GPIO hint meanings

[Aleksandr Rybalko]

On Fri, 06 Sep 2013 16:00:40 -0600
Ian Lepore <ian at FreeBSD.org> 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 at 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.

+1

Looks like it is kind of Freescale i.MX club :)))))

> 
> -- Ian
> 
> 
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-- 
Aleksandr Rybalko <ray at freebsd.org>