From: Nicolas Ferre Date: Mon, 9 May 2011 16:11:37 +0000 (+0200) Subject: dmaengine: at_hdmac: pause: no need to wait for FIFO empty X-Git-Tag: firefly_0821_release~7613^2~1017^2~4^2~7 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=de7a2f9f7b6f5b48d8531ff4c9c9b95cab8a8ce8;p=firefly-linux-kernel-4.4.55.git 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 [commit msg edited for grammer] Signed-off-by: Vinod Koul --- diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c index 2c6bc3aa3dd0..3134003eec8b 100644 --- a/drivers/dma/at_hdmac.c +++ b/drivers/dma/at_hdmac.c @@ -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);