Re: [PATCH 06/14] drm/i915/dp: Change icl_dsc_compute_link_config() DSC BPP iteration

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

On Fri, Jan 31, 2025 at 02:49:59PM +0200, Jani Nikula wrote:
> Instead of iterating the valid BPP array directly, switch to the same
> approach as xelpd_dsc_compute_link_config(), with a separate function to
> check if the DSC BPP is valid. This prepares us for unifying the
> platform specific functions.
> 
> 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 | 33 +++++++++++++++++++------
>  1 file changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 4e7b3dd4067c..ac67f2d2f86a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2069,6 +2069,26 @@ static int intel_dp_dsc_bpp_step_x16(const struct intel_connector *connector)
>  	return 16 / incr;
>  }
>  
> +/* Note: This is not universally usable! */
> +static bool intel_dp_dsc_valid_bpp(struct intel_dp *intel_dp, int bpp_x16)
> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +	int i;
> +
> +	if (DISPLAY_VER(display) >= 13)
> +		return true;
> +
> +	if (fxp_q4_to_frac(bpp_x16))
> +		return false;
> +
> +	for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp); i++) {
> +		if (fxp_q4_to_int(bpp_x16) == valid_dsc_bpp[i])
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  /*
>   * From a list of valid compressed bpps try different compressed bpp and find a
>   * suitable link configuration that can support it.
> @@ -2082,21 +2102,20 @@ icl_dsc_compute_link_config(struct intel_dp *intel_dp,
>  			    int bpp_step_x16,
>  			    int timeslots)
>  {
> -	int i, ret;
> +	int bpp_x16;
> +	int ret;
>  
> -	for (i = ARRAY_SIZE(valid_dsc_bpp) - 1; i >= 0; i--) {
> -		if (valid_dsc_bpp[i] < fxp_q4_to_int(min_bpp_x16) ||
> -		    valid_dsc_bpp[i] > fxp_q4_to_int(max_bpp_x16))
> +	for (bpp_x16 = max_bpp_x16; bpp_x16 >= min_bpp_x16; bpp_x16 -= bpp_step_x16) {
> +		if (!intel_dp_dsc_valid_bpp(intel_dp, bpp_x16))
>  			continue;
>  
>  		ret = dsc_compute_link_config(intel_dp,
>  					      pipe_config,
>  					      limits,
> -					      valid_dsc_bpp[i] << 4,
> +					      bpp_x16,
>  					      timeslots);
>  		if (ret == 0) {
> -			pipe_config->dsc.compressed_bpp_x16 =
> -				fxp_q4_from_int(valid_dsc_bpp[i]);
> +			pipe_config->dsc.compressed_bpp_x16 = bpp_x16;
>  			return 0;
>  		}
>  	}
> -- 
> 2.39.5
>