Attachment 128339 Details for Bug 98990 – Suggested patch removes oops

[patch] Suggested patch removes oops

0001-drm-dp-mst-fix-kernel-oops-when-turning-off-secondar.patch (text/plain), 2.06 KB, created by Pierre Bossart on 2016-12-05 01:22:20 UTC

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Creator: Pierre Bossart

Created: 2016-12-05 01:22:20 UTC

Size: 2.06 KB

patch

obsolete

>From 6945f9f68a9dc5ea718761b723cab56b128c347b Mon Sep 17 00:00:00 2001
>From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
>Date: Sun, 4 Dec 2016 19:01:36 -0600
>Subject: [PATCH] drm/dp/mst: fix kernel oops when turning off secondary
> monitor
>
>100% reproducible issue found on SKL SkullCanyon NUC with two external
>DP daisy-chained monitors in DP/MST mode. When turning off or changing
>the input of the second monitor the machine stops with a kernel
>oops. This issue happened with 4.8.8 as well as drm/drm-intel-nightly.
>
>This issue is traced to an inconsistent control flow in
>drm_dp_update_payload_part1(): the 'port' pointer is set to NULL at
>the same time as'req_payload.num_slots' is set to zero, but the pointer
>is dereferenced even when req_payload.num_slot is zero.
>
>Fix by adding test condition to make sure both variables
>are used consistently. This removes the kernel oops.
>
>There are still annoying cases where the primary display goes black
>when the secondary display is turned off but it can be recovered from
>by playing with the monitor inputs and power buttons.
>
>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98990
>Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
>---
> drivers/gpu/drm/drm_dp_mst_topology.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
>index aa64448..5481fde 100644
>--- a/drivers/gpu/drm/drm_dp_mst_topology.c
>+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
>@@ -1815,7 +1815,7 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
> 				drm_dp_create_payload_step1(mgr, mgr->proposed_vcpis[i]->vcpi, &req_payload);
> 				mgr->payloads[i].num_slots = req_payload.num_slots;
> 				mgr->payloads[i].vcpi = req_payload.vcpi;
>-			} else if (mgr->payloads[i].num_slots) {
>+			} else if (mgr->payloads[i].num_slots && port != NULL) {
> 				mgr->payloads[i].num_slots = 0;
> 				drm_dp_destroy_payload_step1(mgr, port, port->vcpi.vcpi, &mgr->payloads[i]);
> 				req_payload.payload_state = mgr->payloads[i].payload_state;
>-- 
>2.7.4
>

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