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? > +static struct axi_dmac_desc *axi_dmac_alloc_desc(unsigned int num_sgs) > +{ > + struct axi_dmac_desc *desc; > + > + desc = kzalloc(sizeof(struct axi_dmac_desc) + > + sizeof(struct axi_dmac_sg) * num_sgs, GFP_ATOMIC); we recommend GFP_NOWAIT for these... > +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 > + 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 ? > + > + 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? -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html