On 08/19/2015 06:32 PM, Vinod Koul wrote:
> On Tue, Jul 28, 2015 at 11:38:06AM +0200, Lars-Peter Clausen wrote:
>> + active = axi_dmac_active_desc(chan);
>> + if (!active)
>> + return;
>> +
>> + if (active->cyclic) {
>> + vchan_cyclic_callback(&active->vdesc);
>> + } else {
>> + while (active &&
> do you need to check this, you did that few lines back?
It gets overwritten in the loop.
[...]
>
>> +static struct dma_async_tx_descriptor *axi_dmac_prep_slave_sg(
>> + struct dma_chan *c, struct scatterlist *sgl,
>> + unsigned int sg_len, enum dma_transfer_direction direction,
>> + unsigned long flags, void *context)
>> +{
>> + struct axi_dmac_chan *chan = to_axi_dmac_chan(c);
>> + struct axi_dmac_desc *desc;
>> + struct scatterlist *sg;
>> + unsigned int i;
>> +
>> + if (direction != chan->direction)
>
> are the channels unidirectional
yes.
>
>> + return NULL;
>> +
>> + desc = axi_dmac_alloc_desc(sg_len);
>> + if (!desc)
>> + return NULL;
>> +
>> + for_each_sg(sgl, sg, sg_len, i) {
>> + if (!axi_dmac_check_addr(chan, sg_dma_address(sg)) ||
>> + !axi_dmac_check_len(chan, sg_dma_len(sg))) {
>> + kfree(desc);
>> + return NULL;
>> + }
>> +
>> + if (direction == DMA_DEV_TO_MEM)
>> + desc->sg[i].dest_addr = sg_dma_address(sg);
>> + else
>> + desc->sg[i].src_addr = sg_dma_address(sg);
> where is device side programming ?
in the start_transfer() function.
>
>> +
>> + if (axi_dmac_dest_is_mem(chan) && axi_dmac_src_is_mem(chan))
>> + chan->direction = DMA_MEM_TO_MEM;
>> + else if (!axi_dmac_dest_is_mem(chan) && axi_dmac_src_is_mem(chan))
>> + chan->direction = DMA_MEM_TO_DEV;
>> + else if (axi_dmac_dest_is_mem(chan) && !axi_dmac_src_is_mem(chan))
>> + chan->direction = DMA_DEV_TO_MEM;
>> + else
>> + chan->direction = DMA_DEV_TO_DEV;
>
> ok this seems to answer my other question but is this something we are
> specifying in SW or capability of a channel?
That's a capability of the hardware.
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