How do I put iMX28 in standby/sleep-mode?

[SamGandhi]

Hello,

I am working on iMX28 design for industrial application (no lcd display etc.) We are running linux 3.1.X on this board. I am interested in exploring possibility of putting MX28 into standby/sleep-mode. I am looking at i.MX28 reference manual (#MCIMX28RM, Rev 1, 2010) and I can't seem to find section/register that describes how to activate those modes. Is there other document that describes how to do power management on i.MX28.

Also has anyone done this successfully while running Linux?

-Sam

[bonzo · Accepted solution]

Try testing standby modes with the usr/sbin/rtcwake utility.

$ rtcwake –d /dev/rtc0 –s 5 –m standby

-s 5 sets the number of seconds before the system wakes up.  –m standby places it into standby mode (sleep is another option).

The source for rtcwake can be found in ltib/rpm/BUILD/util-linux-ng-2.13/sys-utils after extracting it from ltib.  You may need to set some kernel options as well to include this in the rootfs  (I forgot which ones, but it may be part of imx-test).  The source code illustrates how to handle sleep and RTC wakeup.  Adding another wakeup source (i.e. Modem) should be relatively straight-forward.

Also, look at the rtc-test source code in ltib/rpm/BUILD/imx-test-10.12.01/test/mxc_rtc for more examples.

Be sure to apply the attached patches or the USB will stop working after a while when going from runàstandbyàrun. (SDK 1012).

[SamGandhi]

Hello Fabio,

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cat /sys/power/state already shows mem as its value.

I also noticed that pm.c in 2.6.35 kernel that freescale officially releases as part of its BSP has lot more features but they don't seemed to be merged upstream to 3.1.X kernel.

BTW, is there a freescale hosted git/svn repository that one can look if one wanted to get latest code?

Sam

[fabio_estevam]

I haven´t tried this on MX28, but I think you can do:

echo mem > /sys/power/state

Regards,

Fabio Estevam