linux-kernel - Re: [PATCH net-next 2/2] drivers: net: dsa: mt7530: MT7530 optional GPIO support

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Message-ID: <CALW65jaqciOiRxJxzPiEADgpmKa7-q2QfQnBdaVMcOa5YDHjRA@mail.gmail.com>
Date:   Mon, 11 Jan 2021 21:40:00 +0800
From:   DENG Qingfang <dqfext@...il.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        netdev <netdev@...r.kernel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>, linux-kernel@...r.kernel.org,
        René van Dorst <opensource@...rst.com>,
        Frank Wunderlich <frank-w@...lic-files.de>
Subject: Re: [PATCH net-next 2/2] drivers: net: dsa: mt7530: MT7530 optional
 GPIO support

On Mon, Jan 11, 2021 at 7:04 PM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> FYI, Documentation/driver-api/gpio/consumer.rst says:
>
>   For output GPIOs, the value provided becomes the initial output value.
>   This helps avoid signal glitching during system startup.
>
> Setting the pin to be an output, and then setting its initial value
> does not avoid the glitch. You may wish to investigate whether you
> can set the value before setting the pin as an output to avoid this
> issue.
>

So, setting the Output Enable bit _after_ setting the direction and
initial value should avoid this issue. Right?