Date: Fri, 6 Sep 2013 16:51:47 -0600 From: Warner Losh <imp@bsdimp.com> To: Ian Lepore <ian@FreeBSD.org> Cc: freebsd-embedded <freebsd-embedded@FreeBSD.org> Subject: Re: GPIO hint meanings Message-ID: <E6F64811-B28B-4B79-AC2D-1407E03E6ADF@bsdimp.com> In-Reply-To: <1378506465.1111.489.camel@revolution.hippie.lan> References: <1378488150.1637.5.camel@localhost> <CAB=2f8yEx4UPc1QeHP%2BbJCDadDRvBJyvTkPjztVv4VG5uoULQw@mail.gmail.com> <097A9AFF-D291-4D9F-92CC-12E5E453F7C7@bsdimp.com> <1378504840.1111.480.camel@revolution.hippie.lan> <A42A2E89-E650-4FF4-ACE3-556A8FF02E22@bsdimp.com> <1378506465.1111.489.camel@revolution.hippie.lan>
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On Sep 6, 2013, at 4:27 PM, Ian Lepore wrote: > On Fri, 2013-09-06 at 16:13 -0600, Warner Losh wrote: >> On Sep 6, 2013, at 4:00 PM, Ian Lepore wrote: >>=20 >>> On Fri, 2013-09-06 at 13:42 -0600, Warner Losh wrote: >>>> On Sep 6, 2013, at 12:31 PM, Luiz Otavio O Souza wrote: >>>>=20 >>>>> On 6 September 2013 14:22, Sean Bruno <sean_bruno@yahoo.com> = wrote: >>>>>=20 >>>>>> I think I have a fairly firm grasp on what some of the mips/gpio = hints >>>>>> mean, e.g.: >>>>>>=20 >>>>>> hint.gpio.0.pinmask >>>>>> hint.gpioled.0.at >>>>>> hint.gpioled.0.name >>>>>> hint.gpioled.0.pins >>>>>>=20 >>>>>> Fairly straightforward. >>>>>>=20 >>>>>> Now, what do these mean/do: >>>>>>=20 >>>>>> hint.gpio.0.function_set >>>>>> hint.gpio.0.function_clear >>>>>>=20 >>>>>> ? >>>>>>=20 >>>>>> Sean >>>>>>=20 >>>>>> p.s. I think I'll take this and thrash together a gpioled(4) and = gpio(4) >>>>>> man page if I can understand better. >>>>>>=20 >>>>>=20 >>>>>=20 >>>>> Hi Sean, >>>>>=20 >>>>> Some of the GPIO pins on this SoC family (ar724x, ar71xx and = ar9xxx) can be >>>>> set between GPIO and an alternate function. So adding a pin to = function_set >>>>> enables this alternate function and the function_clear disables it >>>>> (sometimes the bootloader doesn't initialize properly those pins). >>>>>=20 >>>>> Each SoC has its own set of pins and functions. >>>>>=20 >>>>> For ar71xx the pins 0 and 1 can be used as additional SPI chip = select >>>>> outputs, pins 9 and 10 are used for UART and there are also = reserved pins >>>>> for a SLIC/I2S interface. >>>>=20 >>>>=20 >>>> We really need a pinmux/pinctl type interface for this which is = standard across drivers/platforms. >>>>=20 >>>=20 >>> The more ARM SoCs I look at, the less I think we could design a = single >>> pinmux api that works for all of them. The number of things that = can be >>> controlled varies from almost-nothing to chips that let you select = from >>> one of a dozen different resistor strengths for pullup or pulldown = per >>> pin. And that's not to mention really crazy things like = daisy-chaining >>> pins so the signal also goes to another pin which can be forced as = an >>> input even though it's normally a device output. >>=20 >> Linux is able to have one, although I'm not sure how they handle the = daisy-chain... that's a new one on me... >>=20 >=20 > Maybe they just don't, since it's a weird enough thing that probably > nothing uses it. I only discovered it because the datasheet said it = was > a potential workaround for an erratum that had to do with a device not > handling a pin properly. Yea, I think that linux doesn't implement that level...=20 > The semi-related thing I've been pondering lately is clock and power > management. I don't even care about dynamic stuff, just a simple = common > way for a driver to figure out what clock(s) and/or power need to be = on > for it to run, and a common api for turning them on would be nice. > (Whether clocks and power should be two separate APIs or not is a = basic > question.) I think the two are interrelated enough they need to at lest be = co-releated. But I'd love to see that... Warner=
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