[PATCH v5 4/5] dmaengine: dw-axi-dmac: use atomic polling for suspend acknowledgment

[James Hilliard]

The pause loop delays after its final status read, so an acknowledgment
that arrives during that delay is cleared without being observed and
the caller receives -EAGAIN.

Use readx_poll_timeout_atomic() to check the status after the final delay.
Keep the two-microsecond polling interval, 40-microsecond timeout and
-EAGAIN return value when suspension is not acknowledged.

Fixes: 1fe20f1b8454 ("dmaengine: Introduce DW AXI DMAC driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
---
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
index 040c12d07db2..1a53fbc951a9 100644
--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
@@ -1219,7 +1219,8 @@ static int dma_chan_pause(struct dma_chan *dchan)
 {
 	struct axi_dma_chan *chan = dchan_to_axi_dma_chan(dchan);
 	unsigned long flags;
-	unsigned int timeout = 20; /* timeout iterations */
+	u32 status;
+	int ret;
 	u64 val;
 
 	spin_lock_irqsave(&chan->vc.lock, flags);
@@ -1250,12 +1251,9 @@ static int dma_chan_pause(struct dma_chan *dchan)
 		}
 	}
 
-	do  {
-		if (axi_chan_irq_read(chan) & DWAXIDMAC_IRQ_SUSPENDED)
-			break;
-
-		udelay(2);
-	} while (--timeout);
+	ret = readx_poll_timeout_atomic(axi_chan_irq_read, chan,
+					status, status & DWAXIDMAC_IRQ_SUSPENDED,
+					2, 40);
 
 	axi_chan_irq_clear(chan, DWAXIDMAC_IRQ_SUSPENDED);
 
@@ -1263,7 +1261,7 @@ static int dma_chan_pause(struct dma_chan *dchan)
 
 	spin_unlock_irqrestore(&chan->vc.lock, flags);
 
-	return timeout ? 0 : -EAGAIN;
+	return ret ? -EAGAIN : 0;
 }
 
 /* Called in chan locked context */

-- 
2.53.0