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Re: [PATCH v6 10/10] ASoC: rockchip_i2s: modify DMA max burst to 1

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在 2015年10月15日 16:53, Lars-Peter Clausen 写道:
> On 10/15/2015 03:36 AM, Shawn Lin wrote:
> [...]
>> +
>> +	if (snd_dmaengine_pcm_get_caps(&pdev->dev, &dma_caps) == 0) {
>> +		if (dma_caps.max_burst > 4) {
>> +			i2s->playback_dma_data.maxburst = 4;
>> +			i2s->capture_dma_data.maxburst = 4;
>> +		} else {
>> +			i2s->playback_dma_data.maxburst = 1;
>> +			i2s->capture_dma_data.maxburst = 1;
> So this is what this is all about? I though you might have to program some
> FIFO threshold registers in the peripheral itself.
>
> But it seems all this does is to read the maximum burst length from the DMA
> controller only to tell the DMA controller that this is the maximum burst
> length it should use. That seems rather unnecessary.
>
> The maxburst field of the dma_data indicates the maximum burst length that
> the audio peripheral can handle. Typically this is the number of samples the
> audio FIFO can receive without overflowing after sending the DMA request
> signal. Since as the name suggests this is the maximum burst size the DMA
> controller is free to choose a burst size smaller than this when writing
> data to the peripheral.
>
> So in your case instead of introducing all these facilities to query the
> maximum burst size it should be OK to simply reduce the burst size in the
> DMA controller itself when it gets a request with a burst size larger than
> it can handle, or is there a reason why this is not possible?
Agree with Lars, it's better to fix on DMA driver side since issue 
caused by dma-controller instead of i2s controller
>
> - Lars
>
>
>

-- 
Jianqun Xu | Software engineer | 18750760928


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[PATCH v6 0/10] Fix broken DMAFLUSHP on Rockchips platform Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 04/10] ARM: dts: Add arm,pl330-broken-no-flushp quirk for rk3288 platform Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 01/10] DMA: pl330: support burst mode for dev-to-mem and mem-to-dev transmit Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
    Re: [PATCH v6 01/10] DMA: pl330: support burst mode for dev-to-mem  and mem-to-dev transmit Vinod Koul <vinod.koul@intel.com> - 2015-10-15 06:10 +0200
      Re: [PATCH v6 01/10] DMA: pl330: support burst mode for dev-to-mem  and mem-to-dev transmit Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 09:00 +0200
  [PATCH v6 02/10] Documentation: arm-pl330: add description of arm,pl330-broken-no-flushp Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 05/10] ARM: dts: Add arm,pl330-broken-no-flushp quirk for rk3xxx platform Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 10/10] ASoC: rockchip_i2s: modify DMA max burst to 1 Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
    Re: [PATCH v6 10/10] ASoC: rockchip_i2s: modify DMA max burst to  1 Lars-Peter Clausen <lars@metafoo.de> - 2015-10-15 11:00 +0200
      Re: [PATCH v6 10/10] ASoC: rockchip_i2s: modify DMA max burst to 1 Jianqun Xu <jay.xu@rock-chips.com> - 2015-10-15 12:50 +0200
  [PATCH v6 07/10] DMA: pl330: add max burst for dmaengine Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 03/10] DMA: pl330: add quirk for broken no flushp Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 06/10] DMA: dmaengine: expose max burst capability to clients Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 03:40 +0200
  [PATCH v6 08/10] spi: rockchip: modify DMA max burst to 1 Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 04:00 +0200
  [PATCH v6 09/10] snd: dmaengine-pcm: add snd_dmaengine_pcm_get_caps interface Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 04:00 +0200
    Re: [alsa-devel] [PATCH v6 09/10] snd: dmaengine-pcm: add  snd_dmaengine_pcm_get_caps interface kbuild test robot <lkp@intel.com> - 2015-10-15 05:10 +0200
    Re: [PATCH v6 09/10] snd: dmaengine-pcm: add  snd_dmaengine_pcm_get_caps interface Vinod Koul <vinod.koul@intel.com> - 2015-10-15 06:10 +0200
      Re: [PATCH v6 09/10] snd: dmaengine-pcm: add  snd_dmaengine_pcm_get_caps interface Shawn Lin <shawn.lin@rock-chips.com> - 2015-10-15 09:00 +0200

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