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* [Intel-gfx] [PATCH v1] drm/i915: Bump up CDCLK to eliminate underruns on TGL
@ 2020-01-08 12:26 Stanislav Lisovskiy
  2020-01-08 14:01 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
                   ` (3 more replies)
  0 siblings, 4 replies; 6+ messages in thread
From: Stanislav Lisovskiy @ 2020-01-08 12:26 UTC (permalink / raw)
  To: intel-gfx

There seems to be some undocumented bandwidth
bottleneck/dependency which scales with CDCLK,
causing FIFO underruns when CDCLK is too low,
even when it's correct from BSpec point of view.

Currently for TGL platforms we calculate
min_cdclk initially based on pixel_rate divided
by 2, accounting for also plane requirements,
however in some cases the lowest possible CDCLK
doesn't work and causing the underruns.

Explicitly stating here that this seems to be currently
rather a Hack, than final solution.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Bugzilla: https://gitlab.freedesktop.org/drm/intel/issues/402
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 7d1ab1e5b7c3..3db4060ed190 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -2004,6 +2004,13 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
 	/* Account for additional needs from the planes */
 	min_cdclk = max(intel_planes_min_cdclk(crtc_state), min_cdclk);
 
+	if (IS_GEN(dev_priv, 12)) {
+		if (min_cdclk <= DIV_ROUND_UP(crtc_state->pixel_rate, 2)) {
+			min_cdclk = min(min_cdclk * 2,
+				    ((int)dev_priv->max_cdclk_freq));
+		}
+	}
+
 	if (min_cdclk > dev_priv->max_cdclk_freq) {
 		DRM_DEBUG_KMS("required cdclk (%d kHz) exceeds max (%d kHz)\n",
 			      min_cdclk, dev_priv->max_cdclk_freq);
-- 
2.24.1.485.gad05a3d8e5

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^ permalink raw reply related	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2020-01-09 11:58 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-08 12:26 [Intel-gfx] [PATCH v1] drm/i915: Bump up CDCLK to eliminate underruns on TGL Stanislav Lisovskiy
2020-01-08 14:01 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2020-01-08 14:55 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-01-08 17:16 ` [Intel-gfx] [PATCH v1] " Matt Roper
2020-01-09 11:30   ` Lisovskiy, Stanislav
2020-01-09 11:58 ` [Intel-gfx] ✓ Fi.CI.IGT: success for " Patchwork

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