[PATCH] UBUNTU: SAUCE: i915_bpo: drm/i915/skl: Do not enter MST mode during DP probing for DisplayPort MST-enabled hub

[Timo Aaltonen]

From: Gary Wang <gary.c.wang at intel.com>

BugLink: http://bugs.launchpad.net/bugs/1532127

It was found out that DP MST-enabled hub is causing problems of DP link
computation on SKL-U, and need to disable its MST support.

This is a workaround, and need to be fixed further.

References: https://bugs.freedesktop.org/show_bug.cgi?id=91791

Signed-off-by: Gary Wang <gary.c.wang at intel.com>
Signed-off-by: Timo Aaltonen <timo.aaltonen at canonical.com>
---
 ubuntu/i915/intel_dp.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
 mode change 100644 => 100755 ubuntu/i915/intel_dp.c

diff --git a/ubuntu/i915/intel_dp.c b/ubuntu/i915/intel_dp.c
old mode 100644
new mode 100755
index daa1ce2..de89b8f
--- a/ubuntu/i915/intel_dp.c
+++ b/ubuntu/i915/intel_dp.c
@@ -4042,12 +4042,16 @@ intel_dp_probe_oui(struct intel_dp *intel_dp)
 static bool
 intel_dp_probe_mst(struct intel_dp *intel_dp)
 {
+	struct drm_device *dev = intel_dp_to_dev(intel_dp);
 	u8 buf[1];
 
 	if (!intel_dp->can_mst)
 		return false;
 
-	if (intel_dp->dpcd[DP_DPCD_REV] < 0x12)
+	//TO-DO, this is workaround for test purpose only on disabling DP 1.2 MST
+	//SKL-U suffers error from DP data link computation with DP MST enabled.
+	//fix-BUG https://bugs.freedesktop.org/show_bug.cgi?id=91791
+	if (intel_dp->dpcd[DP_DPCD_REV] < 0x12 || IS_SKYLAKE(dev))
 		return false;
 
 	if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_MSTM_CAP, buf, 1)) {
-- 
2.5.0