From: Forrest Shi <b29...@freescale.com>
dma status check function fsl_tx_status is heavily called in
a tight loop and the desc lock in fsl_tx_status contended by
the dma status update function. this caused the dma performance
degrades much.
this patch releases the lock in the fsl_tx_status function.
I believe it has no neglect impact on the following call of
dma_async_is_complete(...).
we can see below three conditions will be identified as success
a) x < complete < use
b) x < complete+N < use+N
c) x < complete < use+N
here complete is the completed_cookie, use is the last_used
cookie, x is the querying cookie, N is MAX cookie
when chan->completed_cookie is being read, the last_used may
be incresed. Anyway it has no neglect impact on the dma status
decision.
Signed-off-by: Forrest Shi <xuelin....@freescale.com>
---
drivers/dma/fsldma.c | 5 -----
1 files changed, 0 insertions(+), 5 deletions(-)
diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
index 8a78154..1dca56f 100644
--- a/drivers/dma/fsldma.c
+++ b/drivers/dma/fsldma.c
@@ -986,15 +986,10 @@ static enum dma_status fsl_tx_status(struct dma_chan
*dchan,
struct fsldma_chan *chan = to_fsl_chan(dchan);
dma_cookie_t last_complete;
dma_cookie_t last_used;
- unsigned long flags;
-
- spin_lock_irqsave(&chan->desc_lock, flags);
last_complete = chan->completed_cookie;
last_used = dchan->cookie;
- spin_unlock_irqrestore(&chan->desc_lock, flags);
-
dma_set_tx_state(txstate, last_complete, last_used, 0);
return dma_async_is_complete(cookie, last_complete, last_used);
}
--
1.7.0.4
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