[PATCH v3 5/5] drm/i915/dsc: Check if dsc prefill sufficient for vblank

[Nautiyal, Ankit K]

On 1/6/2025 10:21 PM, Mitul Golani wrote:
> Check if dsc prefill latency is sufficient for vblank.
>
> --v2:
> - Consider chroma downscaling factor in latency calculation. [Ankit]
> - Replace function name from dsc_prefill_time to dsc_prefill_latency.
>
> Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
> ---
>   drivers/gpu/drm/i915/display/skl_watermark.c | 25 ++++++++++++++++++++
>   1 file changed, 25 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c b/drivers/gpu/drm/i915/display/skl_watermark.c
> index 95f60819fe0a..900e1c54450d 100644
> --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> @@ -2292,6 +2292,30 @@ static int icl_build_plane_wm(struct intel_crtc_state *crtc_state,
>   	return 0;
>   }
>   
> +static int
> +dsc_prefill_latency(const struct intel_crtc_state *crtc_state)
> +{
> +	const struct intel_crtc_scaler_state *scaler_state =
> +					&crtc_state->scaler_state;
> +	int hscale = scaler_state->scalers[0].hscale;
> +	int vscale = scaler_state->scalers[0].vscale;
> +
> +	if (!crtc_state->dsc.compression_enable)
> +		return 0;
> +	/*
> +	 * FIXME: CDCLK Prefill adjustment to add
> +	 */

I am not sure about this.


> +	if (scaler_state->scaler_users) {
> +		int chroma_downscaling_factor =
> +			crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR444 ? 2 : 1;

Ycbcr420 as mentioned in previous patch.


> +
> +		return DIV_ROUND_UP(15 * crtc_state->linetime * hscale * vscale *

This again need to have hscale and vscale right shifted by 16 like the 
previous patch.

Also, it would be good to add bspec reference in commit message.

Regards,

Ankit

> +				    chroma_downscaling_factor, 10);
> +	}
> +
> +	return 0;
> +}
> +
>   static int
>   scaler_prefill_latency(const struct intel_crtc_state *crtc_state)
>   {
> @@ -2333,6 +2357,7 @@ skl_is_vblank_too_short(const struct intel_crtc_state *crtc_state,
>   	return crtc_state->framestart_delay +
>   		intel_usecs_to_scanlines(adjusted_mode, latency) +
>   		scaler_prefill_latency(crtc_state) +
> +		dsc_prefill_latency(crtc_state) +
>   		wm0_lines >
>   		adjusted_mode->crtc_vtotal - adjusted_mode->crtc_vblank_start;
>   }