[PATCH v2 01/12] drm/i915/dp_mst: Use the correct connector while computing the link BPP limit on MST

[Luca Coelho]

On Mon, 2025-04-28 at 16:31 +0300, Imre Deak wrote:
> Atm, on an MST link in DSC mode
> intel_dp_compute_config_link_bpp_limits() calculates the maximum link
> bpp limit using the MST root connector's DSC capabilities. That's not
> correct in general: the decompression could be performed by a branch
> device downstream of the root branch device or the sink itself.
> 
> Fix the above by passing to intel_dp_compute_config_link_bpp_limits()
> the actual connector being modeset, containing the correct DSC
> capabilities.
> 
> Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> Fixes: 1c5b72daff46 ("drm/i915/dp: Set the DSC link limits in intel_dp_compute_config_link_bpp_limits")
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c     | 7 ++++---
>  drivers/gpu/drm/i915/display/intel_dp.h     | 1 +
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 5 +++--
>  3 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 607aea1bf6fa2..d63aea7ee9c80 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2523,6 +2523,7 @@ intel_dp_dsc_compute_pipe_bpp_limits(struct intel_dp *intel_dp,
>  
>  bool
>  intel_dp_compute_config_limits(struct intel_dp *intel_dp,
> +			       struct intel_connector *connector,
>  			       struct intel_crtc_state *crtc_state,
>  			       bool respect_downstream_limits,
>  			       bool dsc,
> @@ -2576,7 +2577,7 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
>  	intel_dp_test_compute_config(intel_dp, crtc_state, limits);
>  
>  	return intel_dp_compute_config_link_bpp_limits(intel_dp,
> -						       intel_dp->attached_connector,
> +						       connector,
>  						       crtc_state,
>  						       dsc,
>  						       limits);
> @@ -2637,7 +2638,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  	joiner_needs_dsc = intel_dp_joiner_needs_dsc(display, num_joined_pipes);
>  
>  	dsc_needed = joiner_needs_dsc || intel_dp->force_dsc_en ||
> -		     !intel_dp_compute_config_limits(intel_dp, pipe_config,
> +		     !intel_dp_compute_config_limits(intel_dp, connector, pipe_config,
>  						     respect_downstream_limits,
>  						     false,
>  						     &limits);
> @@ -2671,7 +2672,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  			    str_yes_no(ret), str_yes_no(joiner_needs_dsc),
>  			    str_yes_no(intel_dp->force_dsc_en));
>  
> -		if (!intel_dp_compute_config_limits(intel_dp, pipe_config,
> +		if (!intel_dp_compute_config_limits(intel_dp, connector, pipe_config,
>  						    respect_downstream_limits,
>  						    true,
>  						    &limits))
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> index 9189db4c25946..98f90955fdb1d 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -194,6 +194,7 @@ void intel_dp_wait_source_oui(struct intel_dp *intel_dp);
>  int intel_dp_output_bpp(enum intel_output_format output_format, int bpp);
>  
>  bool intel_dp_compute_config_limits(struct intel_dp *intel_dp,
> +				    struct intel_connector *connector,
>  				    struct intel_crtc_state *crtc_state,
>  				    bool respect_downstream_limits,
>  				    bool dsc,
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index d19ef1fef452b..49b836cd8816c 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -621,12 +621,13 @@ adjust_limits_for_dsc_hblank_expansion_quirk(struct intel_dp *intel_dp,
>  
>  static bool
>  mst_stream_compute_config_limits(struct intel_dp *intel_dp,
> -				 const struct intel_connector *connector,
> +				 struct intel_connector *connector,
>  				 struct intel_crtc_state *crtc_state,
>  				 bool dsc,
>  				 struct link_config_limits *limits)
>  {
> -	if (!intel_dp_compute_config_limits(intel_dp, crtc_state, false, dsc,
> +	if (!intel_dp_compute_config_limits(intel_dp, connector,
> +					    crtc_state, false, dsc,
>  					    limits))
>  		return false;
>  

Makes sense.

Reviewed-by: Luca Coelho <luciano.coelho at intel.com>

--
Cheers,
Luca.