Hi Linus, On 11/19/2012 11:40 AM, Linus Walleij wrote: > On Mon, Nov 19, 2012 at 9:52 AM, Peter Ujfalusi <peter.ujfalusi@xxxxxx> 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. My guess it was out of fun. On BealgeBoard GPIO13 from twl4030 is free (LEDSYNC/GPIO.13) so it could have been used for this, or GPIO16/17 as well. > 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... I have already sent a series to support the PWMs in twl4030/6030: https://lkml.org/lkml/2012/11/8/219 It adds support for both type of PWMs (the one named as PWM and the ones named as LED since they are just PWMs). We already have leds/leds-pwm driver in upstream so we are going to use that if there is a led connected to one of them: https://lkml.org/lkml/2012/11/12/222 We can use the backlight-pwm if the LCD backlight has been hooked to one of the PWM (as it is done on SDP4430). This is why I was thinking of adding gpio/gpio-pwm driver. With that we can use the PWM as GPO line. > Sounds correct, Sascha? > >> Either way this is wrong IMHO to handle the LEDA/B via the gpio-twl4030 driver. > > It's confusing indeed. > > So what we're dealing with is: a LED-specific PWM, being used > as a PWM with eternal dutycycle and then being used as GPIO. > > Well, we get to deal with it ... :-/ gpio/gpio-pwm driver? -- Péter -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
