netdev - Re: [PATCH v5 net-next 08/13] net: phy: marvell-88q2xxx: add support for temperature sensor

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Message-ID: <0f9c8083-7287-40af-a084-98c692166b40@roeck-us.net>
Date: Thu, 1 Feb 2024 10:26:23 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Dimitri Fedrau <dima.fedrau@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jean Delvare <jdelvare@...e.com>,
	Stefan Eichenberger <eichest@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v5 net-next 08/13] net: phy: marvell-88q2xxx: add support
 for temperature sensor

On Thu, Feb 01, 2024 at 05:14:35PM +0100, Dimitri Fedrau wrote:
> Am Thu, Feb 01, 2024 at 05:34:05AM -0800 schrieb Guenter Roeck:
> > On 1/31/24 23:11, Dimitri Fedrau wrote:
> > > Am Wed, Jan 31, 2024 at 04:17:06PM +0100 schrieb Andrew Lunn:
> > > > > +static int mv88q2xxx_hwmon_probe(struct phy_device *phydev)
> > > > > +{
> > > > > +	struct device *dev = &phydev->mdio.dev;
> > > > > +	struct device *hwmon;
> > > > > +	char *hwmon_name;
> > > > > +	int ret;
> > > > > +
> > > > > +	/* Enable temperature sensor interrupt */
> > > > > +	ret = phy_set_bits_mmd(phydev, MDIO_MMD_PCS,
> > > > > +			       MDIO_MMD_PCS_MV_TEMP_SENSOR1,
> > > > > +			       MDIO_MMD_PCS_MV_TEMP_SENSOR1_INT_EN);
> > > > 
> > > > You enable an interrupt, but i don't see any changes to the interrupt
> > > > handler to handle any interrupts which are generated?
> > > > 
> > > Hi Andrew,
> > > 
> > > you are right. Have to remove these lines. Besides enabling the interrupt
> > > in MDIO_MMD_PCS_MV_TEMP_SENSOR1, there are two further register writes
> > > necessary to make the interrupt propagate. I didn't want it to propagate.
> > > Anyway it's wrong. I couldn't find a good solution to use the temperature
> > > interrupt. Will have a look into this, and probably figuring out how to
> > > do so. But it won't be part of this patch series.
> > > 
> > 
> > From hwmon perspective, the expected use of such an interrupt would be
> > to call hwmon_notify_event() with the affected limit attribute as argument.
> > This would notify the thermal subsystem if the sensor is registered with it
> > (your patch doesn't set the necessary flag when registering the driver,
> > so this would not happen), it will send a notification to the sysfs
> > attribute, and generate a udev event.
> >
> Thanks, noted it down. Didn't know about the notification to the thermal
> subsystem and the generated udev event. :)
> 

Note that you'd have to add something like

	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),

to the code to register the sensor as thermal zone.

Guenter