[2/2] drm/i915/mst: filter out the display mode exceed sink's capability
diff mbox series

Message ID 20200526182313.4005-3-lyude@redhat.com
State New
Headers show
Series
  • drm/probe_helper, i915: Validate MST modes against PBN limits
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Commit Message

Lyude Paul May 26, 2020, 6:23 p.m. UTC
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.

v2: Using mgr->base.lock to protect full_pbn.
v3: Add ctx lock.
v4:
* 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

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>
Tested-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 | 39 ++++++++++++++++++---
 1 file changed, 35 insertions(+), 4 deletions(-)

Comments

Imre Deak July 7, 2020, 11:12 p.m. UTC | #1
On Tue, May 26, 2020 at 02:23:10PM -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.
> 
> v2: Using mgr->base.lock to protect full_pbn.
> v3: Add ctx lock.
> v4:
> * 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
> 
> 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>
> Tested-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 | 39 ++++++++++++++++++---
>  1 file changed, 35 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index d18b406f2a7d2..cf052095ad785 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -610,15 +610,42 @@ static int intel_dp_mst_get_modes(struct drm_connector *connector)
>  	return intel_dp_mst_get_ddc_modes(connector);
>  }
>  
> +static int
> +intel_dp_mst_mode_clock_exceeds_pbn_bw(struct drm_connector *connector,
> +				       struct drm_modeset_acquire_ctx *ctx,
> +				       int clock, int bpp)
> +{
> +	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 = (to_intel_connector(connector))->port;

					intel_connector

> +	int ret = MODE_OK;
> +
> +	if (!mgr)

As a NULL check this would be bogus, but also connector->mst_port and so
mst_mgr too should be always non-NULL?

> +		return ret;
> +
> +	ret = drm_modeset_lock(&mgr->base.lock, ctx);
> +	if (ret == -EDEADLK)
> +		return ret;
> +
> +	if (port->full_pbn &&

How could full_pbn be unset?

> +	    drm_dp_calc_pbn_mode(clock, bpp, false) > port->full_pbn)
> +		ret = MODE_CLOCK_HIGH;
> +
> +	return ret;
> +}
> +
>  static enum drm_mode_status
> -intel_dp_mst_mode_valid(struct drm_connector *connector,
> -			struct drm_display_mode *mode)
> +intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
> +			    struct drm_display_mode *mode,
> +			    struct drm_modeset_acquire_ctx *ctx)
>  {
>  	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;
>  	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;
> @@ -632,7 +659,11 @@ intel_dp_mst_mode_valid(struct drm_connector *connector,
>  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>  	mode_rate = intel_dp_link_required(mode->clock, 18);
>  
> -	/* TODO - validate mode against available PBN for link */
> +	ret = intel_dp_mst_mode_clock_exceeds_pbn_bw(connector, ctx,
> +						     mode->clock, 24);

Why 24 bpp and not 18?

Nit: could be checked after max_rate/max_dotclk for consistency.

> +	if (ret != MODE_OK)
> +		return ret;
> +
>  	if (mode->clock < 10000)
>  		return MODE_CLOCK_LOW;
>  
> @@ -671,7 +702,7 @@ 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
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index d18b406f2a7d2..cf052095ad785 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -610,15 +610,42 @@  static int intel_dp_mst_get_modes(struct drm_connector *connector)
 	return intel_dp_mst_get_ddc_modes(connector);
 }
 
+static int
+intel_dp_mst_mode_clock_exceeds_pbn_bw(struct drm_connector *connector,
+				       struct drm_modeset_acquire_ctx *ctx,
+				       int clock, int bpp)
+{
+	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 = (to_intel_connector(connector))->port;
+	int ret = MODE_OK;
+
+	if (!mgr)
+		return ret;
+
+	ret = drm_modeset_lock(&mgr->base.lock, ctx);
+	if (ret == -EDEADLK)
+		return ret;
+
+	if (port->full_pbn &&
+	    drm_dp_calc_pbn_mode(clock, bpp, false) > port->full_pbn)
+		ret = MODE_CLOCK_HIGH;
+
+	return ret;
+}
+
 static enum drm_mode_status
-intel_dp_mst_mode_valid(struct drm_connector *connector,
-			struct drm_display_mode *mode)
+intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
+			    struct drm_display_mode *mode,
+			    struct drm_modeset_acquire_ctx *ctx)
 {
 	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;
 	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;
@@ -632,7 +659,11 @@  intel_dp_mst_mode_valid(struct drm_connector *connector,
 	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(mode->clock, 18);
 
-	/* TODO - validate mode against available PBN for link */
+	ret = intel_dp_mst_mode_clock_exceeds_pbn_bw(connector, ctx,
+						     mode->clock, 24);
+	if (ret != MODE_OK)
+		return ret;
+
 	if (mode->clock < 10000)
 		return MODE_CLOCK_LOW;
 
@@ -671,7 +702,7 @@  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,