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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Fri, 21 May 2021 13:44:49 +0200
Message-ID: <CAPDyKFr3YbHJG4+ZUiwQym54udEERSygj8=QA0FoL6U5x3S7Dw@mail.gmail.com>
Subject: Re: [PATCH] brcmfmac: Obtain reset GPIO
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Arend van Spriel <arend.vanspriel@broadcom.com>,
        Arend van Spriel <aspriel@gmail.com>,
        Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>,
        Chi-hsien Lin <chi-hsien.lin@infineon.com>,
        Wright Feng <wright.feng@infineon.com>,
        Chung-hsien Hsu <chung-hsien.hsu@infineon.com>,
        linux-wireless <linux-wireless@vger.kernel.org>
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On Thu, 20 May 2021 at 01:41, Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Tue, May 11, 2021 at 10:48 AM Ulf Hansson <ulf.hansson@linaro.org> wrote:
>
> > I think this boils down to that to allow the mmc core to detect and
> > initialize the SDIO card, it needs to manage potential reset pins as
> > well.
> >
> > In cases when the SDIO func driver may need to execute a reset, the
> > mmc core provides two APIs, mmc_hw|sw_reset().
> >
> > Does this make sense to you?
>
> I think so, in this case (Samsung Janice on Ux500) the boot loader
> desserts reset so we are fine, but I think it should be utilized properly
> somehow, the vendor went to lots of trouble to put this reset line
> there physically.
>
> What is my next step? :D

Have a look at the mmc-pwrseq simple DT bindings.
Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.yaml

If things are as simple as I hope/think, all you should need to do is
to add a mmc-pwrseq node where you specify the GPIO reset line. Then
from the mmc controller node, just add a phandle to the mmc-pwrseq
node and things should just work. :-)

git grep mmc-pwrseq should give you a bunch of references of existing users.

Kind regards
Uffe