[PATCH v2] ASoC: meson: aiu: fifo-spdif: soft reset the S/PDIF datapath on start/stop

[PATCH v2] ASoC: meson: aiu: fifo-spdif: soft reset the S/PDIF datapath on start/stop

[Christian Hewitt]

The I2S FIFO soft-resets its fast domain on start (AIU_RST_SOFT bit 0 +
AIU_I2S_SYNC read in aiu_fifo_i2s_trigger), mirroring the downstream
vendor driver's audio_out_i2s_enable(). The S/PDIF FIFO has no equivalent:
it only toggles the IEC958 DCU, so a stale datapath FIFO can be replayed,
producing the "machine gun noise" buffer underrun - on start when switching
outputs, and on stop when playback ends. The latter is audible on devices
with an always-on S/PDIF-fed DAC (e.g. the ES7144 on the WeTek Play2).

The vendor driver resets the IEC958 fast domain (AIU_RST_SOFT bit 2) on
both enable and disable (audio_hw_958_enable), and when reconfiguring
(audio_hw_958_reset clears AIU_958_DCU_FF_CTRL then resets). Do the same:
reset before enabling the DCU on start, and after disabling it on stop.

Fixes: 6ae9ca9ce986bf ("ASoC: meson: aiu: add i2s and spdif support")
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
---
Changes from v1:
- Add missing fixes tag
- Trigger AIU_RST_SOFT_958_FAST then disable DCU as in the vendor driver

 sound/soc/meson/aiu-fifo-spdif.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/soc/meson/aiu-fifo-spdif.c b/sound/soc/meson/aiu-fifo-spdif.c
index e0e00ec026dc..a9861c5d6637 100644
--- a/sound/soc/meson/aiu-fifo-spdif.c
+++ b/sound/soc/meson/aiu-fifo-spdif.c
@@ -24,6 +24,7 @@
 #define AIU_MEM_IEC958_CONTROL_MODE_16BIT	BIT(7)
 #define AIU_MEM_IEC958_CONTROL_MODE_LINEAR	BIT(8)
 #define AIU_MEM_IEC958_BUF_CNTL_INIT		BIT(0)
+#define AIU_RST_SOFT_958_FAST			BIT(2)
 
 #define AIU_FIFO_SPDIF_BLOCK			8
 
@@ -68,11 +69,15 @@ static int fifo_spdif_trigger(struct snd_pcm_substream *substream, int cmd,
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		snd_soc_component_write(component, AIU_RST_SOFT,
+					AIU_RST_SOFT_958_FAST);
 		fifo_spdif_dcu_enable(component, true);
 		break;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 	case SNDRV_PCM_TRIGGER_STOP:
+		snd_soc_component_write(component, AIU_RST_SOFT,
+					AIU_RST_SOFT_958_FAST);
 		fifo_spdif_dcu_enable(component, false);
 		break;
 	default:
-- 
2.43.0

Re: [PATCH v2] ASoC: meson: aiu: fifo-spdif: soft reset the S/PDIF datapath on start/stop

[Ferass El Hafidi]

Hi Christian,

On Sat, 27 Jun 2026 12:50, Christian Hewitt <christianshewitt@gmail.com> wrote:
>The I2S FIFO soft-resets its fast domain on start (AIU_RST_SOFT bit 0 +
>AIU_I2S_SYNC read in aiu_fifo_i2s_trigger), mirroring the downstream
>vendor driver's audio_out_i2s_enable(). The S/PDIF FIFO has no equivalent:
>it only toggles the IEC958 DCU, so a stale datapath FIFO can be replayed,
>producing the "machine gun noise" buffer underrun - on start when switching
>outputs, and on stop when playback ends. The latter is audible on devices
>with an always-on S/PDIF-fed DAC (e.g. the ES7144 on the WeTek Play2).
>
>The vendor driver resets the IEC958 fast domain (AIU_RST_SOFT bit 2) on
>both enable and disable (audio_hw_958_enable), and when reconfiguring
>(audio_hw_958_reset clears AIU_958_DCU_FF_CTRL then resets). Do the same:
>reset before enabling the DCU on start, and after disabling it on stop.
>
>Fixes: 6ae9ca9ce986bf ("ASoC: meson: aiu: add i2s and spdif support")
>Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>

You may have forgotten to add Martin's R-b here.

Best regards,
Ferass

Re: [PATCH v2] ASoC: meson: aiu: fifo-spdif: soft reset the S/PDIF datapath on start/stop

[Christian Hewitt]

> On 27 Jun 2026, at 5:08 pm, Ferass El Hafidi <funderscore@postmarketos.org> wrote:
> 
> Hi Christian,
> 
> On Sat, 27 Jun 2026 12:50, Christian Hewitt <christianshewitt@gmail.com> wrote:
>> The I2S FIFO soft-resets its fast domain on start (AIU_RST_SOFT bit 0 +
>> AIU_I2S_SYNC read in aiu_fifo_i2s_trigger), mirroring the downstream
>> vendor driver's audio_out_i2s_enable(). The S/PDIF FIFO has no equivalent:
>> it only toggles the IEC958 DCU, so a stale datapath FIFO can be replayed,
>> producing the "machine gun noise" buffer underrun - on start when switching
>> outputs, and on stop when playback ends. The latter is audible on devices
>> with an always-on S/PDIF-fed DAC (e.g. the ES7144 on the WeTek Play2).
>> 
>> The vendor driver resets the IEC958 fast domain (AIU_RST_SOFT bit 2) on
>> both enable and disable (audio_hw_958_enable), and when reconfiguring
>> (audio_hw_958_reset clears AIU_958_DCU_FF_CTRL then resets). Do the same:
>> reset before enabling the DCU on start, and after disabling it on stop.
>> 
>> Fixes: 6ae9ca9ce986bf ("ASoC: meson: aiu: add i2s and spdif support")
>> Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
> 
> You may have forgotten to add Martin's R-b here.

100%, but I also missed amending the commit description for the v2 change so
there’s a v3 where it’s been added. Sorry for the noise everyone, seems I am
a little out of practice at submitting things.

CH.