[PATCH 2/4] drm/i915: Fix system resume if PCI device remained enabled

Imre Deak
2016-04-18T07:04:20Z

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.

CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
CC: stable@vger.kernel.org
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
drivers/gpu/drm/i915/i915_drv.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index d550ae2..7eaa93e 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -803,7 +803,7 @@ static int i915_drm_resume(struct drm_device *dev)
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
@@ -814,6 +814,13 @@ static int i915_drm_resume_early(struct drm_device *dev)
* FIXME: This should be solved with a special hdmi sink device or
* similar so that power domains can be employed.
*/
+
+ 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;
+ }
+
if (pci_enable_device(dev->pdev)) {
ret = -EIO;
goto out;
--
2.5.0