[alsa-devel] [PATCH v1 2/3] ASoC: rsnd: Allow reconfiguration of clock rate

[Jiada Wang]

From: Timo Wischer <twischer at de.adit-jv.com>

Currently after clock rate is started in .prepare reconfiguration
of clock rate is not allowed, unless the stream is stopped.

But there is use case in Gstreamer ALSA sink, in case of changed caps
Gsreatmer reconfigs and it calls snd_pcm_hw_free() before snd_pcm_prepre().
See gstreamer1.0-plugins-base/
gst-libs/gst/audio/gstaudiobasesink.c: gst_audio_base_sink_setcaps():
- gst_audio_ring_buffer_release()
- gst_audio_sink_ring_buffer_release()
- gst_alsasink_unprepare()
- snd_pcm_hw_free()
is called before
- gst_audio_ring_buffer_acquire()
- gst_audio_sink_ring_buffer_acquire()
- gst_alsasink_prepare()
- set_hwparams()
- snd_pcm_hw_params()
- snd_pcm_prepare()

The issue mentioned in this commit can be reproduced with the following
aplay patch:

    >diff --git a/aplay/aplay.c b/aplay/aplay.c
    >@@ -2760,6 +2760,8 @@ static void playback_go(int fd, size_t loaded,
    >      header(rtype, name);
    >      set_params();
    >+     hwparams.rate = (hwparams.rate == 48000) ? 44100 : 48000;
    >+     set_params();
    >
    >      while (loaded > chunk_bytes && written < count && !in_aborting)
    >      {
    >              if (pcm_write(audiobuf + written, chunk_size) <= 0)

$ aplay -Dplughw:0,0,0 -c8 -fS24_LE -r48000 /dev/zero
rcar_sound ec500000.sound: SSI parent/child should use same rate
rcar_sound ec500000.sound: ssi[3] : prepare error -22
rcar_sound ec500000.sound: ASoC: cpu DAI prepare error: -22
rsnd_link0: ASoC: prepare FE rsnd_link0 failed

this patch address the issue by stop clock in .hw_free,
to allow reconfiguration of clock rate without stop of the stream.

Signed-off-by: Timo Wischer <twischer at de.adit-jv.com>
Signed-off-by: Jiada Wang <jiada_wang at mentor.com>
---
 sound/soc/sh/rcar/ssi.c | 53 +++++++++++++++++++++++++++++------------
 1 file changed, 38 insertions(+), 15 deletions(-)

diff --git a/sound/soc/sh/rcar/ssi.c b/sound/soc/sh/rcar/ssi.c
index f6a7466622ea..f43937d2c588 100644
--- a/sound/soc/sh/rcar/ssi.c
+++ b/sound/soc/sh/rcar/ssi.c
@@ -286,7 +286,7 @@ static int rsnd_ssi_master_clk_start(struct rsnd_mod *mod,
 	if (rsnd_ssi_is_multi_slave(mod, io))
 		return 0;
 
-	if (ssi->usrcnt > 0) {
+	if (ssi->rate) {
 		if (ssi->rate != rate) {
 			dev_err(dev, "SSI parent/child should use same rate\n");
 			return -EINVAL;
@@ -471,13 +471,9 @@ static int rsnd_ssi_init(struct rsnd_mod *mod,
 			 struct rsnd_dai_stream *io,
 			 struct rsnd_priv *priv)
 {
-	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
-
 	if (!rsnd_ssi_is_run_mods(mod, io))
 		return 0;
 
-	ssi->usrcnt++;
-
 	rsnd_mod_power_on(mod);
 
 	rsnd_ssi_config_init(mod, io);
@@ -505,18 +501,8 @@ static int rsnd_ssi_quit(struct rsnd_mod *mod,
 		return -EIO;
 	}
 
-	rsnd_ssi_master_clk_stop(mod, io);
-
 	rsnd_mod_power_off(mod);
 
-	ssi->usrcnt--;
-
-	if (!ssi->usrcnt) {
-		ssi->cr_own	= 0;
-		ssi->cr_mode	= 0;
-		ssi->wsr	= 0;
-	}
-
 	return 0;
 }
 
@@ -525,6 +511,7 @@ static int rsnd_ssi_hw_params(struct rsnd_mod *mod,
 			      struct snd_pcm_substream *substream,
 			      struct snd_pcm_hw_params *params)
 {
+	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
 	struct rsnd_dai *rdai = rsnd_io_to_rdai(io);
 	unsigned int fmt_width = snd_pcm_format_width(params_format(params));
 
@@ -536,6 +523,11 @@ static int rsnd_ssi_hw_params(struct rsnd_mod *mod,
 		return -EINVAL;
 	}
 
+	if (!rsnd_ssi_is_run_mods(mod, io))
+		return 0;
+
+	ssi->usrcnt++;
+
 	return 0;
 }
 
@@ -913,6 +905,35 @@ static int rsnd_ssi_prepare(struct rsnd_mod *mod,
 	return rsnd_ssi_master_clk_start(mod, io);
 }
 
+static int rsnd_ssi_hw_free(struct rsnd_mod *mod, struct rsnd_dai_stream *io,
+			    struct snd_pcm_substream *substream)
+{
+	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
+
+	if (!rsnd_ssi_is_run_mods(mod, io))
+		return 0;
+
+	if (!ssi->usrcnt) {
+		struct rsnd_priv *priv = rsnd_mod_to_priv(mod);
+		struct device *dev = rsnd_priv_to_dev(priv);
+
+		dev_err(dev, "%s usrcnt error\n", rsnd_mod_name(mod));
+		return -EIO;
+	}
+
+	rsnd_ssi_master_clk_stop(mod, io);
+
+	ssi->usrcnt--;
+
+	if (!ssi->usrcnt) {
+		ssi->cr_own	= 0;
+		ssi->cr_mode	= 0;
+		ssi->wsr	= 0;
+	}
+
+	return 0;
+}
+
 static struct rsnd_mod_ops rsnd_ssi_pio_ops = {
 	.name		= SSI_NAME,
 	.probe		= rsnd_ssi_common_probe,
@@ -926,6 +947,7 @@ static struct rsnd_mod_ops rsnd_ssi_pio_ops = {
 	.pcm_new	= rsnd_ssi_pcm_new,
 	.hw_params	= rsnd_ssi_hw_params,
 	.prepare	= rsnd_ssi_prepare,
+	.hw_free	= rsnd_ssi_hw_free,
 	.get_status	= rsnd_ssi_get_status,
 };
 
@@ -1012,6 +1034,7 @@ static struct rsnd_mod_ops rsnd_ssi_dma_ops = {
 	.pcm_new	= rsnd_ssi_pcm_new,
 	.fallback	= rsnd_ssi_fallback,
 	.hw_params	= rsnd_ssi_hw_params,
+	.hw_free	= rsnd_ssi_hw_free,
 	.prepare	= rsnd_ssi_prepare,
 	.get_status	= rsnd_ssi_get_status,
 };
-- 
2.19.2