net/mlx5: Expose NIC temperature via hardware monitoring kernel API

Expose NIC temperature by implementing hwmon kernel API, which turns
current thermal zone kernel API to redundant.

For each one of the supported and exposed thermal diode sensors, expose
the following attributes:
1) Input temperature.
2) Highest temperature.
3) Temperature label:
   Depends on the firmware capability, if firmware doesn't support
   sensors naming, the fallback naming convention would be: "sensorX",
   where X is the HW spec (MTMP register) sensor index.
4) Temperature critical max value:
   refers to the high threshold of Warning Event. Will be exposed as
   `tempY_crit` hwmon attribute (RO attribute). For example for
   ConnectX5 HCA's this temperature value will be 105 Celsius, 10
   degrees lower than the HW shutdown temperature).
5) Temperature reset history: resets highest temperature.

For example, for dualport ConnectX5 NIC with a single IC thermal diode
sensor will have 2 hwmon directories (one for each PCI function)
under "/sys/class/hwmon/hwmon[X,Y]".

Listing one of the directories above (hwmonX/Y) generates the
corresponding output below:

$ grep -H -d skip . /sys/class/hwmon/hwmon0/*

Output
=======================================================================
/sys/class/hwmon/hwmon0/name:mlx5
/sys/class/hwmon/hwmon0/temp1_crit:105000
/sys/class/hwmon/hwmon0/temp1_highest:48000
/sys/class/hwmon/hwmon0/temp1_input:46000
/sys/class/hwmon/hwmon0/temp1_label:asic
grep: /sys/class/hwmon/hwmon0/temp1_reset_history: Permission denied

In addition, displaying the sensors data via lm_sensors generates the
corresponding output below:

$ sensors

Output
=======================================================================
mlx5-pci-0800
Adapter: PCI adapter
asic:         +46.0°C  (crit = +105.0°C, highest = +48.0°C)

mlx5-pci-0801
Adapter: PCI adapter
asic:         +46.0°C  (crit = +105.0°C, highest = +48.0°C)

CC: Jean Delvare <jdelvare@suse.com>
Signed-off-by: Adham Faris <afaris@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230807180507.22984-3-saeed@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/Kconfig

@@ -12,6 +12,7 @@ config MLX5_CORE
 	depends on MLXFW || !MLXFW
 	depends on PTP_1588_CLOCK_OPTIONAL
 	depends on PCI_HYPERV_INTERFACE || !PCI_HYPERV_INTERFACE
+	depends on HWMON || !HWMON
 	help
 	  Core driver for low level functionality of the ConnectX-4 and
 	  Connect-IB cards by Mellanox Technologies.

drivers/net/ethernet/mellanox/mlx5/core/Makefile

@@ -82,7 +82,7 @@ endif
 mlx5_core-$(CONFIG_MLX5_BRIDGE)    += esw/bridge.o esw/bridge_mcast.o esw/bridge_debugfs.o \
 				      en/rep/bridge.o
 
-mlx5_core-$(CONFIG_THERMAL)        += thermal.o
+mlx5_core-$(CONFIG_HWMON)          += hwmon.o
 mlx5_core-$(CONFIG_MLX5_MPFS)      += lib/mpfs.o
 mlx5_core-$(CONFIG_VXLAN)          += lib/vxlan.o
 mlx5_core-$(CONFIG_PTP_1588_CLOCK) += lib/clock.o