Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH 0/5] PM: Enable option of re-use runtime PM callbacks at system suspend | Date | Fri, 29 Nov 2013 15:02:07 +0100 |
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On Friday, November 29, 2013 02:52:20 PM Rafael J. Wysocki wrote: > On Friday, November 29, 2013 10:32:06 AM Ulf Hansson wrote:
[...]
> > For the same reasons, I believe we should trust drivers/subsystems, to > > understand when it makes sense for them to re-use all of the runtime > > PM callbacks during system suspend and not just the .runtime_suspend > > callback. > > > > That is in principle what I and Alan, who came up with this idea, are > > suggesting. > > The problem with it is, as I said, the subsystem-level code you're calling > back through pm_generic_suspend_late_runtime() (and the other resume function) > has to be implemented in a specific way for things to work. So it goes like > this: "OK, now I'm not runtime-suspended, so I need to do something about that. > Why don't I call back to the layer above me that has just called me (and that > surely won't do anything after I return, right?), so that it does the right > thing (which it surely will do, of course?) and calls my runtime PM callback > as expected". > > And now suppose that your subsystem-level callbacks look like this (pseudo code): > > a_suspend_late(dev) > { > if (successful(pm_generic_suspend_late(dev))) > do_X(dev); > } > > a_runtime_suspend(dev) > { > if (successful(pm_generic_runtime_suspend(dev))) > do_Y(dev); > } > > Then, if the driver uses your pm_generic_suspend_late_runtime(), the actually > executed code will be (assuming dev is not runtime-suspended): > > a_suspend_late(dev) > driver->suspend_late(dev) > a_runtime_suspend(dev) > driver->runtime_suspend(dev) > do_Y(dev) > do_X(dev) > > So what if do_X(dev) after do_Y(dev) doesn't actually work? > > And what you actually want is > > driver->runtime_suspend(dev) > do_Y(dev)
That should have been
driver->runtime_suspend(dev) do_X(dev)
because do_Y(dev) is for runtime suspend. Sorry.
And of course, the subsystem-level code you're developing the driver for may not do the do_X(dev) thing at all, in which case all will work. But what if someone tries to use the driver with a different subsystem-level code (like a new PM domain)?
Rafael
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