CM-T3530: Linux: Power management
Overview
The Linux kernel for CM-T3530 may be built with support for very low power sleep mode and dynamic frequency scaling.
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Use cm_t35_pm_defconfig kernel configuration file to build the Linux kernel with enabled power management features. |
Frequency scaling
The Linux kernel for CM-T3530 utilizes cpu-freq framework for dynamic frequency scaling.
The CPU frequency can be changed on the fly using the following commands:
echo userspace > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor echo <frequency> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
The frequency should be specified in MHz.
Suspend to RAM
The Linux kernel for CM-T3530 supports very low power sleep mode. Use the following commands to suspend the system:
mount -t debugfs debug /sys/kernel/debug/ echo <wakeup timeout> /sys/kernel/debug/pm_debug/wakeup_timer_seconds echo 1 > /sys/kernel/debug/pm_debug/enable_off_mode echo 1 > /sys/kernel/debug/pm_debug/voltage_off_while_idle echo disabled > /sys/devices/platform/serial8250/power/wakeup echo disabled > /sys/devices/platform/serial8250.0/power/wakeup echo disabled > /sys/devices/platform/serial8250.1/power/wakeup echo disabled > /sys/devices/platform/serial8250.2/power/wakeup echo mem > /sys/power/state
Limitations
- The only wake-up source is the internal OMAP3 timer
- The USB host driver should be compiled as loadable kernel module. It must be unloaded to allow the system enter the sleep mode.
- The USB OTG driver should be excluded from the kernel
- The video capture drivers should be excluded from the kernel
