[Intel-gfx] [PATCH v2] drm/i915: Clamp min_cdclk to max_cdclk_freq to unblock 8K

From: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
To: intel-gfx@lists.freedesktop.org
Subject: [Intel-gfx] [PATCH v2] drm/i915: Clamp min_cdclk to max_cdclk_freq to unblock 8K
Date: Thu,  2 Jul 2020 12:15:26 +0300	[thread overview]
Message-ID: <20200702091526.10096-1-stanislav.lisovskiy@intel.com> (raw)

We still need "Bump up CDCLK" workaround otherwise getting
underruns - however currently it blocks 8K as CDCLK = Pixel rate,
in 8K case would require CDCLK to be around 1 Ghz which is not
possible.

v2: - Convert to expression(max(min_cdclk, min(pixel_rate, max_cdclk))
      (Ville Syrjälä)
    - Use type specific min_t, max_t(Ville Syrjälä)

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 45f7f33d1144..8f9320e1e249 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -2080,8 +2080,15 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
 	 * Explicitly stating here that this seems to be currently
 	 * rather a Hack, than final solution.
 	 */
-	if (IS_TIGERLAKE(dev_priv))
-		min_cdclk = max(min_cdclk, (int)crtc_state->pixel_rate);
+	if (IS_TIGERLAKE(dev_priv)) {
+		/*
+		 * Clamp to max_cdclk_freq in case pixel rate is higher,
+		 * in order not to break an 8K, but still leave W/A at place.
+		 */
+		min_cdclk = max_t(int, min_cdclk,
+				  min_t(int, crtc_state->pixel_rate,
+					dev_priv->max_cdclk_freq));
+	}
 
 	if (min_cdclk > dev_priv->max_cdclk_freq) {
 		drm_dbg_kms(&dev_priv->drm,
-- 
2.24.1.485.gad05a3d8e5

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