drm/i915: BDW PSR: Add single frame update support.

When link is in stand by and PSR exit is triggered by a primary or sprite
plane flip this mode allows only one single updated frame to be send to
display than get back to PSR immediately.

Reviewed-by: Vijay Purushothaman <vijay.a.purushothaman@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -2409,6 +2409,7 @@ enum punit_power_well {
 #define EDP_PSR_BASE(dev)                       (IS_HASWELL(dev) ? 0x64800 : 0x6f800)
 #define EDP_PSR_CTL(dev)			(EDP_PSR_BASE(dev) + 0)
 #define   EDP_PSR_ENABLE			(1<<31)
+#define   BDW_PSR_SINGLE_FRAME			(1<<30)
 #define   EDP_PSR_LINK_DISABLE			(0<<27)
 #define   EDP_PSR_LINK_STANDBY			(1<<27)
 #define   EDP_PSR_MIN_LINK_ENTRY_TIME_MASK	(3<<25)

drivers/gpu/drm/i915/intel_dp.c

@@ -1723,6 +1723,7 @@ static void intel_edp_psr_enable_source(struct intel_dp *intel_dp)
 		val |= EDP_PSR_TP2_TP3_TIME_0us;
 		val |= EDP_PSR_TP1_TIME_0us;
 		val |= EDP_PSR_SKIP_AUX_EXIT;
+		val |= IS_BROADWELL(dev) ? BDW_PSR_SINGLE_FRAME : 0;
 	} else
 		val |= EDP_PSR_LINK_DISABLE;