clk: add device tree fixed-factor-clock binding support

Add support for DT "fixed-factor-clock" binding to the common fixed
factor clock support.
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Christian Ruppert <christian.ruppert@abilis.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

Documentation/devicetree/bindings/clock/fixed-factor-clock.txt

+Binding for simple fixed factor rate clock sources.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "fixed-factor-clock".
+- #clock-cells : from common clock binding; shall be set to 0.
+- clock-div: fixed divider.
+- clock-mult: fixed multiplier.
+- clocks: parent clock.
+
+Optional properties:
+- clock-output-names : From common clock binding.
+
+Example:
+	clock {
+		compatible = "fixed-factor-clock";
+		clocks = <&parentclk>;
+		#clock-cells = <0>;
+		div = <2>;
+		mult = <1>;
+	};

drivers/clk/clk-fixed-factor.c

@@ -11,6 +11,7 @@
 #include <linux/clk-provider.h>
 #include <linux/slab.h>
 #include <linux/err.h>
+#include <linux/of.h>
 
 /*
  * DOC: basic fixed multiplier and divider clock that cannot gate
@@ -96,3 +97,38 @@ struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
 
 	return clk;
 }
+#ifdef CONFIG_OF
+/**
+ * of_fixed_factor_clk_setup() - Setup function for simple fixed factor clock
+ */
+void __init of_fixed_factor_clk_setup(struct device_node *node)
+{
+	struct clk *clk;
+	const char *clk_name = node->name;
+	const char *parent_name;
+	u32 div, mult;
+
+	if (of_property_read_u32(node, "clock-div", &div)) {
+		pr_err("%s Fixed factor clock <%s> must have a clock-div property\n",
+			__func__, node->name);
+		return;
+	}
+
+	if (of_property_read_u32(node, "clock-mult", &mult)) {
+		pr_err("%s Fixed factor clock <%s> must have a clokc-mult property\n",
+			__func__, node->name);
+		return;
+	}
+
+	of_property_read_string(node, "clock-output-names", &clk_name);
+	parent_name = of_clk_get_parent_name(node, 0);
+
+	clk = clk_register_fixed_factor(NULL, clk_name, parent_name, 0,
+					mult, div);
+	if (!IS_ERR(clk))
+		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+}
+EXPORT_SYMBOL_GPL(of_fixed_factor_clk_setup);
+CLK_OF_DECLARE(fixed_factor_clk, "fixed-factor-clock",
+		of_fixed_factor_clk_setup);
+#endif

include/linux/clk-provider.h

@@ -325,6 +325,8 @@ struct clk *clk_register_mux_table(struct device *dev, const char *name,
 		void __iomem *reg, u8 shift, u32 mask,
 		u8 clk_mux_flags, u32 *table, spinlock_t *lock);
 
+void of_fixed_factor_clk_setup(struct device_node *node);
+
 /**
  * struct clk_fixed_factor - fixed multiplier and divider clock
  *