drm/i915: Read out display FIFO size on VLV/CHV

VLV/CHV have similar DSPARB registers as older platforms, just more of
them due to more planes. Add a bit of code to read out the current FIFO
split from the registers. Will be useful later when we improve the WM
calculations.

v2: Add display_mmio_offset to DSPARB

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 258d6a7..7d11bca 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4065,7 +4065,7 @@
 #define   DPINVGTT_STATUS_MASK			0xff
 #define   DPINVGTT_STATUS_MASK_CHV		0xfff
 
-#define DSPARB			0x70030
+#define DSPARB			(dev_priv->info.display_mmio_offset + 0x70030)
 #define   DSPARB_CSTART_MASK	(0x7f << 7)
 #define   DSPARB_CSTART_SHIFT	7
 #define   DSPARB_BSTART_MASK	(0x7f)
@@ -4073,6 +4073,9 @@
 #define   DSPARB_BEND_SHIFT	9 /* on 855 */
 #define   DSPARB_AEND_SHIFT	0
 
+#define DSPARB2			(VLV_DISPLAY_BASE + 0x70060) /* vlv/chv */
+#define DSPARB3			(VLV_DISPLAY_BASE + 0x7006c) /* chv */
+
 /* pnv/gen4/g4x/vlv/chv */
 #define DSPFW1			(dev_priv->info.display_mmio_offset + 0x70034)
 #define   DSPFW_SR_SHIFT		23