On Tue, Feb 18, 2014 at 10:20 PM, Jassi Brar <jaswinder.singh@xxxxxxxxxx> wrote: > 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). Initially I interpreted interleaved template the same. But, Lars corrected me in the subsequent discussion and let me put it here briefly, In the interleaved template, each frame represents a line of size denoted by chunk.size and the stride by icg. 'numf' represent number of frames i.e. number of lines. In video frame context, chunk.size -> hsize chunk.icg -> stride numf -> vsize and frame_size is always 1 as it will have only one chunk in a line. So, the API would not allow to pass multiple frames and we came up with a resolution to pass an array of interleaved template structs to handle this. Srikanth > > -Jassi > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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
