[+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?
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]
Bjorn
[1] https://git.kernel.org/linus/eb6779d4c505
