hwmon: (pmbus) Clear generic status alarms with CLEAR_FAULTS

Some hwmon alarms fall back to STATUS_WORD summary bits when no individual limit alarm is available. On PMBus 1.2 and newer devices, pmbus_get_boolean() acknowledges these alarms with the same byte-data write used for detailed status registers. For example, PB_STATUS_INPUT is 0x2000, so it is truncated to zero when passed to _pmbus_write_byte_data(). The resulting write cannot acknowledge the input alarm. PMBus 1.3 Part II, sections 10.2.4 and 10.2.5, excludes ordinary STATUS_BYTE and STATUS_WORD summary bits from individual clearing. Their summary bits clear when the underlying status bits clear, so changing this to a word-data write would not fix the generic input alarm either. Use the existing page CLEAR_FAULTS path for generic STATUS_WORD alarms, including devices whose status accessor uses STATUS_BYTE. Keep individual byte writes for detailed status registers on PMBus 1.2 and newer devices. As with the existing older-device fallback, CLEAR_FAULTS can clear other latched status; an active condition can reassert its status.

VRVishnu Razdan committed 2 months ago