[Gta04-owner] 8mW sleep for Beagle Board

[Dr. H. Nikolaus Schaller]

Am 04.01.2013 um 10:21 schrieb Radek Polak:

> On Thursday, January 03, 2013 01:09:53 AM NeilBrown wrote:
> 
>> On Tue, 1 Jan 2013 16:29:45 +0100 Radek Polak <psonek2 at seznam.cz> wrote:
>>> Hi,
>>> i found this mail:
>>> 
>>> https://groups.google.com/forum/?fromgroups=#!topic/beagleboard/GXqO9rRsy
>>> Cg
>>> 
>>> Do i count right? 8mW means 2mA on 4V battery. I wonder if we could apply
>>> this also on GTA04.
>> 
>> The first patch is a useful guide for writing similar code for the GTA04.
>> The remainder aren't particularly relevant I think - the relevant
>> functionality is already in mainline.
> 
> I wonder about the HW changes - if they can be also applied on GTA04.

It is on the GTA04A5 todo list. At least the "disable 26MHz oscillator" patch.

But don't expect a dramatic effect: the oscillator is specified as 2mA max. at 1.8V, i.e.
up to 1mA from battery which can be saved.

> 
>> I've recently refreshed my understanding of the power-use situation and how
>> to make some real progress on it soon.
>> There are two parts that are needed.
>> 1/ the OMAP3 SoC need to enter 'off-mode' during suspend.
>> 2/ the twl4030 needs to turn various regulators off during off-mode.
>> 
>> The patch patch in the post you linked addresses the 2nd point.
> 
> I have tried to uncomment your twl scripts, but it did no difference. But that 
> was quite expected...
> 
>> You can get SoC to enter off-mode by compiling with PM_DEBUG=y, and
>> echo 1 > /sys/kernel/debug/omap/enable-off-mode
>> (or some file name like that).
>> 
>> One problem is that when you resume from off mode the USB ports don't work.
>> This makes it hard to use the 3G modem for example.
>> 
>> So we need to find out why USB doesn't work, and fix that.
>> We also need to find out if off-mode breaks anything else.
> 
> I'll try to play with it during weekend.
> 
> Thanks a lot Neil for your pointers!
> 
> Btw i am running 3.7 kernel now for like week and no regression spotted yet. 
> Great work!
> 
> Regards
> 
> Radek
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