On 10/17/15 11:14, Glen Barber wrote:
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

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.

Intel i7-4700. I tried suspend with the i915kms driver active, hoping that would do the trick, but it didn't work.

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

The workaround there is just to take netif, wpa_supplicant, dhclient, and rtsold down in rc.suspend and bring them back up in rc.resume.

[1] https://github.com/freebsd/freebsd-base-graphics.git branch


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