From: Robert Hancock robert.hancock@calian.com
commit e958b5884725dac86d36c1e7afe5a55f31feb0b2 upstream.
This patch is based on one in the Xilinx kernel tree, "ASoc: xlnx: Make buffer bytes multiple of period bytes" by Devarsh Thakkar. The same issue exists in the mainline version of the driver. The original patch description is as follows:
"The Xilinx Audio Formatter IP has a constraint on period bytes to be multiple of 64. This leads to driver changing the period size to suitable frames such that period bytes are multiple of 64.
Now since period bytes and period size are updated but not the buffer bytes, this may make the buffer bytes unaligned and not multiple of period bytes.
When this happens we hear popping noise as while DMA is being done the buffer bytes are not enough to complete DMA access for last period of frame within the application buffer boundary.
To avoid this, align buffer bytes too as multiple of 64, and set another constraint to always enforce number of periods as integer. Now since, there is already a rule in alsa core to enforce Buffer size = Number of Periods * Period Size this automatically aligns buffer bytes as multiple of period bytes."
Fixes: 6f6c3c36f091 ("ASoC: xlnx: add pcm formatter platform driver") Cc: Devarsh Thakkar devarsh.thakkar@xilinx.com Signed-off-by: Robert Hancock robert.hancock@calian.com Link: https://lore.kernel.org/r/20220107214711.1100162-2-robert.hancock@calian.com Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/soc/xilinx/xlnx_formatter_pcm.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-)
--- a/sound/soc/xilinx/xlnx_formatter_pcm.c +++ b/sound/soc/xilinx/xlnx_formatter_pcm.c @@ -37,6 +37,7 @@ #define XLNX_AUD_XFER_COUNT 0x28 #define XLNX_AUD_CH_STS_START 0x2C #define XLNX_BYTES_PER_CH 0x44 +#define XLNX_AUD_ALIGN_BYTES 64
#define AUD_STS_IOC_IRQ_MASK BIT(31) #define AUD_STS_CH_STS_MASK BIT(29) @@ -368,12 +369,32 @@ static int xlnx_formatter_pcm_open(struc snd_soc_set_runtime_hwparams(substream, &xlnx_pcm_hardware); runtime->private_data = stream_data;
- /* Resize the period size divisible by 64 */ + /* Resize the period bytes as divisible by 64 */ err = snd_pcm_hw_constraint_step(runtime, 0, - SNDRV_PCM_HW_PARAM_PERIOD_BYTES, 64); + SNDRV_PCM_HW_PARAM_PERIOD_BYTES, + XLNX_AUD_ALIGN_BYTES); if (err) { dev_err(component->dev, - "unable to set constraint on period bytes\n"); + "Unable to set constraint on period bytes\n"); + return err; + } + + /* Resize the buffer bytes as divisible by 64 */ + err = snd_pcm_hw_constraint_step(runtime, 0, + SNDRV_PCM_HW_PARAM_BUFFER_BYTES, + XLNX_AUD_ALIGN_BYTES); + if (err) { + dev_err(component->dev, + "Unable to set constraint on buffer bytes\n"); + return err; + } + + /* Set periods as integer multiple */ + err = snd_pcm_hw_constraint_integer(runtime, + SNDRV_PCM_HW_PARAM_PERIODS); + if (err < 0) { + dev_err(component->dev, + "Unable to set constraint on periods to be integer\n"); return err; }