Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted
Dear Maintainer,
I investigated a bit more this issue and upon further reading these
sources regarding similar hardware:
- Backlight init fails on Surface 3 if module load order is wrong [1]
- Linux on the Dell Venue 8 Pro [2]
I gave a try at recompiling the linux kernel 5.8 from buster backports
with these two main changes (full diff below):
> $ diff /boot/config-5.8.0-0.bpo.2-amd64 config-t100ta
> # [...]
> < CONFIG_I2C_DESIGNWARE_PCI=m
> ---
> > CONFIG_I2C_DESIGNWARE_PCI=y
> 8327c8327
> < # CONFIG_PWM_CRC is not set
> ---
> > CONFIG_PWM_CRC=y
> # [...]
The resulting kernel allows indeed to adjust the screen backlight and to
completely turn it off, even though the following error message still
appears:
> asus kernel: i915 0000:00:02.0: [drm] *ERROR* Failed to own gpio for
> panel control
Now the T100TA manages to go to suspend with the screen being completely
turned off, when otherwise it usually stays turned on and just blank. I
am not sure if the device can actually suspend to ram, even with this
change only the suspend-to-idle seems available:
> $ cat /sys/power/mem_sleep
> [s2idle]
Nevertheless, battery life is improved with this change.
Do you think this configuration can be applied as default? Baytrail
chipset based devices would benefit of it.
Cheers
[1] https://gitlab.freedesktop.org/drm/intel/-/issues/26
[2] https://www.studioteabag.com/science/dell-venue-pro-linux/
Full kernel configuration diff:
> diff /boot/config-5.8.0-0.bpo.2-amd64 config-t100ta
> 5c5
> < CONFIG_CC_VERSION_TEXT="gcc-8 (Debian 8.3.0-6) 8.3.0"
> ---
> > CONFIG_CC_VERSION_TEXT="gcc (Debian 8.3.0-6) 8.3.0"
> 4134c4134
> < CONFIG_I2C_DESIGNWARE_PCI=m
> ---
> > CONFIG_I2C_DESIGNWARE_PCI=y
> 8327c8327
> < # CONFIG_PWM_CRC is not set
> ---
> > CONFIG_PWM_CRC=y
> 9138c9138
> < CONFIG_SYSTEM_TRUSTED_KEYS="debian/certs/debian-uefi-certs.pem"
> ---
> > CONFIG_SYSTEM_TRUSTED_KEYS=""
> 9296,9302c9296
> < CONFIG_DEBUG_INFO=y
> < # CONFIG_DEBUG_INFO_REDUCED is not set
> < # CONFIG_DEBUG_INFO_COMPRESSED is not set
> < # CONFIG_DEBUG_INFO_SPLIT is not set
> < # CONFIG_DEBUG_INFO_DWARF4 is not set
> < # CONFIG_DEBUG_INFO_BTF is not set
> < # CONFIG_GDB_SCRIPTS is not set
> ---
> > # CONFIG_DEBUG_INFO is not set
Reply to: