Re: USB driver for MPC850/823

At 10:35 AM 3/8/00 +0100, Björn Lundberg wrote:

The driver is developed under Malek's 2.2.5 for embedded PPC.
Since the documentation has been a bit poor for the USB host mode, much
had to be done with trial and error. Some of which is left in the
source.
Most changes are in new source files but some changes has been done in
commproc.c and .h to support RISC timers and more DPRAM (microcode
alert).
For some reason I couldn't use USB buffers in SDRAM, only DPRAM!?
As stated earlier on the list it's developed on an 850, but I haven't
found anything that says it won't work on an 823.

I have started looking at your code to try understand some of the
roadblocks that I have hit. I have ISOC in/out working on the 823 USB. My
IN and OUT packets are from main system Dram. You dont say what the problem
was, but if the problem is; the data sent was garbage, not what you
prepared, the problem may be memory mapping. The CPM wants to access
physical memory addresses. You use a macro __pa for this, but I dont think
that works for all cases of user and kernel memory. I grepped and found:

#define PAGE_OFFSET     0xc0000000
#define __pa(x)                 ((unsigned long)(x)-PAGE_OFFSET)

Look at virt_to_phys(x); but that only does kmalloc'ed memory. There seems
to be many mapping macros/routines but I don't know if one works for ANY
virtual address to its physical address.

Does anyone have a pointer to a document that thoroughly describes memory
mapping, both for the x86 and the ppc?



Steve Calfee	--	embedded systems consultant
calfee@home.com
cell phone: (510) 468-5837
Kerbango phone: (408) 517-3355
home office ph: (510) 657-6039


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