Re: [BUG] net/mlx5: missing sysfs hwmon entry for ConnectX-4 cards

Tariq Toukan
2024-10-16T07:05:37Z

On 15/10/2024 18:06, Jakub Kicinski wrote:
> On Thu, 10 Oct 2024 17:11:21 +0200 Til Kaiser wrote:
>> I noticed on our dual-port 100G ConnectX-4 cards (MT27700 Family)
>> running Linux Kernel version 6.6.56 and the latest ConnectX-4 firmware
>> version 12.28.2302 that we do not have a sysfs hwmon entry for reading
>> temperature values.
>> When running Kernel version 6.6.32, the hwmon entry is there again, and
>> I can read the temperature values of those cards.
>> Strangely, this problem doesn't occur on our ConnectX-4 Lx cards
>> (MT27710 Family), regardless of which Kernel version I use.
>>
>> I looked into the mlx5 core driver and noticed that it is checking the
>> MCAM register here:
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/net/ethernet/mellanox/mlx5/core/hwmon.c?h=v6.6.56#n380.
>> When I removed that check, the hwmon entry reappeared again.
>>
>> Looking into recent mlx5 commits regarding this MCAM register, I found
>> this commit:
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.6.56&id=fb035aa9a3f8fd327ab83b15a94929d2b9045995.
>> When I reverted this commit, the hwmon entry also reappeared again.
>>
>> I also found a firmware bug fix regarding that register inside the
>> ConnectX-4 Lx bug fix history here (Ref. 2339971):
>> https://docs.nvidia.com/networking/display/connectx4lxfirmwarev14321900/bug+fixes+history.
>> I couldn't find such a firmware fix for the non-Lx ConnectX-4 cards. So,
>> I'm unsure whether this might be a mlx5 driver or firmware issue.
>
> Hi, any word on this? Sounds like a fairly straightforward problem.
>

Hi,

Thanks for your report.

The hwmon sysfs entry should appear only on capable device/fw.

The driver initially used a wrong offset for the cap bit, until noticed
and fixes.

According to your description above, it seems to me that your FW doesn't
have the cap bit enabled. When reverting to the wrong offset, the driver
"happen" to point to some other enabled but unrelated feature..

Let me double check with the FW team regarding your specific FW
version/device.

Regards,
Tariq