[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
reason.

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

Regards,
Andreas
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