dmaengine: rcar-dmac: Add for_each_rcar_dmac_chan() helper

Add a helper macro for iterating over all DMAC channels, taking into
account the channel mask.  Use it where appropriate, to simplify code.

Restore "reverse Christmas tree" order of local variables while adding a
new variable.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20210128084455.2237256-3-geert+renesas@glider.beSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/sh/rcar-dmac.c

@@ -209,6 +209,10 @@ struct rcar_dmac {
 
 #define to_rcar_dmac(d)		container_of(d, struct rcar_dmac, engine)
 
+#define for_each_rcar_dmac_chan(i, dmac, chan)						\
+	for (i = 0, chan = &(dmac)->channels[0]; i < (dmac)->n_channels; i++, chan++)	\
+		if (!((dmac)->channels_mask & BIT(i))) continue; else
+
 /*
  * struct rcar_dmac_of_data - This driver's OF data
  * @chan_offset_base: DMAC channels base offset
@@ -817,15 +821,11 @@ static void rcar_dmac_chan_reinit(struct rcar_dmac_chan *chan)
 
 static void rcar_dmac_stop_all_chan(struct rcar_dmac *dmac)
 {
+	struct rcar_dmac_chan *chan;
 	unsigned int i;
 
 	/* Stop all channels. */
-	for (i = 0; i < dmac->n_channels; ++i) {
-		struct rcar_dmac_chan *chan = &dmac->channels[i];
-
-		if (!(dmac->channels_mask & BIT(i)))
-			continue;
-
+	for_each_rcar_dmac_chan(i, dmac, chan) {
 		/* Stop and reinitialize the channel. */
 		spin_lock_irq(&chan->lock);
 		rcar_dmac_chan_halt(chan);
@@ -1828,9 +1828,10 @@ static int rcar_dmac_probe(struct platform_device *pdev)
 		DMA_SLAVE_BUSWIDTH_2_BYTES | DMA_SLAVE_BUSWIDTH_4_BYTES |
 		DMA_SLAVE_BUSWIDTH_8_BYTES | DMA_SLAVE_BUSWIDTH_16_BYTES |
 		DMA_SLAVE_BUSWIDTH_32_BYTES | DMA_SLAVE_BUSWIDTH_64_BYTES;
+	const struct rcar_dmac_of_data *data;
+	struct rcar_dmac_chan *chan;
 	struct dma_device *engine;
 	struct rcar_dmac *dmac;
-	const struct rcar_dmac_of_data *data;
 	unsigned int i;
 	int ret;
 
@@ -1916,11 +1917,8 @@ static int rcar_dmac_probe(struct platform_device *pdev)
 
 	INIT_LIST_HEAD(&engine->channels);
 
-	for (i = 0; i < dmac->n_channels; ++i) {
-		if (!(dmac->channels_mask & BIT(i)))
-			continue;
-
-		ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i], data, i);
+	for_each_rcar_dmac_chan(i, dmac, chan) {
+		ret = rcar_dmac_chan_probe(dmac, chan, data, i);
 		if (ret < 0)
 			goto error;
 	}