There is a strange interaction with drivers which use DMA if the cache
starts off in a dirty state. Buffer space which the driver reads (but has
not previously written) can contain zero bytes from alloc_priv(). This can
cause corruption of the memory used by DMA for incoming data.
Fix this and add a comment to explain the problem.
This allows the dwc2 driver to work correctly with driver model, for
example.
Signed-off-by: Simon Glass <sjg@chromium.org>
5a8a8045a9