[Bug 97055] Black screens on A10-8780P (Carrizo) + R7 M260/M265 (Topaz) Combo

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97055

            Bug ID: 97055
           Summary: Black screens on A10-8780P (Carrizo) + R7 M260/M265
                    (Topaz) Combo
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: critical
          Priority: medium
         Component: DRM/AMDgpu
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: darktjm at gmail.com

Created attachment 125267
  --> https://bugs.freedesktop.org/attachment.cgi?id=125267&action=edit
dmesg from my latest boot (with some wifi messages at end deleted for privacy)

I have an HP Pavilion 17-g133cl with A10 Carrizo+Topaz.  I struggled for
hours/days to get this to actually display anything at all using the amdgpu
driver.  In the mean time, efifb works perfectly every time (except of course
no 3d, no X resolution switching, no brightness control, and slow enough that
video playing is also impossible).  Since it seemed like there were just issues
powering up the display controller correctly, I decided at first to add my
notes to https://bugzilla.kernel.org/show_bug.cgi?id=117591 but my symptoms
(and cures) are, indeed, different.  After much blind playing with my system (I
have no way to ssh in, and the keyboard is flaky as well, so that was a lot of
fun), I made the following observations:

  - kernel power management options appeared to have no effect
  - sometimes (very rarely), it just starts working, regardless
  - once it starts working for more than 1 minute, it stays working
  - often, it starts partially working, by giving me a flickering display
  - often, it starts working with a stable display, only to start flickering
again after a few seconds (very rarely even going completely black gain)
  - my first way of fixing it is fairly reliable, but almost always requires at
least one blind reboot before it starts giving my a display:  xrandr --output
eDP --crtc 1 (added to my .xinitrc)
   - if, when it finally comes up, it is flickering, it can be cured by
toggling the crtc between 0 and 1 often enough until it remains stable for at
least a minute.
   - if crtc 1 is enabled when X is killed, the machine goes blank and hangs
hard; switching consoles while X is up works, though (although the consoles
remain black).
   - changing the crtc to 1 in X does nothing for the console; only X displays
anything.  I have not tried to write a libdrm program to make the console
switch to crtc 1, nor have I managed to trace where the crtc list comes from,
or how to force it in the amdgpu driver itself.
   - if, instead of playing with the crtc, I play with power management again,
I seem to be able to get it working by booting once with power management
enabled, then rebooting with it disabled, and then it works (video in console
as well as X, and no crtc switching necessary).  However, that may just have
been how it decides to work today, and tomorrow it will no longer work.

I get identical behavior with kernels 4.6.2, 4.6.3, 4.6.4, 4.7-rc4 (which I
decided to try given the supposed major amdgpu overhaul), 4.4.15 (which I
decided to try given that the poster of the kernel.org bug was using Ubuntu's
4.4 kernel) (all on Gentoo; with the exception of 4.7-rc4, this is with
Gentoo's fbdecor patches, but I obviously have that disabled while working
through this problem).

Overall, this is very weird and frustrating.  I've had power management issues
with previous Radeon laptops (all of them), but the gpu pm issue usually
manifested as hard locks while playing games with power management enabled, not
this crap.  I have a feeling that anything that gets it to work only gets it to
work due to random chance, and it's just that I'm beating at it often enough
that I finally hit the jackpot at some point, and it keeps working correctly
until I power cycle for an extended period again.  I also get the feeling that
I must be a major masochist to keep using ATI/AMD hardware, given that in 15+
years of using it I've never had an experience better than "meh, mostly works".
 If I weren't dead broke, I'd have chucked this machine over a freeway overpass
and bought something else.

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