[PATCH] ASoC: meson: axg-frddr: set fifo depth according to the period

[PATCH] ASoC: meson: axg-frddr: set fifo depth according to the period

[Jerome Brunet]

When the period is small, using all the FRDDR fifo depth increases the
latency of the playback because the following device won't start pulling
data until the fifo reaches the depth set. We can adjust this depth so trim
it down for small periods.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 sound/soc/meson/axg-frddr.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/sound/soc/meson/axg-frddr.c b/sound/soc/meson/axg-frddr.c
index c3ae8ac30745..8ed114de0bdf 100644
--- a/sound/soc/meson/axg-frddr.c
+++ b/sound/soc/meson/axg-frddr.c
@@ -11,6 +11,7 @@
 #include <linux/regmap.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
+#include <sound/pcm_params.h>
 #include <sound/soc.h>
 #include <sound/soc-dai.h>
 
@@ -46,11 +47,28 @@ static int g12a_frddr_dai_prepare(struct snd_pcm_substream *substream,
 	return 0;
 }
 
+static int axg_frddr_dai_hw_params(struct snd_pcm_substream *substream,
+				   struct snd_pcm_hw_params *params,
+				   struct snd_soc_dai *dai)
+{
+	struct axg_fifo *fifo = snd_soc_dai_get_drvdata(dai);
+	unsigned int period, depth, val;
+
+	period = params_period_bytes(params);
+
+	/* Trim the FIFO depth if the period is small to improve latency */
+	depth = min(period, fifo->depth);
+	val = (depth / AXG_FIFO_BURST) - 1;
+	regmap_update_bits(fifo->map, FIFO_CTRL1, CTRL1_FRDDR_DEPTH_MASK,
+			   CTRL1_FRDDR_DEPTH(val));
+
+	return 0;
+}
+
 static int axg_frddr_dai_startup(struct snd_pcm_substream *substream,
 				 struct snd_soc_dai *dai)
 {
 	struct axg_fifo *fifo = snd_soc_dai_get_drvdata(dai);
-	unsigned int val;
 	int ret;
 
 	/* Enable pclk to access registers and clock the fifo ip */
@@ -61,11 +79,6 @@ static int axg_frddr_dai_startup(struct snd_pcm_substream *substream,
 	/* Apply single buffer mode to the interface */
 	regmap_update_bits(fifo->map, FIFO_CTRL0, CTRL0_FRDDR_PP_MODE, 0);
 
-	/* Use all fifo depth */
-	val = (fifo->depth / AXG_FIFO_BURST) - 1;
-	regmap_update_bits(fifo->map, FIFO_CTRL1, CTRL1_FRDDR_DEPTH_MASK,
-			   CTRL1_FRDDR_DEPTH(val));
-
 	return 0;
 }
 
@@ -84,6 +97,7 @@ static int axg_frddr_pcm_new(struct snd_soc_pcm_runtime *rtd,
 }
 
 static const struct snd_soc_dai_ops axg_frddr_ops = {
+	.hw_params	= axg_frddr_dai_hw_params,
 	.startup	= axg_frddr_dai_startup,
 	.shutdown	= axg_frddr_dai_shutdown,
 };
-- 
2.30.2

Re: [PATCH] ASoC: meson: axg-frddr: set fifo depth according to the period

[Mark Brown]

On Wed, 7 Apr 2021 16:57:14 +0200, Jerome Brunet wrote:
> When the period is small, using all the FRDDR fifo depth increases the
> latency of the playback because the following device won't start pulling
> data until the fifo reaches the depth set. We can adjust this depth so trim
> it down for small periods.

Applied to

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

Thanks!

[1/1] ASoC: meson: axg-frddr: set fifo depth according to the period
      commit: 6f68accaa8641b70b698da659216f82f87537869

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