linux-kernel - Re: [RFC PATCH net-next 2/2] net: dsa: mt7530: introduce MMIO driver for MT7988 SoC

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Message-ID: <20230328141628.ahteqtqniey45wb6@skbuf>
Date:   Tue, 28 Mar 2023 17:16:28 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sam Shih <Sam.Shih@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        John Crispin <john@...ozen.org>, Felix Fietkau <nbd@....name>
Subject: Re: [RFC PATCH net-next 2/2] net: dsa: mt7530: introduce MMIO driver
 for MT7988 SoC

On Tue, Mar 28, 2023 at 02:08:18PM +0100, Daniel Golle wrote:
> I agree that using regmap would be better and I have evaluated that
> approach as well. As regmap doesn't allow lock-skipping and mt7530.c is
> much more complex than xrs700x in the way indirect access to its MDIO bus
> and interrupts work, using regmap accessors for everything would not be
> trivial.
> 
> So here we can of course use regmap_read_poll_timeout and a bunch of
> readmap_write operations. However, each of them will individually acquire
> and release the mdio bus mutex while the current code acquires the lock
> at the top of the function and then uses unlocked operations.
> regmap currently doesn't offer any way to skip the locking and/or perform
> locking manually. regmap_read, regmap_write, regmap_update_bits, ... always
> acquire and release the lock on each operation.

What does struct regmap_config :: disable_locking do?