MLK-18875: ASoC: fsl_asrc_m2m: refine the last period size

The output size of asrc for a dedicate input is uncertain.

For example, if the input size is 1k, the output ratio is
2, so the output size should be 2k. but the actual output
size is not 2k,  is less than 2k. if we set the dma size
to be 2k, the dma can't get enough data that can't finish
the transmission, then there will be

"output DMA task timeout"

So we need to set the dma size a proper value but we don't know
how many data less than expected. so we defined the last period
size for assumption of reduced size.

The last period size should not be too large, if it is large
there will be

"input DMA task timeout"

The reason is the output FIFO is full, which will block the
input data comsumption.

In this patch, the last period size is set to the difference
of configured buffer size and the expected output size, plus
a fix size.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Cosmin-Gabriel Samoila <cosmin.samoila@nxp.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/sound/soc/fsl/fsl_asrc.h b/sound/soc/fsl/fsl_asrc.h
index d377955758be..d65481c92107 100644
--- a/sound/soc/fsl/fsl_asrc.h
+++ b/sound/soc/fsl/fsl_asrc.h
@@ -24,7 +24,7 @@
 #define ASRC_DMA_BUFFER_SIZE		(1024 * 48 * 4)
 #define ASRC_MAX_BUFFER_SIZE		(1024 * 48)
 #define ASRC_OUTPUT_LAST_SAMPLE_MAX	32
-#define ASRC_OUTPUT_LAST_SAMPLE		16
+#define ASRC_OUTPUT_LAST_SAMPLE		4
 
 #define IDEAL_RATIO_RATE		1000000