linux-kernel - Re: [PATCH net-next] net: ethernet: ti: davinci_mdio: switch to readl/writel

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Message-ID: <5e37fb17-ccf8-540e-0cdc-bc3b71ccf259@ti.com>
Date:   Fri, 29 Mar 2019 11:11:23 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     "David S. Miller" <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>,
        Sekhar Nori <nsekhar@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH net-next] net: ethernet: ti: davinci_mdio: switch to
 readl/writel_relaxed()

Hi Arnd,

On 29.03.19 03:00, Arnd Bergmann wrote:
> On Fri, Mar 29, 2019 at 1:10 AM Grygorii Strashko
> <grygorii.strashko@...com> wrote:
>>
>> Switch to readl/writel_relaxed() APIs, because this is recommended
>> API and the MDIO block is reused on Keystone 2 SoCs
>> where LE/BE modes are supported.
>>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> 
> In general, my recommendation would be to use readl/writel instead of
> readl_relaxed/writel_relaxed everywhere, because they have much
> more predictible behavior. If you want to use the _relaxed version
> in the fast-path for data traffic, that is usually fine, but then I would
> add a comment next to it to explain why it is safe there without extra
> barriers to serialize with spinlocks and DMA.
> 

it's not fast path, so readl/writel should be ok. I'll resend.

-- 
Best regards,
grygorii