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[PATCH 4.2.y-ckt 09/53] drm/radeon: fix DP link training issue with second 4K monitor

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4.2.8-ckt11 -stable review patch.  If anyone has any objections, please let me know.

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

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: Kamal Mostafa <kamal@canonical.com>
---
 drivers/gpu/drm/radeon/radeon_dp_auxch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/radeon/radeon_dp_auxch.c b/drivers/gpu/drm/radeon/radeon_dp_auxch.c
index 3b0c229..db64e00 100644
--- 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_dp_aux *aux, struct drm_dp_aux_msg *msg
 
 	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);
 
-- 
2.7.4

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[4.2.y-ckt stable] Linux 4.2.8-ckt11 stable review Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:00 +0200
  [PATCH 4.2.y-ckt 19/53] ALSA: usb-audio: Yet another Phoneix Audio device quirk Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:00 +0200
  [PATCH 4.2.y-ckt 32/53] net: fec: only clear a queue's work bit if the queue was emptied Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 27/53] macvtap: segmented packet is consumed Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 42/53] net_sched: update hierarchical backlog too Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 30/53] bridge: fix igmp / mld query parsing Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 24/53] workqueue: fix rebind bound workers warning Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 25/53] ocfs2: fix posix_acl_create deadlock Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 39/53] ipv4/fib: don't warn when primary address is missing if in_dev is dead Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
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  [PATCH 4.2.y-ckt 46/53] net: fix infoleak in llc Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 37/53] net: use skb_postpush_rcsum instead of own implementations Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 34/53] net/route: enforce hoplimit max value Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
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  [PATCH 4.2.y-ckt 36/53] route: do not cache fib route info on local routes with oif Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 43/53] sch_htb: update backlog as well Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 14/53] drm/i915: Bail out of pipe config compute loop on LPT Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
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  [PATCH 4.2.y-ckt 29/53] arm64: bpf: jit JMP_JSET_{X,K} Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 17/53] vfs: add vfs_select_inode() helper Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 41/53] net_sched: introduce qdisc_replace() helper Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
  [PATCH 4.2.y-ckt 18/53] vfs: rename: check backing inode being equal Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:10 +0200
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  [PATCH 4.2.y-ckt 10/53] drm/radeon: fix PLL sharing on DCE6.1 (v2) Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:20 +0200
  [PATCH 4.2.y-ckt 04/53] regmap: spmi: Fix regmap_spmi_ext_read in multi-byte case Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:20 +0200
  [PATCH 4.2.y-ckt 13/53] Input: max8997-haptic - fix NULL pointer dereference Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:20 +0200
  [PATCH 4.2.y-ckt 11/53] get_rock_ridge_filename(): handle malformed NM entries Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:20 +0200
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  [PATCH 4.2.y-ckt 09/53] drm/radeon: fix DP link training issue with second 4K monitor Kamal Mostafa <kamal@canonical.com> - 2016-05-24 20:20 +0200

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