On Fri, Nov 01, 2024 at 10:11:11AM +0800, Jason Wang wrote: > On Fri, Nov 1, 2024 at 9:54 AM <qiang4.zhang@xxxxxxxxxxxxxxx> wrote: > > > > From: Qiang Zhang <qiang4.zhang@xxxxxxxxx> > > > > Virtio core unconditionally reset and restore status for all virtio > > devices before calling restore method. This breaks some virtio drivers > > which don't need to do anything in suspend and resume because they > > just want to keep device state retained. > > The challenge is how can driver know device doesn't need rest. I actually don't remember why do we do reset on restore. Do you? > For example, PCI has no_soft_reset which has been done in the commit > "virtio: Add support for no-reset virtio PCI PM". > > And there's a ongoing long discussion of adding suspend support in the > virtio spec, then driver know it's safe to suspend/resume without > reset. > > > > > Virtio GPIO is a typical example. GPIO states should be kept unchanged > > after suspend and resume (e.g. output pins keep driving the output) and > > Virtio GPIO driver does nothing in freeze and restore methods. But the > > reset operation in virtio_device_restore breaks this. > > Is this mandated by GPIO or virtio spec? If yes, let's quote the revelant part. > > > > > Since some devices need reset in suspend and resume while some needn't, > > create a new helper function for the original reset and status restore > > logic so that virtio drivers can invoke it in their restore method > > if necessary. > > How are those drivers classified? > > > > > Signed-off-by: Qiang Zhang <qiang4.zhang@xxxxxxxxx> > > Thanks
