netdev - Re: atlantic: weird hwmon temperature readings with AQC107 NIC (kernel 5.2/5.3)

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Date:   Tue, 24 Sep 2019 16:30:48 +0200
From:   Holger Hoffstätte <holger@...lied-asynchrony.com>
To:     Netdev <netdev@...r.kernel.org>,
        Igor Russkikh <igor.russkikh@...antia.com>
Subject: Re: atlantic: weird hwmon temperature readings with AQC107 NIC
 (kernel 5.2/5.3)

On 9/24/19 4:16 PM, Holger Hoffstätte wrote:
> Hi,
> 
> I recently upgraded my home network with two AQ107-based NICs and a
> multi-speed switch. Everything works great, but I couldn't help but notice
> very weird hwmon temperature output (which I wanted to use for monitoring
> and alerting).
> 
> Both cards identify as:
> 
> $lspci -v -s 06:00.0
> 06:00.0 Ethernet controller: Aquantia Corp. AQC107 NBase-T/IEEE 802.3bz Ethernet Controller [AQtion] (rev 02)
>      Subsystem: ASUSTeK Computer Inc. AQC107 NBase-T/IEEE 802.3bz Ethernet Controller [AQtion]
> 
> In one machine lm_sensors says:
> 
> eth0-pci-0200
> Adapter: PCI adapter
> PHY Temperature: +315.1°C
> 
> This seems quite wrong since the card is only slightly warm to the touch, and
> 315.1 is exactly 255 + 60.1 - the latter value feels more like the actual
> temperature.
> 
> On a second machine it says:
> 
> eth0-pci-0600
> Adapter: PCI adapter
> PHY Temperature: +6977.0°C
> 
> I feel qualified to say that is definitely wrong as well, since the machine is
> currently not melting its way to the earth's core, and also only slightly warm
> to the touch. :)
> 
> Both cards also reported wrong values with kernel 5.2, but since I'm on 5.3.1
> I might as well report the current wrongness.
> 
> Do we know who's to blame here - motherboards, NICs, driver, kernel, hwmon
> infrastructure? I believe the hwmon patches landed first in 5.2.

Another observation: the hwmon output immediately becomes sane (~58°)
when I down the link with ifconfig. As soon as I bring the link back up,
the temperature jumps from 58° to 6976° in one second.
It seems that the presence of the carrier somehow mangles the sensor
readings. I hope this helps to find the issue.

thanks,
Holger