I am debugging a pwmtachtool<->hwmon interaction problem, observed when OpenBMC image is running on an AST2600 EVB, which is connected to a SensorsBoard and a Fan (Host is not connected). The running OpenBMC image was built using bitbake, and it includes recipes-phosphor/configuration/entity-manager/SensorBoard.json, customized for this SensorBoard. Verified that I2C sensors on the SensorsBoard are accessible via i2ctools, and behave as expected. However, running "pwmtachtool <dev_id> --get-fan-speed <fan_num>" consistently reports "Fan speed is 0", even though phy Fan is properly connected. For example:
/usr/local/bin/pwmtachtool 0 --get-fan-speed 0 --verbose
GET_TACH_SPEED:rpm value 0
Fan 0 speed is 0
cat /sys/class/hwmon/hwmon0/fan0_input
0
Looking closely at the pwmtachtool codepath, I am seeing that it calls pwmtach_action(), which reads "/sys/class/hwmon/hwmon<dev_id>/fan", which is always 0. Tried all <dev_id>/ combinations, exposed by sysfs: same result. So far, unable to figure out why this is so. I would really appreciate all recommendations for how to debug this problem.
Additional details:
ll /sys/class/hwmon/
lrwxrwxrwx 1 root root 0 Feb 16 08:52 hwmon0 -> ../../devices/platform/ahb/ahb:apb/1e610000.pwm-tacho-controller/hwmon/hwmon0
lrwxrwxrwx 1 root root 0 Feb 16 08:52 hwmon1 -> ../../devices/platform/iio-hwmon/hwmon/hwmon1
lrwxrwxrwx 1 root root 0 Feb 26 22:20 hwmon2 -> ../../devices/platform/ahb/ahb:apb/ahb:apb:bus@1e78a000/1e78a480.i2c-bus/i2c-8/8-004d/hwmon/hwmon2
ll /sys/class/hwmon/hwmon0/*
lrwxrwxrwx 1 root root 0 Feb 26 22:20 /sys/class/hwmon/hwmon0/device -> ../../../1e610000.pwm-tacho-controller
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan0_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan10_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan11_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan12_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan13_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan14_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan15_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan1_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan2_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan3_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan4_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan5_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan6_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan7_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan8_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/fan9_input
-r--r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/name
lrwxrwxrwx 1 root root 0 Feb 26 22:20 /sys/class/hwmon/hwmon0/of_node -> ../../../../../../../firmware/devicetree/base/ahb/apb/pwm-tacho-controller@1e610000
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm0
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm1
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm10
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm11
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm12
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm13
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm14
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm15
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm2
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm3
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm4
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm5
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm6
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm7
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm8
-rw-r--r-- 1 root root 4096 Feb 26 22:20 /sys/class/hwmon/hwmon0/pwm9
lrwxrwxrwx 1 root root 0 Feb 16 08:52 /sys/class/hwmon/hwmon0/subsystem -> ../../../../../../../class/hwmon
-rw-r--r-- 1 root root 4096 Feb 16 08:52 /sys/class/hwmon/hwmon0/uevent
