On Thu, Jan 29, 2026 at 10:41:48PM +0530, Ankit Nautiyal wrote:
> Similar to the DP SST, refactor mst_stream_compute_config() to iterate
> over joiner candidates and select the minimal joiner configuration that
> satisfies the mode requirements. This prepares the logic for future changes
> that will consider DSC slice overhead.
> 
> v2:
>  - Move the check for dotclock in the new helper and check for both DSC and
>    non-DSC case. In case the check fails for non-DSC, fallback to DSC
>    configuration. (Imre)
>  - Propagate the return value from the core helper:
>    mst_stream_compute_link_for_joined_pipes(). (Imre)
> 
> Signed-off-by: Ankit Nautiyal <[email protected]>
> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 46 ++++++++++++++++-----
>  1 file changed, 35 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c 
> b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 55b2ccb45e43..c0d854b107b5 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -602,12 +602,16 @@ static int 
> mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
>  {
>       struct intel_display *display = to_intel_display(encoder);
>       struct intel_dp *intel_dp = to_primary_dp(encoder);
> +     const struct drm_display_mode *adjusted_mode =
> +             &pipe_config->hw.adjusted_mode;
>       struct intel_connector *connector =
>               to_intel_connector(conn_state->connector);
> +     int max_dotclk = display->cdclk.max_dotclk_freq;
>       struct link_config_limits limits;
>       bool dsc_needed, joiner_needs_dsc;
>       int ret = 0;
>  
> +     max_dotclk *= num_joined_pipes;
>       joiner_needs_dsc = intel_dp_joiner_needs_dsc(display, num_joined_pipes);
>  
>       dsc_needed = joiner_needs_dsc || intel_dp->force_dsc_en ||
> @@ -621,7 +625,7 @@ static int 
> mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
>               if (ret == -EDEADLK)
>                       return ret;
>  
> -             if (ret)
> +             if (ret || adjusted_mode->clock > max_dotclk)
>                       dsc_needed = true;
>       }
>  
> @@ -664,6 +668,9 @@ static int 
> mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
>                                                 pipe_config->dp_m_n.tu);
>               if (ret)
>                       return ret;
> +
> +             if (adjusted_mode->clock > max_dotclk)
> +                     return -EINVAL;
>       }
>  
>       if (ret)
> @@ -689,7 +696,8 @@ static int mst_stream_compute_config(struct intel_encoder 
> *encoder,
>       const struct drm_display_mode *adjusted_mode =
>               &pipe_config->hw.adjusted_mode;
>       int num_joined_pipes;
> -     int ret = 0;
> +     int num_pipes;
> +     int ret = -EINVAL;
>  
>       if (pipe_config->fec_enable &&
>           !intel_dp_supports_fec(intel_dp, connector, pipe_config))
> @@ -702,16 +710,32 @@ static int mst_stream_compute_config(struct 
> intel_encoder *encoder,
>       pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
>       pipe_config->has_pch_encoder = false;
>  
> -     num_joined_pipes = intel_dp_num_joined_pipes(intel_dp, connector,
> -                                                  
> adjusted_mode->crtc_hdisplay,
> -                                                  adjusted_mode->crtc_clock);
> -     if (num_joined_pipes > 1)
> -             pipe_config->joiner_pipes = GENMASK(crtc->pipe + 
> num_joined_pipes - 1, crtc->pipe);
> +     for (num_pipes = 1; num_pipes <= I915_MAX_PIPES; num_pipes++) {
> +             if (connector->force_joined_pipes &&
> +                 num_pipes != connector->force_joined_pipes)
> +                     continue;
> +
> +             num_joined_pipes = num_pipes;

No need for two variables, fixing that:
Reviewed-by: Imre Deak <[email protected]>

> +
> +             if (!intel_dp_can_join(display, num_joined_pipes))
> +                     continue;
> +
> +             if (adjusted_mode->hdisplay >
> +                 num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
> +                     continue;
> +
> +             if (num_joined_pipes > 1)
> +                     pipe_config->joiner_pipes = GENMASK(crtc->pipe + 
> num_joined_pipes - 1,
> +                                                         crtc->pipe);
> +
> +             ret = mst_stream_compute_link_for_joined_pipes(encoder,
> +                                                            pipe_config,
> +                                                            conn_state,
> +                                                            
> num_joined_pipes);
> +             if (!ret)
> +                     break;
> +     }
>  
> -     ret = mst_stream_compute_link_for_joined_pipes(encoder,
> -                                                    pipe_config,
> -                                                    conn_state,
> -                                                    num_joined_pipes);
>       if (ret)
>               return ret;
>  
> -- 
> 2.45.2
> 

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