[PATCH] drm/i915/vdsc: Add bpc check in intel_dsc_compute_params

[Srikanth V, NagaVenkata]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Suraj
> Kandpal
> Sent: Thursday, September 26, 2024 10:04 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>; Kandpal, Suraj
> <suraj.kandpal at intel.com>
> Subject: [PATCH] drm/i915/vdsc: Add bpc check in
> intel_dsc_compute_params
> 
> DSC does not support bpc under 8. Return an error if that happens to be the
> case.
> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_vdsc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c
> b/drivers/gpu/drm/i915/display/intel_vdsc.c
> index 8158e3702ed5..39bf8bee106c 100644
> --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
> +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
> @@ -297,6 +297,11 @@ int intel_dsc_compute_params(struct
> intel_crtc_state *pipe_config)
> 
>  	vdsc_cfg->bits_per_pixel = pipe_config->dsc.compressed_bpp_x16;
> 
> +	if (vdsc_cfg->bites_per_pixel < 8) {
> +		drm_dbg_kms(&dev_priv->drm, "DSC bpc requirements not
> met\n");
> +		return -EINVAL;
> +	}
> +

Check for minimum bits_per_pixel must be according to output pixel format.
For 444, it's 8.
For 422, it's 7.
For 420, it's 6.

Moreover, the failure reported was on minimum BPC, not on minimum BPP.
We should be checking vdsc_cfg->bits_per_component.

>  	/*
>  	 * According to DSC 1.2 specs in Section 4.1 if native_420 is set
>  	 * we need to double the current bpp.
> --
> 2.43.2