Hi Bjorn,
On Fri, 26 Feb 2021 at 23:22, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> [+cc Rafael, Dave (author of 42eca2302146), Vaibhav, linux-pm]
>
> On Fri, Feb 26, 2021 at 11:37:12AM +0100, Loic Poulain wrote:
> > Hi Bjorn,
> >
> > Trying to support runtime suspend in a driver, which puts the device
> > in D3hot and wait either for host/driver initiated resume
> > (runtime_get), or device initiated resume (PME).
> >
> > But, given that old change: 42eca2302146 ("PCI: Don't touch card regs
> > after runtime suspend D3")
> >
> > PME that was enabled from pci_finish_runtime_suspend() is not enabled
> > anymore for almost all drivers in case of runtime-suspend. The only
> > way to enable this is by calling pci_wake_from_d3() from the PCI device
> > driver's runtime_suspend() callback, but this function fails if the
> > device wake_up is not enabled, which makes sense since it targets
> > system-wide sleep wake-up (and wake-up is user/distro policy).
> >
> > So is there a proper way to allow PME while the device is runtime
> > suspended, without having to tell the user to enabled 'unrelated' wake_up
> > capability?
>
> pci_pm_runtime_suspend() calls pci_finish_runtime_suspend(), which
> enables wake-up, unless "pci_dev->state_saved". IIUC we should be
> enabling wake-up unless the driver has called pci_save_state() itself.
>
> So I infer that your driver does call pci_save_state() and the PCI
> core does not enable wake-up. Right?
Right.
>
> Why does your driver call pci_save_state()? In most cases I don't
> think drivers should need to do that themselves because the PCI core
> will do it for them. E.g., see Vaibhav's recent eb6779d4c505 ("e1000:
> use generic power management") [1]
Thanks for the pointer, I was storing the PCI state in order to
restore it when the device is crashing and lose its PCI context. But I
can do that one time once the device is initialized. I've applied the
same changes as you pointed, and it works as expected.
Thanks,
Loic
