drm/i915/cdclk: Remove the assumption that cdclk divider==2 when using squashing

Currently we have a hardcoded assumption that the cdclk divider
(2*cd2x divider) is always 2 when squashing is used. While that
is true for all current platforms it might not hold in the future.
So eliminate the assumption and calculate the correct divider
from the other parameters.

v2: s/cd2x divider/cdclk divider/ (Gustavo)
    s/clock/unsquashed_cdclk/ (Gustavo)

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231211221636.29658-1-ville.syrjala@linux.intel.com

Author: vsyrjala

drivers/gpu/drm/i915/display/intel_cdclk.c

@@ -1880,9 +1880,9 @@ static void _bxt_set_cdclk(struct drm_i915_private *dev_priv,
 {
 	int cdclk = cdclk_config->cdclk;
 	int vco = cdclk_config->vco;
-	u32 val;
+	int unsquashed_cdclk;
 	u16 waveform;
-	int clock;
+	u32 val;
 
 	if (HAS_CDCLK_CRAWL(dev_priv) && dev_priv->display.cdclk.hw.vco > 0 && vco > 0 &&
 	    !cdclk_pll_is_unknown(dev_priv->display.cdclk.hw.vco)) {
@@ -1899,15 +1899,13 @@ static void _bxt_set_cdclk(struct drm_i915_private *dev_priv,
 
 	waveform = cdclk_squash_waveform(dev_priv, cdclk);
 
-	if (waveform)
-		clock = vco / 2;
-	else
-		clock = cdclk;
+	unsquashed_cdclk = DIV_ROUND_CLOSEST(cdclk * cdclk_squash_len,
+					     cdclk_squash_divider(waveform));
 
 	if (HAS_CDCLK_SQUASH(dev_priv))
 		dg2_cdclk_squash_program(dev_priv, waveform);
 
-	val = bxt_cdclk_cd2x_div_sel(dev_priv, clock, vco) |
+	val = bxt_cdclk_cd2x_div_sel(dev_priv, unsquashed_cdclk, vco) |
 		bxt_cdclk_cd2x_pipe(dev_priv, pipe);
 
 	/*