On Thu, 2025-11-27 at 19:50 +0200, Imre Deak wrote:
> Add intel_dp_mode_valid_with_dsc() and call this for an SST/MST mode
> validation to prepare for a follow-up change using a way to verify
> the
> mode's required BW the same way this is done elsewhere during state
> computation (which in turn depends on the mode's effective data rate
> with the corresponding BW overhead).
> 
> Signed-off-by: Imre Deak <[email protected]>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c     | 57 +++++++++++++++----
> --
>  drivers/gpu/drm/i915/display/intel_dp.h     |  7 +++
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 29 ++++-------
>  3 files changed, 57 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 9deb99eda8813..b40edf4febcb7 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1579,24 +1579,20 @@ intel_dp_mode_valid(struct drm_connector
> *_connector,
>                       dsc_slice_count =
>                               drm_dp_dsc_sink_max_slice_count(conn
> ector->dp.dsc_dpcd,
>                                                               true
> );
> +                     dsc = dsc_max_compressed_bpp &&
> dsc_slice_count;
>               } else if (drm_dp_sink_supports_fec(connector-
> >dp.fec_capability)) {
> -                     dsc_max_compressed_bpp =
> -
>                               intel_dp_dsc_get_max_compressed_bpp(display,
> -                                                                
> max_link_clock,
> -                                                                
> max_lanes,
> -                                                                
> target_clock,
> -                                                                
> mode->hdisplay,
> -                                                                
> num_joined_pipes,
> -                                                                
> output_format,
> -                                                                
> pipe_bpp, 64);
> -                     dsc_slice_count =
> -
>                               intel_dp_dsc_get_slice_count(connector,
> -                                                         
> target_clock,
> -                                                          mode-
> >hdisplay,
> -                                                         
> num_joined_pipes);
> +                     unsigned long bw_overhead_flags = 0;
> +
> +                     if (!drm_dp_is_uhbr_rate(max_link_clock))
> +                             bw_overhead_flags |=
> DRM_DP_BW_OVERHEAD_FEC;
> +
> +                     dsc =
> intel_dp_mode_valid_with_dsc(connector,
> +                                                       
> max_link_clock, max_lanes,
> +                                                       
> target_clock, mode->hdisplay,
> +                                                       
> num_joined_pipes,
> +                                                       
> output_format, pipe_bpp,
> +                                                       
> bw_overhead_flags);
>               }
> -
> -             dsc = dsc_max_compressed_bpp && dsc_slice_count;
>       }
>  
>       if (intel_dp_joiner_needs_dsc(display, num_joined_pipes) &&
> !dsc)
> @@ -2704,6 +2700,35 @@ static int
> compute_max_compressed_bpp_x16(struct intel_connector *connector,
>       return max_link_bpp_x16;
>  }
>  
> +bool intel_dp_mode_valid_with_dsc(struct intel_connector *connector,
> +                               int link_clock, int lane_count,
> +                               int mode_clock, int mode_hdisplay,
> +                               int num_joined_pipes,
> +                               enum intel_output_format
> output_format,
> +                               int pipe_bpp, unsigned long
> bw_overhead_flags)

bw_overhead_flags is not used in this patch. But I see that this is
being used in the next patch.

Reviewed-by: Vinod Govindapillai <[email protected]>

> +{
> +     struct intel_display *display = to_intel_display(connector);
> +     int dsc_max_compressed_bpp;
> +     int dsc_slice_count;
> +
> +     dsc_max_compressed_bpp =
> +             intel_dp_dsc_get_max_compressed_bpp(display,
> +                                                 link_clock,
> +                                                 lane_count,
> +                                                 mode_clock,
> +                                                 mode_hdisplay,
> +                                                
> num_joined_pipes,
> +                                                 output_format,
> +                                                 pipe_bpp, 64);
> +     dsc_slice_count =
> +             intel_dp_dsc_get_slice_count(connector,
> +                                          mode_clock,
> +                                          mode_hdisplay,
> +                                          num_joined_pipes);
> +
> +     return dsc_max_compressed_bpp && dsc_slice_count;
> +}
> +
>  /*
>   * Calculate the output link min, max bpp values in limits based on
> the pipe bpp
>   * range, crtc_state and dsc mode. Return true on success.
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> b/drivers/gpu/drm/i915/display/intel_dp.h
> index 489b8c945da39..0ec7baec7a8e8 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -150,6 +150,13 @@ u16 intel_dp_dsc_get_max_compressed_bpp(struct
> intel_display *display,
>                                       enum intel_output_format
> output_format,
>                                       u32 pipe_bpp,
>                                       u32 timeslots);
> +
> +bool intel_dp_mode_valid_with_dsc(struct intel_connector *connector,
> +                               int link_clock, int lane_count,
> +                               int mode_clock, int mode_hdisplay,
> +                               int num_joined_pipes,
> +                               enum intel_output_format
> output_format,
> +                               int pipe_bpp, unsigned long
> bw_overhead_flags);
>  bool intel_dp_dsc_valid_compressed_bpp(struct intel_dp *intel_dp,
> int bpp_x16);
>  u8 intel_dp_dsc_get_slice_count(const struct intel_connector
> *connector,
>                               int mode_clock, int mode_hdisplay,
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 0db6ed2d9664c..e3f8679e95252 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -1462,8 +1462,6 @@ mst_connector_mode_valid_ctx(struct
> drm_connector *_connector,
>               DRM_DP_BW_OVERHEAD_MST |
> DRM_DP_BW_OVERHEAD_SSC_REF_CLK;
>       int ret;
>       bool dsc = false;
> -     u16 dsc_max_compressed_bpp = 0;
> -     u8 dsc_slice_count = 0;
>       int target_clock = mode->clock;
>       int num_joined_pipes;
>  
> @@ -1522,31 +1520,22 @@ mst_connector_mode_valid_ctx(struct
> drm_connector *_connector,
>               return 0;
>       }
>  
> -     if (intel_dp_has_dsc(connector)) {
> +     if (intel_dp_has_dsc(connector) &&
> drm_dp_sink_supports_fec(connector->dp.fec_capability)) {
>               /*
>                * TBD pass the connector BPC,
>                * for now U8_MAX so that max BPC on that platform
> would be picked
>                */
>               int pipe_bpp =
> intel_dp_dsc_compute_max_bpp(connector, U8_MAX);
>  
> -             if (drm_dp_sink_supports_fec(connector-
> >dp.fec_capability)) {
> -                     dsc_max_compressed_bpp =
> -
>                               intel_dp_dsc_get_max_compressed_bpp(display,
> -                                                                
> max_link_clock,
> -                                                                
> max_lanes,
> -                                                                
> target_clock,
> -                                                                
> mode->hdisplay,
> -                                                                
> num_joined_pipes,
> -                                                                
> INTEL_OUTPUT_FORMAT_RGB,
> -                                                                
> pipe_bpp, 64);
> -                     dsc_slice_count =
> -
>                               intel_dp_dsc_get_slice_count(connector,
> -                                                         
> target_clock,
> -                                                          mode-
> >hdisplay,
> -                                                         
> num_joined_pipes);
> -             }
> +             if (!drm_dp_is_uhbr_rate(max_link_clock))
> +                     bw_overhead_flags |= DRM_DP_BW_OVERHEAD_FEC;
>  
> -             dsc = dsc_max_compressed_bpp && dsc_slice_count;
> +             dsc = intel_dp_mode_valid_with_dsc(connector,
> +                                                max_link_clock,
> max_lanes,
> +                                                target_clock,
> mode->hdisplay,
> +                                                num_joined_pipes,
> +                                               
> INTEL_OUTPUT_FORMAT_RGB, pipe_bpp,
> +                                               
> bw_overhead_flags);
>       }
>  
>       if (intel_dp_joiner_needs_dsc(display, num_joined_pipes) &&
> !dsc) {

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