linux-kernel - [PATCH v3 02/15] dmaengine: omap: Add support for pause/resume in cyclic dma mode

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Date:	Fri, 14 Sep 2012 15:05:45 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, Tony Lindgren <tony@...mide.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Vinod Koul <vinod.koul@...el.com>, Dan Williams <djbw@...com>,
	Jarkko Nikula <jarkko.nikula@...mer.com>
Cc:	alsa-devel@...a-project.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Janusz Krzysztofik <jkrzyszt@....icnet.pl>,
	Ricardo Neri <ricardo.neri@...com>,
	Lars-Peter Clausen <lars@...afoo.de>
Subject: [PATCH v3 02/15] dmaengine: omap: Add support for pause/resume in cyclic dma mode

The audio stack used omap_stop_dma/omap_start_dma to pause/resume the DMA.
This method has been used for years on OMAP based products.
We only allow pause/resume when the DMA has been configured in cyclic mode
which is used by the audio stack.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
CC: Russell King <rmk+kernel@....linux.org.uk>
---
 drivers/dma/omap-dma.c | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
index b77a40d..71d7869 100644
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c
@@ -34,6 +34,7 @@ struct omap_chan {
 	struct dma_slave_config	cfg;
 	unsigned dma_sig;
 	bool cyclic;
+	bool paused;
 
 	int dma_ch;
 	struct omap_desc *desc;
@@ -470,11 +471,14 @@ static int omap_dma_terminate_all(struct omap_chan *c)
 	 */
 	if (c->desc) {
 		c->desc = NULL;
-		omap_stop_dma(c->dma_ch);
+		/* Avoid stopping the dma twice */
+		if (!c->paused)
+			omap_stop_dma(c->dma_ch);
 	}
 
 	if (c->cyclic) {
 		c->cyclic = false;
+		c->paused = false;
 		omap_dma_unlink_lch(c->dma_ch, c->dma_ch);
 	}
 
@@ -487,14 +491,30 @@ static int omap_dma_terminate_all(struct omap_chan *c)
 
 static int omap_dma_pause(struct omap_chan *c)
 {
-	/* FIXME: not supported by platform private API */
-	return -EINVAL;
+	/* Pause/Resume only allowed with cyclic mode */
+	if (!c->cyclic)
+		return -EINVAL;
+
+	if (!c->paused) {
+		omap_stop_dma(c->dma_ch);
+		c->paused = true;
+	}
+
+	return 0;
 }
 
 static int omap_dma_resume(struct omap_chan *c)
 {
-	/* FIXME: not supported by platform private API */
-	return -EINVAL;
+	/* Pause/Resume only allowed with cyclic mode */
+	if (!c->cyclic)
+		return -EINVAL;
+
+	if (c->paused) {
+		omap_start_dma(c->dma_ch);
+		c->paused = false;
+	}
+
+	return 0;
 }
 
 static int omap_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
-- 
1.7.12

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