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Message-ID: <ZTHH7vwG7hRneZls@octopus>
Date: Fri, 20 Oct 2023 09:21:02 +0900
From: AKASHI Takahiro <takahiro.akashi@...aro.org>
To: andy.shevchenko@...il.com
Cc: sudeep.holla@....com, cristian.marussi@....com, robh+dt@...nel.org,
krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
linus.walleij@...aro.org, Oleksii_Moisieiev@...m.com,
linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [RFC v2 0/5] gpio: add pinctrl based generic gpio driver
Hi Andy,
On Fri, Oct 20, 2023 at 12:27:58AM +0300, andy.shevchenko@...il.com wrote:
> Thu, Oct 05, 2023 at 11:58:38AM +0900, AKASHI Takahiro kirjoitti:
> > This is a revised version of my previous RFC[1]. Although I modified
> > the commits to make them look SCMI-independent, they are still posted
> > as RFC because I have never tested them on real hardware.
> >
> > (background)
> > I'm currently working on implementing SCMI pinctrl/gpio drivers
> > on U-Boot[2]. Although the pinctrl driver for the kernel[3] was submitted
> > by EPAM, it doesn't contain the gpio driver and I believe that we should
> > discuss a couple of points on the kernel side to finalize my design for
> > U-Boot.
> >
> > So this RFC is intended for reviews, especially to raise some issues.
> >
> > 1) how to obtain a value on an input pin
> > All the existing gpio drivers are set to obtain a value on an input
> > pin by accessing the hardware directly. In SCMI case, however, this is
> > just impossible in its nature and must be supported via a protocol
> > using "Input-value" configuration type. (See the spec[4], table-23.)
> >
> > The current pinconf framework is missing the feature (the pinconf
> > parameter and a helper function). See patch#1, #2 and #3.
> >
> > Please note that there is an issue around the pin configuration in
> > EPAM's current pinctrl driver as I commented[5].
> >
> > 2) DT bindings
> > I would like to propose a generic binding for pinctrl based gpio driver.
> > This allows a "consumer" driver to handle gpio pins like as other
> > normal gpio controllers support. (patch#5)
> >
> > 3) generic GPIO driver
> > Based on (2), I tried to prototype a generic driver in patch#4.
> > Thanks to a set of existing pinctrl_gpio helper functions, except (1),
> > It seems that the driver can be implemented not relying on pin controller
> > specific code, at least for SCMI pinctrl.
> >
> > I will appreciate any comments.
>
> Any comment here: I'm listed as a designated reviewer of GPIO patches, why am I
> not Cc'ed on this?
My apologies. I will add you in Cc.
> I definitely have some comments against the code (no DT,
> though). Please, use (up-to-date) MAINTAINERS in your v3.
Please don't hesitate to make comments here on v2 so that I can
include your reviews in v3.
Thanks,
-Takahiro Akashi
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
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