Re: Can't even enter X after kernel 4.12

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 05-12-17 16:42, Chris Chiu wrote:
> On Tue, Dec 5, 2017 at 6:40 AM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Hi Chris,
>>
>> On 30-11-17 07:27, Chris Chiu wrote:
>>>
>>> Hi,
>>>       I have a Intel cherry trail machine Haier HR101CW (CPU: x5-Z8350)
>>> which used to work fine in kernel 4.11, fails to enter X after I
>>> upgrade to kernel version later than 4.12. Even the latest 4.15, it
>>> can't even enter X now. There's no panic, oops and even no obvious
>>> error log. The panel backlight seems to be off but keyboard still
>>> responds.
>>>
>>>       Then I tried to do bisect, it tells me the commit
>>> [b7ecf663c75eed1e764f57281f9508c49c18516e] ACPI / bus: Introduce a
>>> list of ids for "always present" devices is the one which causes this.
>>> After I revert this commit, the display back to normal.
>>>
>>>       Maybe the DSDT file would help for your reference.
>>> https://gist.github.com/mschiu77/e84687cc928ac644117baf05aef47f16
>>
>>
>> Hmm, Daniel Drake from Endless send me a Vios LTH17 machine which
>> has similar symptoms. If this is indeed the same issue then adding:
>> i915.fastboot=1 to the kernel commandline should fix this.
>>
>> This is going to be the default for newer kernels soon-ish (4.16
>> I think), so we can use this as a workaround for now.
>>
>> As for the commit you bisected this to, can you try just commenting
>> out the: "80862288" entry in always_present_ids in
>> drivers/acpi/x86/utils.c ? I think that is triggering the problem.
>>
>> Without that entry we don't get backlight control, so if you
>> comment it you will likely not be able to control brightness,
>> so i915.fastboot=1 is a better fix, but it would be good to know
>> if commenting out just that entry fixes things (and breaks
>> brightness control).
>>
>> Without i915.fastboot=1 the i915 driver quickly turns the
>> backlight off and on again at boot, which I guess is confusing
>> the LCD panel...
>>
>> Regards,
>>
>> Hans
>>
> 
> Hmm...the i915.fastboot=1 seems not work on my Haier machine here.
> However, comment out the: "80862288" entry in always_present_ids in
> drivers/acpi/x86/utils.c do work. Do you need anything on this special
> machine?

On the VIOS LTH17 I just need i915.fastboot=1 and then things work
(with a 4.14 kernel) the 80862288 entry in that table makes Linux bind
to the pwm controller in the Z8350, which is usually used for brightness
control.

Do you get a brightness slider in gnome3 with the 80862288 entry commented
out? And does it work ?

Regards,

Hans