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From patchwork Fri Jul 8 15:37:35 2016
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Content-Type: text/plain; charset="utf-8"
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MIME-Version: 1.0
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Content-Transfer-Encoding: 7bit
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Subject: drm/amdgpu: Disable RPM helpers while reprobing connectors on resume
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From: cpaul@redhat.com
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X-Patchwork-Id: 97837
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Message-Id: <1467992256-23832-1-git-send-email-cpaul@redhat.com>
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To: amd-gfx@lists.freedesktop.org
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Cc: Tom St Denis <tom.stdenis@amd.com>, Jammy Zhou <Jammy.Zhou@amd.com>,
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open list <linux-kernel@vger.kernel.org>, stable@vger.kernel.org,
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"open list:RADEON and AMDGPU DRM DRIVERS"
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<dri-devel@lists.freedesktop.org>,
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Alex Deucher <alexander.deucher@amd.com>, Lyude <cpaul@redhat.com>,
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Flora Cui <Flora.Cui@amd.com>,
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=?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>,
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Monk Liu <Monk.Liu@amd.com>
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Date: Fri, 8 Jul 2016 11:37:35 -0400
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Just about all of amdgpu's connector probing functions try to acquire
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runtime PM refs. If we try to do this in the context of
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amdgpu_resume_kms by calling drm_helper_hpd_irq_event(), we end up
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deadlocking the system.
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Since we're guaranteed to be holding the spinlock for RPM in
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amdgpu_resume_kms, and we already know the GPU is in working order, we
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need to prevent the RPM helpers from trying to run during the initial
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connector reprobe on resume.
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There's a couple of solutions I've explored for fixing this, but this
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one by far seems to be the simplest and most reliable (plus I'm pretty
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sure that's what disable_depth is there for anyway).
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Reproduction recipe:
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- Get any laptop dual GPUs using PRIME
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- Make sure runtime PM is enabled for amdgpu
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- Boot the machine
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- If the machine managed to boot without hanging, switch out of X to
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another VT. This should definitely cause X to hang infinitely.
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Cc: stable@vger.kernel.org
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Signed-off-by: Lyude <cpaul@redhat.com>
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---
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drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 12 ++++++++++++
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1 file changed, 12 insertions(+)
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diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
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index 6e92008..46c1fee 100644
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--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
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+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
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@@ -1841,7 +1841,19 @@ int amdgpu_resume_kms(struct drm_device *dev, bool resume, bool fbcon)
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}
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drm_kms_helper_poll_enable(dev);
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+
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+ /*
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+ * Most of the connector probing functions try to acquire runtime pm
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+ * refs to ensure that the GPU is powered on when connector polling is
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+ * performed. Since we're calling this from a runtime PM callback,
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+ * trying to acquire rpm refs will cause us to deadlock.
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+ *
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+ * Since we're guaranteed to be holding the rpm lock, it's safe to
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+ * temporarily disable the rpm helpers so this doesn't deadlock us.
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+ */
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+ dev->dev->power.disable_depth++;
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drm_helper_hpd_irq_event(dev);
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+ dev->dev->power.disable_depth--;
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if (fbcon) {
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amdgpu_fbdev_set_suspend(adev, 0);
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