Re: PROBLEM: Acer D255E Backlight out for 10 seconds with ACPI

[joeyli <jlee@suse.com>]

Hi Dan, 

於 四，2012-09-27 於 14:09 -0400，Dan 提到：
> On Wed, Sep 26, 2012 at 7:19 PM, joeyli <jlee@suse.com> wrote:
> > 於 三，2012-09-26 於 16:48 -0400，Dan 提到：
> >> Hello,
> >>
> >> Apologies if this was sent to the wrong place.
> >>
> >> With an Acer AOD255E netbook, the backlight goes out for exactly 10
> >> seconds before returning while booting.
> >>
> >> This is a backlight issue and not KMS, as I can shine a flashlight at
> >> the screen and still see boot text scrolling.
> >>
> >> With "acpi=off" appended to the kernel line, this no longer occurs (Fn
> >> key backlight controls still work with this appended). With every

It's a clue for that problem is happen in acpi, but sometimes the Fn key
on notebook is changed by BIOS, need check DSDT. 

> >> other acpi option I have tried, this still occurs though. This
> >> includes "acpi_backlight" and "acpi_display_output". With
> >> "acpi_backlight=vendor" the entry in /sys/class/backlight changes from
> >> acpi_video0 to acer_wmi, but backlight still goes out.
> >>
> >> Otherwise backlight works correctly.
> >
> > Could you please try this kernel parameter?
> > video.use_bios_initial_backlight=0
> >
> >
> > Thanks
> > Joey Lee
> >
> 
> Same results with that kernel parameter applied.
> 

This parameter works when _BQC used indexed value but not direct use
brightness value.
One possible thing is BIOS really set the initial index or brightness
level to lowest level.

> Just to make it clear when this is happening:
> The BIOS screen and bootloader work fine. This occurs during the boot
> process while the systemd text is scrolling (or with the splash screen
> in the case of Ubuntu). I have not been able to pin down any event
> during the boot process that triggers it. It seems to be based on time
> after the kernel loads. I can tell by the difference booting from a
> HDD vs a SSD. With a HDD, it will occur earlier in the process (close
> to the time init is called) since booting takes longer. With an SSD,
> the backlight goes out close to the time the login screen appears.
> 
> Once the backlight is out, it will stay out for exactly 10 seconds
> before returning no matter what is on the screen.
> 

What's your value of max brightness? Please run:
 # cat /sys/class/backlight/acpi_video0/max_brightness

Please also manually change brightness level after your system boot
finished, and look at does it changed or have problem like reversed?
 # echo 10 > /sys/class/backlight/acpi_video0/brightness

And, 
Please attached your acpidump:
 # acpidump > acpidump.dat


Thanks
Joey Lee


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