[Letux-kernel] Revisiting offmode - ehci - idleosc-off - 19mA

Andreas Kemnade andreas at kemnade.info
Sat Feb 24 17:35:56 CET 2018


I am at the moment reevaluating offmode together with the idleosc
turned off. With the 3.7 kernel it created trouble, so it was disabled
(writing 1 to >/sys/kernel/debug/pm_debug/enable_off_mode enables it)

Now I am trying again with letux-4.16-rc2

I got < 20mA suspend current without loading omap3_isp and ehci-omap
and still a led on.
The behaviour of ehci-omap is quite interesting.

After suspend (with increased current consumption, 34mA) the modem
and I have to rmmod ehci-omap ; modprobe ehci-omap to have it available

If I do another pair of rmmod ehci-omap ; modprobe ehci-omap
the modem disappears and I have to rfkill block/unblock it.
That behaviour is also different.

Now I tried my suspend hack again and I am at 19mA with ehci-omap
So with my patch + offmode + rmmod/modprobe after resume
we have quite nice pm.
The known downside of idleosc off was the trouble with suspend while
charging. I will check with idleosc off disabled again to see what
advantages offmode gives alone.

I am still analysing an old thread when I was discussing with NeilBrown
about ehci-omap which contains all kind of esoteric things
like modprobe ehci-omap ; rmmod ehci-omap ; modprobe ehci-omap and then
suspend with currents like 17mA.
Or decreasing(!!!) current by enabling the modem.
Now I am retrying with idleosc off, so I would expect even lower values.

I think the offmode switch should be at a more prominent place.
Hidden in a debugfs and behing CONFIG_PM_DEBUG is a bad place.
Ideas? Default in devicetree and overridable via sysfs?

PS: everything measured with modem off. I had some 28mA with modem
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