GTA series power design

[Neng-Yu Tu (Tony Tu)]

Dear Harald:
> 
> I think there needs to be a lot of research/planning into the high-level
> power management profiles.  I think top-down engineering is the better
> approach here.
> 

Yes, but this comes from 2 point of view, 1 from linux itself, the other 
one is product specific/centric. handhold/portable device is heavily 
hardware based power management and custom fine tune process. Do we have 
better way out of here?

I think this is some of the essential question of linux in embedded device.

> 
>> *What PMU should we use for 6400/6410 (if we use)
> 
> Samsung has designed a special PMU to accompany the 6400/6410.
> Actually, one of their partners in Germany or Austria did the PMU
> design.  I think it is very hard to find any other stock component 
> 

Yes, Samsung S5M8750 one. But there still do not have any product using 
6400 in MP scale yet. It hard to tell it at really reliable stage ;)

And we will also have document openness issue need to fix with samsung 
first.

>> **WLAN (SDIO/SPI?)
> 
> SDIO has better software support.  SPI only if high-speed SPI (higher
> clock rates, e.g. 25-40MHz)
> 

I think should keep using SDIO if possible, but still need SD/MMC card 
interface is the problem.


I saw the 6400 support MIPI HSI interface, but I did not see any thinmg 
in market using this yet (some 3G HSDPA chipset seems support it, but 
non -popular in module)



>> **Bluetooth (USB/others?)
> 
> USB is a bad choice since it both consumes a lot of power in the
> software stack and host cpu, as well as the lack for proper wakeup
> handling (separate gpio/irq lines, complex software resume path, etc.)
> 

I don't think we will keep using USB for this :)



>> **Accelerometer (SPI)
>> **GPS (UART)
> 
>> **GSM/EDGE (UART)
> 
> Only GSM/GPRS/EDGE will run on traditional UART.  3G chipset usually
> have dual-ported memory interface.  I strongly recommend to not use USB
> here for the same reasons as with bluetooth.

EDGE still could use UART, but some 3G module seems trend to use USB. 
Also have different multiplexer need to implement.


>> suit for device power management?
> 
> the problem is mostly that the existing software deals a lot with what I
> would call 'power control', i.e. setting the devices into their power
> states.  high-level power management will have to come from product
> specification.
> 
> The product specification would have to include individual power states
> of the device, and specify power consumption targets for the individual
> stages.
> 

Following type of product may be the case, switch behavior base on 
different case, just saw in news recently.

http://www.modumobile.com/

Tony Tu