[PATCH RFC] clk: add gpio controlled clock
Jyri Sarha
jsarha at ti.com
Fri Nov 1 10:01:20 EDT 2013
The added clk-gpio is a basic clock that can be enabled and disabled
trough a gpio output. The DT binding document for the clock is also
added.
Signed-off-by: Jyri Sarha <jsarha at ti.com>
---
.../devicetree/bindings/clock/gpio-clock.txt | 21 +++
drivers/clk/Makefile | 1 +
drivers/clk/clk-gpio.c | 154 ++++++++++++++++++++
include/linux/clk-provider.h | 25 ++++
4 files changed, 201 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/gpio-clock.txt
create mode 100644 drivers/clk/clk-gpio.c
diff --git a/Documentation/devicetree/bindings/clock/gpio-clock.txt b/Documentation/devicetree/bindings/clock/gpio-clock.txt
new file mode 100644
index 0000000..54fea39
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/gpio-clock.txt
@@ -0,0 +1,21 @@
+Binding for simple gpio controlled clock.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "gpio-clock".
+- #clock-cells : from common clock binding; shall be set to 0.
+- enable-gpios : GPIO reference for enabling and disabling the clock.
+
+Optional properties:
+- clocks: Maximum of one parent clock is supported.
+
+Example:
+ clock {
+ compatible = "gpio-clock";
+ clocks = <&parentclk>;
+ #clock-cells = <0>;
+ enable-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
+ };
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 7d74d06..81b65a3 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-fixed-rate.o
obj-$(CONFIG_COMMON_CLK) += clk-gate.o
obj-$(CONFIG_COMMON_CLK) += clk-mux.o
obj-$(CONFIG_COMMON_CLK) += clk-composite.o
+obj-$(CONFIG_COMMON_CLK) += clk-gpio.o
# SoCs specific
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835.o
diff --git a/drivers/clk/clk-gpio.c b/drivers/clk/clk-gpio.c
new file mode 100644
index 0000000..54f21d9
--- /dev/null
+++ b/drivers/clk/clk-gpio.c
@@ -0,0 +1,154 @@
+/*
+ * Copyright (C) 2012 Texas Instruments
+ * Author: Jyri Sarha <jsarha at ti.com>
+ *
+ * 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 controlled clock implementation
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+#include <linux/err.h>
+
+/**
+ * DOC: basic gpio controlled clock which can be enabled and disabled
+ * with gpio output
+ * Traits of this clock:
+ * prepare - clk_(un)prepare only ensures parent is (un)prepared
+ * enable - clk_enable and clk_disable are functional & control gpio
+ * rate - inherits rate from parent. No clk_set_rate support
+ * parent - fixed parent. No clk_set_parent support
+ */
+
+#define to_clk_gpio(_hw) container_of(_hw, struct clk_gpio, hw)
+
+static int clk_gpio_enable(struct clk_hw *hw)
+{
+ struct clk_gpio *gpio = to_clk_gpio(hw);
+ int value = gpio->active_low ? 0 : 1;
+
+ gpio_set_value(gpio->gpio, value);
+
+ return 0;
+}
+
+static void clk_gpio_disable(struct clk_hw *hw)
+{
+ struct clk_gpio *gpio = to_clk_gpio(hw);
+ int value = gpio->active_low ? 1 : 0;
+
+ gpio_set_value(gpio->gpio, value);
+}
+
+static int clk_gpio_is_enabled(struct clk_hw *hw)
+{
+ struct clk_gpio *gpio = to_clk_gpio(hw);
+ int value = gpio_get_value(gpio->gpio);
+
+ return gpio->active_low ? !value : value;
+}
+
+const struct clk_ops clk_gpio_ops = {
+ .enable = clk_gpio_enable,
+ .disable = clk_gpio_disable,
+ .is_enabled = clk_gpio_is_enabled,
+};
+EXPORT_SYMBOL_GPL(clk_gpio_ops);
+
+/**
+ * clk_register_gpio - register a gpip clock with the clock framework
+ * @dev: device that is registering this clock
+ * @name: name of this clock
+ * @parent_name: name of this clock's parent
+ * @flags: framework-specific flags for this clock
+ * @gpio: gpio to control this clock
+ * @active_low: gpio polarity
+ */
+struct clk *clk_register_gpio(struct device *dev, const char *name,
+ const char *parent_name, unsigned long flags,
+ unsigned int gpio, bool active_low)
+{
+ struct clk_gpio *clk_gpio;
+ struct clk *clk;
+ struct clk_init_data init = { NULL };
+ unsigned long gpio_flags;
+ int err;
+
+ if (active_low)
+ gpio_flags = GPIOF_OUT_INIT_LOW;
+ else
+ gpio_flags = GPIOF_OUT_INIT_HIGH;
+
+ err = gpio_request_one(gpio, gpio_flags, name);
+ if (err) {
+ pr_err("%s: Error requesting clock control gpio %u\n",
+ __func__, gpio);
+ return ERR_PTR(-EINVAL);
+ }
+
+ clk_gpio = kzalloc(sizeof(struct clk_gpio), GFP_KERNEL);
+ if (!clk_gpio) {
+ pr_err("%s: could not allocate gpio clk\n", __func__);
+ gpio_free(gpio);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ init.name = name;
+ init.ops = &clk_gpio_ops;
+ init.flags = flags | CLK_IS_BASIC;
+ init.parent_names = (parent_name ? &parent_name : NULL);
+ init.num_parents = (parent_name ? 1 : 0);
+
+ clk_gpio->gpio = gpio;
+ clk_gpio->active_low = active_low;
+ clk_gpio->hw.init = &init;
+
+ clk = clk_register(dev, &clk_gpio->hw);
+
+ if (IS_ERR(clk)) {
+ gpio_free(gpio);
+ kfree(clk_gpio);
+ }
+
+ return clk;
+}
+EXPORT_SYMBOL_GPL(clk_register_gpio);
+
+#ifdef CONFIG_OF
+/**
+ * of_gpio_clk_setup() - Setup function for gpio controlled clock
+ */
+void __init of_gpio_clk_setup(struct device_node *node)
+{
+ struct clk *clk;
+ const char *clk_name = node->name;
+ const char *parent_name;
+ enum of_gpio_flags gpio_flags;
+ int gpio;
+ bool active_low;
+
+ gpio = of_get_named_gpio_flags(node, "enable-gpios", 0, &gpio_flags);
+ if (gpio < 0) {
+ pr_err("%s: GPIO clock <%s> must have a enable-gpios property\n",
+ __func__, node);
+ return;
+ }
+
+ active_low = gpio_flags & OF_GPIO_ACTIVE_LOW;
+
+ parent_name = of_clk_get_parent_name(node, 0);
+
+ clk = clk_register_gpio(NULL, clk_name, parent_name, 0,
+ gpio, active_low);
+ if (!IS_ERR(clk))
+ of_clk_add_provider(node, of_clk_src_simple_get, clk);
+}
+EXPORT_SYMBOL_GPL(of_gpio_clk_setup);
+CLK_OF_DECLARE(gpio_clk, "gpio-clock", of_gpio_clk_setup);
+#endif
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 3493c76..f861568 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -439,6 +439,31 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
struct clk_hw *gate_hw, const struct clk_ops *gate_ops,
unsigned long flags);
+/***
+ * struct clk_gpio - gpio controlled clock
+ *
+ * @hw: handle between common and hardware-specific interfaces
+ * @gpio: gpio
+ * @active_low: gpio polarity
+ *
+ * Clock with a gpio control for enabling and disabling the parent clock.
+ * Implements .enable, .disable and .is_enabled
+ */
+
+struct clk_gpio {
+ struct clk_hw hw;
+ unsigned int gpio;
+ bool active_low;
+};
+
+extern const struct clk_ops clk_gpio_ops;
+
+struct clk *clk_register_gpio(struct device *dev, const char *name,
+ const char *parent_name, unsigned long flags,
+ unsigned int gpio, bool active_low);
+
+void of_gpio_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
--
1.7.9.5
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