[Intel-gfx] [PATCH 2/4] drm/i915/display/dg2: Read CD clock from squasher table

[Mika Kahola <mika.kahola@intel.com>]

To calculate CD clock with squasher unit, we set CD clock ratio to fixed value of 34.
The CD clock value is read from CD clock squasher table.

BSpec: 54034

v2: Read ratio from register (Ville)
    Drop unnecessary local variable (Ville)
    Get CD clock from the given table
v3: Calculate CD clock frequency based on waveform bit pattern (Ville)
[v4: vsyrjala: Actually do a proper blind readout from the hardware]
[v5: vsyrjala: Use has_cdclk_squasher()]

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_cdclk.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
index 7af4cb965060..630a53d4f882 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -1461,6 +1461,7 @@ static void bxt_de_pll_readout(struct drm_i915_private *dev_priv,
 static void bxt_get_cdclk(struct drm_i915_private *dev_priv,
 			  struct intel_cdclk_config *cdclk_config)
 {
+	u32 squash_ctl = 0;
 	u32 divider;
 	int div;
 
@@ -1498,7 +1499,21 @@ static void bxt_get_cdclk(struct drm_i915_private *dev_priv,
 		return;
 	}
 
-	cdclk_config->cdclk = DIV_ROUND_CLOSEST(cdclk_config->vco, div);
+	if (has_cdclk_squasher(dev_priv))
+		squash_ctl = intel_de_read(dev_priv, CDCLK_SQUASH_CTL);
+
+	if (squash_ctl & CDCLK_SQUASH_ENABLE) {
+		u16 waveform;
+		int size;
+
+		size = REG_FIELD_GET(CDCLK_SQUASH_WINDOW_SIZE_MASK, squash_ctl) + 1;
+		waveform = REG_FIELD_GET(CDCLK_SQUASH_WAVEFORM_MASK, squash_ctl) >> (16 - size);
+
+		cdclk_config->cdclk = DIV_ROUND_CLOSEST(hweight16(waveform) *
+							cdclk_config->vco, size * div);
+	} else {
+		cdclk_config->cdclk = DIV_ROUND_CLOSEST(cdclk_config->vco, div);
+	}
 
  out:
 	/*
-- 
2.27.0