linux-kernel - Re: [PATCH] OMAP: add pwm driver using dmtimers.

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Message-ID: <20121213071100.GB9946@avionic-0098.adnet.avionic-design.de>
Date:	Thu, 13 Dec 2012 08:11:00 +0100
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	NeilBrown <neilb@...e.de>
Cc:	Jon Hunter <jon-hunter@...com>,
	Grant Erickson <marathon96@...il.com>,
	linux-omap@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] OMAP: add pwm driver using dmtimers.

On Thu, Dec 13, 2012 at 02:06:35PM +1100, NeilBrown wrote:
> 
> [Thierry: question for you near the end - thanks]
> 
> On Wed, 12 Dec 2012 10:08:28 -0600 Jon Hunter <jon-hunter@...com> wrote:
> 
> > Hi Neil,
> > 
> > On 12/12/2012 02:24 AM, NeilBrown wrote:
[...]
> > > +{
> > > +	struct omap_chip *omap = platform_get_drvdata(pdev);
> > > +	int status = 0;
> > > +
> > > +	status = pwmchip_remove(&omap->chip);
> > > +	if (status < 0)
> > > +		goto done;
> > > +
> > > +	omap_dm_timer_free(omap->dm_timer);
> > 
> > Is it guaranteed that the timer will be disabled at this point?
> 
> Uhmm... it seems that pwm_put() doesn't call pwm_disable(), so I guess it
> might not be disabled.
> Thierry: should pwm_put do that, or do I need a 'free' function in my chip
> ops to do that?

To be honest, I haven't decided yet. =) There have been discussions that
resulted in a request to run pwm_disable() from pwmchip_remove() on all
PWM devices a chip provides.

This isn't implemented yet and I'm not sure about all the side-effects.
I think for now the best way would be to implement .free() within this
driver, or even do an explicit pwm_disable() in the driver's .remove()
function to do this. When I've come to a decision I'll refactor all of
that in one patch across the whole subsystem.

Thierry

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