clk: clk-gpio: Support acquire/release semantics

Add support for the 'gpio-gate-clock-releasing' compatible string. The
behaviour is identical to that of 'gpio-gate-clock' but the gpio is
acquired on 'enable' and released on 'disable'.

Signed-off-by: Richard Oliver <richard.oliver@raspberrypi.com>

Author: roliver-rpi

drivers/clk/clk-gpio.c

@@ -35,6 +35,7 @@
  *
  * @hw:		handle between common and hardware-specific interfaces
  * @gpiod:	gpio descriptor
+ * @dev:	device pointer for acquire/release operations
  *
  * Clock with a gpio control for enabling and disabling the parent clock
  * or switching between two parents by asserting or deasserting the gpio.
@@ -46,9 +47,41 @@
 struct clk_gpio {
 	struct clk_hw	hw;
 	struct gpio_desc *gpiod;
+	struct device *dev;
 };
 
 #define to_clk_gpio(_hw) container_of(_hw, struct clk_gpio, hw)
+static int clk_gpio_gate_acquire(struct clk_hw *hw)
+{
+	struct clk_gpio *clk = to_clk_gpio(hw);
+	struct device *dev = clk->dev;
+
+	clk->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(clk->gpiod)) {
+		int ret = PTR_ERR(clk->gpiod);
+
+		clk->gpiod = NULL;
+		return ret;
+	}
+
+	return 0;
+}
+
+static bool clk_gpio_gate_is_acquired(struct clk_hw *hw)
+{
+	struct clk_gpio *clk = to_clk_gpio(hw);
+
+	return !!clk->gpiod;
+}
+
+static void clk_gpio_gate_release(struct clk_hw *hw)
+{
+	struct clk_gpio *clk = to_clk_gpio(hw);
+	struct device *dev = clk->dev;
+
+	devm_gpiod_put(dev, clk->gpiod);
+	clk->gpiod = NULL;
+}
 
 static int clk_gpio_gate_enable(struct clk_hw *hw)
 {
@@ -79,6 +112,37 @@ static const struct clk_ops clk_gpio_gate_ops = {
 	.is_enabled = clk_gpio_gate_is_enabled,
 };
 
+static int clk_gpio_gate_releasing_enable(struct clk_hw *hw)
+{
+	int ret;
+
+	ret = clk_gpio_gate_acquire(hw);
+	if (ret)
+		return ret;
+
+	return clk_gpio_gate_enable(hw);
+}
+
+static void clk_gpio_gate_releasing_disable(struct clk_hw *hw)
+{
+	clk_gpio_gate_disable(hw);
+	clk_gpio_gate_release(hw);
+}
+
+static int clk_gpio_gate_releasing_is_enabled(struct clk_hw *hw)
+{
+	if (!clk_gpio_gate_is_acquired(hw))
+		return 0;
+
+	return clk_gpio_gate_is_enabled(hw);
+}
+
+static const struct clk_ops clk_gpio_gate_releasing_ops = {
+	.enable = clk_gpio_gate_releasing_enable,
+	.disable = clk_gpio_gate_releasing_disable,
+	.is_enabled = clk_gpio_gate_releasing_is_enabled,
+};
+
 static int clk_sleeping_gpio_gate_prepare(struct clk_hw *hw)
 {
 	struct clk_gpio *clk = to_clk_gpio(hw);
@@ -108,6 +172,37 @@ static const struct clk_ops clk_sleeping_gpio_gate_ops = {
 	.is_prepared = clk_sleeping_gpio_gate_is_prepared,
 };
 
+static int clk_sleeping_gpio_gate_releasing_prepare(struct clk_hw *hw)
+{
+	int ret;
+
+	ret = clk_gpio_gate_acquire(hw);
+	if (ret)
+		return ret;
+
+	return clk_sleeping_gpio_gate_prepare(hw);
+}
+
+static void clk_sleeping_gpio_gate_releasing_unprepare(struct clk_hw *hw)
+{
+	clk_sleeping_gpio_gate_unprepare(hw);
+	clk_gpio_gate_release(hw);
+}
+
+static int clk_sleeping_gpio_gate_releasing_is_prepared(struct clk_hw *hw)
+{
+	if (!clk_gpio_gate_is_acquired(hw))
+		return 0;
+
+	return clk_sleeping_gpio_gate_is_prepared(hw);
+}
+
+static const struct clk_ops clk_sleeping_gpio_gate_releasing_ops = {
+	.prepare = clk_sleeping_gpio_gate_releasing_prepare,
+	.unprepare = clk_sleeping_gpio_gate_releasing_unprepare,
+	.is_prepared = clk_sleeping_gpio_gate_releasing_is_prepared,
+};
+
 /**
  * DOC: basic clock multiplexer which can be controlled with a gpio output
  * Traits of this clock:
@@ -162,6 +257,7 @@ static struct clk_hw *clk_register_gpio(struct device *dev, u8 num_parents,
 	init.flags = CLK_SET_RATE_PARENT;
 
 	clk_gpio->gpiod = gpiod;
+	clk_gpio->dev = dev;
 	clk_gpio->hw.init = &init;
 
 	hw = &clk_gpio->hw;
@@ -174,14 +270,29 @@ static struct clk_hw *clk_register_gpio(struct device *dev, u8 num_parents,
 
 static struct clk_hw *clk_hw_register_gpio_gate(struct device *dev,
 						int num_parents,
-						struct gpio_desc *gpiod)
+						struct gpio_desc *gpiod,
+						bool releasing)
 {
 	const struct clk_ops *ops;
 
-	if (gpiod_cansleep(gpiod))
-		ops = &clk_sleeping_gpio_gate_ops;
-	else
-		ops = &clk_gpio_gate_ops;
+	if (releasing) {
+		/* For releasing variant, confirm GPIO works then release it
+		 * for acquire/release semantics
+		 */
+		if (gpiod_cansleep(gpiod))
+			ops = &clk_sleeping_gpio_gate_releasing_ops;
+		else
+			ops = &clk_gpio_gate_releasing_ops;
+
+		devm_gpiod_put(dev, gpiod);
+		gpiod = NULL;
+	} else {
+		/* Regular variant - keep GPIO and choose appropriate ops */
+		if (gpiod_cansleep(gpiod))
+			ops = &clk_sleeping_gpio_gate_ops;
+		else
+			ops = &clk_gpio_gate_ops;
+	}
 
 	return clk_register_gpio(dev, num_parents, gpiod, ops);
 }
@@ -201,8 +312,11 @@ static int gpio_clk_driver_probe(struct platform_device *pdev)
 	struct gpio_desc *gpiod;
 	struct clk_hw *hw;
 	bool is_mux;
+	bool is_releasing;
 
 	is_mux = of_device_is_compatible(node, "gpio-mux-clock");
+	is_releasing =
+		of_device_is_compatible(node, "gpio-gate-clock-releasing");
 
 	num_parents = of_clk_get_parent_count(node);
 	if (is_mux && num_parents != 2) {
@@ -219,7 +333,9 @@ static int gpio_clk_driver_probe(struct platform_device *pdev)
 	if (is_mux)
 		hw = clk_hw_register_gpio_mux(dev, gpiod);
 	else
-		hw = clk_hw_register_gpio_gate(dev, num_parents, gpiod);
+		hw = clk_hw_register_gpio_gate(dev, num_parents, gpiod,
+					       is_releasing);
+
 	if (IS_ERR(hw))
 		return PTR_ERR(hw);
 
@@ -229,6 +345,7 @@ static int gpio_clk_driver_probe(struct platform_device *pdev)
 static const struct of_device_id gpio_clk_match_table[] = {
 	{ .compatible = "gpio-mux-clock" },
 	{ .compatible = "gpio-gate-clock" },
+	{ .compatible = "gpio-gate-clock-releasing" },
 	{ }
 };