clk: add accuracy support for fixed clock

This patch adds support for accuracy retrieval on fixed clocks.
It also adds a new dt property called 'clock-accuracy' to define the clock
accuracy.

This can be usefull for oscillator (RC, crystal, ...) definitions which are
always given an accuracy characteristic.

Signed-off-by: Boris BREZILLON <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

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

···
 - clock-frequency : frequency of clock in Hz. Should be a single cell.
 
 Optional properties:
+- clock-accuracy : accuracy of clock in ppb (parts per billion).
+		   Should be a single cell.
 - gpios : From common gpio binding; gpio connection to clock enable pin.
 - clock-output-names : From common clock binding.
 
···
 		compatible = "fixed-clock";
 		#clock-cells = <0>;
 		clock-frequency = <1000000000>;
+		clock-accuracy = <100>;
 	};

drivers/clk/clk-fixed-rate.c

···
 	return to_clk_fixed_rate(hw)->fixed_rate;
 }
 
+static unsigned long clk_fixed_rate_recalc_accuracy(struct clk_hw *hw,
+		unsigned long parent_accuracy)
+{
+	return to_clk_fixed_rate(hw)->fixed_accuracy;
+}
+
 const struct clk_ops clk_fixed_rate_ops = {
 	.recalc_rate = clk_fixed_rate_recalc_rate,
+	.recalc_accuracy = clk_fixed_rate_recalc_accuracy,
 };
 EXPORT_SYMBOL_GPL(clk_fixed_rate_ops);
 
 /**
- * clk_register_fixed_rate - register fixed-rate clock with the clock framework
+ * clk_register_fixed_rate_with_accuracy - register fixed-rate clock with the
+ *					   clock framework
  * @dev: device that is registering this clock
  * @name: name of this clock
  * @parent_name: name of clock's parent
  * @flags: framework-specific flags
  * @fixed_rate: non-adjustable clock rate
+ * @fixed_accuracy: non-adjustable clock rate
  */
-struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
-		const char *parent_name, unsigned long flags,
-		unsigned long fixed_rate)
+struct clk *clk_register_fixed_rate_with_accuracy(struct device *dev,
+		const char *name, const char *parent_name, unsigned long flags,
+		unsigned long fixed_rate, unsigned long fixed_accuracy)
 {
 	struct clk_fixed_rate *fixed;
 	struct clk *clk;
···
 
 	/* struct clk_fixed_rate assignments */
 	fixed->fixed_rate = fixed_rate;
+	fixed->fixed_accuracy = fixed_accuracy;
 	fixed->hw.init = &init;
 
 	/* register the clock */
 	clk = clk_register(dev, &fixed->hw);
-
 	if (IS_ERR(clk))
 		kfree(fixed);
 
 	return clk;
+}
+EXPORT_SYMBOL_GPL(clk_register_fixed_rate_with_accuracy);
+
+/**
+ * clk_register_fixed_rate - register fixed-rate clock with the clock framework
+ * @dev: device that is registering this clock
+ * @name: name of this clock
+ * @parent_name: name of clock's parent
+ * @flags: framework-specific flags
+ * @fixed_rate: non-adjustable clock rate
+ */
+struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		unsigned long fixed_rate)
+{
+	return clk_register_fixed_rate_with_accuracy(dev, name, parent_name,
+						     flags, fixed_rate, 0);
 }
 EXPORT_SYMBOL_GPL(clk_register_fixed_rate);
 
···
 	struct clk *clk;
 	const char *clk_name = node->name;
 	u32 rate;
+	u32 accuracy = 0;
 
 	if (of_property_read_u32(node, "clock-frequency", &rate))
 		return;
 
+	of_property_read_u32(node, "clock-accuracy", &accuracy);
+
 	of_property_read_string(node, "clock-output-names", &clk_name);
 
-	clk = clk_register_fixed_rate(NULL, clk_name, NULL, CLK_IS_ROOT, rate);
+	clk = clk_register_fixed_rate_with_accuracy(NULL, clk_name, NULL,
+						    CLK_IS_ROOT, rate,
+						    accuracy);
 	if (!IS_ERR(clk))
 		of_clk_add_provider(node, of_clk_src_simple_get, clk);
 }

include/linux/clk-provider.h

···
 struct clk_fixed_rate {
 	struct		clk_hw hw;
 	unsigned long	fixed_rate;
+	unsigned long	fixed_accuracy;
 	u8		flags;
 };
 
···
 struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
 		const char *parent_name, unsigned long flags,
 		unsigned long fixed_rate);
+struct clk *clk_register_fixed_rate_with_accuracy(struct device *dev,
+		const char *name, const char *parent_name, unsigned long flags,
+		unsigned long fixed_rate, unsigned long fixed_accuracy);
 
 void of_fixed_clk_setup(struct device_node *np);