netdev - Re: [PATCH net-next 3/3] net: phy: realtek: add hwmon support for temp sensor on RTL822x

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Message-ID: <8d052f8f-d539-45ba-ba21-0a459057f313@lunn.ch>
Date: Fri, 10 Jan 2025 22:10:57 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Heiner Kallweit <hkallweit1@...il.com>
Cc: Russell King - ARM Linux <linux@...linux.org.uk>,
	Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Jean Delvare <jdelvare@...e.com>
Subject: Re: [PATCH net-next 3/3] net: phy: realtek: add hwmon support for
 temp sensor on RTL822x

> - over-temp alarm remains set, even if temperature drops below threshold

> +int rtl822x_hwmon_init(struct phy_device *phydev)
> +{
> +	struct device *hwdev, *dev = &phydev->mdio.dev;
> +	const char *name;
> +
> +	/* Ensure over-temp alarm is reset. */
> +	phy_clear_bits_mmd(phydev, MDIO_MMD_VEND2, RTL822X_VND2_TSALRM, 3);

So it is possible to clear the alarm.

I know you wanted to experiment with this some more....

If the alarm is still set, does that prevent the PHY renegotiating the
higher link speed? If you clear the alarm, does that allow it to
renegotiate the higher link speed? Or is a down/up still required?
Does an down/up clear the alarm if the temperature is below the
threshold?

Also, does HWMON support clearing alarms? Writing a 0 to the file? Or
are they supported to self clear on read?

I'm wondering if we are heading towards ABI issues? You have defined:

- over-temp alarm remains set, even if temperature drops below threshold

so that kind of eliminates the possibility of implementing self
clearing any time in the future. Explicit clearing via a write is
probably O.K, because the user needs to take an explicit action.  Are
there other ABI issues i have not thought about.

	Andrew