[+cc Rafael, linux-pm, linux-kernel] On Wed, Jun 27, 2018 at 10:15:50PM +0200, Jean Delvare wrote: > Hi Jarkko, > > On Tue, 26 Jun 2018 17:39:12 +0300, Jarkko Nikula wrote: > > Commit 9c8088c7988 ("i2c: i801: Don't restore config registers on > > runtime PM") nullified the runtime PM suspend/resume callback pointers > > while keeping the runtime PM enabled. This causes that device stays in > > D0 power state and sysfs /sys/bus/pci/devices/.../power/runtime_status > > shows "error" when runtime PM framework attempts to autosuspend the > > device. > > > > This is due PCI bus runtime PM which checks for driver runtime PM > > callbacks and returns with -ENOSYS if they are not set. Fix this by > > having a shared dummy runtime PM callback that returns with success. > > > > Fixes: a9c8088c7988 ("i2c: i801: Don't restore config registers on runtime PM") > > I don't want to sound like I'm trying to decline all responsibility for > a regression I caused, but frankly, if just using SIMPLE_DEV_PM_OPS() > breaks runtime PM, then it's the PM model which is broken, not the > i2c-i801 driver. > > I will boldly claim that the PCI bus runtime code is simply wrong in > returning -ENOSYS in the absence of runtime PM callbacks, and it should > be changed to return 0 instead. Or whoever receives that -ENOSYS should > not treat it as an error - whatever makes more sense. > > Having to add dummy functions in every PCI driver that doesn't need to > do anything special for runtime PM sounds plain stupid. It should be > pretty obvious that a whole lot of drivers are going to use > SIMPLE_DEV_PM_OPS() because it exists and seems to do what they want, > and all of them will be bugged because the PCI core is doing something > silly and unexpected. > > So please let's fix it at the PCI subsystem core level. Adding Bjorn > and the linux-pci list to Cc. Thanks Jean. What you describe does sound broken. I think the PM guys (cc'd) will have a better idea of how to deal with this.