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Date: Thu, 21 May 2015 12:31:42 -0700
From: Stephen Boyd <sboyd@...eaurora.org>
To: Sergej Sawazki <ce3a@....de>
Cc: mturquette@...aro.org, jsarha@...com, linux-kernel@...r.kernel.org,
linux-clk@...r.kernel.org
Subject: Re: [PATCH RFC v1] clk: add gpio controlled clock multiplexer
On 05/14, Sergej Sawazki wrote:
> 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
[..]
> +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;
> + }
It would be better to have separate clk_ops for the case where
there isn't a gpiod_ena gpio. Also, this driver isn't DT
specific, so the error message is misleading.
> +
> + gpiod_set_value(clk->gpiod_ena, 1);
> +
> + return 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;
Doesn't seem possible if num_parents is correct. Please drop.
> +
> + gpiod_set_value(clk->gpiod_sel, index);
> +
> + return 0;
> +}
> +
[...]
> +/**
> + * 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));
What if the error is probe defer? We should be silent in such a
situation. I see this is mostly copy/paste from gpio-gate.c so
perhaps we should fix that one too.
> + return ERR_PTR(err);
> + }
> + clk_gpio_mux->gpiod_sel = gpiod_sel;
> +
> + if (gpiod_ena != NULL) {
Style nitpick:
if (gpiod_ena) {
is preferred.
> + 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;
Should we make sure num_parents is 2?
> +
> + clk_gpio_mux->hw.init = &init;
> +
> + clk = clk_register(dev, &clk_gpio_mux->hw);
But no if (dev) devm_*() trick here?
> +
> + if (!IS_ERR(clk))
> + return clk;
> +
> + if (!dev) {
> + kfree(clk_gpio_mux);
> + gpiod_put(gpiod_ena);
Isn't gpiod_ena optional? And so calling gpiod_put() here might
cause a warning?
Actually I wonder why we wouldn't just make this a gpio-mux
without enable/disable support? If we want to do enable/disable,
we can parent the gpio gate to this mux. Alternatively, we could
combine the gpio-gate file and this new mux file into one file
and support both compatible strings. There's quite a bit of
duplicated code so this may be a better approach.
> + 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;
This is only used on place and never assigned otherwise, why not
just use 0 in place of flags?
> +
> + 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) {
Should that be 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);
kcalloc() please.
> + 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);
pr_debug
> + 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),
please use kzalloc(sizeof(*data), GFP_KERNEL); style
> + 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
--
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a Linux Foundation Collaborative Project
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