ASoC: rsnd: add rsnd_dma_alloc()

R-Car sound DMA will be used from SSI/SRC.
dma.c doesn't alloc DMA handler in .probe timing, because we don't
know what kind of DMA transfer will be used then.
Thus, SSI/SRC have *rsnd_mod for DMA. rsnd_dma_attach() will allocate
it and attach it to system.
It will be PIO mode if it can't alloc DMA handler.

In case of MIX is used, rsnd_dma_attach() will be called twice from SSI.
To avoid duplicate allocation, current rsnd_dma_attach() is checking
allocated DMA handler. This DMA related operation is a little bit
difficult to understand.
This patch adds new rsnd_dma_alloc() and separates allocation and attach
for readable code.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/dma.c

@@ -753,7 +753,7 @@ static void rsnd_dma_of_path(struct rsnd_mod *this,
 	}
 }
 
-int rsnd_dma_attach(struct rsnd_dai_stream *io, struct rsnd_mod *mod,
+static int rsnd_dma_alloc(struct rsnd_dai_stream *io, struct rsnd_mod *mod,
 			  struct rsnd_mod **dma_mod)
 {
 	struct rsnd_mod *mod_from = NULL;
@@ -761,6 +761,7 @@ int rsnd_dma_attach(struct rsnd_dai_stream *io, struct rsnd_mod *mod,
 	struct rsnd_priv *priv = rsnd_io_to_priv(io);
 	struct rsnd_dma_ctrl *dmac = rsnd_priv_to_dmac(priv);
 	struct device *dev = rsnd_priv_to_dev(priv);
+	struct rsnd_dma *dma;
 	struct rsnd_mod_ops *ops;
 	enum rsnd_mod_type type;
 	int (*attach)(struct rsnd_dai_stream *io, struct rsnd_dma *dma,
@@ -800,9 +801,6 @@ int rsnd_dma_attach(struct rsnd_dai_stream *io, struct rsnd_mod *mod,
 		type	= RSND_MOD_AUDMA;
 	}
 
-	if (!(*dma_mod)) {
-		struct rsnd_dma *dma;
-
 	dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
 	if (!dma)
 		return -ENOMEM;
@@ -827,13 +825,21 @@ int rsnd_dma_attach(struct rsnd_dai_stream *io, struct rsnd_mod *mod,
 	dma->dst_addr = rsnd_dma_addr(io, mod_to,   is_play, 0);
 	dma->mod_from = mod_from;
 	dma->mod_to   = mod_to;
-	}
 
-	ret = rsnd_dai_connect(*dma_mod, io, type);
+	return 0;
+}
+
+int rsnd_dma_attach(struct rsnd_dai_stream *io, struct rsnd_mod *mod,
+		    struct rsnd_mod **dma_mod)
+{
+	if (!(*dma_mod)) {
+		int ret = rsnd_dma_alloc(io, mod, dma_mod);
+
 		if (ret < 0)
 			return ret;
+	}
 
-	return 0;
+	return rsnd_dai_connect(*dma_mod, io, (*dma_mod)->type);
 }
 
 int rsnd_dma_probe(struct rsnd_priv *priv)