[Letux-kernel] power management problems in ehci-omap

Andreas Kemnade andreas at kemnade.info
Tue Feb 6 19:40:20 CET 2018

On Tue, 6 Feb 2018 10:16:23 -0800
Tony Lindgren <tony at atomide.com> wrote:

> * Andreas Kemnade <andreas at kemnade.info> [180206 18:04]:
> > On Tue, 6 Feb 2018 09:17:37 -0800
> > Tony Lindgren <tony at atomide.com> wrote:  
> > > uarts=$(find /sys/class/tty/tty[SO]*/power/ -type d 2>/dev/null)
> > > for uart in $uarts; do
> > > 	echo enabled > $uart/wakeup 2>&1
> > > 	echo auto > $uart/control 2>&1
> > > done
> > >   
> > 
> > hmm, this looks a bit like runtime suspend.  
> Not only that, it enables wakeup for UART also for suspend :)
We are using the rtc for wakeup and measure discharge of battery
for a time frame of about 300 seconds.

> That is if your dts has it configured with interrupts-extended
> for the console UART like omap3-beagle-xm.dts has for example.
> Seems like the gta04 dts don't have these.. And you also want
> to have chosen with stdout-path = &uart3 or whatever the debug
> UART is for earlycon to work.
> > I mean suspend aka echo mem >/sys/power/state
> >   
> > > echo -n 1 > /sys/kernel/debug/pm_debug/enable_off_mode  
> And the above will enable SoC and PMIC off modes, which will also
> take the suspend power to some much much lower value :) You need
> to configure the PMIC too depending if the oscillator can be turned
> off, in that case set "ti,twl4030-power-idle-osc-off". That too
> seems to be missing in gta04 dts files..
It was in our tree. It can be enabled for the gta04a5. We have even done
that. But then suspend while charging breaks. I have no idea how to do a
proper if-not-charging-power-idle-osc-off patch... 

Yes there are other places where we can optimize suspend current. But
lets first find out why ehci-omap seems to cause trouble here.
So we are looking for around 15mA of additional suspend current when the
module is loaded. 
Shouldn't the reset line of the phy (usb-nop-xceiv) be set to low when
going to suspend? I do not see code how to do it. I guess that is the

root at letux:~# cat /sys/bus/platform/devices/48064800.ehci/power/runtime_status 

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