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[RESEND,3/6] dma: rcar-dma: check if complete DMA packet received but not processed

Message ID 1442776262-2503-4-git-send-email-hamzahfrq.sub@gmail.com
State Superseded
Delegated to: Geert Uytterhoeven
Headers show

Commit Message

hamzahfrq.sub@gmail.com Sept. 20, 2015, 7:10 p.m. UTC
From: Muhammad Hamza Farooq <mfarooq@visteon.com>

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 <mfarooq@visteon.com>
---
 drivers/dma/sh/rcar-dmac.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
diff mbox

Patch

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index c3753e1..668fd2b 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;
@@ -1238,6 +1246,10 @@  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;