This is a note to let you know that I've just added the patch titled
drm/i915: Fix system resume if PCI device remained enabled
to the 4.5-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-i915-fix-system-resume-if-pci-device-remained-enabled.patch
and it can be found in the queue-4.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From dab9a2663f4e688106c041f7cd2797a721382f0a Mon Sep 17 00:00:00 2001
From: Imre Deak <imre.deak@xxxxxxxxx>
Date: Mon, 18 Apr 2016 14:45:54 +0300
Subject: drm/i915: Fix system resume if PCI device remained enabled
MIME-Version: 1.0
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From: Imre Deak <imre.deak@xxxxxxxxx>
commit dab9a2663f4e688106c041f7cd2797a721382f0a upstream.
During system resume we depended on pci_enable_device() also putting the
device into PCI D0 state. This won't work if the PCI device was already
enabled but still in D3 state. This is because pci_enable_device() is
refcounted and will not change the HW state if called with a non-zero
refcount. Leaving the device in D3 will make all subsequent device
accesses fail.
This didn't cause a problem most of the time, since we resumed with an
enable refcount of 0. But it fails at least after module reload because
after that we also happen to leak a PCI device enable reference: During
probing we call drm_get_pci_dev() which will enable the PCI device, but
during device removal drm_put_dev() won't disable it. This is a bug of
its own in DRM core, but without much harm as it only leaves the PCI
device enabled. Fixing it is also a bit more involved, due to DRM
mid-layering and because it affects non-i915 drivers too. The fix in
this patch is valid regardless of the problem in DRM core.
v2:
- Add a code comment about the relation of this fix to the freeze/thaw
vs. the suspend/resume phases. (Ville)
- Add a code comment about the inconsistent ordering of set power state
and device enable calls. (Chris)
CC: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
CC: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/1460979954-14503-1-git-send-email-imre.deak@xxxxxxxxx
(cherry picked from commit 44410cd0bfb26bde9288da34c190cc9267d42a20)
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.c | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -797,7 +797,7 @@ static int i915_drm_resume(struct drm_de
static int i915_drm_resume_early(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
- int ret = 0;
+ int ret;
/*
* We have a resume ordering issue with the snd-hda driver also
@@ -808,6 +808,36 @@ static int i915_drm_resume_early(struct
* FIXME: This should be solved with a special hdmi sink device or
* similar so that power domains can be employed.
*/
+
+ /*
+ * Note that we need to set the power state explicitly, since we
+ * powered off the device during freeze and the PCI core won't power
+ * it back up for us during thaw. Powering off the device during
+ * freeze is not a hard requirement though, and during the
+ * suspend/resume phases the PCI core makes sure we get here with the
+ * device powered on. So in case we change our freeze logic and keep
+ * the device powered we can also remove the following set power state
+ * call.
+ */
+ ret = pci_set_power_state(dev->pdev, PCI_D0);
+ if (ret) {
+ DRM_ERROR("failed to set PCI D0 power state (%d)\n", ret);
+ goto out;
+ }
+
+ /*
+ * Note that pci_enable_device() first enables any parent bridge
+ * device and only then sets the power state for this device. The
+ * bridge enabling is a nop though, since bridge devices are resumed
+ * first. The order of enabling power and enabling the device is
+ * imposed by the PCI core as described above, so here we preserve the
+ * same order for the freeze/thaw phases.
+ *
+ * TODO: eventually we should remove pci_disable_device() /
+ * pci_enable_enable_device() from suspend/resume. Due to how they
+ * depend on the device enable refcount we can't anyway depend on them
+ * disabling/enabling the device.
+ */
if (pci_enable_device(dev->pdev)) {
ret = -EIO;
goto out;
Patches currently in stable-queue which might be from imre.deak@xxxxxxxxx are
queue-4.5/drm-i915-ddi-fix-edp-vdd-handling-during-booting-and-suspend-resume.patch
queue-4.5/drm-i915-fix-system-resume-if-pci-device-remained-enabled.patch
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