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

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Date:	Mon, 5 Dec 2011 11:26:40 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	NeilBrown <neilb@...e.de>
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

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?

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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