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

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Date:   Tue, 24 Sep 2019 16:55:27 +0200
From:   Holger Hoffstätte <holger@...lied-asynchrony.com>
To:     Igor Russkikh <Igor.Russkikh@...antia.com>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: atlantic: weird hwmon temperature readings with AQC107 NIC
 (kernel 5.2/5.3)

On 9/24/19 4:32 PM, Igor Russkikh wrote:
> We've recently found out that as well, could you try applying the following patch:
> 
> diff --git a/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_utils_fw2x.c
> b/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_utils_fw2x.c
> index da726489e3c8..08b026b41571 100644
> --- a/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_utils_fw2x.c
> +++ b/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_utils_fw2x.c
> @@ -337,7 +337,7 @@ static int aq_fw2x_get_phy_temp(struct aq_hw_s *self, int *temp)
>          /* Convert PHY temperature from 1/256 degree Celsius
>           * to 1/1000 degree Celsius.
>           */
> -       *temp = temp_res  * 1000 / 256;
> +       *temp = (temp_res & 0xFFFF)  * 1000 / 256;
> 
>          return 0;
>   }

Well, what do you know!

eth0-pci-0600
Adapter: PCI adapter
PHY Temperature:  +63.5°C

This looks like it aligns with reality. :-)

> Funny thing is that this value gets readout from HW memory, all the readouts are
> done by full dwords, but the value is only word width. High word of that dword

I suspected upper-word-garbage but of course don't know internals.

> is estimated cable length. On short cables we use it is often zero ;)

:D

When you send the proper patch feel free to add:
Tested-by: Holger Hoffstätte <holger@...lied-asynchrony.com>

Thanks again for the quick help!

Holger