[BUG] ACPI battery: BAT1 status "Not charging" and capacity frozen at 99% while discharging (ASUS TUF A16 FA608UMI)

[BUG] ACPI battery: BAT1 status "Not charging" and capacity frozen at 99% while discharging (ASUS TUF A16 FA608UMI)

[calvitohq]

Hi,

On an ASUS TUF Gaming A16 (FA608UMI), running on battery, the ACPI
battery reports status "Not charging" and the capacity stays frozen at
99% even though the battery is actively discharging (~11 W measured via
current_now). Expected status while on battery is "Discharging".

Hardware:
- DMI: ASUS TUF Gaming A16, product FA608UMI (1.0), board FA608UMI
- CPU: AMD Ryzen 7 260 w/ Radeon 780M Graphics

Software:
- Distro: Bazzite (Fedora 44 atomic)
- Kernel: 7.2.4-ogc3.1.fc44.x86_64

Symptom:
With AC offline (ACAD/online=0), repeated reads give a stable (not
oscillating) "Not charging":

  /sys/class/power_supply/BAT1/status       -> "Not charging" (stable)
  /sys/class/power_supply/BAT1/capacity     -> 99 (frozen; no change over ~40 min)
  /sys/class/power_supply/BAT1/current_now  -> 617000 (~0.62 A, ~11 W drain)
  /sys/class/power_supply/BAT1/charge_now   -> 4379000 (frozen)
  /sys/class/power_supply/BAT1/charge_full  -> 4424000

UPower consequently reports state "fully-charged", percentage 99% and a
bogus "time to empty", so the desktop shows no meaningful percentage
while actually discharging.

This looks related to the existing report for the ASUS Vivobook 18
M1807HA (Launchpad bug 2152185), where status oscillates between
"Discharging"/"Not charging" while on battery due to inconsistent ACPI
_BST values. Here it is stuck rather than oscillating.

dmesg shows:
  ACPI: battery: Slot [BAT1] (battery present)
  ACPI: battery: new hook: ASUS Battery Extension

I suspect this needs a DMI-matched quirk in drivers/acpi/battery.c to
force "Discharging" when no AC supply is online, as suggested in that
earlier report.

I have the DSDT/SSDT (acpidump) available if needed, and I'm happy to
test patches.

Thanks,
Marco