct drm_modeset_acquire_ctx *ctx,
> +			      enum drm_mode_status *status);
> +
>  	/**
>  	 * @best_encoder:
>  	 *
> -- 
> 2.26.2
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

[PATCH v3 2/2] drm/i915/mst: filter out the display mode exceed sink's capability

[Lyude Paul]

From: Lee Shawn C <shawn.c.lee@intel.com>

So far, max dot clock rate for MST mode rely on physcial
bandwidth limitation. It would caused compatibility issue
if source display resolution exceed MST hub output ability.

For example, source DUT had DP 1.2 output capability.
And MST docking just support HDMI 1.4 spec. When a HDMI 2.0
monitor connected. Source would retrieve EDID from external
and get max resolution 4k@60fps. DP 1.2 can support 4K@60fps
because it did not surpass DP physical bandwidth limitation.
Do modeset to 4k@60fps, source output display data but MST
docking can't output HDMI properly due to this resolution
already over HDMI 1.4 spec.

Refer to commit <fcf463807596> ("drm/dp_mst: Use full_pbn
instead of available_pbn for bandwidth checks").
Source driver should refer to full_pbn to evaluate sink
output capability. And filter out the resolution surpass
sink output limitation.

Changes since v1:
* Using mgr->base.lock to protect full_pbn.
Changes since v2:
* Add ctx lock.
Changes since v3:
* s/intel_dp_mst_mode_clock_exceed_pbn_bandwidth/
  intel_dp_mst_mode_clock_exceeds_pbn_bw/
* Use the new drm_connector_helper_funcs.mode_valid_ctx to properly pipe
  down the drm_modeset_acquire_ctx that the probe helpers are using, so
  we can safely grab &mgr->base.lock without deadlocking
Changes since v4:
* Move drm_dp_calc_pbn_mode(mode->clock, bpp, false) > port->full_pbn
  check
* Fix the bpp we use in drm_dp_calc_pbn_mode()
* Drop leftover (!mgr) check
* Don't check for if full_pbn is unset. To be clear - it _can_ be unset,
  but if it is then it's certainly a bug in DRM or a non-compliant sink
  as full_pbn should always be populated by the time we call
  ->mode_valid_ctx.
  We should workaround non-compliant sinks with full_pbn=0, but that
  should happen in the DP MST helpers so we can estimate the full_pbn
  value as best we can.

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Co-developed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 55 ++++++++++++++-------
 1 file changed, 38 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index bdc19b04b2c10..a2d91a4997001 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -639,39 +639,60 @@ static int intel_dp_mst_get_modes(struct drm_connector *connector)
 	return intel_dp_mst_get_ddc_modes(connector);
 }
 
-static enum drm_mode_status
-intel_dp_mst_mode_valid(struct drm_connector *connector,
-			struct drm_display_mode *mode)
+static int
+intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
+			    struct drm_display_mode *mode,
+			    struct drm_modeset_acquire_ctx *ctx,
+			    enum drm_mode_status *status)
 {
 	struct drm_i915_private *dev_priv = to_i915(connector->dev);
 	struct intel_connector *intel_connector = to_intel_connector(connector);
 	struct intel_dp *intel_dp = intel_connector->mst_port;
+	struct drm_dp_mst_topology_mgr *mgr = &intel_dp->mst_mgr;
+	struct drm_dp_mst_port *port = intel_connector->port;
+	const int min_bpp = 18;
 	int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
 	int max_rate, mode_rate, max_lanes, max_link_clock;
+	int ret;
 
-	if (drm_connector_is_unregistered(connector))
-		return MODE_ERROR;
+	if (drm_connector_is_unregistered(connector)) {
+		*status = MODE_ERROR;
+		return 0;
+	}
 
-	if (mode->flags & DRM_MODE_FLAG_DBLSCAN)
-		return MODE_NO_DBLESCAN;
+	if (mode->flags & DRM_MODE_FLAG_DBLSCAN) {
+		*status = MODE_NO_DBLESCAN;
+		return 0;
+	}
 
 	max_link_clock = intel_dp_max_link_rate(intel_dp);
 	max_lanes = intel_dp_max_lane_count(intel_dp);
 
 	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
-	mode_rate = intel_dp_link_required(mode->clock, 18);
+	mode_rate = intel_dp_link_required(mode->clock, min_bpp);
 
-	/* TODO - validate mode against available PBN for link */
-	if (mode->clock < 10000)
-		return MODE_CLOCK_LOW;
+	ret = drm_modeset_lock(&mgr->base.lock, ctx);
+	if (ret)
+		return ret;
 
-	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
-		return MODE_H_ILLEGAL;
+	if (mode_rate > max_rate || mode->clock > max_dotclk ||
+	    drm_dp_calc_pbn_mode(mode->clock, min_bpp, false) > port->full_pbn) {
+		*status = MODE_CLOCK_HIGH;
+		return 0;
+	}
+
+	if (mode->clock < 10000) {
+		*status = MODE_CLOCK_LOW;
+		return 0;
+	}
 
-	if (mode_rate > max_rate || mode->clock > max_dotclk)
-		return MODE_CLOCK_HIGH;
+	if (mode->flags & DRM_MODE_FLAG_DBLCLK) {
+		*status = MODE_H_ILLEGAL;
+		return 0;
+	}
 
-	return intel_mode_valid_max_plane_size(dev_priv, mode);
+	*status = intel_mode_valid_max_plane_size(dev_priv, mode);
+	return 0;
 }
 
 static struct drm_encoder *intel_mst_atomic_best_encoder(struct drm_connector *connector,
@@ -700,7 +721,7 @@ intel_dp_mst_detect(struct drm_connector *connector,
 
 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,
+	.mode_valid_ctx = intel_dp_mst_mode_valid_ctx,
 	.atomic_best_encoder = intel_mst_atomic_best_encoder,
 	.atomic_check = intel_dp_mst_atomic_check,
 	.detect_ctx = intel_dp_mst_detect,
-- 
2.26.2

Re: [PATCH v3 2/2] drm/i915/mst: filter out the display mode exceed sink's capability

[Imre Deak]

On Fri, Jul 10, 2020 at 03:31:44PM -0400, Lyude Paul wrote:
> From: Lee Shawn C <shawn.c.lee@intel.com>
> 
> So far, max dot clock rate for MST mode rely on physcial
> bandwidth limitation. It would caused compatibility issue
> if source display resolution exceed MST hub output ability.
> 
> For example, source DUT had DP 1.2 output capability.
> And MST docking just support HDMI 1.4 spec. When a HDMI 2.0
> monitor connected. Source would retrieve EDID from external
> and get max resolution 4k@60fps. DP 1.2 can support 4K@60fps
> because it did not surpass DP physical bandwidth limitation.
> Do modeset to 4k@60fps, source output display data but MST
> docking can't output HDMI properly due to this resolution
> already over HDMI 1.4 spec.
> 
> Refer to commit <fcf463807596> ("drm/dp_mst: Use full_pbn
> instead of available_pbn for bandwidth checks").
> Source driver should refer to full_pbn to evaluate sink
> output capability. And filter out the resolution surpass
> sink output limitation.
> 
> Changes since v1:
> * Using mgr->base.lock to protect full_pbn.
> Changes since v2:
> * Add ctx lock.
> Changes since v3:
> * s/intel_dp_mst_mode_clock_exceed_pbn_bandwidth/
>   intel_dp_mst_mode_clock_exceeds_pbn_bw/
> * Use the new drm_connector_helper_funcs.mode_valid_ctx to properly pipe
>   down the drm_modeset_acquire_ctx that the probe helpers are using, so
>   we can safely grab &mgr->base.lock without deadlocking
> Changes since v4:
> * Move drm_dp_calc_pbn_mode(mode->clock, bpp, false) > port->full_pbn
>   check
> * Fix the bpp we use in drm_dp_calc_pbn_mode()
> * Drop leftover (!mgr) check
> * Don't check for if full_pbn is unset. To be clear - it _can_ be unset,
>   but if it is then it's certainly a bug in DRM or a non-compliant sink
>   as full_pbn should always be populated by the time we call
>   ->mode_valid_ctx.
>   We should workaround non-compliant sinks with full_pbn=0, but that
>   should happen in the DP MST helpers so we can estimate the full_pbn
>   value as best we can.

I guess when the connector gets unplugged full_pbn would also get reset
but pruning all modes in that case is ok.

> 
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Cooper Chiou <cooper.chiou@intel.com>
> Co-developed-by: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
> Signed-off-by: Lyude Paul <lyude@redhat.com>

Reviewed-and-tested-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 55 ++++++++++++++-------
>  1 file changed, 38 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index bdc19b04b2c10..a2d91a4997001 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -639,39 +639,60 @@ static int intel_dp_mst_get_modes(struct drm_connector *connector)
>  	return intel_dp_mst_get_ddc_modes(connector);
>  }
>  
> -static enum drm_mode_status
> -intel_dp_mst_mode_valid(struct drm_connector *connector,
> -			struct drm_display_mode *mode)
> +static int
> +intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
> +			    struct drm_display_mode *mode,
> +			    struct drm_modeset_acquire_ctx *ctx,
> +			    enum drm_mode_status *status)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->dev);
>  	struct intel_connector *intel_connector = to_intel_connector(connector);
>  	struct intel_dp *intel_dp = intel_connector->mst_port;
> +	struct drm_dp_mst_topology_mgr *mgr = &intel_dp->mst_mgr;
> +	struct drm_dp_mst_port *port = intel_connector->port;
> +	const int min_bpp = 18;
>  	int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
>  	int max_rate, mode_rate, max_lanes, max_link_clock;
> +	int ret;
>  
> -	if (drm_connector_is_unregistered(connector))
> -		return MODE_ERROR;
> +	if (drm_connector_is_unregistered(connector)) {
> +		*status = MODE_ERROR;
> +		return 0;
> +	}
>  
> -	if (mode->flags & DRM_MODE_FLAG_DBLSCAN)
> -		return MODE_NO_DBLESCAN;
> +	if (mode->flags & DRM_MODE_FLAG_DBLSCAN) {
> +		*status = MODE_NO_DBLESCAN;
> +		return 0;
> +	}
>  
>  	max_link_clock = intel_dp_max_link_rate(intel_dp);
>  	max_lanes = intel_dp_max_lane_count(intel_dp);
>  
>  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> -	mode_rate = intel_dp_link_required(mode->clock, 18);
> +	mode_rate = intel_dp_link_required(mode->clock, min_bpp);
>  
> -	/* TODO - validate mode against available PBN for link */
> -	if (mode->clock < 10000)
> -		return MODE_CLOCK_LOW;
> +	ret = drm_modeset_lock(&mgr->base.lock, ctx);
> +	if (ret)
> +		return ret;
>  
> -	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
> -		return MODE_H_ILLEGAL;
> +	if (mode_rate > max_rate || mode->clock > max_dotclk ||
> +	    drm_dp_calc_pbn_mode(mode->clock, min_bpp, false) > port->full_pbn) {
> +		*status = MODE_CLOCK_HIGH;
> +		return 0;
> +	}
> +
> +	if (mode->clock < 10000) {
> +		*status = MODE_CLOCK_LOW;
> +		return 0;
> +	}
>  
> -	if (mode_rate > max_rate || mode->clock > max_dotclk)
> -		return MODE_CLOCK_HIGH;
> +	if (mode->flags & DRM_MODE_FLAG_DBLCLK) {
> +		*status = MODE_H_ILLEGAL;
> +		return 0;
> +	}
>  
> -	return intel_mode_valid_max_plane_size(dev_priv, mode);
> +	*status = intel_mode_valid_max_plane_size(dev_priv, mode);
> +	return 0;
>  }
>  
>  static struct drm_encoder *intel_mst_atomic_best_encoder(struct drm_connector *connector,
> @@ -700,7 +721,7 @@ intel_dp_mst_detect(struct drm_connector *connector,
>  
>  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,
> +	.mode_valid_ctx = intel_dp_mst_mode_valid_ctx,
>  	.atomic_best_encoder = intel_mst_atomic_best_encoder,
>  	.atomic_check = intel_dp_mst_atomic_check,
>  	.detect_ctx = intel_dp_mst_detect,
> -- 
> 2.26.2
>