On Mon, Mar 10, 2014 at 9:30 PM, Jassi Brar <jassisinghbrar@xxxxxxxxx> wrote:
> On Thu, Mar 6, 2014 at 7:18 PM, Srikanth Thokala <sthokal@xxxxxxxxxx> wrote:
>
>> +static struct dma_async_tx_descriptor *
>> +xilinx_vdma_dma_prep_interleaved(struct dma_chan *dchan,
>> + struct dma_interleaved_template *xt,
>> + unsigned long flags)
>> +{
>> + struct xilinx_vdma_chan *chan = to_xilinx_chan(dchan);
>> + struct xilinx_vdma_tx_descriptor *desc;
>> + struct xilinx_vdma_tx_segment *segment;
>> + struct xilinx_vdma_tx_segment *prev = NULL;
>> + int i;
>> +
>> + if ((xt->dir != DMA_MEM_TO_DEV) && (xt->dir != DMA_DEV_TO_MEM))
>> + return NULL;
>> +
>> + if (!xt->numf || !xt->sgl[0].size)
>> + return NULL;
>> +
>> + /* Allocate a transaction descriptor. */
>> + desc = xilinx_vdma_alloc_tx_descriptor(chan);
>> + if (!desc)
>> + return NULL;
>> +
>> + dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
>> + desc->async_tx.tx_submit = xilinx_vdma_tx_submit;
>> + desc->async_tx.cookie = 0;
>> + async_tx_ack(&desc->async_tx);
>> +
>> + /* Build the list of transaction segments. */
>> + for (i = 0; i < xt->frame_size; i++) {
>> + struct xilinx_vdma_desc_hw *hw;
>> +
>> + /* Allocate the link descriptor from DMA pool */
>> + segment = xilinx_vdma_alloc_tx_segment(chan);
>> + if (!segment)
>> + goto error;
>> +
>> + /* Fill in the hardware descriptor */
>> + hw = &segment->hw;
>> + hw->vsize = xt->numf;
>> + hw->hsize = xt->sgl[0].size;
>> + hw->stride = xt->sgl[0].icg <<
>> + XILINX_VDMA_FRMDLY_STRIDE_STRIDE_SHIFT;
>>
> It seems the xt->frame_size is (should be?) always going to be 1?
> If yes, the for-loop isn't needed.
> If no, you should probably use 'i' as the index to sgl[], and not always 0.
It can be either
'1': User can queue each segment and submit all the segments at once as a
single async tx descriptor. I am using this for scatter-gather mode of
operation where the src_start/dst_start is different for each segment.
'Number of frames': In this case the driver gets contiguous frame buffer memory
and it prepares segments with addresses as multiples of
src_start/dst_start.
Please let me know if you see any issues in this implementation.
Thanks
Srikanth
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