drm/i915/d13: Add Wa_16015201720 disabling clock gating for PIPEDMC-A/B

Add a workaround making sure that PIPEDMC-A/B is enabled when the
firmware needs these on D13 platforms to save/restore the registers
backed by the PW_1 and PW_A power wells.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220727164523.1621361-2-imre.deak@intel.com
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index d38939a..0d1b002 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1892,6 +1892,13 @@
 #define CLKGATE_DIS_PSL(pipe) \
 	_MMIO_PIPE(pipe, _CLKGATE_DIS_PSL_A, _CLKGATE_DIS_PSL_B)
 
+#define _CLKGATE_DIS_PSL_EXT_A		0x4654C
+#define _CLKGATE_DIS_PSL_EXT_B		0x46550
+#define   PIPEDMC_GATING_DIS		REG_BIT(12)
+
+#define CLKGATE_DIS_PSL_EXT(pipe) \
+	_MMIO_PIPE(pipe, _CLKGATE_DIS_PSL_EXT_A, _CLKGATE_DIS_PSL_EXT_B)
+
 /*
  * Display engine regs
  */