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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMpxmJVN3f5vWZoUpgsM0kocmBYSO=T0OeoG--5rQi9=jk2t2g@mail.gmail.com>
Date:   Fri, 3 Jan 2020 10:51:09 +0100
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Frank Rowand <frowand.list@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Chris Brandt <chris.brandt@...esas.com>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC 0/2] gpio: of: Add DT overlay support for GPIO hogs

pon., 30 gru 2019 o 14:38 Geert Uytterhoeven <geert+renesas@...der.be>
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