Hi Bartosz, On Wed Nov 12, 2025 at 2:55 PM CET, Bartosz Golaszewski wrote: > Bjorn, Konrad: I should have Cc'ed you on v1 but I just went with what > came out of b4 --auto-to-cc. It only gave me arm-msm. :( Patch 7 from > this series however impacts Qualcomm platforms. It's a runtime dependency > of patches 8 and 9. Would you mind Acking it so that I can take it into > an immutable branch that I'll make available to Mark Brown for him to > take patches 8-10 through the ASoC and regulator trees for v6.19? > > Problem statement: GPIOs are implemented as a strictly exclusive > resource in the kernel but there are lots of platforms on which single > pin is shared by multiple devices which don't communicate so need some > way of properly sharing access to a GPIO. What we have now is the > GPIOD_FLAGS_BIT_NONEXCLUSIVE flag which was introduced as a hack and > doesn't do any locking or arbitration of access - it literally just hand > the same GPIO descriptor to all interested users. > > The proposed solution is composed of three major parts: the high-level, > shared GPIO proxy driver that arbitrates access to the shared pin and > exposes a regular GPIO chip interface to consumers, a low-level shared > GPIOLIB module that scans firmware nodes and creates auxiliary devices > that attach to the proxy driver and finally a set of core GPIOLIB > changes that plug the former into the GPIO lookup path. > > The changes are implemented in a way that allows to seamlessly compile > out any code related to sharing GPIOs for systems that don't need it.
The problem here is that the aarch64 defconfig has ARCH_QCOM enabled
and thus it will get enabled for any platforms, right?
I haven't grokked everything, but does GPIO_SHARED=y makes any sense
without GPIO_SHARED_PROXY? It seems to me that the probing of shared
pins will be deferred indefinitely.
> The practical use-case for this are the powerdown GPIOs shared by
> speakers on Qualcomm db845c platform, however I have also extensively
> tested it using gpio-virtuser on arm64 qemu with various DT
> configurations.
>
> I'm Cc'ing some people that may help with reviewing/be interested in
> this: OF maintainers (because the main target are OF systems initially),
> Mark Brown because most users of GPIOD_FLAGS_BIT_NONEXCLUSIVE live
> in audio or regulator drivers and one of the goals of this series is
> dropping the hand-crafted GPIO enable counting via struct
> regulator_enable_gpio in regulator core), Andy and Mika because I'd like
> to also cover ACPI (even though I don't know about any ACPI platform that
> would need this at the moment, I think it makes sense to make the
> solution complete), Dmitry (same thing but for software nodes), Mani
> (because you have a somewhat related use-case for the PERST# signal and
> I'd like to hear your input on whether this is something you can use or
> maybe it needs a separate, implicit gpio-perst driver similar to what
> Krzysztof did for reset-gpios) and Greg (because I mentioned this to you
> last week in person and I also use the auxiliary bus for the proxy
> devices).
This broke my board (using the arm64 defconfig, works without
GPIO_SHARED of course). I'm seeing two issues here with my board
(arch/arm64/boot/dts/ti/k3-am67a-kontron-sa67*):
(1) It's GPIO controller (gpio-davinci) doesn't support
.get_direction so I'm getting ENOTSUPP during probing of the
(some?) shared GPIOs.
(2) GPIO_SHARED_PROXY is default m in the defconfig, but I need the
pins for the root filesystem medium, i.e. the SD card regulators.
-michael
signature.asc
Description: PGP signature
