FAILED: patch "[PATCH] drm/i915: Disable LTTPR support when the DPCD rev < 1.4" failed to apply to 5.12-stable tree

The patch below does not apply to the 5.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 264613b406eb0d74cd9ca582c717c5e2c5a975ea Mon Sep 17 00:00:00 2001
From: Imre Deak <[email protected]>
Date: Wed, 17 Mar 2021 21:01:49 +0200
Subject: [PATCH] drm/i915: Disable LTTPR support when the DPCD rev < 1.4
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By the specification the 0xF0000-0xF02FF range is only valid when the DPCD revision is 1.4 or higher. Disable LTTPR support if this isn't so.

Trying to detect LTTPRs returned corrupted values for the above DPCD range at least on a Skylake host with an LG 43UD79-B monitor with a DPCD revision 1.2 connected.

v2: Add the actual version check.
v3: Fix s/DRPX/DPRX/ typo.

index d46cd205241c..2c98335c260c 100644
@@ -3709,9 +3709,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 {
 	int ret;
 
-	intel_dp_lttpr_init(intel_dp);
-
-	if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd))
+	if (intel_dp_init_lttpr_and_dprx_caps(intel_dp) < 0)
 		return false;
 
 	/*

index 6a1f76bd8c75..9cb7c28027f0 100644
@@ -11,7 +11,7 @@
 struct intel_crtc_state;
 struct intel_dp;
 
-int intel_dp_lttpr_init(struct intel_dp *intel_dp);
+int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp);
 
 void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 			       const struct intel_crtc_state *crtc_state,