[U-Boot] [PATCH 09/14] fdt: Add polarity-aware gpio functions to fdtdec

[Stephen Warren]

On 10/31/2012 05:59 PM, Simon Glass wrote:
> Hi,
> 
> On Fri, Oct 26, 2012 at 12:17 AM, Lucas Stach <dev at lynxeye.de> wrote:
>> Am Donnerstag, den 25.10.2012, 19:31 -0700 schrieb Simon Glass:
>>> From: Sean Paul <seanpaul at chromium.org>
>>>
>>> Add get and set gpio functions to fdtdec that take into account the
>>> polarity field in fdtdec_gpio_state.flags.
>>>
>> In another thread Stephen Warren and I came to the conclusion that we
>> most likely should remove this polarity flag from the GPIO bindings.
>>
>> Currently it is only for the USB VBUS GPIO which should move over to
>> regulators once they land in U-Boot. Do you have any other applications
>> for this flag, so we might reconsider removing it?
>>
> 
> Well, any time you have a flag which is inverted in meaning, it can be
> useful. We have several switches on the board which can be active high
> or low, and polarity is used for that.
> 
> In fact, it would be nice IMO to be able to specify input/output as
> well. I know the exynos bindings do this. There is a noddy function
> called fdtdec_setup_gpio() in U-Boot which really needs to be sorted
> out. I discussed with Stephen some time ago how GPIOs should be
> SOC-specific and it should be possible to set up a GPIO with a single
> call, as Linux does. The more information there is in the binding, the
> more it can do automatically.
> 
> Does the Tegra Linux GPIO binding still have a polarity?

Yes it does, although in practice it can't be used (and hence should
really be removed), since not all GPIO bindings have such a flag, so
there is always a need for a separate property to indicate the polarity
(c.f. fixed-regulator with GPIO control bindings for example).