Re: [microblaze-uclinux] general questions S-IIE

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi Rick,

RH wrote:
> 1 -Not sure what the limitation is with the bram and the net vanilla, 
> but I now you can minimize the cache in microblaze to save bram if needed.
> 2- That module is only 1M that sounds really tight, but for a very basic 
> setup may work. You need to configure it over the 0x80000000 space.

If the kernel networking / tcp-ip support is not configured, it is 
possible to bring up a small kernel and filesystem image in under 1Mb. 
It's pretty tight, and there's not a lot you can do with it, but it's 
possible.

One idea that should be relatively easy to implement is to execute the 
kernel code directly out of flash, saving the SRAM purely for data and 
stack.  This would require some work in the link script, and in the 
early kernel bootup, but wouldn't be too bad.  Then, the kernel code 
size isn't really a problem, but being limited to 1MB data/stack is 
still pretty restrictive.

> By the way,  did somebody tried the MAC lite, is there a compatible 
> driver?. Iam not sure if that one is free (sounds like it)

I think the emaclite is polled, rather than interrupt driven?  This 
could be supported in a device driver but it would be much less 
efficient, and have a greater likelihood of dropping incoming packets. 
For bare bones tcp/ip support with v low bandwidth connections, maybe it 
would be appropriate.

Driver support shouldn't be too hard, you could probably start with the 
adapter.c file in drivers/net/xilinx_emac, and trim it downto fit, then 
add a kernel thread/timer to do the read polling.

Regards,

John


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