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From:   Benjamin Gaignard <benjamin.gaignard@linaro.org>
Date:   Tue, 20 Nov 2018 09:38:30 +0100
Message-ID: <CA+M3ks6nnj69KJay=nGS=RP2jEkPa0wibfVkwYN9-CSq=fHowg@mail.gmail.com>
Subject: Re: [PATCH 2/3] pinctrl: stm32: protect configuration registers with
 a hwspinlock
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-stm32@st-md-mailman.stormreply.com,
        Benjamin GAIGNARD <benjamin.gaignard@st.com>
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Le lun. 19 nov. 2018 =C3=A0 13:20, Linus Walleij <linus.walleij@linaro.org>=
 a =C3=A9crit :
>
> On Tue, Nov 13, 2018 at 10:51 AM Benjamin Gaignard
> <benjamin.gaignard@linaro.org> wrote:
>
> > If a hwspinlock if defined in device tree use it to protect
> > configuration registers.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.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