[PATCH 2/2] drm/i915/dp: Check for HAS_DSC_3ENGINES while configuring DSC slices

[Kandpal, Suraj]

> -----Original Message-----
> From: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
> Sent: Monday, April 14, 2025 8:13 AM
> To: intel-gfx at lists.freedesktop.org; intel-xe at lists.freedesktop.org
> Cc: Kandpal, Suraj <suraj.kandpal at intel.com>; stable at vger.kernel.org;
> Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
> Subject: [PATCH 2/2] drm/i915/dp: Check for HAS_DSC_3ENGINES while
> configuring DSC slices
> 
> DSC 12 slices configuration is used for some specific cases with Ultrajoiner. This
> can be supported only when each of the 4 joined pipes have 3 DSC engines
> each.
> 
> Add the missing check for 3 DSC engines support before using 3 DSC slices per
> pipe.
> 
> Fixes: be7f5fcdf4a0 ("drm/i915/dp: Enable 3 DSC engines for 12 slices")
> Cc: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> Cc: Suraj Kandpal <suraj.kandpal at intel.com>
> Cc: <stable at vger.kernel.org> # v6.14+
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>

LGTM,
Reviewed-by: Suraj Kandpal <suraj.kandpal at intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index aeb14a5455fd..d7a30d0992b7 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1050,10 +1050,11 @@ u8 intel_dp_dsc_get_slice_count(const struct
> intel_connector *connector,
>  		u8 test_slice_count = valid_dsc_slicecount[i] *
> num_joined_pipes;
> 
>  		/*
> -		 * 3 DSC Slices per pipe need 3 DSC engines,
> -		 * which is supported only with Ultrajoiner.
> +		 * 3 DSC Slices per pipe need 3 DSC engines, which is supported
> only
> +		 * with Ultrajoiner only for some platforms.
>  		 */
> -		if (valid_dsc_slicecount[i] == 3 && num_joined_pipes != 4)
> +		if (valid_dsc_slicecount[i] == 3 &&
> +		    (!HAS_DSC_3ENGINES(display) || num_joined_pipes != 4))
>  			continue;
> 
>  		if (test_slice_count >
> --
> 2.34.1