Re: [PATCH/RFC 0/2] gpio: of: Add DT overlay support for GPIO hogs

[Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>]

pon., 30 gru 2019 o 14:38 Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
napisał(a):
>
>         Hi all,
>
> As GPIO hogs are configured at GPIO controller initialization time,
> adding/removing GPIO hogs in Device Tree overlays currently does not
> work.  Hence this patch series adds support for that, by registering an
> of_reconfig notifier, as is already done for platform, i2c, and SPI
> devices.
>
> Perhaps this would be better served through a pinctrl-gpio driver?
> Pinctrl is already working fine with DT overlays, as the pinctrl-*
> properties are part of the slave device node, and thus looked up at
> slave device node attachment time, not at pin controller initialization
> time.
>
> In my particular use case (talking to SPI devices connected to a PMOD
> connector on the RSK+RZA1 development board), the GPIO performs board
> level muxing of a.o. the SPI MOSI/MISO/SCK signals.  Hence the hog
> really needs to be active only while talking to the SPI device, so the
> muxing could (in theory) be done upon demand.
> But how to describe that in DT, and implement it (using Runtime PM?)?
>

I may be missing the whole picture, but from your description this
sounds like a job for the mux framework. Maybe we could make runtime
PM aware of muxing for this type of use-cases?

Bart