linux-kernel - Re: [PATCH 2/3] pinctrl: stm32: protect configuration registers with a hwspinlock

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Message-ID: <CA+M3ks6nnj69KJay=nGS=RP2jEkPa0wibfVkwYN9-CSq=fHowg@mail.gmail.com>
Date:   Tue, 20 Nov 2018 09:38:30 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...com>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com,
        Benjamin GAIGNARD <benjamin.gaignard@...com>
Subject: Re: [PATCH 2/3] pinctrl: stm32: protect configuration registers with
 a hwspinlock

Le lun. 19 nov. 2018 à 13:20, Linus Walleij <linus.walleij@...aro.org> a écrit :
>
> On Tue, Nov 13, 2018 at 10:51 AM Benjamin Gaignard
> <benjamin.gaignard@...aro.org> wrote:
>
> > If a hwspinlock if defined in device tree use it to protect
> > configuration registers.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...com>
>
> Patch applied with Alex' ACK.

Thanks

>
> Out of curiosity: what is it protecting against?
> I would guess simultaneous access from another CPU
> but the commit doesn't say.
>
> Simultaneous access from two CPUs makes it extra important
> that all register access is read-modify-write, so I'd have a second
> check over the code to make sure this is the case.

Yes it is to protect configuration registers from being used at the same by
cortexA and cortexM.

>
> Yours,
> Linus Walleij