On Wed, Apr 23, 2025 at 11:32 AM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote: > > On Tue, Apr 22, 2025 at 1:43 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > > > On Tue, Apr 22, 2025 at 8:28 AM Lukas Wunner <lukas@xxxxxxxxx> wrote: > > > > > > [cc += Rafael, linux-acpi] > > > > > > On Mon, Apr 21, 2025 at 10:05:59PM +0200, Heiner Kallweit wrote: > > > > If there's no platform support for transition to D3cold, then > > > > pci_set_power_state(dev, D3cold) still returns 0, even though > > > > power state is transitioned to D3hot only. We called > > > > pci_enable_wake(dev, D3cold, wakeup) before, therefore PME for > > > > D3hot may not be enabled. Is this a bug? > > > > On platforms using ACPI, no it isn't. > > > > Internally, pci_enable_wake() evaluates _DSW and it doesn't > > distinguish between D3hot and D3cold as per the spec. > > > > > > Background: > > > > In __pci_set_power_state we have the following: > > > > > > > > error = pci_set_low_power_state(dev, PCI_D3hot, locked); > > > > if (pci_platform_power_transition(dev, PCI_D3cold)) > > > > return error; > > > > > > > > The acpi_pci_set_power_state() stub returns -ENODEV. > > > > Therefore, if error=0, __pci_set_power_state() will > > > > return 0 if pci_platform_power_transition() fails. > > > > > > pci_prepare_to_sleep() calls pci_target_state() right at the top. > > > > > > If wakeup is supported and enabled, pci_target_state() is supposed > > > to find the deepest power state supporting wakeup. If D3cold doesn't > > > support wakeup, D3hot or a shallower state is returned. > > > > > > Hence I don't quite understand how the scenario you're describing > > > could occur in practice. Are you seeing actual issues and have tracked > > > them down to incorrect handling in pci_prepare_to_sleep()? > > On non-ACPI systems pci_target_state() just looks at the device > capabilities. The described scenario can happen if device supports > wake from D3cold, but platform has no means to switch a device to > D3cold. I'm thinking of e.g. RTL8125 on ARM. Typically I don't expect > an issue because boot-up default on these devices is to have PME wake > from all states enabled. So it's more of a theoretical exercise at the > moment. I just see that pci_target_state() won't return D3cold for non-ACPI systems. Therefore sorry for the noise.
