drm/i915/mtl: Fix rawclk for Meteorlake PCH

MTL has a fixed rawclk of 38400Khz. Register does not need to be
reprogrammed.

Bspec: 49304
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220818234202.451742-13-radhakrishna.sripada@intel.com

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

@@ -3036,6 +3036,13 @@ u32 intel_read_rawclk(struct drm_i915_private *dev_priv)
 
 	if (INTEL_PCH_TYPE(dev_priv) >= PCH_DG1)
 		freq = dg1_rawclk(dev_priv);
+	else if (INTEL_PCH_TYPE(dev_priv) >= PCH_MTP)
+		/*
+		 * MTL always uses a 38.4 MHz rawclk.  The bspec tells us
+		 * "RAWCLK_FREQ defaults to the values for 38.4 and does
+		 * not need to be programmed."
+		 */
+		freq = 38400;
 	else if (INTEL_PCH_TYPE(dev_priv) >= PCH_CNP)
 		freq = cnp_rawclk(dev_priv);
 	else if (HAS_PCH_SPLIT(dev_priv))