tree 019e1877e71f0bbacf6ef3aa9f5009c96172875d
parent b37cccf031bdcaba2f461cdb5a2b93ebbd0af03c
author Maciej W. Rozycki <macro@linux-mips.org> 1404569686 +0100
committer David S. Miller <davem@davemloft.net> 1404858627 -0700

defxx: Add missing DMA synchronisation calls

This adds DMA synchronisation calls needed in the receive path:

1. To retrieve the Receive Status word that is prepended by the PDQ DMA
   engine in the receive buffer, and provides information about the
   frame received, including its size and any errors.

2. To make data received available for copying in the small-frame case
   (size <= SKBUFF_RX_COPYBREAK) where the original DMA buffer will be
   returned to the receive descriptor ring and therefore its mapping
   retained.

   With DMA mapping error handling in place, added by the other patch,
   this may now also trigger where an attempt to map a newly allocated
   buffer for DMA has failed.  In that case data from the original buffer
   will be copied out and the buffer returned to the DMA descriptor ring.

These calls may do nothing when data is in the host DMA addressing range
of the FDDI interface, such as always on 32-bit systems, however their
absence makes frame reception stop functioning reliably on systems that
have memory beyond the low 4GB of the address space.

Reported-by: Robert Coerver <Robert.Coerver@ll.mit.edu>
Tested-by: Robert Coerver <Robert.Coerver@ll.mit.edu>
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>