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Date:   Wed, 29 Mar 2023 18:39:03 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Daniel Golle <daniel@makrotopia.org>
Cc:     netdev@vger.kernel.org, linux-mediatek@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Sean Wang <sean.wang@mediatek.com>,
        Landen Chao <Landen.Chao@mediatek.com>,
        DENG Qingfang <dqfext@gmail.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Sam Shih <Sam.Shih@mediatek.com>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        John Crispin <john@phrozen.org>, Felix Fietkau <nbd@nbd.name>
Subject: Re: [RFC PATCH net-next v3 11/15] net: dsa: mt7530: skip locking if
 MDIO bus isn't present
Message-ID: <022e2a44-31de-4667-9474-6a8518ca030a@lunn.ch>
References: <cover.1680105013.git.daniel@makrotopia.org>
 <4e6d1cbba2ff16cad5b9ac48ccdf4407f45c7857.1680105013.git.daniel@makrotopia.org>
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On Wed, Mar 29, 2023 at 04:59:47PM +0100, Daniel Golle wrote:
> As MT7530 and MT7531 internally use 32-bit wide registers, each access
> to any register of the switch requires several operations on the MDIO
> bus. Hence if there is congruent access, e.g. due to PCS or PHY
> polling, this can mess up and interfere with another ongoing register
> access sequence.
> 
> However, the MDIO bus mutex is only relevant for MDIO-connected
> switches. Prepare switches which have there registers directly mapped
> into the SoCs register space via MMIO which do not require such
> locking. There we can simply use regmap's default locking mechanism.
> 
> Hence guard mutex operations to only be performed in case of MDIO
> connected switches.
> 
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew