linux-kernel - Re: [PATCH] i2c: designware: separate ops for system_sleep_pm and runtime

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Message-ID: <20150520203810.2fa5b489@xhacker>
Date:	Wed, 20 May 2015 20:38:10 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	<wsa@...-dreams.de>
CC:	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] i2c: designware: separate ops for system_sleep_pm and
 runtime_pm

On Wed, 20 May 2015 20:34:30 +0800
Jisheng Zhang <jszhang@...vell.com> wrote:

> Dear Mika,
> 
> On Wed, 20 May 2015 15:15:06 +0300
> Mika Westerberg <mika.westerberg@...ux.intel.com> wrote:
> 
> > On Wed, May 20, 2015 at 07:34:22PM +0800, Jisheng Zhang wrote:
> > > Sorry for confusion. Considering one platform which doesn't support power off
> > > the i2c host but it can disable the host's clock. So in such platform, when
> > > the host is runtime suspended, its clock is disabled, then i2c_dw_disable() will
> > > hang when s2ram.
> > 
> > Right. This happens also when the platform powers off the device.
> > 
> > > Except using the runtime pm API to ensure the host is in
> > > a correct state, is there any other solution? AFAIK, 'dev->power.direct_complete'
> > > doesn't help such case.
> > 
> > What I had in mind is something like below:
> > 
> > static int i2c_dw_prepare(struct device *dev)
> > {
> > 	return pm_runtime_suspended(dev);
> > }
> > 
> > static void i2c_dw_complete(struct device *dev)
> > {
> > 	if (dev->power.direct_complete)
> > 		pm_request_resume(dev);
> > }
> > 
> > In other words it checks if the device is already runtime suspended and
> > prevents ->suspend() etc. from being called.
> 
> What amazing! I wrote the same code as yours after sending out the last email.
> 
> > 
> > If that does not work (I didn't try as this problem does not exist on
> 
> It works! How to submit the patch? Do you mind if I cook the patch and add
> you signed-off?
> 

PS: If you cook the patch instead,  feel free to add my acked-by and tested-by

Thanks a lot for the direct_complete idea,
Jisheng
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