Commit cd78809f authored Dec 17, 2009 by Dan Williams

ioat3: fix p-disabled q-continuation



When continuing a pq calculation the driver needs 3 extra sources.  The
driver can perform a 3 source calculation with a single descriptor, but
needs an extended descriptor to process up to 8 sources in one
operation.  However, in the p-disabled case only one extra source is
needed.  When continuing a p-disabled operation there are occasions
(i.e. 0 < src_cnt % 8 < 3) where the tail operation does not need an
extended descriptor.  Properly account for this fact otherwise invalid
'dmacount' values will be written to hardware usually causing the
channel to halt with 'invalid descriptor' errors.

Cc: <stable@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

parent 22763c5c

drivers/dma/ioat/dma_v3.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -650,9 +650,11 @@ __ioat3_prep_pq_lock(struct dma_chan c, enum sum_check_flags result,

		num_descs = ioat2_xferlen_to_descs(ioat, len);
		/* we need 2x the number of descriptors to cover greater than 3
		* sources
		* sources (we need 1 extra source in the q-only continuation
		* case and 3 extra sources in the p+q continuation case.
		*/
		if (src_cnt > 3 \|\| flags & DMA_PREP_CONTINUE) {
		if (src_cnt + dmaf_p_disabled_continue(flags) > 3 \|\|
		(dmaf_continue(flags) && !dmaf_p_disabled_continue(flags))) {
		with_ext = 1;
		num_descs *= 2;
		} else