From 19d78a61be6dd707dcec298c486303d4ba2c840a Mon Sep 17 00:00:00 2001 From: Dimitri Sivanich Date: Fri, 6 May 2011 10:33:44 -0500 Subject: 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 Signed-off-by: Dan Williams --- drivers/dma/ioat/dma_v2.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) 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 @@ int ioat2_alloc_chan_resources(struct dma_chan *c) 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 @@ int ioat2_alloc_chan_resources(struct dma_chan *c) 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; -- cgit v1.1