clk: add gpio controlled clock multiplexer

Add a common clock driver for basic gpio controlled clock multiplexers.
This driver can be used for devices like 5V41068A or 831721I from IDT
or for discrete multiplexer circuits. The 'select' pin selects one of
two parent clocks.

Cc: Jyri Sarha <[e-mail]>
Signed-off-by: Sergej Sawazki <[e-mail]>
[[e-mail]: Fix error paths to free memory and do it
in the correct order]
Signed-off-by: Stephen Boyd <[e-mail]>

Documentation/devicetree/bindings/clock/gpio-mux-clock.txt

···
+Binding for simple gpio clock multiplexer.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "gpio-mux-clock".
+- clocks: list of two references to parent clocks.
+- #clock-cells : from common clock binding; shall be set to 0.
+- select-gpios : GPIO reference for selecting the parent clock.
+
+Example:
+	clock {
+		compatible = "gpio-mux-clock";
+		clocks = <&parentclk1>, <&parentclk2>;
+		#clock-cells = <0>;
+		select-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
+	};

drivers/clk/clk-gpio-gate.c

···
 /*
  * Copyright (C) 2013 - 2014 Texas Instruments Incorporated - http://www.ti.com
- * Author: Jyri Sarha <[e-mail]>
+ *
+ * Authors:
+ *    Jyri Sarha <[e-mail]>
+ *    Sergej Sawazki <[e-mail]>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
- * Gpio gated clock implementation
+ * Gpio controlled clock implementation
  */
 
 #include <linux/clk-provider.h>
···
 EXPORT_SYMBOL_GPL(clk_gpio_gate_ops);
 
 /**
- * clk_register_gpio - register a gpip clock with the clock framework
+ * DOC: basic clock multiplexer which can be controlled with a gpio output
+ * Traits of this clock:
+ * prepare - clk_prepare only ensures that parents are prepared
+ * rate - rate is only affected by parent switching.  No clk_set_rate support
+ * parent - parent is adjustable through clk_set_parent
+ */
+
+static u8 clk_gpio_mux_get_parent(struct clk_hw *hw)
+{
+	struct clk_gpio *clk = to_clk_gpio(hw);
+
+	return gpiod_get_value(clk->gpiod);
+}
+
+static int clk_gpio_mux_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct clk_gpio *clk = to_clk_gpio(hw);
+
+	gpiod_set_value(clk->gpiod, index);
+
+	return 0;
+}
+
+const struct clk_ops clk_gpio_mux_ops = {
+	.get_parent = clk_gpio_mux_get_parent,
+	.set_parent = clk_gpio_mux_set_parent,
+	.determine_rate = __clk_mux_determine_rate,
+};
+EXPORT_SYMBOL_GPL(clk_gpio_mux_ops);
+
+static struct clk *clk_register_gpio(struct device *dev, const char *name,
+		const char **parent_names, u8 num_parents, unsigned gpio,
+		bool active_low, unsigned long flags,
+		const struct clk_ops *clk_gpio_ops)
+{
+	struct clk_gpio *clk_gpio;
+	struct clk *clk;
+	struct clk_init_data init = {};
+	unsigned long gpio_flags;
+	int err;
+
+	if (dev)
+		clk_gpio = devm_kzalloc(dev, sizeof(*clk_gpio),	GFP_KERNEL);
+	else
+		clk_gpio = kzalloc(sizeof(*clk_gpio), GFP_KERNEL);
+
+	if (!clk_gpio)
+		return ERR_PTR(-ENOMEM);
+
+	if (active_low)
+		gpio_flags = GPIOF_ACTIVE_LOW | GPIOF_OUT_INIT_HIGH;
+	else
+		gpio_flags = GPIOF_OUT_INIT_LOW;
+
+	if (dev)
+		err = devm_gpio_request_one(dev, gpio, gpio_flags, name);
+	else
+		err = gpio_request_one(gpio, gpio_flags, name);
+	if (err) {
+		if (err != -EPROBE_DEFER)
+			pr_err("%s: %s: Error requesting clock control gpio %u\n",
+					__func__, name, gpio);
+		if (!dev)
+			kfree(clk_gpio);
+
+		return ERR_PTR(err);
+	}
+
+	init.name = name;
+	init.ops = clk_gpio_ops;
+	init.flags = flags | CLK_IS_BASIC;
+	init.parent_names = parent_names;
+	init.num_parents = num_parents;
+
+	clk_gpio->gpiod = gpio_to_desc(gpio);
+	clk_gpio->hw.init = &init;
+
+	if (dev)
+		clk = devm_clk_register(dev, &clk_gpio->hw);
+	else
+		clk = clk_register(NULL, &clk_gpio->hw);
+
+	if (!IS_ERR(clk))
+		return clk;
+
+	if (!dev) {
+		gpiod_put(clk_gpio->gpiod);
+		kfree(clk_gpio);
+	}
+
+	return clk;
+}
+
+/**
+ * clk_register_gpio_gate - register a gpio clock gate with the clock framework
  * @dev: device that is registering this clock
  * @name: name of this clock
  * @parent_name: name of this clock's parent
···
 		const char *parent_name, unsigned gpio, bool active_low,
 		unsigned long flags)
 {
-	struct clk_gpio *clk_gpio = NULL;
-	struct clk *clk = ERR_PTR(-EINVAL);
-	struct clk_init_data init = { NULL };
-	unsigned long gpio_flags;
-	int err;
-
-	if (active_low)
-		gpio_flags = GPIOF_ACTIVE_LOW | GPIOF_OUT_INIT_HIGH;
-	else
-		gpio_flags = GPIOF_OUT_INIT_LOW;
-
-	if (dev)
-		err = devm_gpio_request_one(dev, gpio, gpio_flags, name);
-	else
-		err = gpio_request_one(gpio, gpio_flags, name);
-
-	if (err) {
-		if (err != -EPROBE_DEFER)
-			pr_err("%s: %s: Error requesting clock control gpio %u\n",
-					__func__, name, gpio);
-		return ERR_PTR(err);
-	}
-
-	if (dev)
-		clk_gpio = devm_kzalloc(dev, sizeof(struct clk_gpio),
-					GFP_KERNEL);
-	else
-		clk_gpio = kzalloc(sizeof(struct clk_gpio), GFP_KERNEL);
-
-	if (!clk_gpio) {
-		clk = ERR_PTR(-ENOMEM);
-		goto clk_register_gpio_gate_err;
-	}
-
-	init.name = name;
-	init.ops = &clk_gpio_gate_ops;
-	init.flags = flags | CLK_IS_BASIC;
-	init.parent_names = (parent_name ? &parent_name : NULL);
-	init.num_parents = (parent_name ? 1 : 0);
-
-	clk_gpio->gpiod = gpio_to_desc(gpio);
-	clk_gpio->hw.init = &init;
-
-	clk = clk_register(dev, &clk_gpio->hw);
-
-	if (!IS_ERR(clk))
-		return clk;
-
-	if (!dev)
-		kfree(clk_gpio);
-
-clk_register_gpio_gate_err:
-	if (!dev)
-		gpio_free(gpio);
-
-	return clk;
+	return clk_register_gpio(dev, name,
+			(parent_name ? &parent_name : NULL),
+			(parent_name ? 1 : 0), gpio, active_low, flags,
+			&clk_gpio_gate_ops);
 }
 EXPORT_SYMBOL_GPL(clk_register_gpio_gate);
 
+/**
+ * clk_register_gpio_mux - register a gpio clock mux with the clock framework
+ * @dev: device that is registering this clock
+ * @name: name of this clock
+ * @parent_names: names of this clock's parents
+ * @num_parents: number of parents listed in @parent_names
+ * @gpio: gpio number to gate this clock
+ * @active_low: true if gpio should be set to 0 to enable clock
+ * @flags: clock flags
+ */
+struct clk *clk_register_gpio_mux(struct device *dev, const char *name,
+		const char **parent_names, u8 num_parents, unsigned gpio,
+		bool active_low, unsigned long flags)
+{
+	if (num_parents != 2) {
+		pr_err("mux-clock %s must have 2 parents\n", name);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return clk_register_gpio(dev, name, parent_names, num_parents,
+			gpio, active_low, flags, &clk_gpio_mux_ops);
+}
+EXPORT_SYMBOL_GPL(clk_register_gpio_mux);
+
 #ifdef CONFIG_OF
 /**
- * The clk_register_gpio_gate has to be delayed, because the EPROBE_DEFER
+ * clk_register_get() has to be delayed, because -EPROBE_DEFER
  * can not be handled properly at of_clk_init() call time.
  */
 
-struct clk_gpio_gate_delayed_register_data {
+struct clk_gpio_delayed_register_data {
+	const char *gpio_name;
 	struct device_node *node;
 	struct mutex lock;
 	struct clk *clk;
+	struct clk *(*clk_register_get)(const char *name,
+			const char **parent_names, u8 num_parents,
+			unsigned gpio, bool active_low);
 };
 
-static struct clk *of_clk_gpio_gate_delayed_register_get(
-		struct of_phandle_args *clkspec,
-		void *_data)
+static struct clk *of_clk_gpio_delayed_register_get(
+		struct of_phandle_args *clkspec, void *_data)
 {
-	struct clk_gpio_gate_delayed_register_data *data = _data;
+	struct clk_gpio_delayed_register_data *data = _data;
 	struct clk *clk;
-	const char *clk_name = data->node->name;
-	const char *parent_name;
+	const char **parent_names;
+	int i, num_parents;
 	int gpio;
 	enum of_gpio_flags of_flags;
 
···
 		return data->clk;
 	}
 
-	gpio = of_get_named_gpio_flags(data->node, "enable-gpios", 0,
-						&of_flags);
+	gpio = of_get_named_gpio_flags(data->node, data->gpio_name, 0,
+			&of_flags);
 	if (gpio < 0) {
 		mutex_unlock(&data->lock);
-		if (gpio != -EPROBE_DEFER)
-			pr_err("%s: %s: Can't get 'enable-gpios' DT property\n",
-			       __func__, clk_name);
+		if (gpio == -EPROBE_DEFER)
+			pr_debug("%s: %s: GPIOs not yet available, retry later\n",
+					data->node->name, __func__);
+		else
+			pr_err("%s: %s: Can't get '%s' DT property\n",
+					data->node->name, __func__,
+					data->gpio_name);
 		return ERR_PTR(gpio);
 	}
 
-	parent_name = of_clk_get_parent_name(data->node, 0);
+	num_parents = of_clk_get_parent_count(data->node);
 
-	clk = clk_register_gpio_gate(NULL, clk_name, parent_name, gpio,
-					of_flags & OF_GPIO_ACTIVE_LOW, 0);
-	if (IS_ERR(clk)) {
-		mutex_unlock(&data->lock);
-		return clk;
-	}
+	parent_names = kcalloc(num_parents, sizeof(char *), GFP_KERNEL);
+	if (!parent_names)
+		return ERR_PTR(-ENOMEM);
+
+	for (i = 0; i < num_parents; i++)
+		parent_names[i] = of_clk_get_parent_name(data->node, i);
+
+	clk = data->clk_register_get(data->node->name, parent_names,
+			num_parents, gpio, of_flags & OF_GPIO_ACTIVE_LOW);
+	if (IS_ERR(clk))
+		goto out;
 
 	data->clk = clk;
+out:
 	mutex_unlock(&data->lock);
+	kfree(parent_names);
 
 	return clk;
 }
 
-/**
- * of_gpio_gate_clk_setup() - Setup function for gpio controlled clock
- */
-static void __init of_gpio_gate_clk_setup(struct device_node *node)
+static struct clk *of_clk_gpio_gate_delayed_register_get(const char *name,
+		const char **parent_names, u8 num_parents,
+		unsigned gpio, bool active_low)
 {
-	struct clk_gpio_gate_delayed_register_data *data;
+	return clk_register_gpio_gate(NULL, name, parent_names[0],
+			gpio, active_low, 0);
+}
 
-	data = kzalloc(sizeof(struct clk_gpio_gate_delayed_register_data),
-		       GFP_KERNEL);
+static struct clk *of_clk_gpio_mux_delayed_register_get(const char *name,
+		const char **parent_names, u8 num_parents, unsigned gpio,
+		bool active_low)
+{
+	return clk_register_gpio_mux(NULL, name, parent_names, num_parents,
+			gpio, active_low, 0);
+}
+
+static void __init of_gpio_clk_setup(struct device_node *node,
+		const char *gpio_name,
+		struct clk *(*clk_register_get)(const char *name,
+				const char **parent_names, u8 num_parents,
+				unsigned gpio, bool active_low))
+{
+	struct clk_gpio_delayed_register_data *data;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return;
 
 	data->node = node;
+	data->gpio_name = gpio_name;
+	data->clk_register_get = clk_register_get;
 	mutex_init(&data->lock);
 
-	of_clk_add_provider(node, of_clk_gpio_gate_delayed_register_get, data);
+	of_clk_add_provider(node, of_clk_gpio_delayed_register_get, data);
+}
+
+static void __init of_gpio_gate_clk_setup(struct device_node *node)
+{
+	of_gpio_clk_setup(node, "enable-gpios",
+		of_clk_gpio_gate_delayed_register_get);
 }
 CLK_OF_DECLARE(gpio_gate_clk, "gpio-gate-clock", of_gpio_gate_clk_setup);
+
+void __init of_gpio_mux_clk_setup(struct device_node *node)
+{
+	of_gpio_clk_setup(node, "select-gpios",
+		of_clk_gpio_mux_delayed_register_get);
+}
+CLK_OF_DECLARE(gpio_mux_clk, "gpio-mux-clock", of_gpio_mux_clk_setup);
 #endif

include/linux/clk-provider.h

···
 void of_gpio_clk_gate_setup(struct device_node *node);
 
 /**
+ * struct clk_gpio_mux - gpio controlled clock multiplexer
+ *
+ * @hw:		see struct clk_gpio
+ * @gpiod:	gpio descriptor to select the parent of this clock multiplexer
+ *
+ * Clock with a gpio control for selecting the parent clock.
+ * Implements .get_parent, .set_parent and .determine_rate
+ */
+
+extern const struct clk_ops clk_gpio_mux_ops;
+struct clk *clk_register_gpio_mux(struct device *dev, const char *name,
+		const char **parent_names, u8 num_parents, unsigned gpio,
+		bool active_low, unsigned long flags);
+
+void of_gpio_mux_clk_setup(struct device_node *node);
+
+/**
  * clk_register - allocate a new clock, register it and return an opaque cookie
  * @dev: device that is registering this clock
  * @hw: link to hardware-specific clock data