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

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Date:	Mon, 5 Dec 2011 13:12:30 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Chen Peter-B29397 <B29397@...escale.com>
Cc:	NeilBrown <neilb@...e.de>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Greg KH <greg@...ah.com>, "gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"hzpeterchen@...il.com" <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 12:42 PM, Chen Peter-B29397 <B29397@...escale.com> wrote:
>
>
>> >  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);
>>
>>
> Yes, it is the solution for Neil's case, but I am not sure for all.
> Is it possible to resume driver's itself at driver's shutdown?

Looks like this way is still not good. Maybe we should put all
device into active state first, then set its runtime pm as disabled.

thanks,
-- 
Ming Lei
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