[PATCH v2] drm/i915/dsc: Change rc parameters calculation for DSC 1.1

[Kandpal, Suraj]

> -----Original Message-----
> From: Tseng, William <william.tseng at intel.com>
> Sent: Friday, February 21, 2025 7:27 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Tseng, William <william.tseng at intel.com>; Kandpal, Suraj
> <suraj.kandpal at intel.com>; Heikkila, Juha-pekka <juha-
> pekka.heikkila at intel.com>
> Subject: [PATCH v2] drm/i915/dsc: Change rc parameters calculation for DSC 1.1

I think you missed one of my previous comments in which I asked you to send it to the intel-xe mailing list
So that the CI can test more thoroughly.
Also this patch is causing a regression on DG2 + DSC 1.1 config my guess is it would cause a issue on any
Machine 13 and above with DSC 1.1 when input bpp is 24 and compressed bpp is 18

> 
> When calculating dsc parameters, the rc parameters calculated by
> calculate_rc_params() is incorrect in the case of DSC 1.1 and
> DISPLAY_VER(dev_priv) >= 13. It turns out to be some noise-like lines are
> displayed on a MIPI DSI panel supporting DSC 1.1.
> 
> The function calculate_rc_params() is implemented by following the Table E-2
> in DSC 1.2a and creates incorrect rc parameters for DSC 1.1. As a result, add the
> additional condition (vdsc_cfg->dsc_version_minor >= 2) to get the right
> function to calculate rc parameters for DSC 1.1.
> 
> v1: initial version.
> v2: modify the commit comment and change the condition
>     regarding DSC version checking.
> 
> Cc: Suraj Kandpal <suraj.kandpal at intel.com>
> Cc: Juha-Pekka Heikkil <juha-pekka.heikkila at intel.com>
> Signed-off-by: William Tseng <william.tseng at intel.com>

Needs a closes-by tag

Regards,
Suraj Kandpal

> ---
>  drivers/gpu/drm/i915/display/intel_vdsc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c
> b/drivers/gpu/drm/i915/display/intel_vdsc.c
> index b355c479eda3..b0a7a2179844 100644
> --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
> +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
> @@ -320,7 +320,7 @@ int intel_dsc_compute_params(struct intel_crtc_state
> *pipe_config)
>  	 * upto uncompressed bpp-1, hence add calculations for all the rc
>  	 * parameters
>  	 */
> -	if (DISPLAY_VER(dev_priv) >= 13) {
> +	if (DISPLAY_VER(dev_priv) >= 13 && vdsc_cfg->dsc_version_minor >=
> 2) {
>  		calculate_rc_params(vdsc_cfg);
>  	} else {
>  		if ((compressed_bpp == 8 ||
> --
> 2.34.1