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SubjectRe: [PATCH 3/3] ACPI / PCI / PM: Rework acpi_pci_propagate_wakeup()
On Fri, Jul 21, 2017 at 3:42 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:

> The acpi_pci_propagate_wakeup() routine is there to handle cases in
> which PCI bridges (or PCIe ports) are expected to signal wakeup
> for devices below them, but currently it doesn't do that correctly.
>
> The problem is that acpi_pci_propagate_wakeup() uses
> acpi_pm_set_device_wakeup() for bridges and if that routine is
> called for multiple times to disable wakeup for the same device,
> it will disable it on the first invocation and the next calls
> will have no effect (it works analogously when called to enable
> wakeup, but that is not a problem).
>
> Now, say acpi_pci_propagate_wakeup() has been called for two
> different devices under the same bridge and it has called
> acpi_pm_set_device_wakeup() for that bridge each time. The
> bridge is now enabled to generate wakeup signals. Next,
> suppose that one of the devices below it resumes and
> acpi_pci_propagate_wakeup() is called to disable wakeup for that
> device. It will then call acpi_pm_set_device_wakeup() for the bridge
> and that will effectively disable remote wakeup for all devices under
> it even though some of them may still be suspended and remote wakeup
> may be expected to work for them.
>
> To address this (arguably theoretical) issue, allow
> wakeup.enable_count under struct acpi_device to grow beyond 1 in
> certain situations. In particular, allow that to happen in
> acpi_pci_propagate_wakeup() when wakeup is enabled or disabled
> for PCI bridges, so that wakeup is actually disabled for the
> bridge when all devices under it resume and not when just one
> of them does that.

> - if (wakeup->enable_count > 0)
> - goto out;
> + if (wakeup->enable_count > 0) {
> + if (wakeup->enable_count < max_count)
> + goto inc;
> + else
> + goto out;
> + }

Wouldn't be simpler

if (wakeup->enable_count >= max_count)
goto out;

if (wakeup->enable_count > 0)
goto inc;

If max_count can be <= 0,

if (max_count > 0 && wakeup->enable_count >= max_count)
goto out;


> +inc:
> wakeup->enable_count++;
>
> out:



--
With Best Regards,
Andy Shevchenko

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