Black screen with KABINI with kernel 4.5 with or without DAL

[Boszormenyi Zoltan]

Hi,

we have a bunch of Zotac ZBOX NANO-AQ01 with this APU:

[    2.234372] [drm] initializing kernel modesetting (KABINI 0x1002:0x9832 0x1002:0x0123).

For our application, we force 1440x900 resolution via this modeline ("cvt 1440 900"):

     Modeline    "1440x900"  106.50  1440 1528 1672 1904  900 903 909 934 -hsync +vsync

The application is Chromium in kiosk mode. The problem is that
sometimes the screen stays black after KMS kicks in.

Currently the kernel is 4.5 with or without the DAL WIP patchset, i.e. a "git diff" between
b562e44f507e863c6792946e4e1b1449fbbac85d from Linus's GIT and
629edeae23ba531f6f5ceacf3f1fa71ba5132303 from git://people.freedesktop.org/~agd5f/linux :

commit 629edeae23ba531f6f5ceacf3f1fa71ba5132303
Author: Eric Yang <eric.yang2 at amd.com>
Date:   Wed Mar 16 16:38:28 2016 -0400

     drm/amd/dal: fix division by 0 on boot for dce80

     DCE80 used to have bandwidth parameters initialized with the dce110
     numbers. This was taken out a while ago, leaving the parameters to
     be uninitialized. This causes division by 0 on boot. This change
     resolves this by skipping bandwidth calculation and displaymark
     programming. For now, we will have dce80 always running safemark

     Reviewed-by: Eagle Yeh <eagle.yeh at amd.com>
     Signed-off-by: Eric Yang <eric.yang2 at amd.com>
     Signed-off-by: Alex Deucher <alexander.deucher at amd.com>

We use Xorg 1.16.4 and xf86-video-ati GIT with TearFree, commit ID
10b7c3def58bb34acc38f076bc230e25b454ab79. The same behaviour
is present with 4693b1bd5b5c381e8b7b68a6f7f0c6696d6a68df.

Attached is the dmesg and Xorg logs from both good and bad booting
with the DAL kernel, with "drm.debug=0x1e log_buf_len=1M" kernel options.

Our extra xorg.conf to force the 1440x900 is this:

Section "Monitor"
     Identifier    "HDMI-0"
     Option        "AutoServerLayout" "on"
     Option        "Position" "0 0"
     Modeline    "1440x900"  106.50  1440 1528 1672 1904  900 903 909 934 -hsync +vsync
EndSection

Section "Monitor"
     Identifier    "DisplayPort-0"
     Option        "AutoServerLayout" "on"
     Option        "Position" "0 0"
     Modeline    "1440x900"  106.50  1440 1528 1672 1904  900 903 909 934 -hsync +vsync
EndSection

Section "Device"
     Identifier    "RADEON"
     Driver        "radeon"
     Option        "AutoServerLayout" "on"
     Option        "Monitor-HDMI-0" "HDMI-0"
     Option        "Monitor-DisplayPort-0" "DisplayPort-0"
     Option        "TearFree" "on"
EndSection
Section "Screen"
     Identifier    "SCREEN"
     Option        "AutoServerLayout" "on"
     SubSection "Display"
         Viewport   0 0
         Modes        "1440x900"
         Depth     24
     EndSubSection
EndSection

Can someone fix this black screen problem?

Thanks in advance,
Zoltán Böszörményi

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