suspend/resume on Lenovo X1 (regression from reports on wiki)

[Jung-uk Kim]

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On 2013-09-04 09:29:35 -0400, John Baldwin wrote:
> On Tuesday, September 03, 2013 6:58:55 pm Jung-uk Kim wrote:
>> On 2013-09-03 16:47:47 -0400, John Baldwin wrote:
>>> Even with that hacked so I force vgapm0 and dpms0 to attach, I 
>>> still can't resume in console mode, ...
>> 
>> What happens?  Does it panic, hang, or just no backlight?
> 
> Just no backlight.  It resumes fine and if I do it in multiuser I 
> can ssh in, etc.  It's just the backlight that doesn't resume.  I
> was hopeful dpms.ko would fix that, but it didn't. :(

Ah, that's a well-known problem and we cannot fix it without help of
machine-specific code, e.g., drm1/drm2.  Actually, both acpi_video and
dpms try to restore video settings but nothing worked for Intel GPUs +
LVDS + LCD panel AFAIK.

> I think i915drm has code to specifically turn on the backlight as
> I get some weird error message in the kernel console about a
> timeout trying to turn the panel off during suspend when I'm in X.
So, I guess it has an ordering issue.  If my memory serves, drm1 was
okay with vesa, however.  I *think* it accidentally worked because of
automatic VT-switching, which is still broken for KMS.

Jung-uk Kim
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