Hello,
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.
Kind regards
Til
