drm/i915/display: Check if FBC is fused off

Check if FBC is fused off and handle it.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Martin Peres <martin.peres@linux.intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191026001323.216052-3-jose.souza@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -7743,6 +7743,7 @@ enum {
 #define   CNL_DDI_CLOCK_REG_ACCESS_ON	(1 << 7)
 
 #define SKL_DFSM			_MMIO(0x51000)
+#define   SKL_DFSM_DISPLAY_PM_DISABLE	(1 << 27)
 #define   SKL_DFSM_DISPLAY_HDCP_DISABLE	(1 << 25)
 #define   SKL_DFSM_CDCLK_LIMIT_MASK	(3 << 23)
 #define   SKL_DFSM_CDCLK_LIMIT_675	(0 << 23)

drivers/gpu/drm/i915/intel_device_info.c

@@ -984,6 +984,9 @@ void intel_device_info_runtime_init(struct drm_i915_private *dev_priv)
 
 		if (dfsm & SKL_DFSM_DISPLAY_HDCP_DISABLE)
 			info->display.has_hdcp = 0;
+
+		if (dfsm & SKL_DFSM_DISPLAY_PM_DISABLE)
+			info->display.has_fbc = 0;
 	}
 
 	/* Initialize slice/subslice/EU info */