clk: fixed-factor: Allow for a few clocks to change the parent rate

The only way for a fixed factor clock to change its rate would be to change
its parent rate.

Since passing blindly CLK_SET_RATE_PARENT might break a lot of platforms
that were relying on the fact that the parent rate wouldn't change,
introduce a compatible-based whitelist that will allow clocks to opt-in
that flag.

Signed-off-by: Maxime Ripard <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

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

···
 Optional properties:
 - clock-output-names : From common clock binding.
 
+Some clocks that require special treatments are also handled by that
+driver, with the compatibles:
+  - allwinner,sun4i-a10-pll3-2x-clk
+
 Example:
 	clock {
 		compatible = "fixed-factor-clock";

drivers/clk/clk-fixed-factor.c

···
 EXPORT_SYMBOL_GPL(clk_hw_unregister_fixed_factor);
 
 #ifdef CONFIG_OF
+static const struct of_device_id set_rate_parent_matches[] = {
+	{ .compatible = "allwinner,sun4i-a10-pll3-2x-clk" },
+	{ /* Sentinel */ },
+};
+
 /**
  * of_fixed_factor_clk_setup() - Setup function for simple fixed factor clock
  */
···
 	struct clk *clk;
 	const char *clk_name = node->name;
 	const char *parent_name;
+	unsigned long flags = 0;
 	u32 div, mult;
 
 	if (of_property_read_u32(node, "clock-div", &div)) {
···
 	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,
+	if (of_match_node(set_rate_parent_matches, node))
+		flags |= CLK_SET_RATE_PARENT;
+
+	clk = clk_register_fixed_factor(NULL, clk_name, parent_name, flags,
 					mult, div);
 	if (!IS_ERR(clk))
 		of_clk_add_provider(node, of_clk_src_simple_get, clk);