21.10.2021 20:13, Dmitry Osipenko пишет: > 21.10.2021 18:20, Alan Stern пишет: >> On Thu, Oct 21, 2021 at 06:08:41PM +0300, Dmitry Osipenko wrote: >>> 21.10.2021 17:57, Dmitry Osipenko пишет: >>>> It might be wrong to disable device_may_wakeup() because it will change >>>> the system suspend-resume behaviour, i.e. you won't be able to resume by >>>> USB event, see [1]. >>>> >>>> [1] >>>> https://elixir.bootlin.com/linux/v5.15-rc6/source/drivers/usb/host/xhci-tegra.c#L1962 >>>> >>>> Although, I'm not sure whether this is a correct behaviour to start >>>> with. Previously, before the offending commit, device_wakeup was never >>>> enabled for tegra-xusb. Commit message doesn't explain why wakeup is now >>>> enabled unconditionally, wakeup checks aren't needed at all then. This >>>> makes no sense, please check it with JC Kuo. >>> >>> Although, wakeup could be disabled via sysfs, so it makes sense. Still >>> it's not clear whether it's a correct behaviour to enable wakeup during >>> system suspend by default. If it wakes machine from suspend when USB >>> device is plugged/unplugged, then it's a wrong behaviour. >> >> It depends on the details of how the device works. In most cases we do >> want to enable wakeup by default for host controller devices. The >> reason is simple enough: If some USB device attached to the HC is >> enabled for wakeup and sends a wakeup request, we don't want the request >> to get lost because the HC isn't allowed to forward the request on to >> the CPU. >> >> But we do not want to enable wakeup for root hubs. In particular, we >> don't want to wake up a suspended system merely because a USB device has >> been plugged or unplugged. >> >> Clearly this arrangement depends on the hardware making a distinction >> between wakeup requests originating from the root hub and those simply >> passing through the HC. > > Should USB keyboard be able to wake up every HC or it's a > machine-specific feature? I mean whether key press should wake up HC if wake-up is enabled for the keyboard device. > I'm asking because wakeup works on a typical > Intel hardware, but doesn't work on older Tegra SoCs that use Chipidea > controller. It's not obvious to me whether this is something that > firmware handles for Intel or it's broken on Tegra. Could you please > clarify? If it should work for every HC, then I may try to take a closer > look. >
