Kernel 4.5 radeon.runpm not working properly on Debian Testing

[gradinaruvasile]

Hi,

After upgrade to kernel 4.5 currently in testing i noticed that my laptop heated up more than usual and battery life almost halved. Turns out that the dedicated card is stuck on powered on.
I have a Dell Latitude E6540 with Intel 4600+AMD Radeon HD 8790M muxless switcable graphics and run testing on it.

This is the status when the dedicated card doesnt run anything (under kernel 4.4 it switched to dynoff):

[COLOR=#2E8B57][FONT=Monaco]# cat /sys/kernel/debug/vgaswitcheroo/switch[/FONT][/COLOR]
[COLOR=#2E8B57][FONT=Monaco]0:IGD:+:Pwr:0000:00:02.0[/FONT][/COLOR]
[COLOR=#2E8B57][FONT=Monaco]1:DIS: :Pwr:0000:01:00.0[/FONT][/COLOR]

I looked at Powertop and the system consumed no less than 25W on idle. When the AMD card is off it is ~17 W.
radeon.runpm (this variable controls the dynamic on/off events for the dedicated video card) is by default is set to on in recent kernels and it worked until 4.4. Now it does not seem to be working. Also you cannot force the card to off with

[COLOR=#2E8B57][FONT=Monaco]echo "OFF" > /sys/kernel/debug/vgaswitcheroo/switch[/FONT][/COLOR]

This will disable the card but with kernel warnings and cannot be enabled again.
Setting radeon.runpm=0 in the kernel boot options works as expected though. The card can be switched off/on manually (checked with powertop and when the card is off idle is at ~17W). But i would like the previous dynamic behavior though.
Has anyone encountered this issue?

[haagch]

Probably https://github.com/torvalds/linux/co...45e84f37484218
It was first included in 4.6-rc1 and then backported to 4.5...

https://bugzilla.kernel.org/show_bug.cgi?id=115321

https://bugzilla.kernel.org/show_bug.cgi?id=116581

https://bugzilla.kernel.org/show_bug.cgi?id=116251

It's been reverted in 4.6-rc5 (https://github.com/torvalds/linux/co...bef6f08297417f) and it looks like it is being reverted in stable too: https://www.spinics.net/lists/stable/msg129796.html

[gradinaruvasile]

Thanks for the answer.

In the last link there is the following:

Manual dGPU power down is not currently supported in the Linux driver.

But if i boot with radeon.runpm=0 with the 4.5 kernel i can power it off and on with

echo "OFF" > /sys/kernel/debug/vgaswitcheroo/switch

and

echo "ON" > /sys/kernel/debug/vgaswitcheroo/switch

And it really works, the power usage too drops with ~10w.

[Dea1993]

update to kernel 4.6rc6, with this version i've this output

0:IGD:+:Pwr:0000:00:01.0
1:DIS: :DynOff:0000:04:00.0

instead with kernel 4.6rc5 dgpu is Pwr and i must manually turn OFF