Re: [Intel-gfx] [PATCH] drm/i915/dp: Fix eDP max rate for display 11+

["Shankar, Uma" <uma.shankar@intel.com>]

> -----Original Message-----
> From: Nikula, Jani <jani.nikula@intel.com>
> Sent: Tuesday, June 22, 2021 1:57 PM
> To: intel-gfx@lists.freedesktop.org
> Cc: Nikula, Jani <jani.nikula@intel.com>; Atwood, Matthew S
> <matthew.s.atwood@intel.com>; Shankar, Uma <uma.shankar@intel.com>; Ville
> Syrjälä <ville.syrjala@linux.intel.com>; Souza, Jose <jose.souza@intel.com>
> Subject: [PATCH] drm/i915/dp: Fix eDP max rate for display 11+
> 
> From: Matt Atwood <matthew.s.atwood@intel.com>
> 
> intel_dp_set_source_rates() calls intel_dp_is_edp(), which is unsafe to use before
> intel_encoder->type is set. This causes incorrect max source rate to be used for
> display 11+. On EHL and JSL, HBR3 is used instead of HBR2, and on the other
> affected platforms, HBR2 is used instead of HBR3.
> 
> Move intel_dp_set_source_rates() to after intel_encoder->type is set. Add comment
> to intel_dp_is_edp() describing unsafe usages. Cleanup
> intel_dp_init_connector() while at it.
> 
> Note: The same change was originally added as commit 680c45c767f6
> ("drm/i915/dp: Correctly advertise HBR3 for GEN11+"), but later reverted due to
> issues in CI in commit d3913019602e ("Revert "drm/i915/dp:
> Correctly advertise HBR3 for GEN11+"").
> 
> v2: Alter intel_dp_set_source_rates final position (Ville/Manasi).
>     Remove outdated comment (Ville).
>     Slight optimization of control flow in intel_dp_init_connector.
>     Slight rewording in commit message.

Thanks Jani for digging into this.
Change looks good to me.
Reviewed-by: Uma Shankar <uma.shankar@intel.com>

We can go ahead for merge, once we get more details on the regression which was identified causing its revert.
A full CI run may help. For me, I don't see any reason it should cause regression.

Regards,
Uma Shankar
> Cc: Uma Shankar <uma.shankar@intel.com>
> Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> [Jani: Expand on the commit message.]
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 28 ++++++++++---------------
>  1 file changed, 11 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 6cc03b9e4321..41130aa4b191 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -100,6 +100,8 @@ static const u8 valid_dsc_slicecount[] = {1, 2, 4};
>   *
>   * If a CPU or PCH DP output is attached to an eDP panel, this function
>   * will return true, and false otherwise.
> + *
> + * This function is not safe to use prior to encoder type being set.
>   */
>  bool intel_dp_is_edp(struct intel_dp *intel_dp)  { @@ -5301,8 +5303,6 @@
> intel_dp_init_connector(struct intel_digital_port *dig_port,
>  		     intel_encoder->base.name))
>  		return false;
> 
> -	intel_dp_set_source_rates(intel_dp);
> -
>  	intel_dp->reset_link_params = true;
>  	intel_dp->pps.pps_pipe = INVALID_PIPE;
>  	intel_dp->pps.active_pipe = INVALID_PIPE; @@ -5318,28 +5318,22 @@
> intel_dp_init_connector(struct intel_digital_port *dig_port,
>  		 */
>  		drm_WARN_ON(dev, intel_phy_is_tc(dev_priv, phy));
>  		type = DRM_MODE_CONNECTOR_eDP;
> +		intel_encoder->type = INTEL_OUTPUT_EDP;
> +
> +		/* eDP only on port B and/or C on vlv/chv */
> +		if (drm_WARN_ON(dev, (IS_VALLEYVIEW(dev_priv) ||
> +				      IS_CHERRYVIEW(dev_priv)) &&
> +				port != PORT_B && port != PORT_C))
> +			return false;
>  	} else {
>  		type = DRM_MODE_CONNECTOR_DisplayPort;
>  	}
> 
> +	intel_dp_set_source_rates(intel_dp);
> +
>  	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
>  		intel_dp->pps.active_pipe = vlv_active_pipe(intel_dp);
> 
> -	/*
> -	 * For eDP we always set the encoder type to INTEL_OUTPUT_EDP, but
> -	 * for DP the encoder type can be set by the caller to
> -	 * INTEL_OUTPUT_UNKNOWN for DDI, so don't rewrite it.
> -	 */
> -	if (type == DRM_MODE_CONNECTOR_eDP)
> -		intel_encoder->type = INTEL_OUTPUT_EDP;
> -
> -	/* eDP only on port B and/or C on vlv/chv */
> -	if (drm_WARN_ON(dev, (IS_VALLEYVIEW(dev_priv) ||
> -			      IS_CHERRYVIEW(dev_priv)) &&
> -			intel_dp_is_edp(intel_dp) &&
> -			port != PORT_B && port != PORT_C))
> -		return false;
> -
>  	drm_dbg_kms(&dev_priv->drm,
>  		    "Adding %s connector on [ENCODER:%d:%s]\n",
>  		    type == DRM_MODE_CONNECTOR_eDP ? "eDP" : "DP",
> --
> 2.20.1

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