FAILED: patch "[PATCH] drm/i915: Disable LTTPR support when the LTTPR 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 [off-list ref].

thanks,

greg k-h

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

From 1663ad4936e0679443a315fe342f99636a2420dd Mon Sep 17 00:00:00 2001
From: Imre Deak <redacted>
Date: Wed, 17 Mar 2021 20:49:01 +0200
Subject: [PATCH] drm/i915: Disable LTTPR support when the LTTPR rev < 1.4
MIME-Version: 1.0
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By the specification the 0xF0000 - 0xF02FF range is only valid if the
LTTPR revision at 0xF0000 is at least 1.4. Disable the LTTPR support
otherwise.

Fixes: 7b2a4ab8b0ef ("drm/i915: Switch to LTTPR transparent mode link training")
Cc: <redacted> # v5.11
Cc: Ville Syrjälä <redacted>
Signed-off-by: Imre Deak <redacted>
Reviewed-by: Ville Syrjälä <redacted>
Link: https://patchwork.freedesktop.org/patch/msgid/20210317184901.4029798-4-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index f14ac2694183..7d4e6f3e7e93 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c

@@ -100,17 +100,23 @@ static bool intel_dp_read_lttpr_common_caps(struct intel_dp *intel_dp)
 		return false;
 
 	if (drm_dp_read_lttpr_common_caps(&intel_dp->aux,
-					  intel_dp->lttpr_common_caps) < 0) {
-		intel_dp_reset_lttpr_common_caps(intel_dp);
-		return false;
-	}
+					  intel_dp->lttpr_common_caps) < 0)
+		goto reset_caps;
 
 	drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
 		    "LTTPR common capabilities: %*ph\n",
 		    (int)sizeof(intel_dp->lttpr_common_caps),
 		    intel_dp->lttpr_common_caps);
 
+	/* The minimum value of LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV is 1.4 */
+	if (intel_dp->lttpr_common_caps[0] < 0x14)
+		goto reset_caps;
+
 	return true;
+
+reset_caps:
+	intel_dp_reset_lttpr_common_caps(intel_dp);
+	return false;
 }
 
 static bool