drm/i915/display/dmc: Set DC_STATE_DEBUG_MASK_CORES after firmware load

Specification asks for DC_STATE_DEBUG_MASK_CORES to be set for all
platforms that supports DMC, not only for geminilake and broxton.

While at is also taking the oportunity to simply the code.

BSpec: 7402
BSpec: 49436
Reviewed-by: Imre Deak <imre.deak@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210922215242.66683-1-jose.souza@intel.com

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

@@ -255,20 +255,10 @@ intel_get_stepping_info(struct drm_i915_private *i915,
 
 static void gen9_set_dc_state_debugmask(struct drm_i915_private *dev_priv)
 {
-	u32 val, mask;
-
-	mask = DC_STATE_DEBUG_MASK_MEMORY_UP;
-
-	if (IS_GEMINILAKE(dev_priv) || IS_BROXTON(dev_priv))
-		mask |= DC_STATE_DEBUG_MASK_CORES;
-
 	/* The below bit doesn't need to be cleared ever afterwards */
-	val = intel_de_read(dev_priv, DC_STATE_DEBUG);
-	if ((val & mask) != mask) {
-		val |= mask;
-		intel_de_write(dev_priv, DC_STATE_DEBUG, val);
-		intel_de_posting_read(dev_priv, DC_STATE_DEBUG);
-	}
+	intel_de_rmw(dev_priv, DC_STATE_DEBUG, 0,
+		     DC_STATE_DEBUG_MASK_CORES | DC_STATE_DEBUG_MASK_MEMORY_UP);
+	intel_de_posting_read(dev_priv, DC_STATE_DEBUG);
 }
 
 /**