On 7 November 2013 02:05, Rafael J. Wysocki <r...@rjwysocki.net> wrote: > On Wednesday, November 06, 2013 04:21:48 PM Kevin Hilman wrote: >> On Wed, Nov 6, 2013 at 4:16 PM, Rafael J. Wysocki <r...@rjwysocki.net> wrote: >> > On Wednesday, November 06, 2013 11:48:24 PM Ulf Hansson wrote: >> >> >> >> "Rafael J. Wysocki" <r...@rjwysocki.net> skrev: >> >> >On Wednesday, November 06, 2013 05:02:12 PM Alan Stern wrote: >> >> >> On Wed, 6 Nov 2013, Rafael J. Wysocki wrote: >> >> >> >> >> >> > On Wednesday, November 06, 2013 09:51:42 AM Tomi Valkeinen wrote: >> >> >> > > On 2013-11-05 23:29, Ulf Hansson wrote: >> >> >> > > > On 23 October 2013 12:11, Tomi Valkeinen >> >> ><tomi.valkei...@ti.com> wrote: >> >> >> > > >> Hi, >> >> >> > > >> >> >> >> > > >> I was debugging why clocks were left enabled after removing >> >> >omapdss >> >> >> > > >> driver, and I found this commit: >> >> >> > > >> >> >> >> > > >> fa180eb448fa263cf18dd930143b515d27d70d7b (PM / Runtime: Idle >> >> >devices >> >> >> > > >> asynchronously after probe|release) >> >> >> > > >> >> >> >> > > >> I don't understand how that is supposed to work. >> >> >> > > >> >> >> >> > > >> When a driver is removed, instead of using >> >> >pm_runtime_put_sync() the >> >> >> > > >> commit uses pm_runtime_put(), so the runtime_suspend call is >> >> >queued. But >> >> >> > > >> who is going to handle the queued suspend call, as the driver >> >> >is already >> >> >> > > >> removed? At least in my case, obviously nobody, as I only get >> >> >> > > >> runtime_resume call in my driver, never the runtime_suspend. >> >> >> > > >> >> >> >> > > >> Is there something I need to add to my driver to make this >> >> >work, or >> >> >> > > >> should that part of the patch be reverted? >> >> >> > > > >> >> >> > > > I believe it is quite common that a device driver calls >> >> >> > > > pm_runtime_get_sync as a part of it's remove callback, then it >> >> >> > > > explicitly returns it's resources that has been fetched during >> >> >probe. >> >> >> > > > Like a clk_disable_unprepare for example. >> >> >> > > >> >> >> > > I guess you mean the driver calls pm_runtime_get_sync _and_ >> >> >> > > pm_runtime_put_sync as part of its remove callback? >> >> >> > > >> >> >> > > Probably bus drivers need to do that, but for memory mapped >> >> >devices in a >> >> >> > > SoC, I don't think there's normally any need to do >> >> >> > > pm_runtime_get/put_sync during the remove callback. >> >> >> > > >> >> >> > > > The idea behind the change in __device_release_driver, was to >> >> >try to >> >> >> > > > prevent devices from going active->idle->active and instead >> >> >just >> >> >> > > > remain active (if possible). >> >> >> > > > >> >> >> > > > In your case, which seems like a more modern way of >> >> >implementing >> >> >> > > > "remove", you shall call "pm_runtime_suspend" to make sure the >> >> >> > > > runtime_suspend callbacks gets called. >> >> >> > > >> >> >> > > And as far as I understand, the change creates an explicit >> >> >requirement >> >> >> > > to do either pm_runtime_get/put_sync or pm_runtime_suspend inside >> >> >> > > driver's remove callback. If so, that should be mentioned in big >> >> >red >> >> >> > > letters in the pm-runtime documentation. >> >> >> > > >> >> >> > > The runtime_pm.txt doc does mention something related to this >> >> >(and btw, >> >> >> > > the doc says pm_runtime_put_sync is being called, which is no >> >> >longer >> >> >> > > true), but nothing clear about how the driver remove callback >> >> >must be >> >> >> > > implemented. >> >> >> > >> >> >> > That's correct. >> >> >> > >> >> >> > > I tried grepping the kernel sources to find out if >> >> >pm_runtime_suspend is >> >> >> > > widely used to get SoC platform devices to suspend, but it >> >> >doesn't seem >> >> >> > > like it is. I didn't see pm_runtime_get/put_sync being used in >> >> >remove >> >> >> > > callbacks widely either, but that was more difficult one to grep. >> >> >> > >> >> >> > I think your observations are valid, which unfortunately means that >> >> >we'll >> >> >> > need to revert the commit in question, because it has changed the >> >> >behavior >> >> >> > that drivers are perfectly fine to expect given the existing >> >> >documentation >> >> >> > etc. It looks like the change was premature at least. >> >> >> > >> >> >> > Greg, I wonder if you can queue up a revert of fa180eb448fa for >> >> >3.13, or >> >> >> > do you want me to do that? >> >> >> >> >> >> Would it be better to leave the runtime-idle callbacks (invoked >> >> >during >> >> >> probe) async and revert only the change to __device_release_driver()? >> >> >> >> >> >> Having an async callback after probe shouldn't cause problems, >> >> >because >> >> >> the driver will then be bound (assuming the probe succeeded). >> >> > >> >> >Right. OK, I'll prepare a patch. >> >> >> >> That seems like a good way forward. >> > >> > There you go. >> > >> > --- >> > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> >> > Subject: PM / runtime: Use pm_runtime_put_sync() in >> > __device_release_driver() >> > >> > Commit fa180eb448fa (PM / Runtime: Idle devices asynchronously after >> > probe|release) modified __device_release_driver() to call >> > pm_runtime_put(dev) instead of pm_runtime_put_sync(dev) before >> > detaching the driver from the device. However, that was a mistake, >> > because pm_runtime_put(dev) causes rpm_idle() to be queued up and >> > the driver may be gone already when that function is executed. >> > That breaks the assumptions the drivers have the right to make >> > about the core's behavior on the basis of the existing documentation >> > and actually causes problems to happen, so revert that part of >> > commit fa180eb448fa and restore the previous behavior of >> > __device_release_driver(). >> > >> > Reported-by: Tomi Valkeinen <tomi.valkei...@ti.com> >> > Fixes: fa180eb448fa (PM / Runtime: Idle devices asynchronously after >> > probe|release) >> > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> >> > Cc: 3.10+ <sta...@vger.kernel.org> # 3.10+ >> >> Acked-by: Kevin Hilman <khil...@linaro.org> >> >> I like this fix since I don't want to add any more requirements to drivers.
Agree! > > OK, I've queued this up for 3.13. If not to late: Acked-by: Ulf Hansson <ulf.hans...@linaro.org> BTW, I start creating a patch on the doc to align it to the changes that the "async" patches made. Kind regards Ulf Hansson > > Thanks! > > >> > --- >> > drivers/base/dd.c | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > Index: linux-pm/drivers/base/dd.c >> > =================================================================== >> > --- linux-pm.orig/drivers/base/dd.c >> > +++ linux-pm/drivers/base/dd.c >> > @@ -499,7 +499,7 @@ static void __device_release_driver(stru >> > >> > BUS_NOTIFY_UNBIND_DRIVER, >> > dev); >> > >> > - pm_runtime_put(dev); >> > + pm_runtime_put_sync(dev); >> > >> > if (dev->bus && dev->bus->remove) >> > dev->bus->remove(dev); >> > >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-pm" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > I speak only for myself. > Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/