linux-kernel - Re: [PATCH] hwmon: xgene: access mailbox as RAM

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Date:   Fri, 9 Sep 2016 13:51:28 -0700
From:   Hoan Tran <hotran@....com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-hwmon@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Jean Delvare <jdelvare@...e.com>,
        Ashwin Chaugule <ashwin.chaugule@...aro.org>,
        Duc Dang <dhdang@....com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-doc@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>, Loc Ho <lho@....com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH] hwmon: xgene: access mailbox as RAM

On Fri, Sep 9, 2016 at 1:50 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Friday, September 9, 2016 1:43:17 PM CEST Hoan Tran wrote:
>>
>> > * Are you sure you don't need any smp_rmb()/smp_wmb() barriers
>> > between the accesses?
>>
>> No, we don't need a strict read/write during access PCC subspace. Just
>> make sure all access is committed before PCC send message to the
>> platform which done by PCC mailbox driver.
>>
>
> Ok, got it. The PCC mailbox driver presumably uses writel() to
> send the message, and that implies the necessary barrier
> (unlike writel_relaxed), right?

Yes,

Hoan
>
>         Arnd
>