Date: Fri, 6 Sep 2013 16:13:25 -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: <A42A2E89-E650-4FF4-ACE3-556A8FF02E22@bsdimp.com> In-Reply-To: <1378504840.1111.480.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>
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On Sep 6, 2013, at 4:00 PM, Ian Lepore wrote: > 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. Linux is able to have one, although I'm not sure how they handle the daisy-chain... that's a new one on me... Warnerhelp
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