Public bug reported:
Hi everyone,
I'm experiencing a frustrating brightness regression on my Acer Nitro
AN515-58 laptop (Intel Alder Lake-P / RTX 2050) after updating the
kernel through the Mint Update Manager.
Everything works flawlessly on kernel 7.0.0-14 (physical brightness keys
change the screen light just fine). However, as soon as the system boots
into kernel 7.0.0-28, the screen gets stuck at 100% maximum brightness.
The system creates the usual `/sys/class/backlight/intel_backlight`
folder, but changing the values there has absolutely no physical effect
on the panel.
To save everybody's time, here is a summary of what I've already tried to fix
it:
1. **Modifying ACPI parameters in GRUB:** I tried editing the GRUB
configuration by testing several compatibility flags one by one, specifically
'acpi_backlight=native', 'acpi_backlight=vendor', and 'acpi_backlight=video'. I
updated GRUB after each try, but none of them restored physical control of the
backlight.
2. **Manual tests in the terminal (`/sys`):** The file
`/sys/class/backlight/intel_backlight/max_brightness` reports a limit of 32767.
If I use commands like echo to manually force lower values (e.g., 10000 or
5000) directly into the 'brightness' file, the software register updates, but
the panel physically remains stuck at 100% blinding brightness.
I checked dmesg on the broken kernel (.28) and found a severe ACPI error right
during boot:
[ 3.179431] ACPI BIOS Error (bug): Could not resolve symbol [\_TZ.ETMD],
AE_NOT_FOUND
[ 3.179518] ACPI Error: Aborting method \_SB.IETM._OSC due to previous error
It seems the newer kernel is aborting the Intel IETM method due to a
BIOS symbol mismatch, completely breaking the backlight communication
with the hardware.
For now, I had to downgrade and pin kernel 7.0.0-14 to keep my eyes from
burning, but I wanted to report this here in case other Nitro users are
hitting the same wall, or if this can be tracked/patched upstream.
Any advice or workarounds for newer kernels are highly appreciated.
Thanks! :D :D :D
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2161209
Title:
Brightness stuck at 100% on Acer Nitro AN515-58 (Kernel 7.0.0-28)
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