Re: [Intel-gfx] [PATCH v2] drm/i915/dp: Correctly advertise HBR3 for GEN11+

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Jun 30, 2020 at 04:33:10PM -0700, Matt Atwood wrote:
> intel_dp_set_source_rates() calls intel_dp_is_edp(), which is unsafe to
> use before encoder_type is set. This caused GEN11+ to incorrectly strip
> HBR3 from source rates for edp. Move intel_dp_set_source_rates() to
> after encoder_type is set. Add comment to intel_dp_is_edp() describing
> unsafe usages.
> 
> 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     Remove outdated comment (Ville).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.
> 
> Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>

lgtm
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.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 3df5d901dd9d..c9b93c5706af 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -137,6 +137,8 @@ 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)
>  {
> @@ -8157,8 +8159,6 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>  		     intel_encoder->base.name))
>  		return false;
>  
> -	intel_dp_set_source_rates(intel_dp);
> -
>  	intel_dp->reset_link_params = true;
>  	intel_dp->pps_pipe = INVALID_PIPE;
>  	intel_dp->active_pipe = INVALID_PIPE;
> @@ -8174,28 +8174,22 @@ intel_dp_init_connector(struct intel_digital_port *intel_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->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",
> -- 
> 2.21.3
> 
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-- 
Ville Syrjälä
Intel
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