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drm/amdgpu: Disable RPM helpers while reprobing connectors on resume

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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: stable@vger.kernel.org
Cc: Alex Deucher <alexdeucher@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Lyude <cpaul@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Lyude 2016-07-18 11:41:37 -04:00 committed by Alex Deucher
parent 69ee9742f9
commit 23a1a9e54e
1 changed files with 16 additions and 0 deletions
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16
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
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@ -1911,7 +1911,23 @@ int amdgpu_resume_kms(struct drm_device *dev, bool resume, bool fbcon)
}
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);