linux-kernel - Re: [PATCH v2] can: Fix bug in suspend/resume

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Date:	Fri, 14 Nov 2014 07:05:14 -0800
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Marc Kleine-Budde <mkl@...gutronix.de>
CC:	Kedareswara rao Appana <appana.durga.rao@...inx.com>,
	<wg@...ndegger.com>, <michal.simek@...inx.com>,
	<grant.likely@...aro.org>, <robh+dt@...nel.org>,
	<linux-can@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	Kedareswara rao Appana <appanad@...inx.com>
Subject: Re: [PATCH v2] can: Fix bug in suspend/resume

On Fri, 2014-11-14 at 09:54AM +0100, Marc Kleine-Budde wrote:
> On 11/14/2014 09:16 AM, Kedareswara rao Appana wrote:
> > The drvdata in the suspend/resume is of type struct net_device,
> > not the platform device.Enable the clocks in the suspend before
> > accessing the registers of the CAN.
> > 
> > Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> > ---
> > Changes for v2:
> >   - Removed the struct platform_device* from suspend/resume
> >     as suggest by Lothar.
> >   - The clocks are getting disabled and un prepared at the end of the probe. 
> >     In the suspend the driver is doing a register write.In order
> >     To do that register write we have to again enable and prepare the clocks.
> 
> Please look the at suspend/resume code and count the
> clock_enable/disable manually. After a suspend/resume cycle, you have
> enabled the clock twice, but disabled it once.
> 
> I think you have to abstract the clock handling behind runtime PM. I
> haven't done this myself yet, but the strong feeling that this is a
> possible solution to your problem. These links might help:

I agree, the clock handling looks weird. Also the clk_disable calls in
xcan_get_berr_counter() look suspicious to me, but I might be wrong.
I think you can take a look at gpio-zynq for an example for runtime_pm
usage. I think the usage model in that driver is similar to here.

	Thanks,
	Sören
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