Question regarding the power management
Raj Kumar
I have question regarding power management in kernel. What APIs are
available in linux kernel
for power management are available for device drivers? e.g. Driver is
interested in knowing the system
power startes. Which APIs the driver should register for which it will
get notifications of power states
in system?
Previously in linux kernel pm_register was used which is obselete now.
There are other things as well
like APM and ACPI. But for embedded devices, if the driver is
interested in getting the system power
states from kernel, which APIs are used?
/r
frank.sposaro
Addresses the API Change
http://groups.google.com/group/android-kernel/browse_thread/thread/150dfd8ca32d569d/59855cc803a3dc56?lnk=gst&q=power#59855cc803a3dc56
Thanks
> I have question regardingpowermanagement in kernel. What APIs are
> available in linux kernel
> forpowermanagement are available for device drivers? e.g. Driver is
> interested in knowing the systempowerstartes. Which APIs the driver should register for which it will
frank.sposaro
Any luck on this?
I am trying to trace the full process of how things get shut down when
the phone is suspended.
Where I am at right now is that when the phone is suspended or resumed
the earlysuspend.c
file executes a function and places a earlysuspend struct on a
work_queue.
I'm trying to find the specific android power management that get's
applied over top of the linux PM. (see graph in link below)
Feeling like that graph may be slightly out of date and things moved
around, but I may be missing something.
I wish those writing Android Docs would time stamp everything.
Power
http://source.android.com/porting/power_management.html
----- Attempting to trace the tree above ----
PowerManager
http://developer.android.com/reference/android/os/PowerManager.html
PowerManagerService.java
http://android.git.kernel.org/?p=platform/frameworks/base.git;a=blob;f=services/java/com/android/server/PowerManagerService.java;h=966ecb0bf5e34c61c54a73b22ade873b7e564b23;hb=HEAD
* Not finding /lib/hardware/power.c or /drivers/android/power.c *
sposaro@mobiprog:~/android-source/donut$ find . power.c | grep power.c
./hardware/libhardware_legacy/power/power.c
./msm/arch/mips/au1000/common/power.c
./msm/arch/powerpc/platforms/pseries/power.c
./msm/arch/sparc64/kernel/power.c
./msm/drivers/acpi/power.c ---- Mabey this? ACPI Bus Power
Management, but doesn't look Android Specific. 2002. See link below
./msm/drivers/parisc/power.c -- HP PARISC soft power switch
support drive
./msm/drivers/power/apm_power.c
./msm/drivers/power/pda_power.c
./msm/drivers/input/apm-power.c
./msm/drivers/net/wireless/iwlwifi/iwl-power.c
/*
* acpi_power.c - ACPI Bus Power Management
* ACPI power-managed devices may be controlled in two ways:
* 1. via "Device Specific (D-State) Control"
* 2. via "Power Resource Control".
* This module is used to manage devices relying on Power Resource
Control.
*
* An ACPI "power resource object" describes a software controllable
power
* plane, clock plane, or other resource used by a power managed
device.
* A device may rely on multiple power resources, and a power resource
* may be shared by multiple devices.
*/
http://android.git.kernel.org/?p=kernel/msm.git;a=blob;f=drivers/acpi/power.c;h=c926e7d4a0d619fd5b16a3b8d4806b05bba5aeeb;hb=android-msm-2.6.29-donut
---- Additional NDK Files. These are Android Specific, but on top of
the kernel ----
com_android_server_BatteryService.cpp
http://android.git.kernel.org/?p=platform/frameworks/base.git;a=blob;f=services/jni/com_android_server_BatteryService.cpp;h=8e7cadc6b680fc420d341faa094c71922946fdab;hb=HEAD
com_android_server_HardwareService.cpp
http://android.git.kernel.org/?p=platform/frameworks/base.git;a=blob;f=services/jni/com_android_server_HardwareService.cpp;h=253e6558de36f943dc324415a9c41e6eb23cd308;hb=HEAD
GlobalActions.java was PowerDialog.java
http://android.git.kernel.org/?p=platform/frameworks/policies/base.git;a=blob;f=mid/com/android/internal/policy/impl/GlobalActions.java;h=c7d4b14bb7def6d47f32bc5efaacd91056d51be1;hb=HEAD
Sleep and wake up as shown in dmesg
<6>[16337.332275] request_suspend_state: wakeup (3->0) at
16331561233285 (2010-06-15 01:00:37.811553944 UTC)
<4>[16337.527679] init sharp panel
<6>[16343.192291] request_suspend_state: sleep (0->3) at
16337421218656 (2010-06-15 01:00:43.671569832 UTC)
<4>[16343.234863] deinit sharp panel
/*
* prints "request_suspend_state" above
* all is seems to do is create an earlysuspend struct
* and place it on the work_queue
*/
earlysuspend.c
http://android.git.kernel.org/?p=kernel/msm.git;a=blob;f=kernel/power/earlysuspend.c;h=84bed51dcdce79503d718186775e690560d4637b;hb=HEAD
/* The early_suspend structure defines suspend and resume hooks to be
called
* when the user visible sleep state of the system changes, and a
level to
* control the order. They can be used to turn off the screen and
input
* devices that are not used for wakeup.
* Suspend handlers are called in low to high level order, resume
handlers are
* called in the opposite order. If, when calling
register_early_suspend,
* the suspend handlers have already been called without a matching
call to the
* resume handlers, the suspend handler will be called directly from
* register_early_suspend. This direct call can violate the normal
level order.
*/
earlysuspend.h
http://randomtechinfo.com/sdx/include/earlysuspend.h
power.h
http://android.git.kernel.org/?p=kernel/msm.git;a=blob;f=kernel/power/power.h;h=96cab35c3d22a3f1e337c141439c768dc4e4f4b3;hb=HEAD
> Hi all,
>
> I have question regardingpowermanagement in kernel. What APIs are
> available in linux kernel
> forpowermanagement are available for device drivers? e.g. Driver is
> interested in knowing the systempowerstartes. Which APIs the driver should register for which it will
Mike Chan
post (inline).
Applications:
Once all apps have released their wakelocks
App Framework:
Power manager service decides to suspend the device (if the user turns
off the screen)
by writing "mem" to /sys/power/state
Kernel:
early suspend hooks get called, entry point is:
kerne/power/main.c: state_store()....
196 #ifdef CONFIG_SUSPEND
197 for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
198 if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
199 break;
200 }
201 if (state < PM_SUSPEND_MAX && *s)
202 #ifdef CONFIG_EARLYSUSPEND
203 if (state == PM_SUSPEND_ON || valid_state(state)) {
204 error = 0;
205 request_suspend_state(state);
// Early suspend here (screen off is triggered here)
206 }
207 #else
208 error = enter_state(state);
// Regular linux suspend occurs here
209 #endif
210 #endif
The order which events occurs is the following:
early suspend (triggered by pressing power button to turn screen off)
normal supsend hooks (triggered by last wakelock released from the kernel)
cpu sleep
normal resume
late resume (triggers by pressing power button to turn screen on)
If you want to debug suspend, theres a few things you can do.
enable CONFIG_PM_DEBUG and PM_VERBOSE, which combined will print out
to the dmesg when each driver suspends and resumes
There is also:
/sys/module/wakelock/parameters/debug_mask
/sys/module/earlysuspend/parameters/debug_mask
you can see the debug mask flags here:
http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=kernel/power/earlysuspend.c;h=84bed51dcdce79503d718186775e690560d4637b;hb=android-2.6.32
and
-- Mike
This is more linux PM specific not so much Android, but I don't mind
answering here, just for future reference in case you want a wider
audience.
You can the register_pm_notifier() call which will register a
notifier_block and you will receive events PM_SUSPEND_PREPARE,
PM_POST_SUSPEND etc.. Only a few drivers use this, I suggest you only
use this if you have a particular spot in suspend/resume that you need
to be called. Or your driver doesn't fit well in the device tree
More commonly is to use the struct dev_pm_ops and fill in your
.suspend_noirq .resume_noirq etc...
pm_ops seems to be the new way to suspend instead of just using the
suspend/resume calls in say struct platform_driver. Chances are your
driver's struct will have a struct pm_dev_ops in there somewhere that
you can fill out when you register.
Android has an extra early_suspend hook that gets called before all
linux-pm suspend hooks, which I explain above.
-- Mike
>> /r
>
> --
> unsubscribe: android-kerne...@googlegroups.com
> website: http://groups.google.com/group/android-kernel
>
Raj Kumar
I want to add one more thing here. Also architecture specific power
management will be hooked up with the linux power management framework
like using suspend_set_ops. Which will validate which power management
modes will be supported by the hardware.
i.e when you do cat /sys/power/state
you will see which modes are supported e.g. standby, mem
cheers
raj