linux-kernel - Re: [PATCH] gpio: twl4030: Use only TWL4030_MODULE

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Message-ID: <20121119105759.GU10369@pengutronix.de>
Date:	Mon, 19 Nov 2012 11:57:59 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Peter Ujfalusi <peter.ujfalusi@...com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Grant Likely <grant.likely@...retlab.ca>,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH] gpio: twl4030: Use only TWL4030_MODULE_LED for LED
 configuration

On Mon, Nov 19, 2012 at 11:40:30AM +0100, Linus Walleij wrote:
> On Mon, Nov 19, 2012 at 9:52 AM, Peter Ujfalusi <peter.ujfalusi@...com> wrote:
> 
> > I was actually tempted to remove the whole LED (PWM) thing from the
> > gpio-twl4030 driver. It was a big surprise to me to see something like this in
> > there.
> 
> It looks wrong. In theory I think this should be ripped out and moved to
> drivers/leds/leds-twl4030.c. But that would only be in case it was *always*
> exclusively used for a LED and as you say:
> 
> > It turns out that on BeagleBoard the USB host enable signal is connected to
> > LEDA (PWMA) of twl4030... It is an enable signal. Seriously. So what we do
> > here is either configure the PWMs as full on, or turn it off.
> 
> Sounds like some hardware engineer has been having fun or was
> just out of GPIOs to use... So this LED PWM is also used as a
> GPIO.
> 
> I think this part of the driver should be moved to
> drivers/pwm/pwm-twl4030.c and modeled as a PWM. If some
> platform need to use the PWM as if it was a GPIO then that's just a
> special usecase. (Setting duty cycles to something like
> INT_MAX and just switching polarity to toggle it...)
> 
> If it needs to be used by a LED there needs to be some generic
> LED type just using a standard pwm_request() to get some
> specific PWM, such as leds/leds-pwm.c or so. This way the
> PWM can be used for LEDs if need be or other things...

Either I'm misinterpreting you or you didn't have a look in the tree.
Actually drivers/leds/leds-pwm.c already exists.

> 
> Sounds correct, Sascha?

Yes, the twl4030 pwm should go to drivers/pwm/pwm-twl4030.c.

Sascha


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