[PATCH] clk: add gpio gated clock

Jyri Sarha
2014-09-05T12:21:51Z

The added gpio-gate-clock is a basic clock that can be enabled and
disabled trough a gpio output. The DT binding document for the clock
is also added. For EPROBE_DEFER handling the registering of the clock
has to be delayed until of_clk_get() call time.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
---

This is my final attempt to get this generic gpio controlled basic
clock into mainline. Of course I gladly fix any issues that the patch
may have. However, if there is no response, I give up and move it to TI
specific clocks.

I've been sending this patch as a part of Beaglebone-Black HDMI audio
patch series since last autumn. Since the previous version I have done
some minor cleanups and changed the clock's compatible property from
"gpio-clock" to "gpio-gate-clock". All the file names, comments,
etc. have also been changed accordingly.

Best regards,
Jyri

.../devicetree/bindings/clock/gpio-gate-clock.txt | 21 ++
drivers/clk/Makefile | 1 +
drivers/clk/clk-gpio-gate.c | 204 ++++++++++++++++++++
include/linux/clk-provider.h | 22 +++
4 files changed, 248 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/gpio-gate-clock.txt
create mode 100644 drivers/clk/clk-gpio-gate.c

diff --git a/Documentation/devicetree/bindings/clock/gpio-gate-clock.txt b/Documentation/devicetree/bindings/clock/gpio-gate-clock.txt
new file mode 100644
index 0000000..d3379ff
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/gpio-gate-clock.txt
@@ -0,0 +1,21 @@
+Binding for simple gpio gated clock.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "gpio-gate-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-gate-clock";
+ clocks = <&parentclk>;
+ #clock-cells = <0>;
+ enable-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
+ };
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index f537a0b..5d78710 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -9,6 +9,7 @@ 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-fractional-divider.o
+obj-$(CONFIG_COMMON_CLK) += clk-gpio-gate.o
ifeq ($(CONFIG_OF), y)
obj-$(CONFIG_COMMON_CLK) += clk-conf.o
endif
diff --git a/drivers/clk/clk-gpio-gate.c b/drivers/clk/clk-gpio-gate.c
new file mode 100644
index 0000000..9dde885
--- /dev/null
+++ b/drivers/clk/clk-gpio-gate.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (C) 2013 - 2014 Texas Instruments Incorporated - http://www.ti.com
+ * Author: Jyri Sarha <jsarha@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 gated 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>
+#include <linux/device.h>
+
+/**
+ * DOC: basic gpio gated 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_gate_enable(struct clk_hw *hw)
+{
+ struct clk_gpio *clk = to_clk_gpio(hw);
+
+ gpiod_set_value(clk->gpiod, 1);
+
+ return 0;
+}
+
+static void clk_gpio_gate_disable(struct clk_hw *hw)
+{
+ struct clk_gpio *clk = to_clk_gpio(hw);
+
+ gpiod_set_value(clk->gpiod, 0);
+}
+
+static int clk_gpio_gate_is_enabled(struct clk_hw *hw)
+{
+ struct clk_gpio *clk = to_clk_gpio(hw);
+
+ return gpiod_get_value(clk->gpiod);
+}
+
+const struct clk_ops clk_gpio_gate_ops = {
+ .enable = clk_gpio_gate_enable,
+ .disable = clk_gpio_gate_disable,
+ .is_enabled = clk_gpio_gate_is_enabled,
+};
+EXPORT_SYMBOL_GPL(clk_gpio_gate_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
+ * @gpiod: gpio descriptor to gate this clock
+ */
+struct clk *clk_register_gpio_gate(struct device *dev, const char *name,
+ const char *parent_name, struct gpio_desc *gpiod,
+ 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 (gpiod_is_active_low(gpiod))
+ gpio_flags = GPIOF_OUT_INIT_HIGH;
+ else
+ gpio_flags = GPIOF_OUT_INIT_LOW;
+
+ if (dev)
+ err = devm_gpio_request_one(dev, desc_to_gpio(gpiod),
+ gpio_flags, name);
+ else
+ err = gpio_request_one(desc_to_gpio(gpiod), gpio_flags, name);
+
+ if (err) {
+ pr_err("%s: %s: Error requesting clock control gpio %u\n",
+ __func__, name, desc_to_gpio(gpiod));
+ 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 = gpiod;
+ 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:
+ gpiod_put(gpiod);
+
+ return clk;
+}
+EXPORT_SYMBOL_GPL(clk_register_gpio_gate);
+
+#ifdef CONFIG_OF
+/**
+ * The clk_register_gpio_gate has to be delayed, because the EPROBE_DEFER
+ * can not be handled properly at of_clk_init() call time.
+ */
+
+struct clk_gpio_gate_delayed_register_data {
+ struct device_node *node;
+ struct mutex lock;
+ struct clk *clk;
+};
+
+static struct clk *of_clk_gpio_gate_delayed_register_get(
+ struct of_phandle_args *clkspec,
+ void *_data)
+{
+ struct clk_gpio_gate_delayed_register_data *data = _data;
+ struct clk *clk;
+ const char *clk_name = data->node->name;
+ const char *parent_name;
+ struct gpio_desc *gpiod;
+ int gpio;
+
+ mutex_lock(&data->lock);
+
+ if (data->clk) {
+ mutex_unlock(&data->lock);
+ return data->clk;
+ }
+
+ gpio = of_get_named_gpio_flags(data->node, "enable-gpios", 0, NULL);
+ 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);
+ return ERR_PTR(gpio);
+ }
+ gpiod = gpio_to_desc(gpio);
+
+ parent_name = of_clk_get_parent_name(data->node, 0);
+
+ clk = clk_register_gpio_gate(NULL, clk_name, parent_name, gpiod, 0);
+ if (IS_ERR(clk)) {
+ mutex_unlock(&data->lock);
+ return clk;
+ }
+
+ data->clk = clk;
+ mutex_unlock(&data->lock);
+
+ return clk;
+}
+
+/**
+ * of_gpio_gate_clk_setup() - Setup function for gpio controlled clock
+ */
+void __init of_gpio_gate_clk_setup(struct device_node *node)
+{
+ struct clk_gpio_gate_delayed_register_data *data;
+
+ data = kzalloc(sizeof(struct clk_gpio_gate_delayed_register_data),
+ GFP_KERNEL);
+ if (!data)
+ return;
+
+ data->node = node;
+ mutex_init(&data->lock);
+
+ of_clk_add_provider(node, of_clk_gpio_gate_delayed_register_get, data);
+}
+EXPORT_SYMBOL_GPL(of_gpio_gate_clk_setup);
+CLK_OF_DECLARE(gpio_gate_clk, "gpio-gate-clock", of_gpio_gate_clk_setup);
+#endif
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 411dd7e..ec1581b 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -488,6 +488,28 @@ 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_gate - gpio gated clock
+ *
+ * @hw: handle between common and hardware-specific interfaces
+ * @gpiod: gpio descriptor
+ *
+ * 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;
+ struct gpio_desc *gpiod;
+};
+
+extern const struct clk_ops clk_gpio_gate_ops;
+struct clk *clk_register_gpio_gate(struct device *dev, const char *name,
+ const char *parent_name, struct gpio_desc *gpio,
+ unsigned long flags);
+
+void of_gpio_clk_gate_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