On Wednesday 09 January 2008, Alan Stern wrote: > > > > The USB autosuspend code affects only the controller's USB interface -- > > > it doesn't touch the PCI side. An autosuspended controller will remain > > > in D0. Until somebody tries writing autosuspend code for PCI > > > devices... > > > > Is this likely to happen? > > I don't know of anybody working on it. A minimal prerequisite is that > PCI runtime wakeup processing needs to work right -- which it doesn't. > See > > http://bugzilla.kernel.org/show_bug.cgi?id=6892 And while most of the non-PCI USB host platforms to which I have access don't have that type of issue, their hardware isn't actually set up to offer an analogue of runtime PCI_D3 (for example) power states. In more detail: they generally have some clocks that could be disabled, but for various reasons they need to be left running. Disabling those clocks prevents wakeup from working ... yes, a multi-MHz clock just to detect the D+ (or D-) pullup as it kicks in. Systems using an external PHY will sometimes offer an alternative, when the PHY can issue those wakeup IRQs by itself, but that seems oddly uncommon. - Dave - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
