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

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Message-ID: <20121213153302.05120a6d@notabene.brown>
Date:	Thu, 13 Dec 2012 15:33:02 +1100
From:	NeilBrown <neilb@...e.de>
To:	NeilBrown <neilb@...e.de>
Cc:	Jon Hunter <jon-hunter@...com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	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, 13 Dec 2012 14:06:35 +1100 NeilBrown <neilb@...e.de> wrote:

> > > +	omap_dm_timer_enable(omap->dm_timer);
> > 
> > Do you need to call omap_dm_timer_enable here? _set_load and _set_match
> > will enable the timer. So this should not be necessary.
> 
> True.  That is what you get for copying someone else's code and not
> understanding it fully.

However .... omap_dm_timer_write_counter *doesn't* enable the timer, and
explicitly checks that it is already runtime-enabled.

Does that mean I don't need to call omap_dm_timer_write_counter here?  Or
does it mean that I do need the enable/disable pair?

> 
> > 
> > > +	omap_dm_timer_set_load(omap->dm_timer, autoreload, load_value);
> > > +	omap_dm_timer_set_match(omap->dm_timer, enable, match_value);
> > > +
> > > +	dev_dbg(chip->dev,
> > > +			"load value: %#08x (%d), "
> > > +			"match value: %#08x (%d)\n",
> > > +			load_value, load_value,
> > > +			match_value, match_value);
> > > +
> > > +	omap_dm_timer_set_pwm(omap->dm_timer,
> > > +			      !omap->polarity,
> > > +			      toggle,
> > > +			      trigger);
> > > +
> > > +	/* Set the counter to generate an overflow event immediately. */
> > > +
> > > +	omap_dm_timer_write_counter(omap->dm_timer, DM_TIMER_LOAD_MIN);
> > > +
> > > +	/* Now that we're done configuring the dual-mode timer, disable it
> > > +	 * again. We'll enable and start it later, when requested.
> > > +	 */
> > > +
> > > +	omap_dm_timer_disable(omap->dm_timer);
> > 
> > Similarly the disable should not be needed here either.
> > 


Thanks,
NeilBrown

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