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SubjectRe: [PATCH 1/1] driver core: disable device's runtime pm during shutdown
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Hi,

On Mon, Dec 5, 2011 at 5:56 AM, NeilBrown <neilb@suse.de> wrote:
>
> Hi,
>  this patches causes a problem for me.
>
> Specifically it makes it impossible to power-down a device which uses twl4030
> for power control on an omap3 processor.
>
> To perform the shutdown we need to send a command over the i2c bus.
> The relevant bus is called omap_i2c.1 and this is normally in suspend mode.
> When a request is sent, omap_i2c_xfer uses pm_runtime_get_sync to wake it up,
> performs the transfer, then calls pm_runtime_put to let it go back to sleep.
>
> So it is asleep when the new pm_runtime_disable() call is made, so it stays
> asleep, omap_i2c_xfer cannot wake it, the transfer doesn't happen and the
> system doesn't get powered off.
>
> So here is a device that should *not* have pm disabled at shutdown.
>
> So I feel this fix is a little too heavy-handed.

Maybe the device's runtime PM should not be disabled if
there is no ->shutdown defined in its driver, how about the blew?

diff --git a/drivers/base/core.c b/drivers/base/core.c
index d8b3d89..ca30659 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1743,14 +1743,16 @@ 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);

+ /* Disable the device's runtime power management if
+ * it is to be shutdown*/
if (dev->bus && dev->bus->shutdown) {
dev_dbg(dev, "shutdown\n");
+ pm_runtime_disable(dev);
dev->bus->shutdown(dev);
} else if (dev->driver && dev->driver->shutdown) {
dev_dbg(dev, "shutdown\n");
+ pm_runtime_disable(dev);
dev->driver->shutdown(dev);
}
put_device(dev);

> I don't fully understand the problem scenario described above but it seems to
> me that if the auto-suspend timer can fire after the hardware has been shut
> down, then maybe the hardware-shutdown should be disabling that timer.  Maybe?
>
> Suggestions?
>
> Thanks,
> NeilBrown


thanks,
--
Ming Lei
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