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@intel.com Signed-off-by: Chen-Yu Tsai wens@csie.org
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