[U-Boot-Users] [OT] cs8900 in u-boot

[Vladimir Gurevich]

Hi Robert,

Because cs8900 is mostly ISA-oriented design, its connection is always
a little cludgy and can be done in a number of different ways. I am
not familiar with CSB226, but if you have a relevant piece of its
schematics it could help. Also, the power-up configuration for cs8900
can be stored in serial EPROM. This includes the base address. Cirrus
Logic has a very good application note (AN83) describing all this.

Robert Schwebel wrote:
> However, I do not see anything usefull in u-boot. This is how the port
> area looks after power on: 
> 
> uboot> md.w 0x08000000 10          (1)  (2)  (3)
> 08000000: 0000 a1ff 0000 a1ff 0009 a1ff 0000 a1ff    ................
> 08000010: 0000 a1ff 3136 a1ff 00d6 a1ff 00d6 a1ff    ....61..........

By default cs8900 powers up responding to IO accesses to port 0x300.
Thus, its real base address is probably 0x08000300 in your system.
IO port accesses are emulated by connecting your CS and WE to IOR and 
IOW signals appropriately. Memory accesses may or maynot be possible
depending on the schematics.

Also, make sure you configure your CS2 as 16-bit port. Another thing
to watch for is byte swapping. What I saw when using cs8900 with 
MC68EZ328 is that when you connect the data bus straight, then registers 
are fine, but the buffer area bytes are swapped. We chose to do byte
swapping on the data bus, but had to modify the driver to byte-swap
register values. 

Hope this helps a little.
You can point me to schematics, we could figure out a little bit more.

Best regards,
Vladimir