Gumstix Overo Low Power Standby?

Gumstix Overo Low Power Standby?

[Blazej Kot]

Hi,

I have been working with the linux-pm kernel on the Gumstix Overo,  
seeing how low it's power consumption can go, both during the cpu "on"  
and especially while the CPU is suspended. Thus far, I've had some  
disappointing results, the best I could get is about 500mW while on,  
and 250mW while suspended (ie by running "echo mem > /sys/power/ 
state"). I am led to believe that the OMAP processor is capable of  
much lower power consumption during standby.

I am wondering if anybody in the gumstix community is looking into the  
software support for very-low-power modes on the overo. If so, I am  
wondering what the lowest power levels are which you have reached  
during standby are.

I have seen this:

http://markmail.org/message/ge5hec5f5asp7a67#query:omap%20linux 
%2080%20ma+page:1+mid:t2erlwweknakm767+state:results

Which seems to indicate the lowest power reached is 80mA at 3.3V ->  
0.264 W, which is about what I'm seeing. Is it really true that the  
overo draws a quarter of a watt when doing absolutely nothing?

Thank you,
Blazej

Re: Gumstix Overo Low Power Standby?

[Kevin Hilman]

Blazej Kot <bjk45@cornell.edu> writes:

> I have been working with the linux-pm kernel on the Gumstix Overo,
> seeing how low it's power consumption can go, both during the cpu "on"
> and especially while the CPU is suspended. Thus far, I've had some
> disappointing results, the best I could get is about 500mW while on,
> and 250mW while suspended (ie by running "echo mem > /sys/power/
> state"). I am led to believe that the OMAP processor is capable of
> much lower power consumption during standby.
>
> I am wondering if anybody in the gumstix community is looking into the
> software support for very-low-power modes on the overo. If so, I am
> wondering what the lowest power levels are which you have reached
> during standby are.
>
> I have seen this:
>
> http://markmail.org/message/ge5hec5f5asp7a67#query:omap%20linux
> %2080%20ma+page:1+mid:t2erlwweknakm767+state:results
>
> Which seems to indicate the lowest power reached is 80mA at 3.3V ->
> 0.264 W, which is about what I'm seeing. Is it really true that the
> overo draws a quarter of a watt when doing absolutely nothing?

There are lots of factors involved.

The current OMAP PM branch is focused on minimizing power consumed by
the OMAP SoC itself.  However, there are lots of other things on-board
(audio codecs, regulators, WiFi chipsets etc.) that can consume power
that we may not be currently managing in the omap kernel.

I don't have an Overo so am not familiar with all the on board
peripherals, but you should probably do some experiments where you
can put all the on-board devices into low-power/off states and
run some experiments as well.

In the case of the Beagle results you referenced, I'm pretty sure it
is something on board that is drawing the ~80mA and not on-chip.  I
assume this because setting the OMAP to use OFF-mode in suspend or
idle results in the drop of a few mA reflecting an expected drop in
power consumed by OMAP itself, but still leaving lots of power
consumed.

For example, testing today's PM branch on Beagle gives me roughly the
same numbers as the post you referenced, but slightly better:

- boot idle: 323 mA 

- screen blank: 216 mA 
  # echo 3 > /sys/class/graphics/fb0/blank

- suspend (OMAP retention): 75 mA 
  # echo mem > /sys/power/state

- sleep-while-idle: 75 mA - this same power state as suspend,
  but happens in idle 
  # echo 1 > /sys/power/sleep_while_idle 

- suspend (OMAP off): 72 mA
  # echo 1 > /sys/power/enable_off_mode
  # echo 1 > /sys/power/voltage_off_while_idle

Ultimitately the answer is that more work needs to be done with the
using the regulator framework and/or the drivers for the on-chip
peripherals to be sure they can be powered off when needed.

Hope that helps,

Kevin

Re: Gumstix Overo Low Power Standby?

[Kevin Hilman]

Kevin Hilman <khilman@deeprootsystems.com> writes:

> Blazej Kot <bjk45@cornell.edu> writes:
>
>> I have been working with the linux-pm kernel on the Gumstix Overo,
>> seeing how low it's power consumption can go, both during the cpu "on"
>> and especially while the CPU is suspended. Thus far, I've had some
>> disappointing results, the best I could get is about 500mW while on,
>> and 250mW while suspended (ie by running "echo mem > /sys/power/
>> state"). I am led to believe that the OMAP processor is capable of
>> much lower power consumption during standby.
>>
>> I am wondering if anybody in the gumstix community is looking into the
>> software support for very-low-power modes on the overo. If so, I am
>> wondering what the lowest power levels are which you have reached
>> during standby are.
>>
>> I have seen this:
>>
>> http://markmail.org/message/ge5hec5f5asp7a67#query:omap%20linux
>> %2080%20ma+page:1+mid:t2erlwweknakm767+state:results
>>
>> Which seems to indicate the lowest power reached is 80mA at 3.3V ->
>> 0.264 W, which is about what I'm seeing. Is it really true that the
>> overo draws a quarter of a watt when doing absolutely nothing?
>
> There are lots of factors involved.
>
> The current OMAP PM branch is focused on minimizing power consumed by
> the OMAP SoC itself.  However, there are lots of other things on-board
> (audio codecs, regulators, WiFi chipsets etc.) that can consume power
> that we may not be currently managing in the omap kernel.
>
> I don't have an Overo so am not familiar with all the on board
> peripherals, but you should probably do some experiments where you
> can put all the on-board devices into low-power/off states and
> run some experiments as well.
>
> In the case of the Beagle results you referenced, I'm pretty sure it
> is something on board that is drawing the ~80mA and not on-chip.  I
> assume this because setting the OMAP to use OFF-mode in suspend or
> idle results in the drop of a few mA reflecting an expected drop in
> power consumed by OMAP itself, but still leaving lots of power
> consumed.
>
> For example, testing today's PM branch on Beagle gives me roughly the
> same numbers as the post you referenced, but slightly better:
>
> - boot idle: 323 mA 
>
> - screen blank: 216 mA 
>   # echo 3 > /sys/class/graphics/fb0/blank
>
> - suspend (OMAP retention): 75 mA 
>   # echo mem > /sys/power/state
>
> - sleep-while-idle: 75 mA - this same power state as suspend,
>   but happens in idle 
>   # echo 1 > /sys/power/sleep_while_idle 
>
> - suspend (OMAP off): 72 mA
>   # echo 1 > /sys/power/enable_off_mode
>   # echo 1 > /sys/power/voltage_off_while_idle
>
> Ultimitately the answer is that more work needs to be done with the
> using the regulator framework and/or the drivers for the on-chip
> peripherals to be sure they can be powered off when needed.
>

After digging a little more in the beagle forums, someone has already
done the work to confirm that it is indeed board level design and
issues that are drawing the rest of the power on Beagle.

There's a thread[1] in the beagleboard list about how to get down to
8mW power on Beagle, but it does require hardware changes.  This
should shed some light on the types of things you'd probably have
to do for Overo.

Kevin

[1] http://groups.google.com/group/beagleboard/browse_thread/thread/197a8ef6b46cc828/6e98db4cbe2cebaa?#

Re: Gumstix Overo Low Power Standby?

[Blazej Kot]

On May 20, 2009, at 1:55 PM, Kevin Hilman wrote:

> Kevin Hilman <khilman@deeprootsystems.com> writes:
>
>> Blazej Kot <bjk45@cornell.edu> writes:
>>
>>> I have been working with the linux-pm kernel on the Gumstix Overo,
>>> seeing how low it's power consumption can go, both during the cpu  
>>> "on"
>>> and especially while the CPU is suspended. Thus far, I've had some
>>> disappointing results, the best I could get is about 500mW while on,
>>> and 250mW while suspended (ie by running "echo mem > /sys/power/
>>> state"). I am led to believe that the OMAP processor is capable of
>>> much lower power consumption during standby.
>>>
>>> I am wondering if anybody in the gumstix community is looking into  
>>> the
>>> software support for very-low-power modes on the overo. If so, I am
>>> wondering what the lowest power levels are which you have reached
>>> during standby are.
>>>
>>> I have seen this:
>>>
>>> http://markmail.org/message/ge5hec5f5asp7a67#query:omap%20linux
>>> %2080%20ma+page:1+mid:t2erlwweknakm767+state:results
>>>
>>> Which seems to indicate the lowest power reached is 80mA at 3.3V ->
>>> 0.264 W, which is about what I'm seeing. Is it really true that the
>>> overo draws a quarter of a watt when doing absolutely nothing?
>>
>> There are lots of factors involved.
>>
>> The current OMAP PM branch is focused on minimizing power consumed by
>> the OMAP SoC itself.  However, there are lots of other things on- 
>> board
>> (audio codecs, regulators, WiFi chipsets etc.) that can consume power
>> that we may not be currently managing in the omap kernel.
>>
>> I don't have an Overo so am not familiar with all the on board
>> peripherals, but you should probably do some experiments where you
>> can put all the on-board devices into low-power/off states and
>> run some experiments as well.
>>
>> In the case of the Beagle results you referenced, I'm pretty sure it
>> is something on board that is drawing the ~80mA and not on-chip.  I
>> assume this because setting the OMAP to use OFF-mode in suspend or
>> idle results in the drop of a few mA reflecting an expected drop in
>> power consumed by OMAP itself, but still leaving lots of power
>> consumed.
>>
>> For example, testing today's PM branch on Beagle gives me roughly the
>> same numbers as the post you referenced, but slightly better:
>>
>> - boot idle: 323 mA
>>
>> - screen blank: 216 mA
>>  # echo 3 > /sys/class/graphics/fb0/blank
>>
>> - suspend (OMAP retention): 75 mA
>>  # echo mem > /sys/power/state
>>
>> - sleep-while-idle: 75 mA - this same power state as suspend,
>>  but happens in idle
>>  # echo 1 > /sys/power/sleep_while_idle
>>
>> - suspend (OMAP off): 72 mA
>>  # echo 1 > /sys/power/enable_off_mode
>>  # echo 1 > /sys/power/voltage_off_while_idle
>>
>> Ultimitately the answer is that more work needs to be done with the
>> using the regulator framework and/or the drivers for the on-chip
>> peripherals to be sure they can be powered off when needed.
>>
>
> After digging a little more in the beagle forums, someone has already
> done the work to confirm that it is indeed board level design and
> issues that are drawing the rest of the power on Beagle.
>
> There's a thread[1] in the beagleboard list about how to get down to
> 8mW power on Beagle, but it does require hardware changes.  This
> should shed some light on the types of things you'd probably have
> to do for Overo.
>
> Kevin
>
> [1] http://groups.google.com/group/beagleboard/browse_thread/thread/197a8ef6b46cc828/6e98db4cbe2cebaa?#


Thanks for that, it is an interesting link. I have now reached the new  
low of around 170mW (at 3.28V), but this is high. I basically used the  
TWL (PMC) scripts in the linked post, and also turned off the U6 chip  
on the gumstix, which is the USB PHY layer driver.

Also,  I noticed that my systems becomes unusable after suspending for  
more than abut a minute, and it will not wake from sleep. I will try  
to troubleshot and narrow this down.

I am wondering, is there anyone out there working on PM issues on the  
Gumstix? Perhaps if there are some gumstix company people here they  
can answer what their status is. I will ask around on the gumstix  
emailing list also.

thanks,
Blazej

Re: Gumstix Overo Low Power Standby?

[Dirk Behme]

Blazej Kot wrote:
> 
> On May 20, 2009, at 1:55 PM, Kevin Hilman wrote:
> 
>> Kevin Hilman <khilman@deeprootsystems.com> writes:
>>
>>> Blazej Kot <bjk45@cornell.edu> writes:
>>>
>>>> I have been working with the linux-pm kernel on the Gumstix Overo,
>>>> seeing how low it's power consumption can go, both during the cpu "on"
>>>> and especially while the CPU is suspended. Thus far, I've had some
>>>> disappointing results, the best I could get is about 500mW while on,
>>>> and 250mW while suspended (ie by running "echo mem > /sys/power/
>>>> state"). I am led to believe that the OMAP processor is capable of
>>>> much lower power consumption during standby.
>>>>
>>>> I am wondering if anybody in the gumstix community is looking into the
>>>> software support for very-low-power modes on the overo. If so, I am
>>>> wondering what the lowest power levels are which you have reached
>>>> during standby are.
>>>>
>>>> I have seen this:
>>>>
>>>> http://markmail.org/message/ge5hec5f5asp7a67#query:omap%20linux
>>>> %2080%20ma+page:1+mid:t2erlwweknakm767+state:results
>>>>
>>>> Which seems to indicate the lowest power reached is 80mA at 3.3V ->
>>>> 0.264 W, which is about what I'm seeing. Is it really true that the
>>>> overo draws a quarter of a watt when doing absolutely nothing?
>>>
>>> There are lots of factors involved.
>>>
>>> The current OMAP PM branch is focused on minimizing power consumed by
>>> the OMAP SoC itself.  However, there are lots of other things on-board
>>> (audio codecs, regulators, WiFi chipsets etc.) that can consume power
>>> that we may not be currently managing in the omap kernel.
>>>
>>> I don't have an Overo so am not familiar with all the on board
>>> peripherals, but you should probably do some experiments where you
>>> can put all the on-board devices into low-power/off states and
>>> run some experiments as well.
>>>
>>> In the case of the Beagle results you referenced, I'm pretty sure it
>>> is something on board that is drawing the ~80mA and not on-chip.  I
>>> assume this because setting the OMAP to use OFF-mode in suspend or
>>> idle results in the drop of a few mA reflecting an expected drop in
>>> power consumed by OMAP itself, but still leaving lots of power
>>> consumed.
>>>
>>> For example, testing today's PM branch on Beagle gives me roughly the
>>> same numbers as the post you referenced, but slightly better:
>>>
>>> - boot idle: 323 mA
>>>
>>> - screen blank: 216 mA
>>>  # echo 3 > /sys/class/graphics/fb0/blank
>>>
>>> - suspend (OMAP retention): 75 mA
>>>  # echo mem > /sys/power/state
>>>
>>> - sleep-while-idle: 75 mA - this same power state as suspend,
>>>  but happens in idle
>>>  # echo 1 > /sys/power/sleep_while_idle
>>>
>>> - suspend (OMAP off): 72 mA
>>>  # echo 1 > /sys/power/enable_off_mode
>>>  # echo 1 > /sys/power/voltage_off_while_idle
>>>
>>> Ultimitately the answer is that more work needs to be done with the
>>> using the regulator framework and/or the drivers for the on-chip
>>> peripherals to be sure they can be powered off when needed.
>>>
>>
>> After digging a little more in the beagle forums, someone has already
>> done the work to confirm that it is indeed board level design and
>> issues that are drawing the rest of the power on Beagle.
>>
>> There's a thread[1] in the beagleboard list about how to get down to
>> 8mW power on Beagle, but it does require hardware changes.  This
>> should shed some light on the types of things you'd probably have
>> to do for Overo.
>>
>> Kevin
>>
>> [1] 
>> http://groups.google.com/group/beagleboard/browse_thread/thread/197a8ef6b46cc828/6e98db4cbe2cebaa?# 
>>
> 
> 
> Thanks for that, it is an interesting link. I have now reached the new 
> low of around 170mW (at 3.28V), but this is high. I basically used the 
> TWL (PMC) scripts in the linked post, and also turned off the U6 chip on 
> the gumstix, which is the USB PHY layer driver.
> 
> Also,  I noticed that my systems becomes unusable after suspending for 
> more than abut a minute, and it will not wake from sleep. I will try to 
> troubleshot and narrow this down.

I think to remember there was some discussion about SDRAM self 
refresh. Look for thread "OMAP3: PM: SDRC: ensure mux of SDRC clock 
enable pins for self-refresh" and

http://www.sakoman.net/cgi-bin/gitweb.cgi?p=u-boot-omap3.git;a=commit;h=4025cfbde3611b14c0d4831a5524e5e061128e30

Just guessing, though.

Dirk

> I am wondering, is there anyone out there working on PM issues on the 
> Gumstix? Perhaps if there are some gumstix company people here they can 
> answer what their status is. I will ask around on the gumstix emailing 
> list also.
> 
> thanks,
> Blazej
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-omap" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: Gumstix Overo Low Power Standby?

[Blazej Kot]

On May 27, 2009, at 2:59 PM, Dirk Behme wrote:

> Blazej Kot wrote:
>>
>> Thanks for that, it is an interesting link. I have now reached the  
>> new low of around 170mW (at 3.28V), but this is high. I basically  
>> used the TWL (PMC) scripts in the linked post, and also turned off  
>> the U6 chip on the gumstix, which is the USB PHY layer driver.
>> Also,  I noticed that my systems becomes unusable after suspending  
>> for more than abut a minute, and it will not wake from sleep. I  
>> will try to troubleshot and narrow this down.
>
> I think to remember there was some discussion about SDRAM self  
> refresh. Look for thread "OMAP3: PM: SDRC: ensure mux of SDRC clock  
> enable pins for self-refresh" and
>
> http://www.sakoman.net/cgi-bin/gitweb.cgi?p=u-boot-omap3.git;a=commit;h=4025cfbde3611b14c0d4831a5524e5e061128e30
>
> Just guessing, though.
>
> Dirk

Yes, you are quite right. Kevin Hilman pointed out the patch [1] to  
me, I just applied it and suspend/resume works for at least 5-10  
minutes. I'll try it overnight next :)

One small thing is I had to manually insert and  include for mach/ 
mux.c to the top of sdrc.c for it to compile.

Thanks!
Blazej

PS: I'm now down to 141mW in suspend :) I know a lot of the rest must  
be getting used up in the TPS/TWL PM chip, as it is slightly warm to  
the touch while the OMAP/RAM stack and the only other chip on the  
overo, the USB PHY chip, are stone cold to the touch.

[1] http://marc.info/?l=linux-omap&m=124283570910883&w=2
>