From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: Shawn Guo <shawn.guo@freescale.com>
Cc: Stefan Wahren <stefan.wahren@i2se.com>,
Fabio Estevam <fabio.estevam@freescale.com>,
Thierry Reding <thierry.reding@gmail.com>,
Bryan Wu <cooloney@gmail.com>, Richard Purdie <rpurdie@rpsys.net>,
Sascha Hauer <kernel@pengutronix.de>,
linux-arm-kernel@lists.infradead.org, linux-pwm@vger.kernel.org,
linux-leds@vger.kernel.org
Subject: Re: MX28: leds/pwm: Using pwm driven led as heartbeat leads to kernel warning
Date: Tue, 8 Apr 2014 11:04:43 +0200 [thread overview]
Message-ID: <20140408090443.GD30127@piout.net> (raw)
In-Reply-To: <20140408084951.GI2438@dragon>
On 08/04/2014 at 16:49:52 +0800, Shawn Guo wrote :
> On Tue, Apr 08, 2014 at 10:41:50AM +0200, Alexandre Belloni wrote:
> > On 08/04/2014 at 16:18:49 +0800, Shawn Guo wrote :
> > > On Tue, Apr 08, 2014 at 09:59:16AM +0200, Alexandre Belloni wrote:
> > > > The driver using the PWM should test the flag, have a look at:
> > > > http://lxr.free-electrons.com/source/drivers/leds/leds-pwm.c#L183
> > >
> > > Ah, right, that' how the flag works. Thanks, Alexandre. I send a patch
> > > to set the flag for pwm-mxs driver shortly.
> > >
> >
> > Actually, I had a closer look and I believe using clk_prepare_enable()
> > in .config is wrong. Let me prepare a patch.
>
> Yes, we can split clk_prepare_enable() into clk_prepare() and
> clk_enable(), call the former in .probe() and only the later in .config
> hook.
>
> But it only fixes the problem partially. If you look at Stefan's report
> closely, you can see the warning actually comes from the clk_get_rate()
> call which holds a mutex too.
>
Right, I missed that one. I would say it is still worth doing that
change anyway as using test_bit(PWMF_ENABLED, &pwm->flags) is
unnecessary because clk_enable()/clk_disable() maintain a usage count.
--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
prev parent reply other threads:[~2014-04-08 9:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <53345C93.9040005@i2se.com>
2014-04-04 13:54 ` MX28: leds/pwm: Using pwm driven led as heartbeat leads to kernel warning Stefan Wahren
2014-04-04 14:26 ` Shawn Guo
2014-04-04 15:25 ` Stefan Wahren
2014-04-04 16:44 ` Alexandre Belloni
2014-04-08 7:34 ` Shawn Guo
2014-04-08 7:59 ` Alexandre Belloni
2014-04-08 8:18 ` Shawn Guo
2014-04-08 8:41 ` Alexandre Belloni
2014-04-08 8:49 ` Shawn Guo
2014-04-08 9:04 ` Alexandre Belloni [this message]
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