On Tue, Apr 19, 2022 at 09:05:53AM +0200, Oliver Neukum wrote: > > > On 18.04.22 23:00, Evan Green wrote: > > The documentation for the freeze() method says that it "should quiesce > > the device so that it doesn't generate IRQs or DMA". The unspoken > > consequence of not doing this is that MSIs aimed at non-boot CPUs may > > get fully lost if they're sent during the period where the target CPU is > > offline. > > > > The current behavior of the USB subsystem still allows interrupts to > > come in after freeze, both in terms of remote wakeups and HC events > > related to things like root plug port activity. This can get controllers > > like XHCI, which is very sensitive to lost interrupts, in a wedged > > state. This series attempts to fully quiesce interrupts coming from USB > > across in a freeze or quiescent state. > > > > These patches are grouped together because they serve a united purpose, > > but are actually independent. They could be merged or reverted > > individually. > Hi, > > sorry for being a bit late in this discussion. There was something that > I didn't remember immediately. > > We have a set of quirky devices that need HID_QUIRK_ALWAYS_POLL. > They have the nasty firmware bug that, if you suspend them without > remote wakeup, they will crash or reset themselves. > I am afraid that has an obvious relevance to your cool patches. > I am not completely sure how to deal with this. It seems to me that the > quirk will need to be shifted from HID to core USB and thaw() needs to > be translated into usb_device_reset() + reset_resume() for them, > but I am not really sure about the optimal mechanism. We may not need to do anything. This patch specifically addresses hibernation, not system suspend or runtime suspend. A device crashing or resetting during hibernation is not at all unusual; we should be able to handle such cases properly. The THAW part of suspend-to-hibernation is used only for writing the memory image to permanent storage. I doubt that a malfunctioning HID device would interfere with this process. Alan Stern
