drm/i915/mtl: Fix Wa_16015201720 implementation

The commit 2357f2b2 ("drm/i915/mtl: Initial display workarounds")
extended the workaround Wa_16015201720 to MTL. However the registers
that the original WA implemented moved for MTL.

Implement the workaround with the correct register.

v3: Skip clock gating for pipe C, D DMC's and fix the title

Fixes: 2357f2b2 ("drm/i915/mtl: Initial display workarounds")
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230301201053.928709-2-radhakrishna.sripada@intel.com

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

@@ -424,15 +424,12 @@ static void disable_all_event_handlers(struct drm_i915_private *i915)
 	}
 }
 
-static void pipedmc_clock_gating_wa(struct drm_i915_private *i915, bool enable)
+static void adlp_pipedmc_clock_gating_wa(struct drm_i915_private *i915, bool enable)
 {
 	enum pipe pipe;
 
-	if (DISPLAY_VER(i915) < 13)
-		return;
-
 	/*
-	 * Wa_16015201720:adl-p,dg2, mtl
+	 * Wa_16015201720:adl-p,dg2
 	 * The WA requires clock gating to be disabled all the time
 	 * for pipe A and B.
 	 * For pipe C and D clock gating needs to be disabled only
@@ -448,6 +445,25 @@ static void pipedmc_clock_gating_wa(struct drm_i915_private *i915, bool enable)
 				     PIPEDMC_GATING_DIS, 0);
 }
 
+static void mtl_pipedmc_clock_gating_wa(struct drm_i915_private *i915)
+{
+	/*
+	 * Wa_16015201720
+	 * The WA requires clock gating to be disabled all the time
+	 * for pipe A and B.
+	 */
+	intel_de_rmw(i915, GEN9_CLKGATE_DIS_0, 0,
+		     MTL_PIPEDMC_GATING_DIS_A | MTL_PIPEDMC_GATING_DIS_B);
+}
+
+static void pipedmc_clock_gating_wa(struct drm_i915_private *i915, bool enable)
+{
+	if (DISPLAY_VER(i915) >= 14 && enable)
+		mtl_pipedmc_clock_gating_wa(i915);
+	else if (DISPLAY_VER(i915) == 13)
+		adlp_pipedmc_clock_gating_wa(i915, enable);
+}
+
 void intel_dmc_enable_pipe(struct drm_i915_private *i915, enum pipe pipe)
 {
 	enum intel_dmc_id dmc_id = PIPE_TO_DMC_ID(pipe);

drivers/gpu/drm/i915/i915_reg.h

@@ -1794,9 +1794,11 @@
  * GEN9 clock gating regs
  */
 #define GEN9_CLKGATE_DIS_0		_MMIO(0x46530)
-#define   DARBF_GATING_DIS		(1 << 27)
-#define   PWM2_GATING_DIS		(1 << 14)
-#define   PWM1_GATING_DIS		(1 << 13)
+#define   DARBF_GATING_DIS		REG_BIT(27)
+#define   MTL_PIPEDMC_GATING_DIS_A	REG_BIT(15)
+#define   MTL_PIPEDMC_GATING_DIS_B	REG_BIT(14)
+#define   PWM2_GATING_DIS		REG_BIT(14)
+#define   PWM1_GATING_DIS		REG_BIT(13)
 
 #define GEN9_CLKGATE_DIS_3		_MMIO(0x46538)
 #define   TGL_VRH_GATING_DIS		REG_BIT(31)