On Fri, Jan 31, 2025 at 02:49:54PM +0200, Jani Nikula wrote:
> Commit 1c56e9a39833 ("drm/i915/dp: Get optimal link config to have best
> compressed bpp") tries to find the best compressed bpp for the
> link. However, it iterates from max to min bpp on display 13+, and from
> min to max on other platforms. This presumably leads to minimum
> compressed bpp always being chosen on display 11-12.
>
> Iterate from high to low on all platforms to actually use the best
> possible compressed bpp.
>
> Fixes: 1c56e9a39833 ("drm/i915/dp: Get optimal link config to have best compressed bpp")
> Cc: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v6.7+
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index d1b4fd542a1f..ecf192262eb9 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2073,11 +2073,10 @@ icl_dsc_compute_link_config(struct intel_dp *intel_dp,
> /* Compressed BPP should be less than the Input DSC bpp */
> dsc_max_bpp = min(dsc_max_bpp, output_bpp - 1);
>
> - for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp); i++) {
> - if (valid_dsc_bpp[i] < dsc_min_bpp)
> + 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)
> continue;
> - if (valid_dsc_bpp[i] > dsc_max_bpp)
> - break;
>
> ret = dsc_compute_link_config(intel_dp,
> pipe_config,
> --
> 2.39.5
>
