clk: fixed-rate: Convert into a module platform driver

Adds support for fixed-rate clock providers which have not been
enabled via of_clk_init().

This is required by Device trees overlays that introduce clocks
providers.
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
[sboyd@codeaurora.org: Make new private function static, don't
check clk for NULL when unregistering in driver remove]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/clk-fixed-rate.c

@@ -15,6 +15,7 @@
 #include <linux/io.h>
 #include <linux/err.h>
 #include <linux/of.h>
+#include <linux/platform_device.h>
 
 /*
  * DOC: basic fixed-rate clock that cannot gate
@@ -157,18 +158,16 @@ void clk_hw_unregister_fixed_rate(struct clk_hw *hw)
 EXPORT_SYMBOL_GPL(clk_hw_unregister_fixed_rate);
 
 #ifdef CONFIG_OF
-/**
- * of_fixed_clk_setup() - Setup function for simple fixed rate clock
- */
-void of_fixed_clk_setup(struct device_node *node)
+static struct clk *_of_fixed_clk_setup(struct device_node *node)
 {
 	struct clk *clk;
 	const char *clk_name = node->name;
 	u32 rate;
 	u32 accuracy = 0;
+	int ret;
 
 	if (of_property_read_u32(node, "clock-frequency", &rate))
-		return;
+		return ERR_PTR(-EIO);
 
 	of_property_read_u32(node, "clock-accuracy", &accuracy);
 
@@ -176,9 +175,67 @@ void of_fixed_clk_setup(struct device_node *node)
 
 	clk = clk_register_fixed_rate_with_accuracy(NULL, clk_name, NULL,
 						    0, rate, accuracy);
-	if (!IS_ERR(clk))
-		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+	if (IS_ERR(clk))
+		return clk;
+
+	ret = of_clk_add_provider(node, of_clk_src_simple_get, clk);
+	if (ret) {
+		clk_unregister(clk);
+		return ERR_PTR(ret);
+	}
+
+	return clk;
+}
+
+/**
+ * of_fixed_clk_setup() - Setup function for simple fixed rate clock
+ */
+void of_fixed_clk_setup(struct device_node *node)
+{
+	_of_fixed_clk_setup(node);
 }
 EXPORT_SYMBOL_GPL(of_fixed_clk_setup);
 CLK_OF_DECLARE(fixed_clk, "fixed-clock", of_fixed_clk_setup);
+
+static int of_fixed_clk_remove(struct platform_device *pdev)
+{
+	struct clk *clk = platform_get_drvdata(pdev);
+
+	clk_unregister_fixed_rate(clk);
+
+	return 0;
+}
+
+static int of_fixed_clk_probe(struct platform_device *pdev)
+{
+	struct clk *clk;
+
+	/*
+	 * This function is not executed when of_fixed_clk_setup
+	 * succeeded.
+	 */
+	clk = _of_fixed_clk_setup(pdev->dev.of_node);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	platform_set_drvdata(pdev, clk);
+
+	return 0;
+}
+
+static const struct of_device_id of_fixed_clk_ids[] = {
+	{ .compatible = "fixed-clock" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, of_fixed_clk_ids);
+
+static struct platform_driver of_fixed_clk_driver = {
+	.driver = {
+		.name = "of_fixed_clk",
+		.of_match_table = of_fixed_clk_ids,
+	},
+	.probe = of_fixed_clk_probe,
+	.remove = of_fixed_clk_remove,
+};
+builtin_platform_driver(of_fixed_clk_driver);
 #endif