Comme=
nt # 32
on bug 10264=
6
from Peter
(In reply to L.Y. Sim from comment #30)
> I have this issue on a 3840x1600 Acer XR382CQK w=
ith an RX560 with Kernel
> 4.18.5-1 on Manjaro.=20
>=20
> When I set the refresh rate to 75Hz, severe artifacts and flickering a=
ppear.
>=20
> Both=20
>=20
> echo high > /sys/class/drm/card0/device/power_dpm_force_perform=
ance_level
> and
>=20
> echo low > /sys/class/drm/card0/device/power_dpm_force_performa=
nce_level
>=20
> stop the flickering and artifacting, and I can see via=20
>=20
> cat /sys/class/drm/card0/device/pp_dpm_mclk=20
>=20
> that the memory clocks are set to 1750Mhz and 300Mhz respectively.=20
>=20
> However, if /sys/class/drm/card0/device/power_dpm_force_performance_le=
vel is
> set to auto, I can see (via watching /sys/class/drm/card0/device/pp_dp=
m_mclk
> with time intervals around 0.1s), that the memory clock oscillates rap=
idly
> between 300Mhz, 625Mhz and 1750Mhz.
>=20
> So it seems to me that the rapid change in memory frequency is what's
> causing the flickering.
I think the "rapid change in memory frequency" really is the prob=
lem:
When I=20
echo manual > /sys/class/drm/card0/device/power_dpm_force_performance_l=
evel
and then=20
echo "0" > /sys/class/drm/card0/device/pp_dpm_mclk
or
echo "1" > /sys/class/drm/card0/device/pp_dpm_mclk
or
echo "2" > /sys/class/drm/card0/device/pp_dpm_mclk
there is no more flickering.=20
(This limits the memory clock to 300Mhz, 1000 or 2000Mhz on my RX580 card.
Using Arch Linux kernel 4.18.16 by the way.)
Whereas=20
or
echo "0 1 2" > /sys/class/drm/card0/device/pp_dpm_mclk
or any combination of 2 memory clock frequencies brings flickering back.