[Bug 1912887] Re: Acer Aspire 5742g backlight brightness level is not saved on shutdown

2021-01-23 Thread unti1x
I made a couple more tests and here is what I've found out.

When the backlight is managed by radeon, writing to
/sys/class/backlight/radeon_bl0/brightness doesn't do anything. Although
changing brightness with Fn+Left/Fn+Right works but the value in
/sys/class/backlight/radeon_bl0/brightness doesn't match the actual
brightness at all: it can be 250 but the screen would be really dim and
vice versa.

When I use the kernel without radeon and drm so the backlight is managed
by acpi_video, writing to "/sys/class/backlight/acpi_video0/brightness"
works fine, the value is saved and restored properly unless it was set
to the maximum.

In both cases the brightness is reset on shutdown to the lowest possible
value and it's always the same on the bios boot screen.

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  Acer Aspire 5742g backlight brightness level is not saved on shutdown

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[Bug 1912887] Re: Acer Aspire 5742g backlight brightness level is not saved on shutdown

2021-01-23 Thread Kai-Heng Feng
I think it is, because changing
"/sys/class/backlight/radeon_bl0/brightness" by systemd-backlight
doesn't work.

So it can be 1) brightness won't be change for first time, or 2)
brightness can't be changed early. Either way, it's a driver bug.

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  Acer Aspire 5742g backlight brightness level is not saved on shutdown

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[Bug 1912887] Re: Acer Aspire 5742g backlight brightness level is not saved on shutdown

2021-01-23 Thread unti1x
I don't think this is radeon or drm bug: the problem appears with legacy
fglrx driver, in custom kernel built without radeon and drm support in
rescue mode, and in systems that don't use any of them.

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  Acer Aspire 5742g backlight brightness level is not saved on shutdown

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[Bug 1912887] Re: Acer Aspire 5742g backlight brightness level is not saved on shutdown

2021-01-23 Thread Kai-Heng Feng
Please file a bug against AMD graphics:
https://gitlab.freedesktop.org/drm/amd/issues

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  Acer Aspire 5742g backlight brightness level is not saved on shutdown

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[Bug 1912887] Re: Acer Aspire 5742g backlight brightness level is not saved on shutdown

2021-01-23 Thread unti1x
The problem still appears in the latest mainline kernel.

Linux unti1x-laptop 5.11.0-051100rc4-generic #202101180234 SMP Mon Jan
18 02:36:59 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

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  Acer Aspire 5742g backlight brightness level is not saved on shutdown

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[Bug 1912887] Re: Acer Aspire 5742g backlight brightness level is not saved on shutdown

2021-01-23 Thread Kai-Heng Feng
Please test latest mainline kernel without "acpi_osi=Linux":
https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.11-rc4/amd64/

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  Acer Aspire 5742g backlight brightness level is not saved on shutdown

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