drm/i915: ValleyView mode setting limits and PLL functions

Add some VLV limit structures and update the PLL code.

v2: resolve conflicts, Vijay to re-post with PLL valid checks and fixed limits
v3: re-add dpio write function
v4: squash in Vijay's fixes for the PLL limits and clean up the m/n finder

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Vijay Purushothaman <vijay.a.purushothaman@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 782e5d1..b6f5f10 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -904,6 +904,7 @@
 #define   DPLL_P2_CLOCK_DIV_MASK	0x03000000 /* i915 */
 #define   DPLL_FPA01_P1_POST_DIV_MASK	0x00ff0000 /* i915 */
 #define   DPLL_FPA01_P1_POST_DIV_MASK_PINEVIEW	0x00ff8000 /* Pineview */
+#define   DPLL_LOCK_VLV			(1<<15)
 #define   DPLL_INTEGRATED_CLOCK_VLV	(1<<13)
 
 #define SRX_INDEX		0x3c4