linux-kernel - Re: [Intel-wired-lan] [PATCH v3 09/18] fm10k: Eliminate duplicate barriers on weakly-ordered archs

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Date:   Fri, 16 Mar 2018 09:30:24 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     Netdev <netdev@...r.kernel.org>, Timur Tabi <timur@...eaurora.org>,
        sulrich@...eaurora.org, linux-arm-msm@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [Intel-wired-lan] [PATCH v3 09/18] fm10k: Eliminate duplicate
 barriers on weakly-ordered archs

On Fri, Mar 16, 2018 at 9:16 AM, Sinan Kaya <okaya@...eaurora.org> wrote:
> Code includes wmb() followed by writel(). writel() already has a
> barrier on some architectures like arm64.
>
> This ends up CPU observing two barriers back to back before executing
> the register write.
>
> Since code already has an explicit barrier call, changing writel() to
> writel_relaxed().
>
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>

You can update the writel call in fm10k_tx_map as well.

Of the drivers updated in drivers/net/ethernet/intel/* it looks like
this is the only one that still requires any additional changes.

Thanks.

- Alex