hwmon: (ina2xx) Decouple in0 and curr1 alarms

INA2XX current limits are converted into shunt voltage limits internally
using the shunt resistor value. Once a current limit's corresponding
voltage limit is written to the hardware, shunt voltage and current
alarms are indistinguishable from each other.

This causes two issues:

1. in0/curr1 alarms may be unintentionally cleared by reading from the
   opposite input's alarm.

2. When a limit for either in0 (shunt voltage) or curr1 (current) is
   set, both of their alarms are triggered, and both of their limits
   read nonzero.

An example of this behavior on an INA231:

        # cd /sys/class/hwmon/hwmon0
        # head {curr1,in0}_input
        ==> curr1_input <==
        1713

        ==> in0_input <==
        2
        # echo 1800 >curr1_lcrit
        # head {curr1,in0}_lcrit_alarm
        ==> curr1_lcrit_alarm <==
        1

        ==> in0_lcrit_alarm <==
        0
        # head {in0,curr1}_lcrit_alarm
        ==> in0_lcrit_alarm <==
        1

        ==> curr1_lcrit_alarm <==
        0
        # head {in0,curr1}_lcrit_alarm
        ==> in0_lcrit_alarm <==
        1

        ==> curr1_lcrit_alarm <==
        1

This is because curr1 uses the same underlying masks
(INA226_SHUNT_*_VOLTAGE_MASK) as in0 on the hardware. As a result,
ina2xx_{curr,in}_read() both read the shunt voltage alarms/limits
without considering whether the voltage or current is currently set.

To fix this, track the active alarm type in ina2xx_data and guard
alarm/limit reads with a check that returns zero if the active alarm is
for a different type. The new field is initialized based on the
MASK_ENABLE register's set function, assuming voltage instead of current
when the shunt voltage mask is set.

After this fix, the alarms only read back 1 if their corresponding limit
is set:

        # echo 0 >curr1_lcrit
        # head {curr1,in0}_lcrit_alarm
        ==> curr1_lcrit_alarm <==
        0

        ==> in0_lcrit_alarm <==
        0
        # echo 9999 >curr1_lcrit
        # head {curr1,in0}_lcrit_alarm
        ==> curr1_lcrit_alarm <==
        1

        ==> in0_lcrit_alarm <==
        0
        # echo 9999 >in0_lcrit
        # head {curr1,in0}_lcrit_alarm
        ==> curr1_lcrit_alarm <==
        0

        ==> in0_lcrit_alarm <==
        1

Fixes: 4d5c2d986757 ("hwmon: (ina2xx) Add support for current limits")
Signed-off-by: Jared Kangas <jkangas@redhat.com>
Link: https://patch.msgid.link/20260820-upstream-ina2xx-in0-curr1-alarms-v2-4-fdce35abc41e@redhat.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

0 files changed, 0 insertions, 0 deletions