clk: fixed-rate: Add clk flags for parent accuracy

Some clk providers want to use the accuracy of the parent clk and use
the fixed rate basic type clk to do that. This requires getting the
parent clk and extracting the accuracy before registering the fixed rate
clk. Let's add a flag for this and update the clk_ops to support this.

Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20190830150923.259497-8-sboyd@kernel.org

drivers/clk/clk-fixed-rate.c

@@ -35,7 +35,12 @@ static unsigned long clk_fixed_rate_recalc_rate(struct clk_hw *hw,
 static unsigned long clk_fixed_rate_recalc_accuracy(struct clk_hw *hw,
 		unsigned long parent_accuracy)
 {
-	return to_clk_fixed_rate(hw)->fixed_accuracy;
+	struct clk_fixed_rate *fixed = to_clk_fixed_rate(hw);
+
+	if (fixed->flags & CLK_FIXED_RATE_PARENT_ACCURACY)
+		return parent_accuracy;
+
+	return fixed->fixed_accuracy;
 }
 
 const struct clk_ops clk_fixed_rate_ops = {

include/linux/clk-provider.h

@@ -323,6 +323,10 @@ struct clk_hw {
  * @fixed_rate:	constant frequency of clock
  * @fixed_accuracy: constant accuracy of clock in ppb (parts per billion)
  * @flags:	hardware specific flags
+ *
+ * Flags:
+ * * CLK_FIXED_RATE_PARENT_ACCURACY - Use the accuracy of the parent clk
+ *                                    instead of what's set in @fixed_accuracy.
  */
 struct clk_fixed_rate {
 	struct		clk_hw hw;
@@ -331,6 +335,8 @@ struct clk_fixed_rate {
 	unsigned long	flags;
 };
 
+#define CLK_FIXED_RATE_PARENT_ACCURACY		BIT(0)
+
 extern const struct clk_ops clk_fixed_rate_ops;
 struct clk_hw *__clk_hw_register_fixed_rate(struct device *dev,
 		struct device_node *np, const char *name,