Allocating (placing) BufferDescriptors in Dual-Port RAM (CPM2)

[Vitaly Bordug]

On Sun, 01 Apr 2007 00:26:19 +0200
Robert Staven <robert at stopthespam_remove.staven.no> wrote:

> It's probably basic knowledge, but I still having trouble figure it 
> out.... anyway:
> 
> Working with a SCC in a CPM (MPC8250 running linux 2.6.13-AM)
> 
> I need to place Buffer Descriptors (BD) in the Dual-Port RAM (DPRAM) 
> somewhere....
> But two FCCs, SMC1 and SCC1 are in use, and they might use some part of 
> the DPRAM.
> 
... cpm_dpalloc() will work for you I guess.

> Is there any way to figure out what part of the DPRAM thats free?
> And how to reserve the part I need?
> 
> Robert
> 
> (SCC3 parameter RAM are at 0x8200 in DPRAM so I just place a struct 
> there and assume that linux stays away from this memory area and don't 
> get mad cause I use it without allocating it. Or have I got this wrong to?)
> 

I'd suggest to look at the implemented 8260-like stuff and platform device approach (syslib/pq2_devices.c). Whole immr including DPRAM are is io_block_mapped early by the platform code so
you can do stuff in brackets I guess, but that might look weird and be more complex to debug.

Thanks.

-- 
Sincerely, 
Vitaly