https://bugs.freedesktop.org/show_bug.cgi?id=75985
--- Comment #51 from Lukas Wunner <lu...@wunner.de> ---
(In reply to Maik Freudenberg from comment #31)
> As a sidenote: another user reported 5 Watts additional power draw when
> enabling the audio function. Regardless of this being accurate it should be
> taken into account to not enable it unconditionally since these are mobile
> devices.
On my GK107 I do not see any change in power consumption regardless whether bit
25 at config space offset 0x488 is set or cleared, which is somewhat
disappointing. I also do not see a change in power consumption between PCI
power state D0 and D3hot.
So if it's true that enabling the HDA increases power consumption, that would
seem to only apply to newer cards.
Could somebody verify this: Do you see a consistent drop or increase in power
consumption when enabling/disabling the HDA?
setpci -s 01:00.0 0x488.l=0x0000000:0x2000000 # disable
setpci -s 01:00.0 0x488.l=0x2000000:0x2000000 # enable
Try this a couple of times and see if powertop shows a consistent difference in
power consumption. (The laptop needs to run on battery for this to work, so
disconnect the charger.)
If you *do* see a difference, double-check whether runtime suspending the HDA
to D3hot (using my above-linked switcheroo_devlink_v2 patch set) also shows a
difference. You can force the HDA into D0 or let it autosuspend to D3hot like
this:
echo on > /sys/bus/pci/devices/0000:01:00.1/power/control # disable
echo auto > /sys/bus/pci/devices/0000:01:00.1/power/control # enable
If the reduction in power consumption turns out to be the same in D3hot versus
disabling via bit 25, there's no point in adding D3cold support to hda_intel.c.
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