Power Management on OMAP3 boards
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Revision as of 12:13, 5 April 2013 by Eballetbo (talk | contribs) (Created page with '= Overview = The OMAP3 hardware architecture contains a wealth of power management features. This article will take a brief look at the state of power management. The kernel us…')
Overview
The OMAP3 hardware architecture contains a wealth of power management features. This article will take a brief look at the state of power management.
The kernel used in the article below is built from the linux-2.6.37.y branch from ISEE repositories.
Enable debug options
Power management options ---> -*- Power Management support [*] Power Management Debug Support [*] Extra PM attributes in sysfs for low-level debugging/testing
Mount the debug filesystem:
mount -t debugfs nodev /sys/kernel/debug/
Basic system to suspend
To request the system to suspend just do:
# echo mem > /sys/power/state [ 231.599060] PM: Syncing filesystems ... done. [ 231.620971] Freezing user space processes ... (elapsed 0.02 seconds) done. [ 231.648345] Freezing remaining freezable tasks ... (elapsed 0.02 seconds) done. [ 231.679840] Suspending console(s) (use no_console_suspend to debug)
Sending a character on the console port the system wake up:
[ 231.695251] PM: suspend of devices complete after 8.424 msecs [ 231.695587] PM: late suspend of devices complete after 0.274 msecs [ 268.239837] Powerdomain (core_pwrdm) didn't enter target state 1 [ 268.239868] Powerdomain (usbhost_pwrdm) didn't enter target state 1 [ 268.239868] Could not enter target state in pm_suspend [ 268.240112] PM: early resume of devices complete after 0.122 msecs [ 268.322998] PM: resume of devices complete after 82.860 msecs [ 268.367065] Restarting tasks ... done.
You can also set a time interval to wake up the system:
# echo 5 > /sys/kernel/debug/pm_debug/wakeup_timer_seconds # echo mem > /sys/power/state