[PATCH v5 3/3] drm/i915/edp: eDP Data Overrride

[Kandpal, Suraj]

> 
> On Tue, 19 Aug 2025, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> > We need override certain link rates in favour of the next available
> > higher link rate. The Link rates that need to be overridden are
> > indicated by a mask in VBT. To make sure these modes are skipped we
> > don't add them in them in the sink rates array.
> >
> > --v2
> > -Update the link rates after we have a final set of link rates [Ankit]
> > -Break this patch up [Ankit] -Optimize the assingment during loop
> > [Ankit]
> >
> > --v3
> > -Add protection against broken VBTs [Jani]
> >
> > --v4
> > -Fix build errors
> > -Create a seprate function to check if edp data override is selected
> > and using the correct vbt
> >
> > --v5
> > -Use correct number to check the num of edp rates [Ankit]
> >
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_bios.c | 15 ++++++++++++++-
> > drivers/gpu/drm/i915/display/intel_bios.h |  2 ++
> >  drivers/gpu/drm/i915/display/intel_dp.c   | 22 ++++++++++++++++++++++
> >  3 files changed, 38 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c
> > b/drivers/gpu/drm/i915/display/intel_bios.c
> > index 444ed54f7c35..05a74c3bc9af 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bios.c
> > +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> > @@ -2521,11 +2521,24 @@ int intel_bios_dp_max_lane_count(const struct
> > intel_bios_encoder_data *devdata)  bool
> > intel_bios_encoder_reject_edp_rate(const struct intel_bios_encoder_data
> *devdata,
> >  				   int rate)
> > +{
> > +	return devdata->child.edp_data_rate_override &
> > +edp_rate_override_mask(rate); }
> > +
> > +bool
> > +intel_bios_vbt_supports_edp_data_override(const struct
> > +intel_bios_encoder_data *devdata)
> 
> Why are you adding this function? Earlier versions didn't have it, and the reason
> for its existence isn't explained or clear.
> 

This function was added in v3 (I did add a small mention in the commit message I can maybe elaborate more there)
 in response to one of your comments in which you mentioned the
Possibility of ending up with a broken vbt that masked all the link rates causing us to have no link rate
To drive the edp with this function now checks if we have at least one edp link rate using which we can
Drive edp if not we do not modify the list of sink rates at all.

Regards,
Suraj Kandpal

> BR,
> Jani.
> 
> 
> >  {
> >  	if (!devdata || devdata->display->vbt.version < 263)
> >  		return false;
> >
> > -	return devdata->child.edp_data_rate_override &
> edp_rate_override_mask(rate);
> > +	/*
> > +	 * This means the VBT ends up asking us to override every possible rate
> > +	 * indicating the VBT is broken so skip this
> > +	 */
> > +	if (hweight32(devdata->child.edp_data_rate_override) >=
> BDB_263_VBT_EDP_NUM_RATES)
> > +		return false;
> > +
> > +	return true;
> >  }
> >
> >  static void sanitize_device_type(struct intel_bios_encoder_data
> > *devdata, diff --git a/drivers/gpu/drm/i915/display/intel_bios.h
> > b/drivers/gpu/drm/i915/display/intel_bios.h
> > index 781e08f7eeb2..d24660bcc7f3 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bios.h
> > +++ b/drivers/gpu/drm/i915/display/intel_bios.h
> > @@ -276,5 +276,7 @@ void intel_bios_for_each_encoder(struct intel_display
> *display,
> >  					      const struct
> intel_bios_encoder_data *devdata));
> >
> >  void intel_bios_debugfs_register(struct intel_display *display);
> > +bool
> > +intel_bios_vbt_supports_edp_data_override(const struct
> > +intel_bios_encoder_data *devdata);
> >
> >  #endif /* _INTEL_BIOS_H_ */
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 54d88f24b689..f6fad42182ae 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -4277,6 +4277,26 @@ static void intel_edp_mso_init(struct intel_dp
> *intel_dp)
> >  	intel_dp->mso_pixel_overlap = mso ? info->mso_pixel_overlap : 0;  }
> >
> > +static void
> > +intel_edp_set_data_override_rates(struct intel_dp *intel_dp) {
> > +	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
> > +	int *sink_rates = intel_dp->sink_rates;
> > +	int i, j = 0;
> > +
> > +	if (!intel_bios_vbt_supports_edp_data_override(encoder->devdata))
> > +		return;
> > +
> > +	for (i = 0; i < intel_dp->num_sink_rates; i++) {
> > +		if (intel_bios_encoder_reject_edp_rate(encoder->devdata,
> > +						       intel_dp->sink_rates[i]))
> > +			continue;
> > +
> > +		sink_rates[j++] = intel_dp->sink_rates[i];
> > +	}
> > +	intel_dp->num_sink_rates = j;
> > +}
> > +
> >  static void
> >  intel_edp_set_sink_rates(struct intel_dp *intel_dp)  { @@ -4327,6
> > +4347,8 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp)
> >  		intel_dp->use_rate_select = true;
> >  	else
> >  		intel_dp_set_sink_rates(intel_dp);
> > +
> > +	intel_edp_set_data_override_rates(intel_dp);
> >  }
> >
> >  static bool
> 
> --
> Jani Nikula, Intel