ASoC: rsnd: fallback to PIO mode if DMA mode was failed

Current Renesas R-Car sound driver probe will be failed
if it try to use DMA mode and it couldn't use for some reasons.
But PIO mode works even though in such case.
This patch try to fallback to PIO mode if DMA mode probing was failed.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/core.c

@@ -349,7 +349,7 @@ int rsnd_dma_init(struct rsnd_priv *priv, struct rsnd_dma *dma,
 						     dma_name);
 	if (!dma->chan) {
 		dev_err(dev, "can't get dma channel\n");
-		return -EIO;
+		goto rsnd_dma_channel_err;
 	}
 
 	ret = dmaengine_slave_config(dma->chan, &cfg);
@@ -363,8 +363,15 @@ int rsnd_dma_init(struct rsnd_priv *priv, struct rsnd_dma *dma,
 
 rsnd_dma_init_err:
 	rsnd_dma_quit(priv, dma);
+rsnd_dma_channel_err:
 
-	return ret;
+	/*
+	 * DMA failed. try to PIO mode
+	 * see
+	 *	rsnd_ssi_dma_remove()
+	 *	rsnd_rdai_continuance_probe()
+	 */
+	return -EAGAIN;
 }
 
 void  rsnd_dma_quit(struct rsnd_priv *priv,
@@ -456,6 +463,13 @@ static int rsnd_dai_connect(struct rsnd_mod *mod,
 	return 0;
 }
 
+static void rsnd_dai_disconnect(struct rsnd_mod *mod,
+				struct rsnd_dai_stream *io)
+{
+	mod->io = NULL;
+	io->mod[mod->type] = NULL;
+}
+
 int rsnd_dai_id(struct rsnd_priv *priv, struct rsnd_dai *rdai)
 {
 	int id = rdai - priv->rdai;
@@ -686,6 +700,20 @@ static const struct snd_soc_dai_ops rsnd_soc_dai_ops = {
 	ret;							\
 })
 
+#define rsnd_path_break(priv, io, type)				\
+{								\
+	struct rsnd_mod *mod;					\
+	int id = -1;						\
+								\
+	if (rsnd_is_enable_path(io, type)) {			\
+		id = rsnd_info_id(priv, io, type);		\
+		if (id >= 0) {					\
+			mod = rsnd_##type##_mod_get(priv, id);	\
+			rsnd_dai_disconnect(mod, io);		\
+		}						\
+	}							\
+}
+
 static int rsnd_path_init(struct rsnd_priv *priv,
 			  struct rsnd_dai *rdai,
 			  struct rsnd_dai_stream *io)
@@ -977,6 +1005,44 @@ static const struct snd_soc_component_driver rsnd_soc_component = {
 	.name		= "rsnd",
 };
 
+static int rsnd_rdai_continuance_probe(struct rsnd_priv *priv,
+				       struct rsnd_dai *rdai,
+				       int is_play)
+{
+	struct rsnd_dai_stream *io = is_play ? &rdai->playback : &rdai->capture;
+	int ret;
+
+	ret = rsnd_dai_call(probe, io, rdai);
+	if (ret == -EAGAIN) {
+		/*
+		 * Fallback to PIO mode
+		 */
+
+		/*
+		 * call "remove" for SSI/SRC/DVC
+		 * SSI will be switch to PIO mode if it was DMA mode
+		 * see
+		 *	rsnd_dma_init()
+		 *	rsnd_ssi_dma_remove()
+		 */
+		rsnd_dai_call(remove, io, rdai);
+
+		/*
+		 * remove SRC/DVC from DAI,
+		 */
+		rsnd_path_break(priv, io, src);
+		rsnd_path_break(priv, io, dvc);
+
+		/*
+		 * retry to "probe".
+		 * DAI has SSI which is PIO mode only now.
+		 */
+		ret = rsnd_dai_call(probe, io, rdai);
+	}
+
+	return ret;
+}
+
 /*
  *	rsnd probe
  */
@@ -1038,11 +1104,11 @@ static int rsnd_probe(struct platform_device *pdev)
 	}
 
 	for_each_rsnd_dai(rdai, priv, i) {
-		ret = rsnd_dai_call(probe, &rdai->playback, rdai);
+		ret = rsnd_rdai_continuance_probe(priv, rdai, 1);
 		if (ret)
 			goto exit_snd_probe;
 
-		ret = rsnd_dai_call(probe, &rdai->capture, rdai);
+		ret = rsnd_rdai_continuance_probe(priv, rdai, 0);
 		if (ret)
 			goto exit_snd_probe;
 	}

sound/soc/sh/rcar/ssi.c

@@ -465,8 +465,23 @@ static int rsnd_ssi_dma_probe(struct rsnd_mod *mod,
 static int rsnd_ssi_dma_remove(struct rsnd_mod *mod,
 			       struct rsnd_dai *rdai)
 {
+	struct rsnd_priv *priv = rsnd_mod_to_priv(mod);
+	struct device *dev = rsnd_priv_to_dev(priv);
+
 	rsnd_dma_quit(rsnd_mod_to_priv(mod), rsnd_mod_to_dma(mod));
 
+	/*
+	 * fallback to PIO
+	 *
+	 * SSI .probe might be called again.
+	 * see
+	 *	rsnd_rdai_continuance_probe()
+	 */
+	mod->ops = &rsnd_ssi_pio_ops;
+
+	dev_info(dev, "%s[%d] fallback to PIO mode\n",
+		 rsnd_mod_name(mod), rsnd_mod_id(mod));
+
 	return 0;
 }