SD on Sharp Zaurus 5500 (was: GPLv3 and Mobile Phones)

Oleg Gusev oleg at
Sat Dec 9 22:58:12 CET 2006

Am Samstag, 9. Dezember 2006 22:06 schrieb Michael 'Mickey' Lauer:
> This is just plain wrong. It is extremely hard to come up with an SD
> driver for the Sharp Zaurus 5500, because there is 0 documentation
> about the Locomo custom ASIC used in this particular model.
Sorry for the offtopic, but i think it is a very important issue for
the Linux development. 
AFAIK almost everything you need to know about Locomo ASIC
is already documented. The only undocumented part is the 
SPI clock speed <-> divisor relation. If somebody wants to operate an 
SD card at a lower speed as it is now, he can manually change the 
divisor bits in LOCOMO_SPIMD and measure the clock 
frequency on an SD pin.
What is really missing is the SPI MMC control code,
but it was documented from the very beginning by Sandisk.
A minimal hack can be found here
but somebody more experienced with the mainline
MMC code should write a proper driver.

> I don't know where you got the notion of some "protest against the
> decision made by Sharp", but this is just nonsense.
There was a strong movement against writing a Linux
SD driver without having a vendor chipset documentation.
We have 4-5 of them now, almost all are reverse engineered,
and are simply not comparable in complexity with the Locomo SPI
used on SL-5500. Just take HTC ASIC3 as an example.


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