[Intel-gfx] [PATCH v2] drm/i915/edp: Read link status after exit link training

[Lee, Shawn C]

From: "Lee, Shawn C" <shawn.c.lee at intel.com>

Display driver read DPCD register 0x202, 0x203 and 0x204 to identify
eDP sink status. If PSR exit is ongoing at eDP sink, and eDP source
read these registers at the same time. Panel will report EQ & symbol
lock not done. It will cause panel display flicking.
So driver have to make sure PSR already exit before read link status.

Change log:
v2:
- Use intel_wait_for_register() to replace I915_READ().

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99639
TEST=Reboot DUT and no flicking on local display at login screen

Cc: Cooper Chiou <cooper.chiou at intel.com>
Cc: Gary C Wang <gary.c.wang at intel.com>
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Jim Bride <jim.bride at intel.com>
Cc: Ryan Lin <ryan.lin at intel.com>

Signed-off-by: Shawn Lee <shawn.c.lee at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c |   33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 08834f74d396..099b6c0605a7 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4252,19 +4252,34 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 }
 
 static void
+intel_edp_wait_PSR_exit(struct intel_dp *intel_dp)
+{
+	struct drm_device *dev = intel_dp_to_dev(intel_dp);
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u16 count = 100;
+
+	while (count--)
+		if (!intel_wait_for_register(dev_priv,
+			    EDP_PSR_STATUS_CTL,
+			    (EDP_PSR_STATUS_SENDING_TP1 |
+			     EDP_PSR_STATUS_SENDING_TP2_TP3 |
+			     EDP_PSR_STATUS_SENDING_IDLE |
+			     EDP_PSR_STATUS_AUX_SENDING),
+			     0,
+			     1))
+			return;
+}
+
+static void
 intel_dp_check_link_status(struct intel_dp *intel_dp)
 {
 	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
 	struct drm_device *dev = intel_dp_to_dev(intel_dp);
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
 	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
 
-	if (!intel_dp_get_link_status(intel_dp, link_status)) {
-		DRM_ERROR("Failed to get link status\n");
-		return;
-	}
-
 	if (!intel_encoder->base.crtc)
 		return;
 
@@ -4278,6 +4293,14 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 	if (!intel_dp_link_params_valid(intel_dp))
 		return;
 
+	if (is_edp(intel_dp) && dev_priv->psr.enabled)
+		intel_edp_wait_PSR_exit(intel_dp);
+
+	if (!intel_dp_get_link_status(intel_dp, link_status)) {
+		DRM_ERROR("Failed to get link status\n");
+		return;
+	}
+
 	/* Retrain if Channel EQ or CR not ok */
 	if (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count)) {
 		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
-- 
1.7.9.5