Remi Machet wrote:
I have noticed that the DMA allocation for non-coherent PowerPC
architecture is using a hard coded virtual memory address for its memory
pool. This address is typically 0xFF100000 (set by
CONFIG_CONSISTENT_START) and can conflict with early ioremap in systems
that enable HIGHMEM.
Is there any reason why we have to use an arbitrary virtual address ? If
the virtual address must be known at compile time, can't we use fixmap ?
The hardcoded address predates when fixmap was added to powerpc. It
should be updated to use fixmap.
I also can't figure out why we need to use a virtual address known at
compilation time and cannot just allocate pages using get_free_pages and
mark them as non cacheable and non swappable.
We probably don't need a compile-time address, though we can't just
change the page attributes in-place as the pages will often covered by
large TLB entries.
-Scott
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