dmaengine: mv_xor_v2: Fix clock resource by adding a register clock

On the CP110 components which are present on the Armada 7K/8K SoC we need
to explicitly enable the clock for the registers. However it is not
needed for the AP8xx component, that's why this clock is optional.

With this patch both clock have now a name, but in order to be backward
compatible, the name of the first clock is not used. It allows to still
use this clock with a device tree using the old binding.
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

Documentation/devicetree/bindings/dma/mv-xor-v2.txt

@@ -11,7 +11,11 @@ Required properties:
   interrupts.
 
 Optional properties:
-- clocks: Optional reference to the clock used by the XOR engine.
+- clocks: Optional reference to the clocks used by the XOR engine.
+- clock-names: mandatory if there is a second clock, in this case the
+   name must be "core" for the first clock and "reg" for the second
+   one
+
 
 Example:
 

drivers/dma/mv_xor_v2.c

@@ -163,6 +163,7 @@ struct mv_xor_v2_device {
 	void __iomem *dma_base;
 	void __iomem *glob_base;
 	struct clk *clk;
+	struct clk *reg_clk;
 	struct tasklet_struct irq_tasklet;
 	struct list_head free_sw_desc;
 	struct dma_device dmadev;
@@ -749,13 +750,26 @@ static int mv_xor_v2_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	xor_dev->reg_clk = devm_clk_get(&pdev->dev, "reg");
+	if (PTR_ERR(xor_dev->reg_clk) != -ENOENT) {
+		if (!IS_ERR(xor_dev->reg_clk)) {
+			ret = clk_prepare_enable(xor_dev->reg_clk);
+			if (ret)
+				return ret;
+		} else {
+			return PTR_ERR(xor_dev->reg_clk);
+		}
+	}
+
 	xor_dev->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(xor_dev->clk) && PTR_ERR(xor_dev->clk) == -EPROBE_DEFER)
-		return -EPROBE_DEFER;
+	if (IS_ERR(xor_dev->clk) && PTR_ERR(xor_dev->clk) == -EPROBE_DEFER) {
+		ret = EPROBE_DEFER;
+		goto disable_reg_clk;
+	}
 	if (!IS_ERR(xor_dev->clk)) {
 		ret = clk_prepare_enable(xor_dev->clk);
 		if (ret)
-			return ret;
+			goto disable_reg_clk;
 	}
 
 	ret = platform_msi_domain_alloc_irqs(&pdev->dev, 1,
@@ -866,8 +880,9 @@ static int mv_xor_v2_probe(struct platform_device *pdev)
 free_msi_irqs:
 	platform_msi_domain_free_irqs(&pdev->dev);
 disable_clk:
-	if (!IS_ERR(xor_dev->clk))
 	clk_disable_unprepare(xor_dev->clk);
+disable_reg_clk:
+	clk_disable_unprepare(xor_dev->reg_clk);
 	return ret;
 }