linux-kernel - Re: [PATCH 1/1] driver core: disable device's runtime pm during shutdown

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Date:	Mon, 5 Dec 2011 15:53:38 +1100
From:	NeilBrown <neilb@...e.de>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Greg KH <greg@...ah.com>,
	Peter Chen <peter.chen@...escale.com>, gregkh@...e.de,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	stern@...land.harvard.edu, hzpeterchen@...il.com,
	Igor Grinberg <grinberg@...pulab.co.il>
Subject: Re: [PATCH 1/1] driver core: disable device's runtime pm during
 shutdown

On Mon, 5 Dec 2011 11:26:40 +0800 Ming Lei <tom.leiming@...il.com> wrote:

> Hi,
> 
> On Mon, Dec 5, 2011 at 5:56 AM, NeilBrown <neilb@...e.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?

Thanks, but that won't actually help.

dev->bus->shutdown is i2c_device_shutdown so there is a shutdown method.
However i2c_device_shutdown just finds the driver can calls
driver->shutdown(), and that is the 'shutdown' that is NULL.

Thanks,
NeilBrown



> 
> 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,


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