x86: poll waiting for I/OAT DMA channel status
For certain system configurations a 5 usec udelay before checking I/OAT DMA
channel status is sometimes not sufficient, resulting in a false failure
status and unnecessary freeing of channel resources. Conversely, for many
configurations 5 usec is longer than necessary.
Loop for up to 20 usec waiting for successful status before failing.
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index effd140..54d1a3c 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -507,6 +507,7 @@
struct ioat_ring_ent **ring;
u64 status;
int order;
+ int i = 0;
/* have we already been set up? */
if (ioat->ring)
@@ -547,8 +548,11 @@
ioat2_start_null_desc(ioat);
/* check that we got off the ground */
- udelay(5);
- status = ioat_chansts(chan);
+ do {
+ udelay(1);
+ status = ioat_chansts(chan);
+ } while (i++ < 20 && !is_ioat_active(status) && !is_ioat_idle(status));
+
if (is_ioat_active(status) || is_ioat_idle(status)) {
set_bit(IOAT_RUN, &chan->state);
return 1 << ioat->alloc_order;