GTA series power design

[Harald Welte]

Hi Tony!

On Mon, Mar 31, 2008 at 12:37:41AM +0800, Neng-Yu Tu (Tony Tu) wrote:
> I think one of the most important thing in mobile device is power  
> management design, but up to this point, we still don't have clear  
> picture of power management design abstract layer for application and  
> lower level hardware.

agreed.

> I saw Intel moblin (http://www.moblin.org/projects/projects_ppm.php) has  
> some power management profile as interface for applications. Do we need  
> have smiliar design in hardware power bus and software profile parser  
> middleware?

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.


> *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 

> **WLAN (SDIO/SPI?)

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

> **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.)

> **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.

> **Debug (UART/Others?)

UART + JTAG is just fine

> **lots LED
> **Some mechanical button, some other types

those two don't have particular power management aspects

> **Wolfson I2S

there's litte alternative.  well, AC97. but I think it's not that mcuh
different from I2S

> *Any bus design in hardware we could do for better power management design

I think USB is probably the worst. If you keep away from it, everything
else that the SoC supports, preferrably simple protocols with
DMA-capable host controllers, should be fine.

> *Any power management project existing in open source project that could  
> 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.

-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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