[Nouveau] [Bug 88272] [NVAC] Flickering screen on 1920x1080 monitor with 9400M in MacbookPro 5, 5

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88272

--- Comment #12 from mbazzinotti at gmail.com ---
I've got great news! I believe certain members of #nouveau and I have found a
fix!

`config=NvForcePost=1`

append appropriately to your modprobe statement or use
`nouveau.config=NvForcePost=1` in your kernel cmdline!

I will use this setting longer and report back on its effectiveness at a later
date.

== Background Story ==

I noticed that screen flicker problems disappeared after waking from a
`pm-suspend`. After reporting this to #nouveau, some more light was shed. see
the following IRC snippet (more @
https://people.freedesktop.org/~cbrill/dri-log/index.php?channel=nouveau&date=2017-12-22)

-- snip --
(regarding why pm-suspend solves the flicker bug)
15:58 imirkin: on resume we run the vbios scripts 
15:58 imirkin: on boot, we probably don't because the vbios already has

16:02 imirkin: but it could be that the interpreter skimps on DP support and so
some bits don't run 
16:02 imirkin: or it could be something else entirely 
-- end --

== Tests ==

I have tested this new config option under the following scenarios

1) Boot with mDP adapter plugged in. OK
2) Boot without mDP adapter plugged in. Then, plug in after X has started. OK

Because it works without the mDP adapter being plugged in on boot, it's safe to
say that no "mDP hint" at bootup is required to get some "optional" vbios code
to run. force POSTing is solving the problem, but we don't know why yet. What
is happening differently from normal bootup by this force post?

Perhaps another 2 mmiotrace bootup logs would shed light on this, or someone
more familiar with gpu.

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