[PATCH v2 16/16] drm/i915/dp: compute config for 128b/132b SST w/o DSC

[Imre Deak]

On Thu, Dec 19, 2024 at 11:34:05PM +0200, Jani Nikula wrote:
> Enable basic 128b/132b SST functionality without compression. Reuse
> intel_dp_mtp_tu_compute_config() to figure out the TU after we've
> determined we need to use an UHBR rate.
> 
> It's slightly complicated as the M/N computation is done in different
> places in MST and SST paths, so we need to avoid trashing the values
> later for UHBR.
> 
> If uncompressed UHBR fails, we drop to compressed non-UHBR, which is
> quite likely to fail as well. We still lack 128b/132b SST+DSC.
> 
> We need mst_master_transcoder also for 128b/132b SST. Use cpu_transcoder
> directly. Enhanced framing is "don't care" for 128b/132b link.
> 
> v2: mst_master_transcoder, enhanced framing (Imre)
> 
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 34 +++++++++++++++++--------
>  1 file changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index fba3af338280..d14a42f02ba8 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2525,8 +2525,8 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
>  	limits->min_rate = intel_dp_min_link_rate(intel_dp);
>  	limits->max_rate = intel_dp_max_link_rate(intel_dp);
>  
> -	/* FIXME 128b/132b SST support missing */
> -	if (!is_mst)
> +	/* FIXME 128b/132b SST+DSC support missing */
> +	if (!is_mst && dsc)
>  		limits->max_rate = min(limits->max_rate, 810000);
>  	limits->min_rate = min(limits->min_rate, limits->max_rate);
>  
> @@ -2640,6 +2640,13 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  		 */
>  		ret = intel_dp_compute_link_config_wide(intel_dp, pipe_config,
>  							conn_state, &limits);
> +		if (!ret && intel_dp_is_uhbr(pipe_config))
> +			ret = intel_dp_mtp_tu_compute_config(intel_dp,
> +							     pipe_config,
> +							     pipe_config->pipe_bpp,
> +							     pipe_config->pipe_bpp,
> +							     conn_state,
> +							     0, false);
>  		if (ret)
>  			dsc_needed = true;
>  	}
> @@ -3148,8 +3155,13 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  	pipe_config->limited_color_range =
>  		intel_dp_limited_color_range(pipe_config, conn_state);
>  
> -	pipe_config->enhanced_framing =
> -		drm_dp_enhanced_frame_cap(intel_dp->dpcd);
> +	if (intel_dp_is_uhbr(pipe_config)) {

Nit: no need for {} here and below.

The patch looks ok:
Reviewed-by: Imre Deak <imre.deak at intel.com>

> +		/* 128b/132b SST also needs this */
> +		pipe_config->mst_master_transcoder = pipe_config->cpu_transcoder;
> +	} else {
> +		pipe_config->enhanced_framing =
> +			drm_dp_enhanced_frame_cap(intel_dp->dpcd);
> +	}
>  
>  	if (pipe_config->dsc.compression_enable)
>  		link_bpp_x16 = pipe_config->dsc.compressed_bpp_x16;
> @@ -3180,12 +3192,14 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  
>  	intel_dp_audio_compute_config(encoder, pipe_config, conn_state);
>  
> -	intel_link_compute_m_n(link_bpp_x16,
> -			       pipe_config->lane_count,
> -			       adjusted_mode->crtc_clock,
> -			       pipe_config->port_clock,
> -			       intel_dp_bw_fec_overhead(pipe_config->fec_enable),
> -			       &pipe_config->dp_m_n);
> +	if (!intel_dp_is_uhbr(pipe_config)) {
> +		intel_link_compute_m_n(link_bpp_x16,
> +				       pipe_config->lane_count,
> +				       adjusted_mode->crtc_clock,
> +				       pipe_config->port_clock,
> +				       intel_dp_bw_fec_overhead(pipe_config->fec_enable),
> +				       &pipe_config->dp_m_n);
> +	}
>  
>  	/* FIXME: abstract this better */
>  	if (pipe_config->splitter.enable)
> -- 
> 2.39.5
>