linux-kernel - Re: [net-next PATCH v11 5/9] mfd: an8855: Add support for Airoha AN8855 Switch MFD

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Message-ID: <20241217151852.wj2cbrisv6v4sdl6@skbuf>
Date: Tue, 17 Dec 2024 17:18:52 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	upstream@...oha.com
Subject: Re: [net-next PATCH v11 5/9] mfd: an8855: Add support for Airoha
 AN8855 Switch MFD

On Tue, Dec 17, 2024 at 05:13:39PM +0200, Vladimir Oltean wrote:
> On Sat, Dec 14, 2024 at 04:11:54PM +0100, Christian Marangi wrote:
> > We can see that:
> > - as suggested regmap doesn't cause any performance penality. It does
> >   even produce better result.
> > - the read/set/restore implementation gives worse performance.
> > 
> > So I guess I will follow the path of regmap + cache page. What do you
> > think?
> 
> I'm not seeing results with the "times" variable changed, but in
> general, I guess the "switch regmap + page" and "switch regmap + phy
> regmap" will remain neck and neck in terms of performance, surpassing
> the "switch regmap restore" techniques more and more as "times"
> increases. So going with a PHY regmap probably sounds good.

Could you find a way to reuse Maxime's mdio-regmap.c driver? Either
create separate regmaps for each PHY address, or make that driver
accept a configuration which isn't limited to a single ctx->valid_addr?