Thread (12 messages) 12 messages, 2 authors, 2013-10-31

[PATCH 2/3] dma: edma: Add support for Cyclic DMA

From: Vinod Koul <hidden>
Date: 2013-10-21 07:47:09
Also in: alsa-devel, linux-omap, lkml

On Mon, Sep 23, 2013 at 06:05:14PM -0500, Joel Fernandes wrote:
 
quoted hunk ↗ jump to hunk
@@ -449,6 +455,138 @@ static struct dma_async_tx_descriptor *edma_prep_slave_sg(
 	return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
 }
 
+static struct dma_async_tx_descriptor *edma_prep_dma_cyclic(
+	struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
+	size_t period_len, enum dma_transfer_direction direction,
+	unsigned long tx_flags, void *context)
+{
+	struct edma_chan *echan = to_edma_chan(chan);
+	struct device *dev = chan->device->dev;
+	struct edma_desc *edesc;
+	dma_addr_t src_addr, dst_addr;
+	enum dma_slave_buswidth dev_width;
+	u32 burst;
+	int i, ret, nr_periods;
+
+	if (unlikely(!echan || !buf_len || !period_len))
+		return NULL;
+
+	if (direction == DMA_DEV_TO_MEM) {
+		src_addr = echan->cfg.src_addr;
+		dst_addr = buf_addr;
+		dev_width = echan->cfg.src_addr_width;
+		burst = echan->cfg.src_maxburst;
+	} else if (direction == DMA_MEM_TO_DEV) {
+		src_addr = buf_addr;
+		dst_addr = echan->cfg.dst_addr;
+		dev_width = echan->cfg.dst_addr_width;
+		burst = echan->cfg.dst_maxburst;
+	} else {
+		dev_err(dev, "%s: bad direction?\n", __func__);
+		return NULL;
+	}
+
+	if (dev_width == DMA_SLAVE_BUSWIDTH_UNDEFINED) {
+		dev_err(dev, "Undefined slave buswidth\n");
+		return NULL;
+	}
+
+	if (unlikely(buf_len % period_len)) {
+		dev_err(dev, "Period should be multiple of Buffer length\n");
+		return NULL;
+	}
+
+	nr_periods = (buf_len / period_len) + 1;
?

consider the case of buf = period_len, above makes nr_period = 2.

Or buf len 100, period len 50, makes nr_period = 3

Both doesnt seem right to me?

--
~Vinod
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