Re: [Intel-gfx] [PATCH 1/5] drm/i915/dp: Fix eDP max rate for display 11+

["Manna, Animesh" <animesh.manna@intel.com>]

> -----Original Message-----
> From: Deak, Imre <imre.deak@intel.com>
> Sent: Thursday, August 12, 2021 8:34 PM
> To: Manna, Animesh <animesh.manna@intel.com>
> Cc: intel-gfx@lists.freedesktop.org; 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>; Nikula, Jani <jani.nikula@intel.com>
> Subject: Re: [PATCH 1/5] drm/i915/dp: Fix eDP max rate for display 11+
> 
> On Thu, Aug 12, 2021 at 11:18:02AM +0530, Animesh Manna wrote:
> > 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+"").
> 
> AFAIR, this issue was that TGL started to use TPS4, which somehow broke link
> training on the panel connected to that box. But I think TPS4 is supported on
> TGL, regardless of the link rate used, so this change looks ok wrt. that.
> 
> As a side-note allowing TPS4 only on ports supporting HBR3 looks incorrect, I
> think TPS4 is either supported or not by a platform regardless of what is the max
> link rate. Due to that we may stop using
> TPS4 on EHL/JSL after this patchset, but I think that can be fixed separately.

Ok. HBR3 needs TPS4, maybe lttpr also need TPS4 which need to be handled.

> 
> > Cc: Uma Shankar <uma.shankar@intel.com>
> > Cc: Imre Deak <imre.deak@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> > Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> 
> Reviewed-by: Imre Deak <imre.deak@intel.com>

Thanks for review.

Regards,
Animesh
> 
> > ---
> >  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 75d4ebc66941..4df56af36b3f 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)  { @@ -5294,8 +5296,6
> > @@ 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; @@ -5311,28 +5311,22 @@
> > 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",
> > --
> > 2.29.0
> >