linux-kernel - [PATCH] dmaengine: omap-dma: Fix cyclic suspend/resume

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Date:	Tue, 16 Sep 2014 16:06:25 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	<vinod.koul@...el.com>, <dan.j.williams@...el.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	<dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: [PATCH] dmaengine: omap-dma: Fix cyclic suspend/resume

When the audio stream is paused or suspended we stop the sDMA and when it
is unpsues/resumed we start the channel without reconfiguring it.
The omap_dma_stop() clears the link configuration when we pause the dma, but
it is not setting it back on start. This will result only one audio buffer
to be played back and the DMA will stop, since the linking is disabled.
The link need to be enabled in omap_dma_start() to make sure that cyclic
transfer can continue.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
---
 drivers/dma/omap-dma.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
index 4cf7d9a950d7..13a02ff87f28 100644
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c
@@ -280,6 +280,7 @@ static void omap_dma_assign(struct omap_dmadev *od, struct omap_chan *c,
 static void omap_dma_start(struct omap_chan *c, struct omap_desc *d)
 {
 	struct omap_dmadev *od = to_omap_dma_dev(c->vc.chan.device);
+	uint32_t val;
 
 	if (__dma_omap15xx(od->plat->dma_attr))
 		omap_dma_chan_write(c, CPC, 0);
@@ -288,6 +289,17 @@ static void omap_dma_start(struct omap_chan *c, struct omap_desc *d)
 
 	omap_dma_clear_csr(c);
 
+	if (!__dma_omap15xx(od->plat->dma_attr) && c->cyclic) {
+		val = omap_dma_chan_read(c, CLNK_CTRL);
+
+		if (dma_omap1())
+			val &= ~(1 << 14); /* clear the STOP_LNK bit */
+		else
+			val |= CLNK_CTRL_ENABLE_LNK;
+
+		omap_dma_chan_write(c, CLNK_CTRL, val);
+	}
+
 	/* Enable interrupts */
 	omap_dma_chan_write(c, CICR, d->cicr);
 
-- 
2.1.0

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