[PATCH 2/2] drm/i915/psr: Set frames before SU entry for psr2

[vathsala nagaraju]

Set frames before SU entry value for max resync frame count of
dpcd register 2009, bit field 0:3.

Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
CC: Puthikorn Voravootivat <puthik at chromium.org>
Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju at intel.com>
---
 drivers/gpu/drm/i915/intel_psr.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
index acb5094..04b253f 100644
--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -327,6 +327,7 @@ static void hsw_activate_psr2(struct intel_dp *intel_dp)
 	 */
 	uint32_t idle_frames = max(6, dev_priv->vbt.psr.idle_frames);
 	uint32_t val;
+	uint8_t sink_latency;
 
 	val = idle_frames << EDP_PSR_IDLE_FRAME_SHIFT;
 
@@ -334,8 +335,15 @@ static void hsw_activate_psr2(struct intel_dp *intel_dp)
 	 * mesh at all with our frontbuffer tracking. And the hw alone isn't
 	 * good enough. */
 	val |= EDP_PSR2_ENABLE |
-		EDP_SU_TRACK_ENABLE |
-		EDP_FRAMES_BEFORE_SU_ENTRY;
+		EDP_SU_TRACK_ENABLE;
+
+	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_SINK_SYNCHRONIZATION_LATENCY,
+				&sink_latency)) {
+		sink_latency = sink_latency & DP_MAX_RESYNC_FRAME_CNT_MASK;
+		val |= (sink_latency + 1) << EDP_PSR2_FRAME_BEFORE_SU_SHIFT;
+	} else {
+		val |= EDP_FRAMES_BEFORE_SU_ENTRY;
+	}
 
 	if (dev_priv->vbt.psr.tp2_tp3_wakeup_time > 5)
 		val |= EDP_PSR2_TP2_TIME_2500;
-- 
1.9.1