Date: Fri, 06 Sep 2013 16:00:40 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Warner Losh <imp@bsdimp.com> Cc: freebsd-embedded <freebsd-embedded@FreeBSD.org> Subject: Re: GPIO hint meanings Message-ID: <1378504840.1111.480.camel@revolution.hippie.lan> In-Reply-To: <097A9AFF-D291-4D9F-92CC-12E5E453F7C7@bsdimp.com> References: <1378488150.1637.5.camel@localhost> <CAB=2f8yEx4UPc1QeHP%2BbJCDadDRvBJyvTkPjztVv4VG5uoULQw@mail.gmail.com> <097A9AFF-D291-4D9F-92CC-12E5E453F7C7@bsdimp.com>
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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: > > > On 6 September 2013 14:22, Sean Bruno <sean_bruno@yahoo.com> wrote: > > > >> I think I have a fairly firm grasp on what some of the mips/gpio hints > >> mean, e.g.: > >> > >> hint.gpio.0.pinmask > >> hint.gpioled.0.at > >> hint.gpioled.0.name > >> hint.gpioled.0.pins > >> > >> Fairly straightforward. > >> > >> Now, what do these mean/do: > >> > >> hint.gpio.0.function_set > >> hint.gpio.0.function_clear > >> > >> ? > >> > >> Sean > >> > >> p.s. I think I'll take this and thrash together a gpioled(4) and gpio(4) > >> man page if I can understand better. > >> > > > > > > Hi Sean, > > > > 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). > > > > Each SoC has its own set of pins and functions. > > > > 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. > > > We really need a pinmux/pinctl type interface for this which is standard across drivers/platforms. > 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. -- Ian
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