Power management
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APF9328
APF9328 alone
Power consumption measurements have been done on an APF9328 board.
The results are available in the APF9328 datasheet.
APF9328 connected to a DevLight board
| Functionnality | power needed @ 5V | how to reduce it |
|---|---|---|
| FPGA | xxxmA | don't configure it |
| Ethernet | ifconfig eth0 down | |
| i.MXL (proc + SDRAM + Flash) | ||
| LCD | ||
APF27
Linux configuration
NOW DONE BY DEFAULT IN LATEST APF27 KERNEL CONFIGS
Power management options --->
[*] Power Management support
[*] Power Management Debug Support
[*] Verbose Power Management debugging
[*] Suspend to RAM and standby
[ ] Test suspend/resume and wakealarm during bootup
< > Advanced Power Management Emulation
power management handling is done in arch/arm/mach-mx2/pm_imx27.c
- if you put the APF27 in suspend mode, it could be interesting to be able to wake it with the "User button":
$ make linux-menuconfig
To know if driver is launched
# dmesg | grep Power Power Management for Freescale i.MX2x
Ethernet
fec_old driver currently do not implement CONFIG_PM stuff...
Power-up
- ifconfig eth0 up
Power-down
- ifconfig eth0 down -->> ~ -400 mW
Other devices
Should comply to suspend/resume device drive mechanism.
List available suspend modes
# cat /sys/power/state standby mem
Enter standby mode (i.MX in Doze mode)
# echo standby > /sys/power/state PM: Syncing filesystems ... done. PM: Preparing system for standby sleep Freezing user space processes ... (elapsed 0.00 seconds) done. Freezing remaining freezable tasks ... (elapsed 0.00 seconds) done. PM: Entering standby sleep Suspending console(s) (use no_console_suspend to debug) imx-uart imx-uart.0: preparing suspend imx-uart imx-uart.2: preparing suspend mxc_nand mxc_nand.0: preparing suspend ...
Enter suspend to memory mode (i.MX in Sleep mode)
# echo mem > /sys/power/state !! only an external interrupt can now wake up the i.MX27 !!
Debugging suspend/resume
- pass no_console_suspend as boot parameter:
BIOS> setenv console console=ttySMX0,115200 no_console_suspend BIOS> boot
Known problems
- USB: usb cause system warning :
# echo standby > /sys/power/state PM: Syncing filesystems ... done. Freezing user space processes ... (elapsed 0.01 seconds) done. Freezing remaining freezable tasks ... (elapsed 0.00 seconds) done. ___ apf27_pm_suspend ___ apf27_pm_resume ------------[ cut here ]------------ WARNING: at kernel/hrtimer.c:625 hres_timers_resume+0x3c/0x60() hres_timers_resume() called with IRQs enabled!Modules linked in: gpio [<c002c0d8>] (dump_stack+0x0/0x14) from [<c003c148>] (warn_slowpath+0x70/0x8c) [<c003c0d8>] (warn_slowpath+0x0/0x8c) from [<c0055dfc>] (hres_timers_resume+0x3c/0x60)
