linux-kernel - [PATCH 4.4 72/73] drm/radeon: fix DP link training issue with second 4K monitor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20160517011454.940577036@linuxfoundation.org>
Date:	Mon, 16 May 2016 18:15:42 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Arindam Nath <arindam.nath@....com>,
	Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 4.4 72/73] drm/radeon: fix DP link training issue with second 4K monitor

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arindam Nath <arindam.nath@....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@....com>
Reviewed-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);