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

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

[Robert Staven]

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.

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?)

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

[Vitaly Bordug]

On Sun, 01 Apr 2007 00:26:19 +0200
Robert Staven <robert@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