From: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Date: Fri, 11 May 2018 12:51:40 -0700
Subject: drm/i915/psr: Avoid DPCD reads when panel does not support PSR
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Git-commit: 8cf6da7ef755c8e09094baae941134b771bd4344
Patch-mainline: v4.19-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Ville noticed that we are unncessarily reading DPCD's after knowing
panel did not support PSR. Looks like this check that was present
earlier got removed unintentionally, let's put it back.

While we do this, add the PSR version number in the debug print.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Tarun Vyas <tarun.vyas@intel.com>
Reviewed-by: Vathsala Nagaraju <vathsala.nagaraju@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180511195145.3829-1-dhinakaran.pandiyan@intel.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/i915/intel_psr.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -246,10 +246,12 @@ void intel_psr_init_dpcd(struct intel_dp
 	drm_dp_dpcd_read(&intel_dp->aux, DP_PSR_SUPPORT, intel_dp->psr_dpcd,
 			 sizeof(intel_dp->psr_dpcd));
 
-	if (intel_dp->psr_dpcd[0]) {
-		dev_priv->psr.sink_support = true;
-		DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
-	}
+	if (!intel_dp->psr_dpcd[0])
+		return;
+
+	DRM_DEBUG_KMS("eDP panel supports PSR version %x\n",
+		      intel_dp->psr_dpcd[0]);
+	dev_priv->psr.sink_support = true;
 
 	if (INTEL_GEN(dev_priv) >= 9 &&
 	    (intel_dp->psr_dpcd[0] == DP_PSR2_WITH_Y_COORD_IS_SUPPORTED)) {
@@ -266,8 +268,8 @@ void intel_psr_init_dpcd(struct intel_dp
 		 */
 		dev_priv->psr.sink_psr2_support =
 				intel_dp_get_y_coord_required(intel_dp);
-		DRM_DEBUG_KMS("PSR2 %s on sink", dev_priv->psr.sink_psr2_support
-			      ? "supported" : "not supported");
+		DRM_DEBUG_KMS("PSR2 %ssupported\n",
+			      dev_priv->psr.sink_psr2_support ? "" : "not ");
 
 		if (dev_priv->psr.sink_psr2_support) {
 			dev_priv->psr.colorimetry_support =