On Thu, 2016-11-03 at 15:55 +0800, Chen-Yu Tsai wrote: > According to the DMA engine API documentation, maxburst denotes the > largest possible size of a single transfer, so as not to overflow > destination FIFOs as explained in this excerpt from dmaengine.h > > * @src_maxburst: the maximum number of words (note: words, as in > * units of the src_addr_width member, not bytes) that can be sent > * in one burst to the device. Typically something like half the > * FIFO depth on I/O peripherals so you don't overflow it. This > * may or may not be applicable on memory sources. > * @dst_maxburst: same as src_maxburst but for destination target > * mutatis mutandis. ^^ :) > > The TX FIFO is 64 samples deep for stereo, and the RX FIFO is 16 > samples deep. So maxburst could be 32 and 8 for TX and RX > respectively. > > Unfortunately the sunxi DMA controller driver takes maxburst as > the requested burst size, rather than a limit, and returns an error > for unsupported values. The original value was 4, but some later > SoCs do not officially support this burst size. > > This patch increases maxburst on the TX side to 8, which is supported > by all variants of the sunxi DMA controller. > > Cc: Vinod Koul <vinod.koul@xxxxxxxxx> > Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx> > --- > sound/soc/sunxi/sun4i-codec.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/sound/soc/sunxi/sun4i-codec.c b/sound/soc/sunxi/sun4i- > codec.c > index 61ae502a5061..d867b96d367b 100644 > --- a/sound/soc/sunxi/sun4i-codec.c > +++ b/sound/soc/sunxi/sun4i-codec.c > @@ -886,12 +886,12 @@ static int sun4i_codec_probe(struct > platform_device *pdev) > > /* DMA configuration for TX FIFO */ > scodec->playback_dma_data.addr = res->start + quirks- > >reg_dac_txdata; > - scodec->playback_dma_data.maxburst = 4; > + scodec->playback_dma_data.maxburst = 8; > scodec->playback_dma_data.addr_width = > DMA_SLAVE_BUSWIDTH_2_BYTES; > > /* DMA configuration for RX FIFO */ > scodec->capture_dma_data.addr = res->start + quirks- > >reg_adc_rxdata; > - scodec->capture_dma_data.maxburst = 4; > + scodec->capture_dma_data.maxburst = 8; > scodec->capture_dma_data.addr_width = > DMA_SLAVE_BUSWIDTH_2_BYTES; > > ret = snd_soc_register_codec(&pdev->dev, quirks->codec, > -- > 2.10.2 > -- 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
