This is a note to let you know that I've just added the patch titled
drm/amdgpu: Disable RPM helpers while reprobing connectors on resume
to the 4.7-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-amdgpu-disable-rpm-helpers-while-reprobing-connectors-on-resume.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 23a1a9e54e71593fe5657e883662995d181d2d6b Mon Sep 17 00:00:00 2001
From: Lyude <cpaul@xxxxxxxxxx>
Date: Mon, 18 Jul 2016 11:41:37 -0400
Subject: drm/amdgpu: Disable RPM helpers while reprobing connectors on resume
From: Lyude <cpaul@xxxxxxxxxx>
commit 23a1a9e54e71593fe5657e883662995d181d2d6b upstream.
Just about all of amdgpu's connector probing functions try to acquire
runtime PM refs. If we try to do this in the context of
amdgpu_resume_kms by calling drm_helper_hpd_irq_event(), we end up
deadlocking the system.
Since we're guaranteed to be holding the spinlock for RPM in
amdgpu_resume_kms, and we already know the GPU is in working order, we
need to prevent the RPM helpers from trying to run during the initial
connector reprobe on resume.
There's a couple of solutions I've explored for fixing this, but this
one by far seems to be the simplest and most reliable (plus I'm pretty
sure that's what disable_depth is there for anyway).
Reproduction recipe:
- Get any laptop dual GPUs using PRIME
- Make sure runtime PM is enabled for amdgpu
- Boot the machine
- If the machine managed to boot without hanging, switch out of X to
another VT. This should definitely cause X to hang infinitely.
Changes since v1:
- add appropriate #ifdef checks for CONFIG_PM. This is not very
useful, but it appears some kernel test suites test compiling amdgpu
with CONFIG_PM disabled, which results in this patch breaking the builds
if we don't include this #ifdef
Cc: Alex Deucher <alexdeucher@xxxxxxxxx>
Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Lyude <cpaul@xxxxxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -1841,7 +1841,23 @@ int amdgpu_resume_kms(struct drm_device
}
drm_kms_helper_poll_enable(dev);
+
+ /*
+ * Most of the connector probing functions try to acquire runtime pm
+ * refs to ensure that the GPU is powered on when connector polling is
+ * performed. Since we're calling this from a runtime PM callback,
+ * trying to acquire rpm refs will cause us to deadlock.
+ *
+ * Since we're guaranteed to be holding the rpm lock, it's safe to
+ * temporarily disable the rpm helpers so this doesn't deadlock us.
+ */
+#ifdef CONFIG_PM
+ dev->dev->power.disable_depth++;
+#endif
drm_helper_hpd_irq_event(dev);
+#ifdef CONFIG_PM
+ dev->dev->power.disable_depth--;
+#endif
if (fbcon) {
amdgpu_fbdev_set_suspend(adev, 0);
Patches currently in stable-queue which might be from cpaul@xxxxxxxxxx are
queue-4.7/drm-amdgpu-poll-for-both-connect-disconnect-on-analog-connectors.patch
queue-4.7/drm-radeon-poll-for-both-connect-disconnect-on-analog-connectors.patch
queue-4.7/drm-amdgpu-disable-rpm-helpers-while-reprobing-connectors-on-resume.patch
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