On 12 April 2018 at 19:30, Baolin Wang <baolin.wang@xxxxxxxxxx> wrote: > Hi Vinod, > > On 12 April 2018 at 17:37, Vinod Koul <vinod.koul@xxxxxxxxx> wrote: >> On Wed, Apr 11, 2018 at 08:13:28PM +0800, Baolin Wang wrote: >>> Hi Vinod, >>> >>> On 11 April 2018 at 17:36, Vinod Koul <vinod.koul@xxxxxxxxx> wrote: >>> > On Tue, Apr 10, 2018 at 03:46:06PM +0800, Baolin Wang wrote: >>> > >>> >> +/* >>> >> + * struct sprd_dma_config - DMA configuration structure >>> >> + * @config: dma slave channel config >>> >> + * @fragment_len: specify one fragment transfer length >>> >> + * @block_len: specify one block transfer length >>> >> + * @transcation_len: specify one transcation transfer length >>> >> + * @wrap_ptr: wrap pointer address, once the transfer address reaches the >>> >> + * 'wrap_ptr', the next transfer address will jump to the 'wrap_to' address. >>> >> + * @wrap_to: wrap jump to address >>> >> + * @req_mode: specify the DMA request mode >>> >> + * @int_mode: specify the DMA interrupt type >>> >> + */ >>> >> +struct sprd_dma_config { >>> >> + struct dma_slave_config config; >>> >> + u32 fragment_len; >>> > >>> > why not use _maxburst? >>> >>> Yes, I can use maxburst. >>> >>> > >>> >> + u32 block_len; >>> >> + u32 transcation_len; >>> > >>> > what does block and transaction len refer to here >>> >>> Our DMA has 3 transfer mode: transaction transfer, block transfer and >>> fragment transfer. One transaction transfer can contain several blocks >>> transfer, and each block can be set proper block step. One block can >>> contain several fragments transfer with proper fragment step. It can >>> generate interrupts when one transaction transfer or block transfer or >>> fragment transfer is completed if user set the interrupt type. So here >>> we should set the length for transaction transfer, block transfer and >>> fragment transfer. >> >> what are the max size these types support? > > These types max size definition: > > #define SPRD_DMA_FRG_LEN_MASK GENMASK(16, 0) > > #define SPRD_DMA_BLK_LEN_MASK GENMASK(16, 0) > > #define SPRD_DMA_TRSC_LEN_MASK GENMASK(27, 0) > >>> >>> > >>> >> + phys_addr_t wrap_ptr; >>> >> + phys_addr_t wrap_to; >>> > >>> > this sound sg_list to me, why are we not using that here >>> >>> It is similar to sg list, but it is not one software action, we have >>> hardware registers to help to jump one specified address. >>> >>> > >>> >> + enum sprd_dma_req_mode req_mode; >>> > >>> > Looking at definition of request mode we have frag, block, transaction list >>> > etc.. That should depend upon dma request. If you have been asked to >>> > transfer a list, you shall configure list mode. if it is a single >>> > transaction then it should be transaction mode! >>> >>> If I understand your points correctly, you mean we can specify the >>> request mode when requesting one slave channel by >>> 'dma_request_slave_channel()'. But we need change the request mode >>> dynamically following different transfer task for this channel, so I >>> am afraid we can not specify the request mode of this channel at >>> requesting time. >> >> Nope a channel has nothing to do with request type. You request and grab a >> channel. Then you prepare a descriptor for a dma transaction. Based on >> transaction requested you should intelligently break it down and create a >> descriptor which uses transaction/block/fragment so that DMA throughput is >> efficient. If prepare has sg list then you should use link list mode. >> Further if you support max length, say 16KB and request is for 20KB you may >> break it down for link list with two segments. > > OK. So I can add one more cell to specify the request mode for this channel. > > dmas = <&apdma 11 SPRD_DMA_BLK_REQ> > >> >> Each prep call has flags associated, that can help you configure interrupt >> behaviour. After more thinking, I think this will be not useful for users, since users need configure one DMA channel through different 3 places, specify the request mode in dts, specify the interrupt type through prep call flags, and other configuration need to be configured through 'struct sprd_dma_config'. That is not one good design for users. What do you think? Thanks. -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html