Difference between revisions of "Power management"
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==Links== | ==Links== | ||
| − | * [[ | + | * [[Linux_Dynamic_Frequency_Scaling| Another good way of decreasing mA is to use frequency scaling]] |
* [http://www.linuxjournal.com/article/6699 Power Management in Linux-Based Systems (Linux Journal)] | * [http://www.linuxjournal.com/article/6699 Power Management in Linux-Based Systems (Linux Journal)] | ||
* [http://wiki.davincidsp.com/index.php?title=Startup_shutdown_and_power_management BlackFin way of doing] | * [http://wiki.davincidsp.com/index.php?title=Startup_shutdown_and_power_management BlackFin way of doing] | ||
[[Category:Power Management]] | [[Category:Power Management]] | ||
Revision as of 09:04, 22 February 2012
Page under construction...
Informations on this page are not guaranteed !!
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)
