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

[Jani Nikula <jani.nikula@intel.com>]

On Tue, 19 Aug 2025, Suraj Kandpal <suraj.kandpal@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@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.

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