[3/6] dma: rcar_dma: check if complete DMA packet received but not processed

Commit Message

[e-mail] Sept. 14, 2015, 12:02 p.m. UTC

From: Muhammad Hamza Farooq <[e-mail]>

At high speeds, DMA interrupts come very fast. If there's an interrupt
pending before previous is handled, this method can help return actual
status of the DMA transaction by reading the hardware flag

Signed-off-by: Muhammad Hamza Farooq <[e-mail]>
---
 drivers/dma/sh/rcar-dmac.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

--
1.9.1

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Patch

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 52cd528..653563d 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -314,6 +314,14 @@  static bool rcar_dmac_chan_is_busy(struct rcar_dmac_chan *chan)
 	return (chcr & (RCAR_DMACHCR_DE | RCAR_DMACHCR_TE)) == RCAR_DMACHCR_DE;
 }

+/* Transfer completed but not yet handled */
+static bool rcar_dmac_last_tx_complete(struct rcar_dmac_chan *chan)
+{
+	u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
+
+	return (chcr & RCAR_DMACHCR_TE) == RCAR_DMACHCR_TE;
+}
+
 static void rcar_dmac_chan_start_xfer(struct rcar_dmac_chan *chan)
 {
 	struct rcar_dmac_desc *desc = chan->desc.running;
@@ -1237,6 +1245,10 @@  static enum dma_status rcar_dmac_tx_status(struct dma_chan *chan,
 	unsigned long flags;
 	unsigned int residue;

+	/* Interrupt not yet serviced */
+	if(rcar_dmac_last_tx_complete(rchan))
+		return DMA_COMPLETE;
+
 	status = dma_cookie_status(chan, cookie, txstate);
 	if (status == DMA_COMPLETE || !txstate)
 		return status;