Old suspend/resume issue likely root cause

[Glen Barber]

On Sat, Oct 17, 2015 at 11:09:03AM -0400, Eric McCorkle wrote:
> A while back (in May or June or so), I was attempting to figure out why my
> laptop screen stayed blank on suspend/resume.  I posted some dmesg outputs
> and theorized that it might be something about the devices coming back up in
> the wrong order.  John Baldwin suggested I try doing
> hw.pci.do_power_suspend=0.
> 
> I got tangled up with other projects and had to set it aside.  However, I
> now finally have more information:
> 
> 
> * hw.pci.power_suspend=0 does cause the screen to come back up properly.
> The network (wireless via iwm driver) needs to be re-initialized, but
> everything else seems to work properly.
> 
> * Without hw.pci.power_suspend=0, the issue persists even when booting from
> EFI, so we can rule out some kind of legacy BIOS issue.  The issue manifests
> even with the experimental i915 driver, so we can rule out something with
> the efifb or VGA framebuffer drivers.
> 
> 
> Based on this, it looks pretty likely that the pci bus is the culprit. Any
> suggestions on where to look?

What graphics chipset do you have?  I noticed with dumbbell's i915kms
update branch [1], suspend/resume now works for me with Haswell
graphics, whereas previously I would experience the same blank screen on
resume you report.

(And I also see the iwm(4) reinitialization issue, as well.)

[1] https://github.com/freebsd/freebsd-base-graphics.git branch
    drm-i915-update-38

Glen

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