UM0851 datasheet(233/245 Pages) STMICROELECTRONICS

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UM0851

Power management section

Doc ID 16604 Rev 2

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10.4

Usage and performance

10.4.1

Usage: Linux PM framework

●

The status of the devices which have been setup as the wake up events, is available

through the sysfs interface. Below is the status of the devices that have the capability to

wake up SPEAr from sleep mode.

–

Wake-up source status:

If any of the sources has been enabled to provide wake-up from sleep, its status can be

captured by the following command.

$ cat /sys/devices/platform/spear-eth/power/wakeup

$ enabled

$ cat /sys/devices/platform/spear-rtc/power/wakeup

$ enabled

●

To put the system into sleep mode, execute the following command:

$ echo mem >/sys/power/state

PM: Syncing FileSystems …done

Freezing User Space processes…(elapsed 0.00 seconds) done.

Freezing remaining freezable tasks …(elapsed 0.00 seconds) done

Suspending Console(s) (use no_console_suspend to debug)

●

The system comes out of sleep mode either through the Ethernet Wake, or RTC alarm,

or through GPIO. This has been tested using the following setups:

–

Wake-up through Ethernet

Connect the SPEAR board on the network to Linux PC via a cross cable. Setup

the system IP address for SPEAR.

$ ifconfig eth0 192.168.1.11

Put the system in sleep, using the suspend command. Now from a distant PC

send across the wakeup command.

$ ether-wake <MAC Address of SPEAR)

The SPEAR board comes out of sleep and gives the following debug messages

$ Restarting Tasks … Done

–

Wake-up through RTC

Set Up the RTC alarm as the wakeup event from the application space.

The

command below sets the wakeup event after 10 seconds.

$rtc-wake -s 10

Now Put the system in sleep mode, and the system wakes up in 10 seconds. The

debug prints are same as the ones obtained for the Ethernet.

The SPEAR board comes out of sleep and gives the following debug messages

$ Restarting Tasks … Done

10.4.2

Usage: clock framework

The clock dependency tree can be viewed from user space by typing in the following

command:

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