ASoC: Intel: KMB: Fix random noise at the HDMI output

Random noise could be heard when playing audio to the HDMI output.
This is due to the IEC conversion is invoked in the external loop.
As a result, this additional loop takes up a lot of the processing
cycle.

hdmi_reformat_iec958() process the conversion using an internal loop,
it is safe to move it out from the external loop to avoid unnecessary
processing cycle been spent. Furthermore, ALSA IEC958 plugin works in
32bit format only.

Signed-off-by: Sia Jee Heng <jee.heng.sia@intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210421005546.7534-1-jee.heng.sia@intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/intel/keembay/kmb_platform.c b/sound/soc/intel/keembay/kmb_platform.c
index 0fd1e8f..96741c7 100644 (file)
--- a/sound/soc/intel/keembay/kmb_platform.c
+++ b/sound/soc/intel/keembay/kmb_platform.c
@@ -105,14 +105,15 @@ static unsigned int kmb_pcm_tx_fn(struct kmb_i2s_info *kmb_i2s,
        void *buf = runtime->dma_area;
        int i;
 
+       if (kmb_i2s->iec958_fmt)
+               hdmi_reformat_iec958(runtime, kmb_i2s, tx_ptr);
+
        /* KMB i2s uses two separate L/R FIFO */
        for (i = 0; i < kmb_i2s->fifo_th; i++) {
                if (kmb_i2s->config.data_width == 16) {
                        writel(((u16(*)[2])buf)[tx_ptr][0], i2s_base + LRBR_LTHR(0));
                        writel(((u16(*)[2])buf)[tx_ptr][1], i2s_base + RRBR_RTHR(0));
                } else {
-                       if (kmb_i2s->iec958_fmt)
-                               hdmi_reformat_iec958(runtime, kmb_i2s, tx_ptr);
                        writel(((u32(*)[2])buf)[tx_ptr][0], i2s_base + LRBR_LTHR(0));
                        writel(((u32(*)[2])buf)[tx_ptr][1], i2s_base + RRBR_RTHR(0));
                }