drm/i915: program drain latency regs on ValleyView

This patch adds support for programming drain latency registers of Pondicherry
memory arbiter of Valleyview.

v2: clarify function names (Daniel)
    fix summary typo (Daniel)
v3: add parens (Ben)
    make drain function return bool (Ben)

Acked-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Gajanan Bhat <gajanan.bhat@intel.com>
Reviewed-by: Shobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: Vijay Purushothaman <vijay.a.purushothaman@intel.com>
Reviewed-by: Jesse Barnes <jesse.barnes@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
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 58914b4..2f6576d 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2555,6 +2555,22 @@
 #define   DSPFW_HPLL_CURSOR_MASK	(0x3f<<16)
 #define   DSPFW_HPLL_SR_MASK		(0x1ff)
 
+/* drain latency register values*/
+#define DRAIN_LATENCY_PRECISION_32	32
+#define DRAIN_LATENCY_PRECISION_16	16
+#define VLV_DDL1			0x70050
+#define DDL_CURSORA_PRECISION_32	(1<<31)
+#define DDL_CURSORA_PRECISION_16	(0<<31)
+#define DDL_CURSORA_SHIFT		24
+#define DDL_PLANEA_PRECISION_32		(1<<7)
+#define DDL_PLANEA_PRECISION_16		(0<<7)
+#define VLV_DDL2			0x70054
+#define DDL_CURSORB_PRECISION_32	(1<<31)
+#define DDL_CURSORB_PRECISION_16	(0<<31)
+#define DDL_CURSORB_SHIFT		24
+#define DDL_PLANEB_PRECISION_32		(1<<7)
+#define DDL_PLANEB_PRECISION_16		(0<<7)
+
 /* FIFO watermark sizes etc */
 #define G4X_FIFO_LINE_SIZE	64
 #define I915_FIFO_LINE_SIZE	64