440gx dma transfer with no data change at dest
Kevin Kleinosowski
kevinko at arlut.utexas.edu
Wed Mar 8 08:16:08 EST 2006
I am running a simple test with a software initiated DMA transfer from one
bigphysarea allocated buffer to another bigphysarea allocated buffer.
The destination buffer shows no data changes once the transfer is done.
However, I perform the same simple test using __get_dma_pages() rather
then the bigphysarea_alloc_pages() and the destination does get the
data transfer.
Is there a reason this should fail for bigphysarea? I understand the low
memory addresses needed for the DMA controller on some platforms, but I
didnt think that limitation existed on the PPC. Besides that, the
bigphysarea returns low memory address anyway. Anyone have an idea why?
An old archive email had someone with a similar problem, but there were no
follow-ups to the message.
I have linux 2.4.27-pre3 patched, ppc-linux-gcc (GCC) 3.3.3 (DENX ELDK
3.1.1 3.3.3-9), U-Boot 1.1.2, and GMS 440gx board.
thanks,
Kevin
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