Re: DMA problem - mpc8xx

raul.moreno@telvent.abengoa.com wrote:

Hi everybody,

I am having problems with the serial cpm driver in a mpc866. But I've found
out that my problem comes from the DMA and not really from the driver.  The
Rx and Tx buffers use the DMA and then the sytem hangs. However, if I set
these buffers to internal ram memory (DPRAM), it works. The DMA address is
configured with a kernel parameter in advance setup:
CONFIG_CONSISTENT_START (and the size in CONFIG_CONSISTENT_SIZE), but I
don't know what they are exactly and I could not find a right documentation
about it.
I saw a pair of mailing list where some guys set the
CONFIG_CONSISTENT_START to 0xff100000, but my driver continues failing (and
an error about dma-mapping appears in the boot).

What kernel version?  arch/ppc or arch/powerpc?  What is the error about 
dma-mapping that you get?  What does your memory map look like (in 
particular, is there anything that might be getting mapped in conflict 
with the consistent area at 0xff100000)?

-Scott