On Mon, 6 Jun 2011, Kevin Hilman wrote: > "Rafael J. Wysocki" <rjw@xxxxxxx> writes: > > [..] > > > While it is tempting to try to get away with only two PM callbacks per > > driver instead of four (or even more), it generally is not doable, simply > > because driver callbacks are not executed directly by the core. > > > > The only way to address the problem of code duplication between .suspend() > > and .runtime_suspend() callbacks (and analogously for resume) I see at the > > moment is to make those callbacks execute common routines. > > Makes sense if the "common routines" are in the driver. The problem > arises when the common routines are not actually in the driver, but are > instead at the subsystem (or in this case, device power domain) level. Why should that be a problem? System suspend also invokes the subsystem and power domain methods. > Considering the OMAP I2C driver, it doesn't have (or need) runtime PM > callbacks. It does runtime PM get/put per-xfer, and has no context to > save/restore, so it needs no runtime PM callbacks, or no special PM code > other than runtime PM get/put calls. The device power domain level code > is managing the device clocks, power states, etc.. > > So what the system suspend needs to do is something like: > > 1. block any new xfers from starting > 2. wait for any outstanding xfers > 3. if device is already runtime suspended > - nothing to do > 4. trigger idle transition (at device power domain level) 1 - 2 should be handled at the device level, whereas 3 - 4 are handled at the power domain level. Those are separate callbacks during system suspend. > If runtime PM has not been disabled from userspace, it should always end > at step 3, since the last xfer will always trigger a runtime suspend. > > However, if runtime PM has been disabled from > userspace/pm_runtime_forbid(), we need some way to do step 4. It's this > last 'trigger' step that I'm trying to figure out how a clean way of > implementing, particularily for drivers with no runtime PM callbacks. You're too hung-up on runtime PM. Forget about that and concentrate on system PM instead. Power domains have system-PM callbacks as well as runtime-PM callbacks; use them to do what you want. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
