Re: [PATCH 2/5] e1000e: fix pci device enable counter balance

[Konstantin Khlebnikov]

Bjorn Helgaas wrote:
> [+cc Rafael @sisk.pl]
>
> On Mon, Jan 28, 2013 at 4:09 PM, Bjorn Helgaas<bhelgaas@xxxxxxxxxx>  wrote:
> > [+cc Rafael]
> >
> > On Fri, Jan 18, 2013 at 4:42 AM, Konstantin Khlebnikov
> > <khlebnikov@xxxxxxxxxx>  wrote:
> > > __e1000_shutdown() calls pci_disable_device() at the end, thus __e1000_resume()
> > > should call pci_enable_device_mem() to keep enable counter in balance.
> > >
> > > Bug was introduced in commit 23606cf5d1192c2b17912cb2ef6e62f9b11de133
> > > ("e1000e / PCI / PM: Add basic runtime PM support (rev. 4)") in v2.6.35
> > >
> > > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
> > > Cc: e1000-devel@xxxxxxxxxxxxxxxxxxxxx
> > > Cc: Jeff Kirsher<jeffrey.t.kirsher@xxxxxxxxx>
> > > Cc: Bruce Allan<bruce.w.allan@xxxxxxxxx>
> > > ---
> > >   drivers/net/ethernet/intel/e1000e/netdev.c |    7 +++++++
> > >   1 file changed, 7 insertions(+)
> > >
> > > diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> > > index 2853c11..6bce796 100644
> > > --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> > > +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> > > @@ -5598,6 +5598,13 @@ static int __e1000_resume(struct pci_dev *pdev)
> > >          pci_restore_state(pdev);
> > >          pci_save_state(pdev);
> > >
> > > +       err = pci_enable_device_mem(pdev);
> > > +       if (err) {
> > > +               dev_err(&pdev->dev,
> > > +                       "Cannot re-enable PCI device after suspend.\n");
> > > +               return err;
> > > +       }
> >
> > Reviewed-by: Bjorn Helgaas<bhelgaas@xxxxxxxxxx>
> >
> > Seems right to me, and the other users I looked at (igb, azx,
> > virtio_pci) call pci_disable_device() in .suspend() and call
> > pci_enable_device() in .resume() as you propose to do here.
> >
> > I assume the e1000 folks will handle this patch (and the previous one).
> >
> > > +
> > >          e1000e_set_interrupt_capability(adapter);
> > >          if (netif_running(netdev)) {
> > >                  err = e1000_request_irq(adapter);
>
> I'm still missing something.  In your original report
> (https://lkml.org/lkml/2013/1/1/25), you noticed that "enable_cnt ==
> 0" immediately after boot, after e1000e had claimed the device:

Yep, it rise counter from 0 to 1, and runtime-suspend immediately
decrease it back to 0.

> > Right after boot it looks like this:
> >
> > root@zurg:/sys/bus/pci/devices# lspci
> > ...
> > 00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 04)
> > ...
> > root@zurg:/sys/bus/pci/devices# cat 0000\:00\:19.0/enable
> > 0
> > here must be '1', not '0'
>
> But these patches only change the e1000e suspend/resume path.  How
> could they change the enable_cnt before you've even done a suspend?

suspend/resume and runtime_suspend/runtime_resume callbacks calls the one
set of functions: __e1000_shutdown() / __e1000_resume()

Any suspend-resume cycle breaks enable_ent balance.
Thus right after boot and first runtime-suspend device cannot wake up
due to first sort of bugs and after first s2ram suspend-resume cycle
driver breaks it's enable_cnt and device no longer can sleep due to
second sort of bugs.

> Bjorn

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