linux-kernel - Re: Droid 4: suspend to RAM?

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Message-ID: <20180809082229.GU99251@atomide.com>
Date:   Thu, 9 Aug 2018 01:22:29 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Michael Nazzareno Trimarchi <michael@...rulasolutions.com>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        Sebastian Reichel <sre@...nel.org>, nekit1000@...il.com,
        mpartap@....net, Merlijn Wajer <merlijn@...zup.org>
Subject: Re: Droid 4: suspend to RAM?

* Pavel Machek <pavel@....cz> [180808 21:35]:
> On Wed 2018-08-08 02:05:12, Tony Lindgren wrote:
> > Then for deeper idle modes, you need to also idle UARTs, and unbind or
> > unload USB related modules. You should get to something like 160mW
> > power consumption with mdm6600 enabled and SoC suspended that way.
> 
> That's slightly interesting. echo mem > /sys/power/state should do all
> the work, right? Disable UARTs etc. Plus, is 160mW still a bit high?

Yes suspend will do it, you still need to configure wake-up events
though at least for the UARTs. I think I got enabled mdm6600 to low-power
state after connecting over UART ts27010 and then suspending OHCI:

        ohci=$(find /sys/bus/platform/devices -name \*.ohci)
        devices=$(find ${ohci}/ -type d -name control)
        for device in ${devices}; do
                echo -n "auto" > ${device}/level
                echo -n "control" > ${device}/level
        done

        echo "usb-phy@1" > /sys/bus/platform/drivers/phy-mapphone-mdm6600/unbind

For power consumption, 160mW is high yeah. We currently cannot hit core
retention on omap4 until some GPIO issues are fixed. I've been trying to
think for a good fix for that, but need to debug it more when I get a chance.

>From few months ago, I recall I got droid4 to run at around 65mW idle
with WLAN connected and modem off with my test hacks. With modem on
and USB suspended I think I got to around 100mW.

Then I recall measuring droid4 with stock android in flight mode
measuring at around 15 - 30mW. But that requires off mode to work on
omap4, maybe we'll get to that too at some point after core retention.

Regards,

Tony