Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted

From	William Sones <william.r.sones@googlemail.com>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted
Date	2021-01-15 19:00 +0100
Message-ID	<BxBya-8wo-9@gated-at.bofh.it> (permalink)
References	<AYocp-qM-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Hi Everyone

I've recompiled the Debian Backports kernel 5.9.6 (with config changes
documented above by devfra@inventati.org) on the Asus T100TA along with an
i915 driver (in the firmware-misc-nonfree package) from Debian
buster-backports. I can confirm screen backlight can be adjusted and power
consumption is reduced. I also ran dmesg after triggering hibernation
(closing the laptop). It suggests the laptop is now moving into idle
without a problem, but can't enter into hibernation. It still seems to be
unable to find crystalcove, but now can control backlight with PWM.

Hope this helps!

Will

$sudo dmesg
...
[    0.000000] DMI: ASUSTeK COMPUTER INC. T100TAM/T100TAM, BIOS T100TAM.205
07/25/2014
...
[    3.972360] i915 0000:00:02.0: vgaarb: deactivate vga console
[    3.973773] i915 0000:00:02.0: vgaarb: changed VGA decodes:
olddecodes=io+mem,decodes=io+mem:owns=io+mem
[    3.974167] i915 0000:00:02.0: cannot find GPIO chip gpio_crystalcove,
deferring
[    3.974169] i915 0000:00:02.0: [drm] *ERROR* Failed to own gpio for
panel control
[    3.974697] i915 0000:00:02.0: [drm] Using PMIC PWM for LCD backlight
control
[    3.981676] [drm] Initialized i915 1.6.0 20200715 for 0000:00:02.0 on
minor 0
...
[ 3196.039364] PM: suspend entry (s2idle)
[ 3196.058281] Filesystems sync: 0.018 seconds
[ 3196.061135] (NULL device *): firmware: direct-loading firmware
regulatory.db
[ 3196.068645] (NULL device *): firmware: direct-loading firmware
brcm/brcmfmac43241b4-sdio.txt
[ 3196.068741] (NULL device *): firmware: direct-loading firmware
brcm/brcmfmac43241b4-sdio.bin
[ 3196.070542] (NULL device *): firmware: direct-loading firmware
intel/fw_sst_0f28.bin
[ 3196.071389] (NULL device *): firmware: direct-loading firmware
regulatory.db.p7s
[ 3196.071466] Freezing user space processes ... (elapsed 0.031 seconds)
done.
[ 3196.103199] OOM killer disabled.
[ 3196.103201] Freezing remaining freezable tasks ... (elapsed 0.001
seconds) done.
[ 3196.105184] printk: Suspending console(s) (use no_console_suspend to
debug)
[ 3196.154980] i2c_hid i2c-SIS0817:00: failed to change power setting.
[ 3200.390971] OOM killer enabled.
[ 3200.390973] Restarting tasks ... done.
[ 3200.421981] PM: suspend exit
[ 3217.236676] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

$ apt show firmware-misc-nonfree
Package: firmware-misc-nonfree
Version: 20200918-1~bpo10+1
...

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Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted /dev/fra <devfra@inventati.org> - 2020-10-10 16:40 +0200
  Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted /dev/fra <devfra@inventati.org> - 2020-11-07 23:30 +0100
  Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted Avinash Sonawane <rootkea@gmail.com> - 2020-11-28 07:30 +0100
  Bug#971953: linux-image-5.8: Intel Bay Trail PMIC, laptop screen backlight cannot be adjusted William Sones <william.r.sones@googlemail.com> - 2021-01-15 19:00 +0100

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