Commit de7a2f9f authored May 09, 2011 by Nicolas Ferre Committed by Vinod Koul May 12, 2011

dmaengine: at_hdmac: pause: no need to wait for FIFO empty



With the addition of the "pause" feature, an active wait was introduced
to check the "FIFO empty" event. This event was not always happening and
a timout contition was needed.
But, in some cases, this event depend on the peripheral connected to the
channel that is paused: FIFO becomes empty if the peripheral consumes data.
The timeout is pretty difficult to evaluate. Moreover, this check is not
needed.
In conclusion, it seems sensible to entirely remove the checking of
"FIFO empty" status when pausing.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
[commit msg edited for grammer]
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

parent eb8590b5

drivers/dma/at_hdmac.c

+0 −16

Original line number	Diff line number	Diff line
		@@ -933,25 +933,9 @@ static int atc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
		dev_vdbg(chan2dev(chan), "atc_control (%d)\n", cmd);

		if (cmd == DMA_PAUSE) {
		int pause_timeout = 1000;

		spin_lock_bh(&atchan->lock);

		dma_writel(atdma, CHER, AT_DMA_SUSP(chan_id));

		/* wait for FIFO to be empty */
		while (!(dma_readl(atdma, CHSR) & AT_DMA_EMPT(chan_id))) {
		if (pause_timeout-- > 0) {
		/* the FIFO can only drain if the peripheral
		* is still requesting data:
		* -> timeout if it is not the case. */
		dma_writel(atdma, CHDR, AT_DMA_RES(chan_id));
		spin_unlock_bh(&atchan->lock);
		return -ETIMEDOUT;
		}
		cpu_relax();
		}

		set_bit(ATC_IS_PAUSED, &atchan->status);

		spin_unlock_bh(&atchan->lock);

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