Bug 68631

Summary:	Asus Taichi31 - No second backlight (dark)
Product:	Drivers	Reporter:	Axel (axel.huebl)
Component:	Video(DRI - Intel)	Assignee:	intel-gfx-bugs (intel-gfx-bugs)
Status:	RESOLVED MOVED
Severity:	normal	CC:	aaron.lu, daniel, intel-gfx-bugs, jani.nikula
Priority:	P1
Hardware:	x86-64
OS:	Linux
Kernel Version:	3.13-rc7	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	acpidump dmesg with drm.debug=0xe dmesg with drm.debug=0xe and acpi_backlight=vendor

Description Axel 2014-01-13 01:08:06 UTC

Hi,

I posted my problem already on the linux_acpi mailing list but maybe this is a better place for it [1].

I am using a Asus Taichi31 with two screens (inside and outside on the lid).

The /sys/class/backlight only shows a acpi_video0 and intel_backlight section one can manipulate for the "inner" display.

The problem is: the outer display is working but the backlight is unchangeable set to off (besides that, one can very slightly see that it is indeed creating a picture).

Do you have any suggestions how one could change that?

Thanks a lot!
Axel

[1] http://marc.info/?l=linux-acpi&m=138938058419187&w=2

Comment 1 Aaron Lu 2014-01-13 05:45:49 UTC

It's not clear to me how the 2nd display's backlight should be controlled. Please attach your acpidump, let's see what the firmware interface provides us:
# acpidump > acpidump.txt

Comment 2 Axel 2014-01-13 08:33:52 UTC

I think the main "confusion" is that this laptop actually contains two internal screens of the same type (2x model CMN N133HSG-WJ1).
  https://lh3.ggpht.com/-nnVyB5RUhRQ/UWKPw7GbdcI/AAAAAAAAPCU/kV_RmCfIIvw/s1600/asus_taichi_31_tablet.jpg

I will add the acpidump asap in the evening, thank you Aaron.

Comment 3 Axel 2014-01-13 15:43:19 UTC

Created attachment 121871 [details]
acpidump

The result of sudo acpidump > acidump.txt with mirrored screens set.

Comment 4 Aaron Lu 2014-01-14 03:06:02 UTC

From the ACPI tables, there lists only one device that has backlight control method, so the problem is now: it's not clear how the 2nd screen is supposed be controlled regarding backlight to me.

Jani & Daniel,
Do you have any idea for the mirror screen backlight control problem? There is a link in comment #2 to show what the laptop looks like.

Comment 5 Daniel Vetter 2014-01-14 09:56:51 UTC

No idea at all ... atm we don't even link up backlights with outputs in any way, doing this is probably a requirement to get things going.

Axel, can you please boot with drm.debug=0xe and attach the complete dmesg to this bug?

Comment 6 Axel 2014-01-14 21:55:25 UTC

Created attachment 122131 [details]
dmesg with drm.debug=0xe

$ cat /proc/cmdline

BOOT_IMAGE=/vmlinuz-3.13.0-031300rc7-generic root=UUID=0e7230c6-d126-4b9e-adf3-2cd0add113cd ro drm.debug=0xe

Comment 7 Axel 2014-01-14 22:25:34 UTC

Created attachment 122141 [details]
dmesg with drm.debug=0xe and acpi_backlight=vendor

Maybe that is useful, too.

$ cat /proc/cmdline

BOOT_IMAGE=/vmlinuz-3.13.0-031300rc7-generic root=UUID=0e7230c6-d126-4b9e-adf3-2cd0add113cd ro drm.debug=0xe acpi_backlight=vendor

$ ls /sys/class/backlight/
asus-nb-wmi  intel_backlight

$ ls /proc/acpi/
button/ wakeup

Comment 8 Aaron Lu 2014-01-27 07:40:21 UTC

ping, anyone gets the time to take a look at the attached dmesg?

Comment 9 Axel 2014-01-31 17:34:19 UTC

I am also still motivated to provide more feedback on it :)

Comment 10 Jani Nikula 2014-02-25 10:34:33 UTC

We already track the issue at the fdo bugzilla, closing this one.

https://bugs.freedesktop.org/show_bug.cgi?id=73156

Comment 11 Jani Nikula 2014-02-25 10:37:15 UTC

(In reply to Axel from comment #7)
> $ ls /sys/class/backlight/
> asus-nb-wmi  intel_backlight

What happens if you change backlight using the asus-nb-wmi interface directly, i.e. sudo sh -c "echo N > /sys/class/backlight/asus-nb-wmi/brightness" where N is a value between 0 and `cat /sys/class/backlight/asus-nb-wmi/max_brightness`?

If possible, please reply to the bug at fdo.