[PATCH] ARM: V6 MPCore v6_dma_inv_range RWFO fix

[Russell King - ARM Linux]

On Wed, Nov 24, 2010 at 01:28:06AM +0300, Valentine Barshak wrote:
> Cache ownership must be acqired by reading/writing data from the
> cache line to make cache operation have the desired effect on the
> SMP MPCore CPU. However, the ownership is never aquired in the
> v6_dma_inv_range function when cleaning the first line and
> flushing the last one, in case the address is not aligned
> to D_CACHE_LINE_SIZE boundary.
> Fix this by reading/writing data if needed, before performing
> cache operations.

You should do this on the data _inside_ the requested buffer.  We don't
know if the overlapping cache line shares itself with some atomic
variable, and doing a read-write on it could undo other updates to it.