Re: [alsa-devel] [PATCH 2/3] dma: edma: Add support for Cyclic DMA

On Mon, Sep 23, 2013 at 06:05:14PM -0500, Joel Fernandes wrote:

@@ -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