drm/i915/skl: Derive the max CDCLK from DFSM

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 89fd7c8..760dbeb 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5761,6 +5761,13 @@
 #define HSW_NDE_RSTWRN_OPT	0x46408
 #define  RESET_PCH_HANDSHAKE_ENABLE	(1<<4)
 
+#define SKL_DFSM			0x51000
+#define SKL_DFSM_CDCLK_LIMIT_MASK	(3 << 23)
+#define SKL_DFSM_CDCLK_LIMIT_675	(0 << 23)
+#define SKL_DFSM_CDCLK_LIMIT_540	(1 << 23)
+#define SKL_DFSM_CDCLK_LIMIT_450	(2 << 23)
+#define SKL_DFSM_CDCLK_LIMIT_337_5	(3 << 23)
+
 #define FF_SLICE_CS_CHICKEN2			0x20e4
 #define  GEN9_TSG_BARRIER_ACK_DISABLE		(1<<8)