clk consumer常用接口

#获取句柄
struct clk *clk_get(struct device *dev, const char *id);
struct clk *devm_clk_get(struct device *dev, const char *id);

#prepare 与enable
int clk_enable(struct clk *clk);//使能时钟，不会睡眠
void clk_disable(struct clk *clk);//使能时钟，不会睡眠
int clk_prepare(struct clk *clk); 
void clk_unprepare(struct clk *clk);
int clk_prepare_enable(struct clk *clk) //使能时钟，可能会睡眠 
void clk_disable_unprepare(struct clk *clk) //禁止时钟，可能会睡眠

#parent set and get 
int clk_set_parent(struct clk *clk, struct clk *parent); 
struct clk *clk_get_parent(struct clk *clk);

#速率 set and get
long clk_round_rate(struct clk *clk, unsigned long rate);
int clk_set_rate(struct clk *clk, unsigned long rate);
unsigned long clk_get_rate(struct clk *clk) //获取时钟频率

void clk_put(struct clk *clk);

 实例

设置频率： ret = clk_set_rate(host->clk, 300000);

获得频率： ret = clk_get_rate(host->clk);

devm_clk_get 分析

 devm_clk_get(&dev->dev, NULL); //id 是 “clock-names”中 对应的名字

struct clk *devm_clk_get(struct device *dev, const char *id)
{
	struct clk **ptr, *clk;

	ptr = devres_alloc(devm_clk_release, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	clk = clk_get(dev, id);
	if (!IS_ERR(clk)) {
		*ptr = clk;
		devres_add(dev, ptr);
	} else {
		devres_free(ptr);
	}

	return clk;
}

 clk_get

/*dev_id为设备的名称，对应设备树节点的 21a0000.i2c（dev.of_node->name）*/
/*con_id为“clock-names”*/

struct clk *clk_get(struct device *dev, const char *con_id)
{
	const char *dev_id = dev ? dev_name(dev) : NULL;
	struct clk *clk;

	if (dev && dev->of_node) {
		clk = __of_clk_get_by_name(dev->of_node, dev_id, con_id);
		if (!IS_ERR(clk) || PTR_ERR(clk) == -EPROBE_DEFER)
			return clk;
	}

	return clk_get_sys(dev_id, con_id);
}

__of_clk_get_by_name 

static struct clk *__of_clk_get_by_name(struct device_node *np,
					const char *dev_id,
					const char *name)
{
	struct clk *clk = ERR_PTR(-ENOENT);

	/* Walk up the tree of devices looking for a clock that matches */
	while (np) {
		int index = 0;

		/*
		 * For named clocks, first look up the name in the
		 * "clock-names" property.  If it cannot be found, then
		 * index will be an error code, and of_clk_get() will fail.
		 */
		if (name)
			index = of_property_match_string(np, "clock-names", name);
		clk = __of_clk_get(np, index, dev_id, name);
		if (!IS_ERR(clk)) {
			break;
		} else if (name && index >= 0) {
			if (PTR_ERR(clk) != -EPROBE_DEFER)
				pr_err("ERROR: could not get clock %pOF:%s(%i)\n",
					np, name ? name : "", index);
			return clk;
		}

		/*
		 * No matching clock found on this node.  If the parent node
		 * has a "clock-ranges" property, then we can try one of its
		 * clocks.
		 */
		np = np->parent;
		if (np && !of_get_property(np, "clock-ranges", NULL))
			break;
	}

	return clk;
}

 __of_clk_get

假设: clocks = <&clks IMX6UL_CLK_I2C1>;

设备树读取结果存放在： struct of_phandle_args clkspec

clkspec->np=(ccm)(&clks),  // provider 的device_node (即clks)

clkspec->args_count=1,     //provider 的clock-cells 的属性值(参数数量)

clkspec->args=IMX6UL_CLK_I2C1

static struct clk *__of_clk_get(struct device_node *np, int index,
			       const char *dev_id, const char *con_id)
{
	struct of_phandle_args clkspec;
	struct clk *clk;
	int rc;

	rc = of_parse_phandle_with_args(np, "clocks", "#clock-cells", index,
					&clkspec);//获取device_node 用于匹配 provider
						  //获取 args  用作provider 的get 函数
	if (rc)
		return ERR_PTR(rc);

	clk = __of_clk_get_from_provider(&clkspec, dev_id, con_id);
	of_node_put(clkspec.np);

	return clk;
}

__of_clk_get_from_provider 

struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec,
				       const char *dev_id, const char *con_id)
{
	struct of_clk_provider *provider;
	struct clk *clk = ERR_PTR(-EPROBE_DEFER);
	struct clk_hw *hw;

	if (!clkspec)
		return ERR_PTR(-EINVAL);

	/* Check if we have such a provider in our array */
	mutex_lock(&of_clk_mutex);
	list_for_each_entry(provider, &of_clk_providers, link) {
		if (provider->node == clkspec->np) {
			hw = __of_clk_get_hw_from_provider(provider, clkspec);
			clk = __clk_create_clk(hw, dev_id, con_id);
		}

		if (!IS_ERR(clk)) {
			if (!__clk_get(clk)) {
				__clk_free_clk(clk);
				clk = ERR_PTR(-ENOENT);
			}

			break;
		}
	}
	mutex_unlock(&of_clk_mutex);

	return clk;
}

__of_clk_get_hw_from_provider 

static struct clk_hw *
__of_clk_get_hw_from_provider(struct of_clk_provider *provider,
			      struct of_phandle_args *clkspec)
{
	struct clk *clk;

	if (provider->get_hw)
		return provider->get_hw(clkspec, provider->data);

	clk = provider->get(clkspec, provider->data);
	if (IS_ERR(clk))
		return ERR_CAST(clk);
	return __clk_get_hw(clk);
}