Re: [PATCH v0 03/12] mlxsw: core: Add core environment module for port temperature reading

From: Andrew Lunn <andrew@lunn.ch>
To: Vadim Pasternak <vadimp@mellanox.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"jiri@resnulli.us" <jiri@resnulli.us>
Subject: Re: [PATCH v0 03/12] mlxsw: core: Add core environment module for port temperature reading
Date: Thu, 21 Jun 2018 21:49:17 +0200	[thread overview]
Message-ID: <20180621194917.GC10038@lunn.ch> (raw)
In-Reply-To: <HE1PR0502MB37537B5DCD0D607DFB7C7099A2760@HE1PR0502MB3753.eurprd05.prod.outlook.com>

On Thu, Jun 21, 2018 at 07:17:03PM +0000, Vadim Pasternak wrote:
> 
> 
> > -----Original Message-----
> > From: Andrew Lunn [mailto:andrew@lunn.ch]
> > Sent: Thursday, June 21, 2018 9:35 PM
> > To: Vadim Pasternak <vadimp@mellanox.com>; Guenter Roeck <linux@roeck-
> > us.net>
> > Cc: davem@davemloft.net; netdev@vger.kernel.org; jiri@resnulli.us
> > Subject: Re: [PATCH v0 03/12] mlxsw: core: Add core environment module for
> > port temperature reading
> > 
> > > Hi Andrew,
> > 
> > Adding Guenter Roeck, the HWMON maintainer.
> > 
> > > The temperature of each individual module can be obtained through
> > > ethtool.
> > 
> > You mean via --module-info?
> 
> Yes.
> 
> > 
> > FYI: I plan to add hwmon support to the kernel SFP code. So if you ever decide to
> > swap to the kernel SFP code, not your own, the raw temperatures will be
> > exported.
> > 
> 
> Not sure it'll work for us, since we read SFP/QSFP ports through our SW/FW
> interface.

Can you make fake i2c busses? Pass the i2c transactions to the
firmware?

> But would be nice if you can provide some reference to this code.

drivers/net/phy/sfp.c

> 
> > > The worst temperature is necessary for the system cooling control
> > > decision.
> > 
> > I would expect the system cooling would understand that.
> > 
> 
> In thermal zone infrastructure there is one temperature input.
> How you can consider 64+ different inputs?

I've never used the thermal zone code. But i've used boards with 4
sensors spread around it. If the thermal zone code could not support
that, i would be surprised.

[Goes away and reads https://www.kernel.org/doc/Documentation/thermal/sysfs-api.txt]

So it sounds like, one zone is one sensor. So you actually have
hot-plugable zones, up to 64 of them. It also looks like you can bind
a zone to a cooling device. There does not seem to be a 1:1
mapping. So you should be able to bind 64 zones to one fan. Or if you
have multiple fans, bind a zone to the nearest fan.

But as i said, i'm no expert on this. You really should be posting
these patches on the hwmon list and the linux-pm list. The netdev list
does not have the needed specialist. Once Rui Zhang, Eduardo Valentin,
and Guenter Roack have given them Acked-by, David Miller can then
merge them.

      Andrew