On Mon, Jun 27, 2011 at 12:02 PM, Russell King - ARM Linux linux@arm.linux.org.uk wrote:
The next thing to think about in DMA-land is whether we should total up the size of the SG list and choose whether to flush the individual SG elements or do a full cache flush. There becomes a point where the full cache flush becomes cheaper than flushing each SG element individually.
We noticed that even for a single (large) buffer, any cache flush operation above a certain threshold flushing indiviudal lines become more expensive than flushing the entire cache.
I requested colleagues to look into implenting this threshold in the arch/arm/mm/cache-v7.S file. but I think they ran into trouble and eventually had to give up on it.
Vijay or Srinidhi, can you share your findings?
Thanks, Linus Walleij