Re: [PATCH v13 2/2] drm/i915: Allow "max bpc" property to limit pipe_bpp

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Fri, 2018-10-12 at 00:25 -0700, Radhakrishna Sripada wrote:
> Use the newly added "max bpc" connector property to limit pipe bpp.
> 
> V3: Use drm_connector_state to access the "max bpc" property
> V4: Initialize the drm property, add suuport to DP(Ville)
> V5: Use the property in the connector and fix CI failure(Ville)
> V6: Use the core function to attach max_bpc property, remove the
> redundant
>     clamping of pipe bpp based on connector info
> V7: Fix Checkpatch warnings
> V9: Cleanup connected_sink_max_bpp and fix initial value in DP(Ville)
> V12: Fix debug message(Ville)
> V13: Remove the redundant check and simplify the check logic(Stan)
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Kishore Kadiyala <kishore.kadiyala@intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 49 ++++++++++++++++++++----
> ------------
>  drivers/gpu/drm/i915/intel_dp.c      |  4 +++
>  drivers/gpu/drm/i915/intel_hdmi.c    |  5 ++++
>  3 files changed, 37 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c
> b/drivers/gpu/drm/i915/intel_display.c
> index 980f4ea68e48..0f1f46abe2f5 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -10791,30 +10791,37 @@ static void
> intel_modeset_update_connector_atomic_state(struct drm_device *dev)
>  	drm_connector_list_iter_end(&conn_iter);
>  }
>  
> -static void
> -connected_sink_compute_bpp(struct intel_connector *connector,
> -			   struct intel_crtc_state *pipe_config)
> +static int
> +connected_sink_max_bpp(const struct drm_connector_state *conn_state,
> +		       struct intel_crtc_state *pipe_config)
>  {
> -	const struct drm_display_info *info = &connector-
> >base.display_info;
> -	int bpp = pipe_config->pipe_bpp;
> +	int bpp;
> +	struct drm_display_info *info = &conn_state->connector-
> >display_info;
>  
> -	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] checking for sink bpp
> constrains\n",
> -		      connector->base.base.id,
> -		      connector->base.name);
> -
> -	/* Don't use an invalid EDID bpc value */
> -	if (info->bpc != 0 && info->bpc * 3 < bpp) {
> -		DRM_DEBUG_KMS("clamping display bpp (was %d) to EDID
> reported max of %d\n",
> -			      bpp, info->bpc * 3);
> -		pipe_config->pipe_bpp = info->bpc * 3;
> +	switch (conn_state->max_bpc) {
> +	case 6 ... 7:
> +		bpp = 6 * 3;
> +	case 8 ... 9:
> +		bpp = 8 * 3;
> +		break;
> +	case 10 ... 11:
> +		bpp = 10 * 3;
> +		break;
> +	case 12:
> +		bpp = 12 * 3;
> +		break;
> +	default:
> +		return -EINVAL;
>  	}
>  
> -	/* Clamp bpp to 8 on screens without EDID 1.4 */
> -	if (info->bpc == 0 && bpp > 24) {
> -		DRM_DEBUG_KMS("clamping display bpp (was %d) to
> default limit of 24\n",
> -			      bpp);
> -		pipe_config->pipe_bpp = 24;
> +	if (bpp != pipe_config->pipe_bpp) {
> +		DRM_DEBUG_KMS("Limiting display bpp to %d instead of
> Edid bpp "
> +			      "%d, requested bpp %d, max platform
> bpp %d\n", bpp,
> +			      3 * info->bpc, 3 * conn_state-
> >max_requested_bpc,
> +			      pipe_config->pipe_bpp);
> +		pipe_config->pipe_bpp = bpp;
>  	}
> +	return 0;

That is definitely simplier. However I think there is still one thing:
you now assign pipe_bpp to bpp always if they are not equal. However
bpp(which is literally max_bpc) is supposed to limit pipe_bpp from
above, not from below. What if pipe_bpp < bpp already, then condition
will still be executed and then you'll get pipe_bpp set to higher value
than it was supposed to.
So I guess the condition should be "if (bpp < pipe_config->pipe_bpp)"
or simply do pipe_config->pipe_bpp = min(pipe_config->pipe_bpp, bpp) as
I said in previous email.

>  }
>  
>  static int
> @@ -10845,8 +10852,8 @@ compute_baseline_pipe_bpp(struct intel_crtc
> *crtc,
>  		if (connector_state->crtc != &crtc->base)
>  			continue;
>  
> -		connected_sink_compute_bpp(to_intel_connector(connec
> tor),
> -					   pipe_config);
> +		if (connected_sink_max_bpp(connector_state,
> pipe_config) < 0)
> +			return -EINVAL;
>  	}
>  
>  	return bpp;
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index 13ff89be6ad6..5f594430b2a4 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5735,6 +5735,10 @@ intel_dp_add_properties(struct intel_dp
> *intel_dp, struct drm_connector *connect
>  		intel_attach_force_audio_property(connector);
>  
>  	intel_attach_broadcast_rgb_property(connector);
> +	if (HAS_GMCH_DISPLAY(dev_priv))
> +		drm_connector_attach_max_bpc_property(connector, 6,
> 10);
> +	else if (INTEL_GEN(dev_priv) >= 5)
> +		drm_connector_attach_max_bpc_property(connector, 6,
> 12);
>  
>  	if (intel_dp_is_edp(intel_dp)) {
>  		u32 allowed_scalers;
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
> b/drivers/gpu/drm/i915/intel_hdmi.c
> index 2c53efc463e6..3158ab085a30 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -2103,11 +2103,16 @@ static const struct drm_encoder_funcs
> intel_hdmi_enc_funcs = {
>  static void
>  intel_hdmi_add_properties(struct intel_hdmi *intel_hdmi, struct
> drm_connector *connector)
>  {
> +	struct drm_i915_private *dev_priv = to_i915(connector->dev);
> +
>  	intel_attach_force_audio_property(connector);
>  	intel_attach_broadcast_rgb_property(connector);
>  	intel_attach_aspect_ratio_property(connector);
>  	drm_connector_attach_content_type_property(connector);
>  	connector->state->picture_aspect_ratio =
> HDMI_PICTURE_ASPECT_NONE;
> +
> +	if (!HAS_GMCH_DISPLAY(dev_priv))
> +		drm_connector_attach_max_bpc_property(connector, 8,
> 12);
>  }
>  
>  /*
-- 
Best Regards,

Lisovskiy Stanislav
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