Re: [PATCH v4 4/4] hwmon: (pmbus/fs1412) Add TDK FS1412 and FS1525 driver

[Guenter Roeck <linux@roeck-us.net>]

On Tue, Oct 20, 2026 at 08:02:08PM -0700, Abdurrahman Hussain wrote:
> The TDK FS1412 and FS1525 are 12A and 25A uPOL regulators with PMBus
> telemetry for input voltage, output voltage and temperature, plus the
> matching status registers. The FS1525 also reports output current and
> has an over-temperature warning limit. The FS1412 has neither:
> READ_IOUT and OT_WARN_LIMIT are not in its command table. Both read
> "KDT" from MFR_ID, which the driver checks before binding, and are
> told apart by IC_DEVICE_ID (0x0c for the FS1412, 0x19 for the FS1525).
> 
> VOUT_MODE is read-only and has bit 7 set on both: 0x98 on the FS1412
> (exponent -8) and 0x96 on the FS1525 (exponent -10). Their output
> voltage limits are relative to VOUT_COMMAND, so 0x0133 against a 0.6V
> command is a 120% over-voltage limit on the FS1412. The PMBus core
> converts them now that it supports relative VOUT encoding.
> 
> On the FS1412, OT_WARN_LIMIT answers although it is not in the command
> table, but the part reports OT_WARNING at room temperature, so the
> driver hides the register from the core and only the OT_FAULT_LIMIT
> based attributes are provided.
> 
> When the output is set with an external divider, the FS1412 reports
> READ_VOUT at the feedback pin, so in2_input and its limits all scale
> with the divider in user space. The FS1525 reports READ_VOUT as the
> output voltage and compares it against its warning and under-voltage
> limits as they are, relative to VOUT_COMMAND. Its over-voltage fault
> is an analog comparison at the feedback pin, which would read below
> in2_input on such boards, so the driver hides VOUT_OV_FAULT_LIMIT on
> the FS1525.
> 
> Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>

Applied.

Thanks,
Guenter