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

[Mika Kahola]

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.kah...@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrj...@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 91c19e0a98d7..ee48a6b87184 100644
--- a/drivers/gpu/drm/i915/display/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
@@ -1454,6 +1454,7 @@ 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;
 
@@ -1491,7 +1492,21 @@ 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