I'm not exactly sure how to debug this; but basically, when I =
run OpenGL
applications in windowed mode (i.e. not stretched over the entire rect), I =
get
misaligned vsync (horizontal tearing). It still syncs to the monitor rate -=
it
just misses the actual vblank by quite a bit.
The horizontal tear location depends on the size and position of the window.
For small enough window sizes, the issue becomes les pronounced and eventua=
lly
goes away completely. I can reproduce it in at least two applications - mpv=
(my
primary testing method) and glxgears (although it's more difficult to spot =
in
glxgears due to the less ideal motion). The easiest way for me to reproduce=
it
is by just running `mpv --no-config http=
s://0x0.st/7AL.mkv`.
I've tested a couple of mesa versions ranging from 17.0 to git master and c=
ould
not identify a difference, so I'm not sure if it's a regression or just a p=
lain
bug. I'm also not sure if it's an issue in mesa or in the GPU driver. I did
notice a lot of dmesg spam after startup, but that seems to be =E2=80=9Cnor=
mal=E2=80=9D:
e.g.
[ +0.000304] DMAR: DRHD: handling fault status reg 2
[ +0.000102] DMAR: [DMA Read] Request device [04:00.0] fault addr f4001aa0=
00
[fault reason 06] PTE Read access is not set
[ +0.000170] DMAR: [DMA Read] Request device [04:00.0] fault addr f4001af0=
00
[fault reason 06] PTE Read access is not set
[ +0.000169] DMAR: [DMA Read] Request device [04:00.0] fault addr f4001b50=
00
[fault reason 06] PTE Read access is not set
...
[ +0.068389] amdgpu: [powerplay] [AVFS] Something is broken. See log!
[ +0.002866] amdgpu: [powerplay] Can't find requested voltage id in
vdd_dep_on_sclk table!
[ +0.001712] amdgpu: [powerplay] VDDCI is larger than max VDDCI in VDDCI
Voltage Table!
[ +0.000152] amdgpu: [powerplay] VDDCI is larger than max VDDCI in VDDCI
Voltage Table!
I also noticed this error showing up relatively often (several times a day,
even while the machine is not in use):
[Sep12 17:58] DMAR: DRHD: handling fault status reg 40
[Sep12 17:59] DMAR: DRHD: handling fault status reg 40
Not sure if that's related to anything. The device I'm using is a Sapphire =
RX
560, the kernel version is 4.12.4. I have no ~/.drirc and the `amdgpu` modu=
le
settings are all left default.
P.s. I also noticed a strange issue where starting mpv in fullscreen and th=
en
dragging the window to be slightly bigger causes it to start miscalculating=
the
texture stride and dumping garbage data onto the screen. Unfortunately, I c=
an't
take a screenshot. I'm not sure if this is related, or a separated issue, b=
ut
it may provide a hint.