On Monday, December 20, 2010, Alan Stern wrote: > On Sun, 19 Dec 2010, Rafael J. Wysocki wrote: > > > That said, I think we may do something different that perhaps will make your > > life somewhat easier. > > > > Namely, if your driver doesn't implement any system suspend callbacks > > (i.e. ->suspend(), ->resume(), ->freeze(), ->thaw() etc.) and it doesn't > > want the analogous subsystem callbacks to be executed for the device, it will > > make sense to flag the device as "runtime only", or something like this, > > which make the PM core skip the device in dpm_suspend() etc. > > > > In that case, if a device if flagged as "runtime only", we can avoid > > calling pm_runtime_get_noirq() for it in dpm_prepare() and, analogously, > > calling pm_runtime_put_sync() for it in dpm_complete(). However, we will have > > to fail system suspend (or hibernation) if a "runtime only" device has the > > power.runtime_auto flag unset. > > Or more generally, if pm_runtime_suspended() doesn't return 'true' for > the device. That's not necessary, because the device may be suspended using pm_runtime_suspend() later than we check pm_runtime_suspended(). I'd use the "runtime only" (or perhaps better "no_dpm") flag as a declaration (if set) that the device is going to be suspended with the help of "runtime" callbacks and the driver takes the responsibility for getting things right. > But if the device gets suspended asynchronously, this may > very well happen. For example, an i2c device is originally runtime > suspended, but its device_suspend() call occurs at the same time as the > call for the RTC device, so the i2c device actually happens to be > resumed at that time in order to communicate with the RTC. > > > So, I think we can add a "runtime only" flag working as described above. > > I guess it will also help in the case I've been discussing with Kevin for some > > time (i2c device using runtime PM used by an RTC in a semi-transparent > > fashion). > > > > Alan, what do you think? > > I'm not sure. In this situation, should we worry more that we usually > do about the possibility of a runtime resume occurring after the device > has gone through device_suspend()? Or just depend on the driver to do > everything correctly? The latter. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
