Attempting to diagnose suspend/resume issue

[Eric McCorkle]

A long while ago, I reported my screen not coming back on after resume,
shortly after r274386 went in.  Unfortunately, the follow-on patch
didn't seem to work for me.

(r274386 changed the way devices get powered down/up, and r274397 fixed
a typo in r274386 that tried to power down/up the wrong devices.)

I finally found the time to try and track this thing down, and I got
some information that might prove useful in tracking it down.


* The screen comes back up only for syscons in pixel mode up to r274835.
 As far as I can tell, it doesn't work for vt in any revision (not as
sure about text-mode syscons, but there is at least one revision where
it works for pixel mode, but not text mode)

* Comparing logs from r274385 and r274397, it seems the likely cause is
that the changes in r274386 reordered things so that the VGA driver
attempts to restore the state of the card before its power has been
turned back on (you can clearly see this happening, and you can see the
attempt to restore the state failing).

* Suspend/resume works fine in Linux (I'm not sure how to get linux to
printout a debug trace similar to debug.bootverbose), so the hardware
can't be /that/ broken.

* The order in which things happen during resume seems to be different
between vt and syscons resumes, though I can't tell where vt restores
the state of the card (or the efifb device)

My guess as to the likely cause is that vt also tries to restore the
state of the card before its power has been turned back on similar to
what syscons does after r274386, or else the dual happens during suspend
(it tries to save the state after the device is powered down).  It does
seem a little wierd that syscons would behave differently in that
respect for pixel mode vs text mode, though.

I'm open to suggestions as to what to look at next, or theories as to
what might be the culprit.  I also have dmesg logs for the various
revisions and drivers.

Best,
Eric

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