Patch "drm/radeon: fix DP link training issue with second 4K monitor" has been added to the 4.5-stable tree

Patch "drm/radeon: fix DP link training issue with second 4K monitor" has been added to the 4.5-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    drm/radeon: fix DP link training issue with second 4K monitor

to the 4.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-radeon-fix-dp-link-training-issue-with-second-4k-monitor.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 1a738347df2ee4977459a8776fe2c62196bdcb1b Mon Sep 17 00:00:00 2001
From: Arindam Nath <arindam.nath@amd.com>
Date: Wed, 4 May 2016 23:39:59 +0530
Subject: drm/radeon: fix DP link training issue with second 4K monitor

From: Arindam Nath <arindam.nath@amd.com>

commit 1a738347df2ee4977459a8776fe2c62196bdcb1b upstream.

There is an issue observed when we hotplug a second DP
4K monitor to the system. Sometimes, the link training
fails for the second monitor after HPD interrupt
generation.

The issue happens when some queued or deferred transactions
are already present on the AUX channel when we initiate
a new transcation to (say) get DPCD or during link training.

We set AUX_IGNORE_HPD_DISCON bit in the AUX_CONTROL
register so that we can ignore any such deferred
transactions when a new AUX transaction is initiated.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/radeon/radeon_dp_auxch.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/radeon/radeon_dp_auxch.c
+++ b/drivers/gpu/drm/radeon/radeon_dp_auxch.c
@@ -105,7 +105,7 @@ radeon_dp_aux_transfer_native(struct drm
 
 	tmp &= AUX_HPD_SEL(0x7);
 	tmp |= AUX_HPD_SEL(chan->rec.hpd);
-	tmp |= AUX_EN | AUX_LS_READ_EN;
+	tmp |= AUX_EN | AUX_LS_READ_EN | AUX_HPD_DISCON(0x1);
 
 	WREG32(AUX_CONTROL + aux_offset[instance], tmp);
 


Patches currently in stable-queue which might be from arindam.nath@amd.com are

queue-4.5/drm-radeon-fix-dp-link-training-issue-with-second-4k-monitor.patch