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

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Date:   Wed, 23 Dec 2020 06:25:53 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Jan Engelhardt <jengelh@...i.de>
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 12/23/20 2:41 AM, Jan Engelhardt wrote:
> 
> 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 and since the information about voltages and currents is unpublished by AMD,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.
> 

Currents were always supposed to be unscaled. So this post is again
proving my point.

Either case, the code removing voltage and current support is now upstream.

Guenter