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SubjectRe: [PATCH 1/1] driver core: disable device's runtime pm during shutdown
On Mon, 5 Dec 2011 11:02:38 -0500 (EST) Alan Stern
<stern@rowland.harvard.edu> wrote:

> On Mon, 5 Dec 2011, Ming Lei wrote:
>
> > Sorry, the above is line wrapped badly, see the below:
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index d8b3d89..96b266c 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1743,8 +1743,9 @@ void device_shutdown(void)
> > */
> > list_del_init(&dev->kobj.entry);
> > spin_unlock(&devices_kset->list_lock);
> > - /* Disable all device's runtime power management */
> > - pm_runtime_disable(dev);
> > +
> > + /* put device into active state and forbit runtime pm */
> > + pm_runtime_forbid(dev);
> >
> > if (dev->bus && dev->bus->shutdown) {
> > dev_dbg(dev, "shutdown\n");
>
> We don't want to put devices into the active state when it's not
> necessary. A better approach would be:
>
> /* Don't allow any more runtime suspends */
> pm_runtime_get_noresume(dev);
> pm_runtime_barrier(dev);
>
> Alan Stern

That sounds like a reasonable approach if we really need to do something at
this level. But is this the only place that ->shutdown methods are called
from? If they are called from elsewhere, would those places need the
same pm_runtime protection?

BTW I was wrong when I said that only calling pm_runtime_disable if there was
a ->shutdown function would not work for me. i.e. the following patch does
solve my particular issue (though I'm not sure it is "right").
I was getting confused by the two different devices: the i2c device and the
platform device.
The i2c device has a ->shutdown which does nothing, but doesn't need to wake
up.
The platform device is the one which needs to wake up, but it doesn't have a
->shutdown function is this patch causes it not have pm_runtime disabled.

Thanks,
NeilBrown

diff --git a/drivers/base/core.c b/drivers/base/core.c
index d8b3d89..b9aa5d2 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1743,13 +1743,13 @@ void device_shutdown(void)
*/
list_del_init(&dev->kobj.entry);
spin_unlock(&devices_kset->list_lock);
- /* Disable all device's runtime power management */
- pm_runtime_disable(dev);

if (dev->bus && dev->bus->shutdown) {
+ pm_runtime_disable(dev);
dev_dbg(dev, "shutdown\n");
dev->bus->shutdown(dev);
} else if (dev->driver && dev->driver->shutdown) {
+ pm_runtime_disable(dev);
dev_dbg(dev, "shutdown\n");
dev->driver->shutdown(dev);
}[unhandled content-type:application/pgp-signature]
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