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SubjectRe: [PATCH RFC v1] clk: add gpio controlled clock multiplexer
On 05/14/15 12:40, Sergej Sawazki wrote:
> 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. The optional 'enable' pin can be used to enable or
> disable the clock output.
>
> Signed-off-by: Sergej Sawazki <ce3a@gmx.de>
> ---
> .../devicetree/bindings/clock/gpio-mux-clock.txt | 23 ++
> drivers/clk/Makefile | 1 +
> drivers/clk/clk-gpio-mux.c | 301 +++++++++++++++++++++
> include/linux/clk-provider.h | 26 ++
> 4 files changed, 351 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/clock/gpio-mux-clock.txt
> create mode 100644 drivers/clk/clk-gpio-mux.c
>
> diff --git a/Documentation/devicetree/bindings/clock/gpio-mux-clock.txt b/Documentation/devicetree/bindings/clock/gpio-mux-clock.txt
> new file mode 100644
> index 0000000..2198061
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/gpio-mux-clock.txt
> @@ -0,0 +1,23 @@
> +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.
> +
> +Optional properties:
> +- enable-gpios : GPIO reference for enabling and disabling the clock.

I guess in theory you should not need the enable functionality here. You
could just stack gpio-mux-clock on top of gpio-gate-clock.

Best regards,
Jyri

> +
> +Example:
> + clock {
> + compatible = "gpio-mux-clock";
> + clocks = <&parentclk1>, <&parentclk2>;
> + #clock-cells = <0>;
> + select-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
> + enable-gpios = <&gpio 2 GPIO_ACTIVE_HIGH>;
> + };
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index d965b3f..532a9bd 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -10,6 +10,7 @@ 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
> +obj-$(CONFIG_COMMON_CLK) += clk-gpio-mux.o
> ifeq ($(CONFIG_OF), y)
> obj-$(CONFIG_COMMON_CLK) += clk-conf.o
> endif
> diff --git a/drivers/clk/clk-gpio-mux.c b/drivers/clk/clk-gpio-mux.c
> new file mode 100644
> index 0000000..9e41e92
> --- /dev/null
> +++ b/drivers/clk/clk-gpio-mux.c
> @@ -0,0 +1,301 @@
> +/*
> + * Author: Sergej Sawazki <ce3a@gmx.de>
> + * Based on clk-gpio-gate.c by Jyri Sarha and ti/mux.c by Tero Kristo
> + *
> + * 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 multiplexer implementation
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/gpio.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/of_gpio.h>
> +#include <linux/err.h>
> +#include <linux/device.h>
> +
> +/**
> + * 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
> + * enable - clk_enable and clk_disable are functional & control gpio
> + * rate - rate is only affected by parent switching. No clk_set_rate support
> + * parent - parent is adjustable through clk_set_parent
> + */
> +
> +#define to_clk_gpio_mux(_hw) container_of(_hw, struct clk_gpio_mux, hw)
> +
> +static int clk_gpio_mux_enable(struct clk_hw *hw)
> +{
> + struct clk_gpio_mux *clk = to_clk_gpio_mux(hw);
> +
> + if (!clk->gpiod_ena) {
> + pr_err("%s: %s: DT property 'enable-gpios' not defined\n",
> + __func__, __clk_get_name(hw->clk));
> + return -ENOENT;
> + }
> +
> + gpiod_set_value(clk->gpiod_ena, 1);
> +
> + return 0;
> +}
> +
> +static void clk_gpio_mux_disable(struct clk_hw *hw)
> +{
> + struct clk_gpio_mux *clk = to_clk_gpio_mux(hw);
> +
> + if (!clk->gpiod_ena) {
> + pr_err("%s: %s: DT property 'enable-gpios' not defined\n",
> + __func__, __clk_get_name(hw->clk));
> + return;
> + }
> +
> + gpiod_set_value(clk->gpiod_ena, 0);
> +}
> +
> +static int clk_gpio_mux_is_enabled(struct clk_hw *hw)
> +{
> + struct clk_gpio_mux *clk = to_clk_gpio_mux(hw);
> +
> + if (!clk->gpiod_ena) {
> + pr_err("%s: %s: DT property 'enable-gpios' not defined\n",
> + __func__, __clk_get_name(hw->clk));
> + return -EINVAL;
> + }
> +
> + return gpiod_get_value(clk->gpiod_ena);
> +}
> +
> +static u8 clk_gpio_mux_get_parent(struct clk_hw *hw)
> +{
> + struct clk_gpio_mux *clk = to_clk_gpio_mux(hw);
> +
> + return gpiod_get_value(clk->gpiod_sel);
> +}
> +
> +static int clk_gpio_mux_set_parent(struct clk_hw *hw, u8 index)
> +{
> + struct clk_gpio_mux *clk = to_clk_gpio_mux(hw);
> +
> + if (index > 1)
> + return -EINVAL;
> +
> + gpiod_set_value(clk->gpiod_sel, index);
> +
> + return 0;
> +}
> +
> +const struct clk_ops clk_gpio_mux_ops = {
> + .enable = clk_gpio_mux_enable,
> + .disable = clk_gpio_mux_disable,
> + .is_enabled = clk_gpio_mux_is_enabled,
> + .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);
> +
> +/**
> + * 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
> + * @gpiod_sel: gpio descriptor to select the parent of this clock multiplexer
> + * @gpiod_ena: gpio descriptor to enable the output of this clock multiplexer
> + * @clk_flags: optional flags for basic clock
> + */
> +struct clk *clk_register_gpio_mux(struct device *dev, const char *name,
> + const char **parent_names, u8 num_parents,
> + struct gpio_desc *gpiod_sel, struct gpio_desc *gpiod_ena,
> + unsigned long clk_flags)
> +{
> + struct clk_gpio_mux *clk_gpio_mux = NULL;
> + struct clk *clk = ERR_PTR(-EINVAL);
> + struct clk_init_data init = { NULL };
> + unsigned long gpio_sel_flags, gpio_ena_flags;
> + int err;
> +
> + if (dev)
> + clk_gpio_mux = devm_kzalloc(dev, sizeof(struct clk_gpio_mux),
> + GFP_KERNEL);
> + else
> + clk_gpio_mux = kzalloc(sizeof(struct clk_gpio_mux), GFP_KERNEL);
> +
> + if (!clk_gpio_mux)
> + return ERR_PTR(-ENOMEM);
> +
> + if (gpiod_is_active_low(gpiod_sel))
> + gpio_sel_flags = GPIOF_OUT_INIT_HIGH;
> + else
> + gpio_sel_flags = GPIOF_OUT_INIT_LOW;
> +
> + if (dev)
> + err = devm_gpio_request_one(dev, desc_to_gpio(gpiod_sel),
> + gpio_sel_flags, name);
> + else
> + err = gpio_request_one(desc_to_gpio(gpiod_sel),
> + gpio_sel_flags, name);
> +
> + if (err) {
> + pr_err("%s: %s: Error requesting gpio %u\n",
> + __func__, name, desc_to_gpio(gpiod_sel));
> + return ERR_PTR(err);
> + }
> + clk_gpio_mux->gpiod_sel = gpiod_sel;
> +
> + if (gpiod_ena != NULL) {
> + if (gpiod_is_active_low(gpiod_ena))
> + gpio_ena_flags = GPIOF_OUT_INIT_HIGH;
> + else
> + gpio_ena_flags = GPIOF_OUT_INIT_LOW;
> +
> + if (dev)
> + err = devm_gpio_request_one(dev,
> + desc_to_gpio(gpiod_ena),
> + gpio_ena_flags, name);
> + else
> + err = gpio_request_one(desc_to_gpio(gpiod_ena),
> + gpio_ena_flags, name);
> +
> + if (err) {
> + pr_err("%s: %s: Error requesting gpio %u\n",
> + __func__, name,
> + desc_to_gpio(gpiod_ena));
> + return ERR_PTR(err);
> + }
> + clk_gpio_mux->gpiod_ena = gpiod_ena;
> + }
> +
> + init.name = name;
> + init.ops = &clk_gpio_mux_ops;
> + init.flags = clk_flags | CLK_IS_BASIC;
> + init.parent_names = parent_names;
> + init.num_parents = num_parents;
> +
> + clk_gpio_mux->hw.init = &init;
> +
> + clk = clk_register(dev, &clk_gpio_mux->hw);
> +
> + if (!IS_ERR(clk))
> + return clk;
> +
> + if (!dev) {
> + kfree(clk_gpio_mux);
> + gpiod_put(gpiod_ena);
> + gpiod_put(gpiod_sel);
> + }
> +
> + return clk;
> +}
> +EXPORT_SYMBOL_GPL(clk_register_gpio_mux);
> +
> +#ifdef CONFIG_OF
> +/**
> + * The clk_register_gpio_mux has to be delayed, because the EPROBE_DEFER
> + * can not be handled properly at of_clk_init() call time.
> + */
> +
> +struct clk_gpio_mux_delayed_register_data {
> + struct device_node *node;
> + struct mutex lock;
> + struct clk *clk;
> +};
> +
> +static struct clk *of_clk_gpio_mux_delayed_register_get(
> + struct of_phandle_args *clkspec,
> + void *_data)
> +{
> + struct clk_gpio_mux_delayed_register_data *data = _data;
> + struct clk *clk = ERR_PTR(-EINVAL);
> + const char *clk_name = data->node->name;
> + int i, num_parents;
> + const char **parent_names;
> + struct gpio_desc *gpiod_sel, *gpiod_ena;
> + int gpio;
> + u32 flags = 0;
> +
> + mutex_lock(&data->lock);
> +
> + if (data->clk) {
> + mutex_unlock(&data->lock);
> + return data->clk;
> + }
> +
> + gpio = of_get_named_gpio_flags(data->node, "select-gpios", 0, NULL);
> + if (!gpio_is_valid(gpio))
> + goto err_gpio;
> + gpiod_sel = gpio_to_desc(gpio);
> +
> + gpio = of_get_named_gpio_flags(data->node, "enable-gpios", 0, NULL);
> + if (!gpio_is_valid(gpio)) {
> + if (gpio != -ENOENT)
> + goto err_gpio;
> + else
> + gpiod_ena = NULL;
> + } else {
> + gpiod_ena = gpio_to_desc(gpio);
> + }
> +
> + num_parents = of_clk_get_parent_count(data->node);
> + if (num_parents < 2) {
> + pr_err("mux-clock %s must have 2 parents\n", data->node->name);
> + return clk;
> + }
> +
> + parent_names = kzalloc((sizeof(char *) * num_parents), GFP_KERNEL);
> + if (!parent_names) {
> + kfree(parent_names);
> + return clk;
> + }
> +
> + for (i = 0; i < num_parents; i++)
> + parent_names[i] = of_clk_get_parent_name(data->node, i);
> +
> + clk = clk_register_gpio_mux(NULL, clk_name, parent_names, num_parents,
> + gpiod_sel, gpiod_ena, flags);
> + if (IS_ERR(clk)) {
> + mutex_unlock(&data->lock);
> + return clk;
> + }
> +
> + data->clk = clk;
> + mutex_unlock(&data->lock);
> +
> + return clk;
> +
> +err_gpio:
> + mutex_unlock(&data->lock);
> + if (gpio == -EPROBE_DEFER)
> + pr_warn("%s: %s: GPIOs not yet available, retry later\n",
> + __func__, clk_name);
> + else
> + pr_err("%s: %s: Can't get GPIOs\n",
> + __func__, clk_name);
> + return ERR_PTR(gpio);
> +}
> +
> +/**
> + * of_gpio_mux_clk_setup() - Setup function for gpio controlled clock mux
> + */
> +void __init of_gpio_mux_clk_setup(struct device_node *node)
> +{
> + struct clk_gpio_mux_delayed_register_data *data;
> +
> + data = kzalloc(sizeof(struct clk_gpio_mux_delayed_register_data),
> + GFP_KERNEL);
> + if (!data)
> + return;
> +
> + data->node = node;
> + mutex_init(&data->lock);
> +
> + of_clk_add_provider(node, of_clk_gpio_mux_delayed_register_get, data);
> +}
> +EXPORT_SYMBOL_GPL(of_gpio_mux_clk_setup);
> +CLK_OF_DECLARE(gpio_mux_clk, "gpio-mux-clock", of_gpio_mux_clk_setup);
> +#endif
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 5378c2a..89c6c5b 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -549,6 +549,32 @@ struct clk *clk_register_gpio_gate(struct device *dev, const char *name,
> void of_gpio_clk_gate_setup(struct device_node *node);
>
> /**
> + * struct clk_gpio_mux - gpio controlled clock multiplexer
> + *
> + * @hw: handle between common and hardware-specific interfaces
> + * @gpiod_sel: gpio descriptor to select the parent of this clock multiplexer
> + * @gpiod_ena: gpio descriptor to enable the output of this clock multiplexer
> + *
> + * Clock with a gpio control for selecting the parent clock.
> + * Implements .enable, .disable, .is_enabled, .get_parent, .set_parent and
> + * .determine_rate
> + */
> +
> +struct clk_gpio_mux {
> + struct clk_hw hw;
> + struct gpio_desc *gpiod_sel;
> + struct gpio_desc *gpiod_ena;
> +};
> +
> +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,
> + struct gpio_desc *gpiod_sel, struct gpio_desc *gpiod_ena,
> + unsigned long clk_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
>



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