Created attachment 133866<=
/a> [details]
relevant dmesg output
I have an Alienware 15R3 laptop with hybrid Intel (HD 630) / AMD (RX470)
graphics. I run Arch Linux, up to date as of 2017-08-29.
My issue is that when booting the laptop with a 'normal' kernel command lin=
e,
the dGPU *never* turns off, even when it is not normally needed in desktop
operations. This is confirmed by running powertop, which reports a power dr=
ain
of ~36 W even under basically zero load. This is accompanied by various
[powerplay] error messages in dmesg. As a side effect, the CPU is blocked f=
rom
going to power states below pc2.
If I blacklist amdgpu in the kcl and then force the dGPU to off with acpi_c=
all,
the reported power consumption in powertop drops to ~12 W, with a correspon=
ding
increase in battery time. The CPU is now able to reach pc3.
Booting into Windows 10 also gives me the same battery time as blacklisting
amdgpu in Linux, but also the expected 'on-demand-switching' of the dGPU th=
at I
expect from such a setup. This is just to confirm that this is not a hardwa=
re
issue - it is definitely possible to dynamically switch the dGPU on or off =
from
the OS level, the implementation is just botched in amdgpu.