[PATCH] drm/i915/tgl: Lower cdclk for sub 4k resolutions

[Mika Kahola]

In order to achieve power savings we can tune down CD clock frequency
for sub 4k resolutions. The maximum CD clock frequency for sub 4k
resolutions is set to 172.8 MHz.

Signed-off-by: Mika Kahola <mika.kahola at intel.com>
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 26 +++++++++++++++++++++-
 drivers/gpu/drm/i915/display/intel_cdclk.h |  3 +++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index d0bc42e5039c..1d6c7bc79470 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -2610,6 +2610,24 @@ static int intel_compute_max_dotclk(struct drm_i915_private *dev_priv)
 		return max_cdclk_freq*90/100;
 }
 
+bool mode_is_4k(struct drm_i915_private *dev_priv)
+{
+	struct intel_crtc *crtc;
+	struct intel_crtc_state *pipe_config;
+
+	for_each_intel_crtc(&dev_priv->drm, crtc) {
+		pipe_config = to_intel_crtc_state(crtc->base.state);
+
+		if (pipe_config->base.active) {
+			if (pipe_config->pipe_src_w >= WIDTH_4K &&
+			    pipe_config->pipe_src_h >= HEIGHT_4K)
+				return true;
+		}
+	}
+
+	return false;
+}
+
 /**
  * intel_update_max_cdclk - Determine the maximum support CDCLK frequency
  * @dev_priv: i915 device
@@ -2620,7 +2638,13 @@ static int intel_compute_max_dotclk(struct drm_i915_private *dev_priv)
  */
 void intel_update_max_cdclk(struct drm_i915_private *dev_priv)
 {
-	if (IS_ELKHARTLAKE(dev_priv)) {
+	/*
+	 * Use lower CDCLK frequency on Tigerlake when selected
+	 * mode is less than 4k.
+	 */
+	if (INTEL_GEN(dev_priv) >= 12 && !mode_is_4k(dev_priv)) {
+		dev_priv->max_cdclk_freq = 172800;
+	} else if (IS_ELKHARTLAKE(dev_priv)) {
 		if (dev_priv->cdclk.hw.ref == 24000)
 			dev_priv->max_cdclk_freq = 552000;
 		else
diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.h b/drivers/gpu/drm/i915/display/intel_cdclk.h
index 4d6f7f5f8930..cefb5146ddca 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.h
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.h
@@ -15,6 +15,9 @@ struct intel_atomic_state;
 struct intel_cdclk_state;
 struct intel_crtc_state;
 
+#define WIDTH_4K  3860
+#define HEIGHT_4K 2160
+
 int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state);
 void intel_cdclk_init(struct drm_i915_private *i915);
 void intel_cdclk_uninit(struct drm_i915_private *i915);
-- 
2.17.1