Re: [PATCH 04/14] drm/i915/dp: Pass .4 BPP values to {icl,xelpd}_dsc_compute_link_config()

[Imre Deak <imre.deak@intel.com>]

On Fri, Jan 31, 2025 at 02:49:57PM +0200, Jani Nikula wrote:
> Try to keep the variables in the same domain a bit longer to reduce
> juggling between integers and .4 fixed point. Change parameter order to
> min, max while at it.
> 
> For now, keep the juggling in dsc_compute_compressed_bpp() ensure
> min/max will always have 0 fractional part. To be fixed later.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 28 ++++++++++++++-----------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 02d1a5453b46..b13d806c9de7 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2077,8 +2077,8 @@ static int
>  icl_dsc_compute_link_config(struct intel_dp *intel_dp,
>  			    struct intel_crtc_state *pipe_config,
>  			    const struct link_config_limits *limits,
> -			    int dsc_max_bpp,
> -			    int dsc_min_bpp,
> +			    int min_bpp_x16,
> +			    int max_bpp_x16,
>  			    int pipe_bpp,
>  			    int timeslots)
>  {
> @@ -2086,11 +2086,11 @@ icl_dsc_compute_link_config(struct intel_dp *intel_dp,
>  	int output_bpp = intel_dp_output_bpp(pipe_config->output_format, pipe_bpp);
>  
>  	/* Compressed BPP should be less than the Input DSC bpp */
> -	dsc_max_bpp = min(dsc_max_bpp, output_bpp - 1);
> +	max_bpp_x16 = min(max_bpp_x16, fxp_q4_from_int(output_bpp - 1));
>  
>  	for (i = ARRAY_SIZE(valid_dsc_bpp) - 1; i >= 0; i--) {
> -		if (valid_dsc_bpp[i] < dsc_min_bpp ||
> -		    valid_dsc_bpp[i] > dsc_max_bpp)
> +		if (valid_dsc_bpp[i] < fxp_q4_to_int(min_bpp_x16) ||
> +		    valid_dsc_bpp[i] > fxp_q4_to_int(max_bpp_x16))
>  			continue;
>  
>  		ret = dsc_compute_link_config(intel_dp,
> @@ -2119,8 +2119,8 @@ xelpd_dsc_compute_link_config(struct intel_dp *intel_dp,
>  			      const struct intel_connector *connector,
>  			      struct intel_crtc_state *pipe_config,
>  			      const struct link_config_limits *limits,
> -			      int dsc_max_bpp,
> -			      int dsc_min_bpp,
> +			      int min_bpp_x16,
> +			      int max_bpp_x16,
>  			      int pipe_bpp,
>  			      int timeslots)
>  {
> @@ -2132,10 +2132,9 @@ xelpd_dsc_compute_link_config(struct intel_dp *intel_dp,
>  	bpp_step_x16 = intel_dp_dsc_bpp_step_x16(connector);
>  
>  	/* Compressed BPP should be less than the Input DSC bpp */
> -	dsc_max_bpp = min(dsc_max_bpp << 4, (output_bpp << 4) - bpp_step_x16);
> -	dsc_min_bpp = dsc_min_bpp << 4;
> +	max_bpp_x16 = min(max_bpp_x16, fxp_q4_from_int(output_bpp) - bpp_step_x16);
>  
> -	for (bpp_x16 = dsc_max_bpp; bpp_x16 >= dsc_min_bpp; bpp_x16 -= bpp_step_x16) {
> +	for (bpp_x16 = max_bpp_x16; bpp_x16 >= min_bpp_x16; bpp_x16 -= bpp_step_x16) {
>  		if (intel_dp->force_dsc_fractional_bpp_en &&
>  		    !fxp_q4_to_frac(bpp_x16))
>  			continue;
> @@ -2168,6 +2167,7 @@ static int dsc_compute_compressed_bpp(struct intel_dp *intel_dp,
>  	const struct drm_display_mode *adjusted_mode = &pipe_config->hw.adjusted_mode;
>  	int dsc_min_bpp;
>  	int dsc_max_bpp;
> +	int min_bpp_x16, max_bpp_x16;
>  	int dsc_joiner_max_bpp;
>  	int num_joined_pipes = intel_crtc_num_joined_pipes(pipe_config);
>  
> @@ -2178,11 +2178,15 @@ static int dsc_compute_compressed_bpp(struct intel_dp *intel_dp,
>  								num_joined_pipes);
>  	dsc_max_bpp = min(dsc_joiner_max_bpp, fxp_q4_to_int(limits->link.max_bpp_x16));
>  
> +	/* FIXME: remove the round trip via integers */
> +	min_bpp_x16 = fxp_q4_from_int(dsc_min_bpp);
> +	max_bpp_x16 = fxp_q4_from_int(dsc_max_bpp);
> +
>  	if (DISPLAY_VER(display) >= 13)
>  		return xelpd_dsc_compute_link_config(intel_dp, connector, pipe_config, limits,
> -						     dsc_max_bpp, dsc_min_bpp, pipe_bpp, timeslots);
> +						     min_bpp_x16, max_bpp_x16, pipe_bpp, timeslots);
>  	return icl_dsc_compute_link_config(intel_dp, pipe_config, limits,
> -					   dsc_max_bpp, dsc_min_bpp, pipe_bpp, timeslots);
> +					   min_bpp_x16, max_bpp_x16, pipe_bpp, timeslots);
>  }
>  
>  int intel_dp_dsc_min_src_input_bpc(void)
> -- 
> 2.39.5
>