dmaengine: mmp_pdma: Add reset controller support

Add support to acquire and deassert an optional hardware reset controller
during mmp_pdma_probe(). It is optional because in Marvell devices
such as "marvell,pdma-1.0" the resets property is not a required
property. But in SpacemiT K1 PDMA, "spacemit,k1-pdma" as the dt
binding schema file stated, resets is required.

Signed-off-by: Guodong Xu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: docularxu

drivers/dma/mmp_pdma.c

@@ -16,6 +16,7 @@
 #include <linux/platform_data/mmp_dma.h>
 #include <linux/dmapool.h>
 #include <linux/clk.h>
+#include <linux/reset.h>
 #include <linux/of_dma.h>
 #include <linux/of.h>
 
@@ -1021,6 +1022,7 @@ static int mmp_pdma_probe(struct platform_device *op)
 	struct mmp_pdma_device *pdev;
 	struct mmp_dma_platdata *pdata = dev_get_platdata(&op->dev);
 	struct clk *clk;
+	struct reset_control *rst;
 	int i, ret, irq = 0;
 	int dma_channels = 0, irq_num = 0;
 	const enum dma_slave_buswidth widths =
@@ -1043,6 +1045,11 @@ static int mmp_pdma_probe(struct platform_device *op)
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
 
+	rst = devm_reset_control_get_optional_exclusive_deasserted(pdev->dev,
+								   NULL);
+	if (IS_ERR(rst))
+		return PTR_ERR(rst);
+
 	if (pdev->dev->of_node) {
 		/* Parse new and deprecated dma-channels properties */
 		if (of_property_read_u32(pdev->dev->of_node, "dma-channels",