linux-kernel - [PATCH 4.2.y-ckt 101/273] drm/dp/mst: Reverse order of MST enable and clearing VC payload table.

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Message-Id: <1457391064-6660-102-git-send-email-kamal@canonical.com>
Date:	Mon,  7 Mar 2016 14:48:12 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Andrey Grodzovsky <Andrey.Grodzovsky@....com>,
	Dave Airlie <airlied@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 101/273] drm/dp/mst: Reverse order of MST enable and clearing VC payload table.

4.2.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Andrey Grodzovsky <Andrey.Grodzovsky@....com>

commit c175cd16df272119534058f28cbd5eeac6ff2d24 upstream.

On DELL U3014 if you clear the table before enabling MST it sometimes
hangs the receiver.

Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@....com>
Reviewed-by: Harry Wentland <harry.wentland@....com>
Acked-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 0ec9ad5..2c691b3 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1969,6 +1969,12 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 		mgr->mst_primary = mstb;
 		kref_get(&mgr->mst_primary->kref);
 
+		ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
+							 DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
+		if (ret < 0) {
+			goto out_unlock;
+		}
+
 		{
 			struct drm_dp_payload reset_pay;
 			reset_pay.start_slot = 0;
@@ -1976,12 +1982,6 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 			drm_dp_dpcd_write_payload(mgr, 0, &reset_pay);
 		}
 
-		ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
-					 DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
-		if (ret < 0) {
-			goto out_unlock;
-		}
-
 
 		/* sort out guid */
 		ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, mgr->guid, 16);
-- 
2.7.0