On 18 February 2014 16:58, Srikanth Thokala <sthokal@xxxxxxxxxx> wrote: > On Mon, Feb 17, 2014 at 3:27 PM, Jassi Brar <jaswinder.singh@xxxxxxxxxx> wrote: >> On 15 February 2014 17:30, Srikanth Thokala <sthokal@xxxxxxxxxx> wrote: >>> The current implementation of interleaved DMA API support multiple >>> frames only when the memory is contiguous by incrementing src_start/ >>> dst_start members of interleaved template. >>> >>> But, when the memory is non-contiguous it will restrict slave device >>> to not submit multiple frames in a batch. This patch handles this >>> issue by allowing the slave device to send array of interleaved dma >>> templates each having a different memory location. >>> >> How fragmented could be memory in your case? Is it inefficient to >> submit separate transfers for each segment/frame? >> It will help if you could give a typical example (chunk size and gap >> in bytes) of what you worry about. > > With scatter-gather engine feature in the hardware, submitting separate > transfers for each frame look inefficient. As an example, our DMA engine > supports up to 16 video frames, with each frame (a typical video frame > size) being contiguous in memory but frames are scattered into different > locations. We could not definitely submit frame by frame as it would be > software overhead (HW interrupting for each frame) resulting in video lags. > IIUIC, it is 30fps and one dma interrupt per frame ... it doesn't seem inefficient at all. Even poor-latency audio would generate a higher interrupt-rate. So the "inefficiency concern" doesn't seem valid to me. Not to mean we shouldn't strive to reduce the interrupt-rate further. Another option is to emulate the ring-buffer scheme of ALSA.... which should be possible since for a session of video playback the frame buffers' locations wouldn't change. Yet another option is to use the full potential of the interleaved-xfer api as such. It seems you confuse a 'video frame' with the interleaved-xfer api's 'frame'. They are different. Assuming your one video frame is F bytes long and Gk is the gap in bytes between end of frame [k] and start of frame [k+1] and Gi != Gj for i!=j In the context of interleaved-xfer api, you have just 1 Frame of 16 chunks. Each chunk is Fbytes and the inter-chunk-gap(ICG) is Gk where 0<=k<15 So for your use-case ..... dma_interleaved_template.numf = 1 /* just 1 frame */ dma_interleaved_template.frame_size = 16 /* containing 16 chunks */ ...... //other parameters You have 3 options to choose from and all should work just as fine. Otherwise please state your problem in real numbers (video-frames' size, count & gap in bytes). -Jassi -- 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
