clk: add gpio gated clock

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>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

2 files changed, 205 insertions, 0 deletions

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 27c542ba9e73..92a7f6c02394 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 000000000000..9dde88533684
--- /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