linux-kernel - Re: k10temp: ZEN3 readings are broken

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Date:   Wed, 23 Dec 2020 11:41:51 +0100 (CET)
From:   Jan Engelhardt <jengelh@...i.de>
To:     Guenter Roeck <linux@...ck-us.net>
cc:     Gabriel C <nix.or.die@...glemail.com>, linux-hwmon@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Wei Huang <wei.huang2@....com>
Subject: Re: k10temp: ZEN3 readings are broken


On Tuesday 2020-12-22 04:58, Guenter Roeck wrote:
>On 12/21/20 5:45 PM, Gabriel C wrote:
>> Hello Guenter,
>> 
>> while trying to add ZEN3 support for zenpower out of tree modules, I find out
>> the in-kernel k10temp driver is broken with ZEN3 ( and partially ZEN2 even ).
>
>[...] since I do not have time to actively maintain
>the driver, since each chip variant seems to use different addresses and scales,
>and since the information about voltages and currents is unpublished by AMD,
>I'll remove support for voltage/current readings from the upstream driver.

I support that decision.

/proc/cpuinfo::AMD Ryzen 7 3700X 8-Core Processor, fam 23 model 113 step 0

A synthetic load (perl -e '1 while 1') x 16 shows:
Adapter: PCI adapter
Vcore:        +1.28 V
Vsoc:         +1.02 V
Tctl:         +94.8°C
Tdie:         +94.8°C
Tccd1:        +94.8°C
Icore:       +76.00 A
Isoc:         +6.75 A

A BOINC workload on average:
k10temp-pci-00c3
Adapter: PCI adapter
Vcore:        +1.17 V  
Vsoc:         +1.02 V  
Tctl:         +94.9°C  
Tdie:         +94.9°C  
Tccd1:        +95.0°C  
Icore:       +88.00 A  
Isoc:         +8.00 A  

The BOINC workload, when it momentarily spikes:
Adapter: PCI adapter
Vcore:        +1.32 V  
Vsoc:         +1.02 V  
Tctl:         +94.1°C  
Tdie:         +94.1°C  
Tccd1:        +96.0°C  
Icore:       +105.00 A  
Isoc:         +7.75 A  

For a processor sold as a 65 W part, observing reported sensors as 
88 A x 1.17 V + 8 A x 1.02 V = 111.12 W just can't be. We are off by a 
factor of about 2.