Re: [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.gol...@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;
  }