linux-kernel - Re: [net-next PATCH v11 6/9] net: mdio: Add Airoha AN8855 Switch MDIO Passtrough

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Message-ID: <5aec4a94-3cea-41a4-8500-71472fae51d4@lunn.ch>
Date: Tue, 10 Dec 2024 02:53:34 +0100
From: Andrew Lunn <andrew@...n.ch>
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>,
	Vladimir Oltean <olteanv@...il.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 6/9] net: mdio: Add Airoha AN8855 Switch
 MDIO Passtrough

> +static int an855_phy_restore_page(struct an8855_mfd_priv *priv,
> +				  int phy) __must_hold(&priv->bus->mdio_lock)
> +{
> +	/* Check PHY page only for addr shared with switch */
> +	if (phy != priv->switch_addr)
> +		return 0;
> +
> +	/* Don't restore page if it's not set to switch page */
> +	if (priv->current_page != FIELD_GET(AN8855_PHY_PAGE,
> +					    AN8855_PHY_PAGE_EXTENDED_4))
> +		return 0;
> +
> +	/* Restore page to 0, PHY might change page right after but that
> +	 * will be ignored as it won't be a switch page.
> +	 */
> +	return an8855_mii_set_page(priv, phy, AN8855_PHY_PAGE_STANDARD);
> +}

I don't really understand what is going on here. Maybe the commit
message needs expanding, or the function names changing.

Generally, i would expect a save/restore action. Save the current
page, swap to the PHY page, do the PHY access, and then restore to the
saved page.

	Andrew