[PATCH 0/2] ASoC: meson: axg: fix TDM channel order sync

[PATCH 0/2] ASoC: meson: axg: fix TDM channel order sync

[Jerome Brunet]

On the Amlogic AXG series, the TODDR FIFO may get out of sync with the TDM
decoder if the decoder is started before the FIFO. The channel appears
shifted in memory in an unpredictable way.

To fix this, the trick is to start the FIFO before the TDM decoder. This
way the FIFO is already waiting when the 1st channel is produced and it is
correctly placed in memory.

Jerome Brunet (2):
  ASoC: meson: axg-card: make links nonatomic
  ASoC: meson: axg-tdm-interface: manage formatters in trigger

 sound/soc/meson/axg-card.c          |  1 +
 sound/soc/meson/axg-tdm-interface.c | 26 +++++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

-- 
2.33.0


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[PATCH 1/2] ASoC: meson: axg-card: make links nonatomic

[Jerome Brunet]

Non atomic operations need to be performed in the trigger callback
of the TDM interfaces. Those are BEs but what matters is the nonatomic
flag of the FE in the DPCM context. Just set nonatomic for everything so,
at least, it is clear.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 sound/soc/meson/axg-card.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/soc/meson/axg-card.c b/sound/soc/meson/axg-card.c
index 2b77010c2c5c..cbbaa55d92a6 100644
--- a/sound/soc/meson/axg-card.c
+++ b/sound/soc/meson/axg-card.c
@@ -320,6 +320,7 @@ static int axg_card_add_link(struct snd_soc_card *card, struct device_node *np,
 
 	dai_link->cpus = cpu;
 	dai_link->num_cpus = 1;
+	dai_link->nonatomic = true;
 
 	ret = meson_card_parse_dai(card, np, &dai_link->cpus->of_node,
 				   &dai_link->cpus->dai_name);
-- 
2.33.0


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[PATCH 2/2] ASoC: meson: axg-tdm-interface: manage formatters in trigger

[Jerome Brunet]

So far, the formatters have been reset/enabled using the .prepare()
callback. This was done in this callback because walking the formatters use
a mutex so it could not be done in .trigger(), which is atomic by default.

It turns out there is a problem on capture path of the AXG series.
The FIFO may get out of sync with the TDM decoder if the IP are not enabled
in a specific order. The FIFO must be enabled before the formatter starts
producing data. IOW, we must deal with FE before the BE. The .prepare()
callback is called on the BEs before the FE so it is not OK for the AXG.

The .trigger() callback order can be configured, and it deals with the FE
before the BEs by default. To solve our problem, we just need to start and
stop the formatters from the .trigger() callback. It is OK do so now that
the links have been made 'nonatomic' in the card driver.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 sound/soc/meson/axg-tdm-interface.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/sound/soc/meson/axg-tdm-interface.c b/sound/soc/meson/axg-tdm-interface.c
index 87cac440b369..db077773af7a 100644
--- a/sound/soc/meson/axg-tdm-interface.c
+++ b/sound/soc/meson/axg-tdm-interface.c
@@ -351,13 +351,29 @@ static int axg_tdm_iface_hw_free(struct snd_pcm_substream *substream,
 	return 0;
 }
 
-static int axg_tdm_iface_prepare(struct snd_pcm_substream *substream,
+static int axg_tdm_iface_trigger(struct snd_pcm_substream *substream,
+				 int cmd,
 				 struct snd_soc_dai *dai)
 {
-	struct axg_tdm_stream *ts = snd_soc_dai_get_dma_data(dai, substream);
+	struct axg_tdm_stream *ts =
+		snd_soc_dai_get_dma_data(dai, substream);
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+	case SNDRV_PCM_TRIGGER_RESUME:
+	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		axg_tdm_stream_start(ts);
+		break;
+	case SNDRV_PCM_TRIGGER_SUSPEND:
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
+	case SNDRV_PCM_TRIGGER_STOP:
+		axg_tdm_stream_stop(ts);
+		break;
+	default:
+		return -EINVAL;
+	}
 
-	/* Force all attached formatters to update */
-	return axg_tdm_stream_reset(ts);
+	return 0;
 }
 
 static int axg_tdm_iface_remove_dai(struct snd_soc_dai *dai)
@@ -397,8 +413,8 @@ static const struct snd_soc_dai_ops axg_tdm_iface_ops = {
 	.set_fmt	= axg_tdm_iface_set_fmt,
 	.startup	= axg_tdm_iface_startup,
 	.hw_params	= axg_tdm_iface_hw_params,
-	.prepare	= axg_tdm_iface_prepare,
 	.hw_free	= axg_tdm_iface_hw_free,
+	.trigger	= axg_tdm_iface_trigger,
 };
 
 /* TDM Backend DAIs */
-- 
2.33.0


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Re: [PATCH 0/2] ASoC: meson: axg: fix TDM channel order sync

[Mark Brown]

On Wed, 20 Oct 2021 13:42:15 +0200, Jerome Brunet wrote:
> On the Amlogic AXG series, the TODDR FIFO may get out of sync with the TDM
> decoder if the decoder is started before the FIFO. The channel appears
> shifted in memory in an unpredictable way.
> 
> To fix this, the trick is to start the FIFO before the TDM decoder. This
> way the FIFO is already waiting when the 1st channel is produced and it is
> correctly placed in memory.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/2] ASoC: meson: axg-card: make links nonatomic
      commit: e138233e56e9829e65b6293887063a1a3ccb2d68
[2/2] ASoC: meson: axg-tdm-interface: manage formatters in trigger
      commit: bf5e4887eeddb48480568466536aa08ec7f179a5

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

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