On ma, 2016-04-18 at 09:06 +0100, Chris Wilson wrote: > On Mon, Apr 18, 2016 at 10:04:20AM +0300, Imre Deak wrote: > > 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@xxxxxxxxxxxxxxx> > > CC: stable@xxxxxxxxxxxxxxx > > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> > > --- > > 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; > > + } > > The device should be enabled first, otherwise we are not meant to be > touching its IO space at all (such as twiddling power state). At > least > that is the order pci_enable_device() uses. It's not MMIO or (port) IO but only a PCI config space access that pci_set_power_state() requires, so doesn't need the enabling of PCI resources. AFAICS pci_enable_device() enables power as the first thing. > Either way, upon failure we should be unwinding. I'd rather wouldn't put back the device to D3 state, as further device access may still possible even though resume failed. --Imre -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html