dmaengine: rcar-dmac: Add helpers for clearing DMA channel status

Extract the code to clear the status of one or all channels into their
own helpers, to prepare for the different handling of the R-Car V3U SoC.
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/20210128084455.2237256-4-geert+renesas@glider.beSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/sh/rcar-dmac.c

@@ -336,6 +336,17 @@ static void rcar_dmac_chan_write(struct rcar_dmac_chan *chan, u32 reg, u32 data)
 		writel(data, chan->iomem + reg);
 }
 
+static void rcar_dmac_chan_clear(struct rcar_dmac *dmac,
+				 struct rcar_dmac_chan *chan)
+{
+	rcar_dmac_write(dmac, RCAR_DMACHCLR, BIT(chan->index));
+}
+
+static void rcar_dmac_chan_clear_all(struct rcar_dmac *dmac)
+{
+	rcar_dmac_write(dmac, RCAR_DMACHCLR, dmac->channels_mask);
+}
+
 /* -----------------------------------------------------------------------------
  * Initialization and configuration
  */
@@ -451,7 +462,7 @@ static int rcar_dmac_init(struct rcar_dmac *dmac)
 	u16 dmaor;
 
 	/* Clear all channels and enable the DMAC globally. */
-	rcar_dmac_write(dmac, RCAR_DMACHCLR, dmac->channels_mask);
+	rcar_dmac_chan_clear_all(dmac);
 	rcar_dmac_write(dmac, RCAR_DMAOR,
 			RCAR_DMAOR_PRI_FIXED | RCAR_DMAOR_DME);
 
@@ -1566,7 +1577,7 @@ static irqreturn_t rcar_dmac_isr_channel(int irq, void *dev)
 		 * because channel is already stopped in error case.
 		 * We need to clear register and check DE bit as recovery.
 		 */
-		rcar_dmac_write(dmac, RCAR_DMACHCLR, 1 << chan->index);
+		rcar_dmac_chan_clear(dmac, chan);
 		rcar_dmac_chcr_de_barrier(chan);
 		reinit = true;
 		goto spin_lock_end;