gpio子系统和pinctrl子系统(中)

pinctrl子系统核心实现分析

pinctrl子系统的内容在drivers/pinctrl文件夹下,主要文件有(建议先看看pinctrl内核文档Documentation/pinctrl.txt):
core.c
devicetree.c
pinconf.c
pinmux.c
pinctrl-xxx.c

core.c为pinctrl的核心代码,实现了pinctrl框架,pinmux.c和pinconf.c基于core实现了对pinmux和pinconf的支持,pinctrl-xxx.c为厂商相关的pinctrl实现(又是苦逼的bsp工程师_),当然有些厂商还未采用pinctrl机制,因此就没有对应的实现。最后说一句,pinctrl的实现不许用我们在驱动里调用任何它提供的api,所有的pinctrl动作都是在通用内核代码里完成了,对于驱动工程师是透明的。驱动工程师只需要通过设备树文件就能掌控整个系统的pin管理了,后面分析的过程会证实这一点。

pinctrl在代码层级只与bsp工程师有关,他们需要调用pinctrl api pinctrl_register注册。先引用一张网上截图:
pinctrl子系统框架
对于驱动工程师,只需要通过设备树文件就可以起到配置整个系统pin的目的。有几个概念先理一下,功能和组,功能就是指uart、i2c、spi等这些,组是pin的集合,我们都知道现在的soc的pin中,经常会遇到一个功能可以由不同的pin集合(即组)配置,当然同一时间只能选一个pin集合,因此,当我们要用某个功能的时候,需要告诉它func以及哪一组。下面开始分析pinctrl_register

struct pinctrl_dev *pinctrl_register(struct pinctrl_desc *pctldesc,
				    struct device *dev, void *driver_data)
{
	struct pinctrl_dev *pctldev;
	int ret;

	if (!pctldesc)
		return NULL;
	if (!pctldesc->name)
		return NULL;

	//一般只有pinctrl chip driver需要调用pinctrl_register,pctldev就是软件上pinctrl的抽象
	pctldev = kzalloc(sizeof(*pctldev), GFP_KERNEL);
	if (pctldev == NULL) {
		dev_err(dev, "failed to alloc struct pinctrl_dev\n");
		return NULL;
	}

	/* Initialize pin control device struct */
    //初始化一些成员,后面会遇到它们的
	pctldev->owner = pctldesc->owner;
	pctldev->desc = pctldesc;
	pctldev->driver_data = driver_data;
    //pin_desc_tree用于存放所有的pin信息,由后面即将分析的pinctrl_register_pins来填充
    //所有pin信息来源于输入参数pctldesc,也就是说每个pinctrl chip driver的实现者需要告诉pinctrl
    //子系统该pinctrl chip所有的pin信息
	INIT_RADIX_TREE(&pctldev->pin_desc_tree, GFP_KERNEL);
    //这个由gpio子系统填充信息,还记得of_gpiochip_add_pin_range吧^_^最后总结的时候再结合gpio子系统一起看看这部分
	INIT_LIST_HEAD(&pctldev->gpio_ranges);
	pctldev->dev = dev;
	mutex_init(&pctldev->mutex);

	/* check core ops for sanity */
    //pinctrl_ops是pinctrl chip driver必须要实现的一组回调集合,后面在用到它里面的api时再详细讲解
	if (pinctrl_check_ops(pctldev)) {
		dev_err(dev, "pinctrl ops lacks necessary functions\n");
		goto out_err;
	}

	/* If we're implementing pinmuxing, check the ops for sanity */
    //如果提供了pinmux ops,检查下是否合法
	if (pctldesc->pmxops) {
		if (pinmux_check_ops(pctldev))
			goto out_err;
	}

	/* If we're implementing pinconfig, check the ops for sanity */
    //如果提供了pinconf ops,检查下是否合法
	if (pctldesc->confops) {
		if (pinconf_check_ops(pctldev))
			goto out_err;
	}

	/* Register all the pins */
	dev_dbg(dev, "try to register %d pins ...\n",  pctldesc->npins);
    //第一个核心操作,后面详细分析    ---------> 1
	ret = pinctrl_register_pins(pctldev, pctldesc->pins, pctldesc->npins);
	if (ret) {
		dev_err(dev, "error during pin registration\n");
		pinctrl_free_pindescs(pctldev, pctldesc->pins,
				      pctldesc->npins);
		goto out_err;
	}

	mutex_lock(&pinctrldev_list_mutex);
    //将pctldev加入到全局链表
	list_add_tail(&pctldev->node, &pinctrldev_list);
	mutex_unlock(&pinctrldev_list_mutex);

	//这是第二个核心操作,往往pinctrl设备本身也需要做一些配置,这个函数就是用于处理这个功能---------> 2
	pctldev->p = pinctrl_get(pctldev->dev);

	if (!IS_ERR(pctldev->p)) {
    	//如果pinctrl设备提供了default状态,设置为default状态
		pctldev->hog_default =
			pinctrl_lookup_state(pctldev->p, PINCTRL_STATE_DEFAULT);
		if (IS_ERR(pctldev->hog_default)) {
			dev_dbg(dev, "failed to lookup the default state\n");
		} else {
        	//设置为default状态
			if (pinctrl_select_state(pctldev->p,
						pctldev->hog_default))
				dev_err(dev,
					"failed to select default state\n");
		}

		//如果pinctrl设备提供了sleep状态,获取它,以后再用
		pctldev->hog_sleep =
			pinctrl_lookup_state(pctldev->p,
						    PINCTRL_STATE_SLEEP);
		if (IS_ERR(pctldev->hog_sleep))
			dev_dbg(dev, "failed to lookup the sleep state\n");
	}

	//和调试相关,先忽略吧
	pinctrl_init_device_debugfs(pctldev);

	return pctldev;

out_err:
	mutex_destroy(&pctldev->mutex);
	kfree(pctldev);
	return NULL;
}

总结一下,pinctrl_register主要做了以下工作:

  1. 分配pctldev数据结构,并添加到全局链表pinctrldev_list
  2. 填充pctldev,根据pctldesc里的pin信息注册所有的pin信息到pctldev里的pin_desc_tree管理起来,
  3. 如果该pinctrl对应的设备树里有描述它自己的pin配置信息,那么解析它,并设置为default状态。这一部分是任何一个用到pinctrl设备都会进行的动作(解析、设置状态)
  4. 初始化调试相关的东西

下面先看看pinctrl_register_pins的过程:

static int pinctrl_register_pins(struct pinctrl_dev *pctldev,
				 struct pinctrl_pin_desc const *pins,
				 unsigned num_descs)
{
	unsigned i;
	int ret = 0;

	for (i = 0; i < num_descs; i++) {
    	//遍历传入的所有pin的数据结构,一个个处理它们
        //pinctrl driver会传入所有的pin管脚及对应的名称
		ret = pinctrl_register_one_pin(pctldev,
					       pins[i].number, pins[i].name);
		if (ret)
			return ret;
	}

	return 0;
}

static int pinctrl_register_one_pin(struct pinctrl_dev *pctldev,
				    unsigned number, const char *name)
{
	struct pin_desc *pindesc;

	//查看是否已经存在了
	pindesc = pin_desc_get(pctldev, number);
	if (pindesc != NULL) {
		pr_err("pin %d already registered on %s\n", number,
		       pctldev->desc->name);
		return -EINVAL;
	}

	//分配一个pinctrl子系统用于管理pin的数据结构
	pindesc = kzalloc(sizeof(*pindesc), GFP_KERNEL);
	if (pindesc == NULL) {
		dev_err(pctldev->dev, "failed to alloc struct pin_desc\n");
		return -ENOMEM;
	}

	/* Set owner */
    //指定该pin的拥有者
	pindesc->pctldev = pctldev;

	/* Copy basic pin info */
	if (name) {
    	//如果指定了名字,那么好吧,就用你了
		pindesc->name = name;
	} else {
    	//如果没有指定名字,用默认的格式组合一个
		pindesc->name = kasprintf(GFP_KERNEL, "PIN%u", number);
		if (pindesc->name == NULL) {
			kfree(pindesc);
			return -ENOMEM;
		}
		pindesc->dynamic_name = true;
	}

	//将该pin添加到pctldev里管理起来
	radix_tree_insert(&pctldev->pin_desc_tree, number, pindesc);
	pr_debug("registered pin %d (%s) on %s\n",
		 number, pindesc->name, pctldev->desc->name);
	return 0;
}

下面开始分析第二个核心部分pinctrl_get,注意,这部分是任何一个用到pinctrl设备都会进行的动作(解析、设置状态),所以还必须弄清楚它,它主要的作用就是通过解析该设备的pinctrl信息生成一个pinctrl数据结构,用于管理该设备的pin信息,如有哪些状态、每个状态有哪些设置(设置包括pinmux和pinconf两种,有些设备只用需要pinmux,有些需要pinmux和pinconf)

struct pinctrl *pinctrl_get(struct device *dev)
{
	struct pinctrl *p;

	if (WARN_ON(!dev))
		return ERR_PTR(-EINVAL);

	/*
	 * See if somebody else (such as the device core) has already
	 * obtained a handle to the pinctrl for this device. In that case,
	 * return another pointer to it.
	 */
    //如果已经有其他模块get了,那么pinctrl肯定已经创建好了,直接返回吧
	p = find_pinctrl(dev);
	if (p != NULL) {
		dev_dbg(dev, "obtain a copy of previously claimed pinctrl\n");
		kref_get(&p->users);
		return p;
	}

	//否则,创建一个pinctrl用于管理该设备本身的pin信息
	return create_pinctrl(dev);
}

继续看解析的过程,通过看懂这部分,我们应该就很清楚设备树里需要怎么配置,怎么对整个系统的pin配置起作用的

static struct pinctrl *create_pinctrl(struct device *dev)
{
	struct pinctrl *p;
	const char *devname;
	struct pinctrl_maps *maps_node;
	int i;
	struct pinctrl_map const *map;
	int ret;

	/*
	 * create the state cookie holder struct pinctrl for each
	 * mapping, this is what consumers will get when requesting
	 * a pin control handle with pinctrl_get()
	 */
	p = kzalloc(sizeof(*p), GFP_KERNEL);
	if (p == NULL) {
		dev_err(dev, "failed to alloc struct pinctrl\n");
		return ERR_PTR(-ENOMEM);
	}
	p->dev = dev;
    //每个需要管理的设备都会有对应的pinctrl,每个设备也会有多个状态,如default、sleep等等(内核
    //默认定义了一些,自己也可以随意定义),每个状态又有可能有多种设置。这个需要自己慢慢理解^_^
    //这里的states成员就是用于存放所有的状态的
	INIT_LIST_HEAD(&p->states);
    //这里的dt_maps就是用于存放所有的设置的
	INIT_LIST_HEAD(&p->dt_maps);

	//又是一个复杂的函数,后面分析,它主要用于解析设备树里的信息,生成该设备对应的maps(设置)
	ret = pinctrl_dt_to_map(p);
	if (ret < 0) {
		kfree(p);
		return ERR_PTR(ret);
	}

	devname = dev_name(dev);

	mutex_lock(&pinctrl_maps_mutex);
	/* Iterate over the pin control maps to locate the right ones */
    //遍历所有的的设置,这里遍历的是全局的maps链表,因为它要用到
    //pinctrl_map结构,而p->dt_maps里的不是该类型
	for_each_maps(maps_node, i, map) {
		/* Map must be for this device */
        //检查是否属于俺的设置
		if (strcmp(map->dev_name, devname))
			continue;

		//将该设置加入到pinctrl中,也许有人会奇怪,前面的dt_maps不是已经包含了该设备的所有设置了么,
        //其实这里会对每个设置做进一步处理,然后放入到p中,后面分析
		ret = add_setting(p, map);
		/*
		 * At this point the adding of a setting may:
		 *
		 * - Defer, if the pinctrl device is not yet available
		 * - Fail, if the pinctrl device is not yet available,
		 *   AND the setting is a hog. We cannot defer that, since
		 *   the hog will kick in immediately after the device
		 *   is registered.
		 *
		 * If the error returned was not -EPROBE_DEFER then we
		 * accumulate the errors to see if we end up with
		 * an -EPROBE_DEFER later, as that is the worst case.
		 */
		if (ret == -EPROBE_DEFER) {
			pinctrl_free(p, false);
			mutex_unlock(&pinctrl_maps_mutex);
			return ERR_PTR(ret);
		}
	}
	mutex_unlock(&pinctrl_maps_mutex);

	if (ret < 0) {
		/* If some other error than deferral occured, return here */
		pinctrl_free(p, false);
		return ERR_PTR(ret);
	}

	kref_init(&p->users);

	/* Add the pinctrl handle to the global list */
	mutex_lock(&pinctrl_list_mutex);
    //将每个设备用于控制pin的结构也放到一个全局链表中
	list_add_tail(&p->node, &pinctrl_list);
	mutex_unlock(&pinctrl_list_mutex);

	return p;
}

先总结下create_pinctrl

  1. 创建一个pinctrl,将它加入到全局的pinctrl链表
  2. 解析该设备的说有设备树信息,将解析的状态挂到states里,解析的设置挂到dt_maps(当然,设置同时也挂到全局的maps里去了)

实在不想贴代码了,不过不贴又不好解释清楚_ 继续上pinctrl_dt_to_map吧,它就是实现了上面总结的第二点:

int pinctrl_dt_to_map(struct pinctrl *p)
{
	struct device_node *np = p->dev->of_node;
	int state, ret;
	char *propname;
	struct property *prop;
	const char *statename;
	const __be32 *list;
	int size, config;
	phandle phandle;
	struct device_node *np_config;

	/* CONFIG_OF enabled, p->dev not instantiated from DT */
	if (!np) {
		if (of_have_populated_dt())
			dev_dbg(p->dev,
				"no of_node; not parsing pinctrl DT\n");
		return 0;
	}

	/* We may store pointers to property names within the node */
	of_node_get(np);

	/* For each defined state ID */
	for (state = 0; ; state++) {
		/* Retrieve the pinctrl-* property */
		//pinctrl子系统规定了几个属性,如pinctrl-n,用于指定一个状态对应的设置,从0开始        
		propname = kasprintf(GFP_KERNEL, "pinctrl-%d", state);
        //查找pinctrl-n属性
		prop = of_find_property(np, propname, &size);
		kfree(propname);
		if (!prop)
			break;
        //value对应的就是该状态对应的设置(可能有多个),后面会处理它
		list = prop->value;
		size /= sizeof(*list);

		/* Determine whether pinctrl-names property names the state */
        //读pinctrl-names属性,也属于pinctrl子系统规定的属性,用于指定每个状态的名字,一一对应的
		ret = of_property_read_string_index(np, "pinctrl-names",
						    state, &statename);
		/*
		 * If not, statename is just the integer state ID. But rather
		 * than dynamically allocate it and have to free it later,
		 * just point part way into the property name for the string.
		 */
		if (ret < 0) {
			/* strlen("pinctrl-") == 8 */
            //如果美誉pinctrl-names属性,那么状态名就是index
			statename = prop->name + 8;
		}

		/* For every referenced pin configuration node in it */
        //一个一个处理设置
		for (config = 0; config < size; config++) {
        	//第一个成员规定为配置节点(属于pinctrl的子节点)的引用,因此通过它可以找到该配置节点
			phandle = be32_to_cpup(list++);

			/* Look up the pin configuration node */
			np_config = of_find_node_by_phandle(phandle);
			if (!np_config) {
				dev_err(p->dev,
					"prop %s index %i invalid phandle\n",
					prop->name, config);
				ret = -EINVAL;
				goto err;
			}

			/* Parse the node */
            //找到对应的配置节点了,那么就解析那个配置节点到该设备的这个状态的这个设置中吧,后面继续贴 哎
			ret = dt_to_map_one_config(p, statename, np_config);
			of_node_put(np_config);
			if (ret < 0)
				goto err;
		}

		/* No entries in DT? Generate a dummy state table entry */
		if (!size) {
			ret = dt_remember_dummy_state(p, statename);
			if (ret < 0)
				goto err;
		}
	}

	return 0;

err:
	pinctrl_dt_free_maps(p);
	return ret;
}

继续看dt_to_map_one_config

static int dt_to_map_one_config(struct pinctrl *p, const char *statename,
				struct device_node *np_config)
{
	struct device_node *np_pctldev;
	struct pinctrl_dev *pctldev;
	const struct pinctrl_ops *ops;
	int ret;
	struct pinctrl_map *map;
	unsigned num_maps;

	/* Find the pin controller containing np_config */
	np_pctldev = of_node_get(np_config);
	for (;;) {
    	//找该节点的父节点,就是pinctrl设备啦,我们得通过它获取pctldev,毕竟只有它才有啊
		np_pctldev = of_get_next_parent(np_pctldev);
		if (!np_pctldev || of_node_is_root(np_pctldev)) {
			dev_info(p->dev, "could not find pctldev for node %s, deferring probe\n",
				np_config->full_name);
			of_node_put(np_pctldev);
			/* OK let's just assume this will appear later then */
			return -EPROBE_DEFER;
		}
		pctldev = get_pinctrl_dev_from_of_node(np_pctldev);
		if (pctldev)//拿到就跳出
			break;
		/* Do not defer probing of hogs (circular loop) */
		if (np_pctldev == p->dev->of_node) {
			of_node_put(np_pctldev);
			return -ENODEV;
		}
	}
	of_node_put(np_pctldev);

	/*
	 * Call pinctrl driver to parse device tree node, and
	 * generate mapping table entries
	 */
	ops = pctldev->desc->pctlops;
    //这里就用到了pinctrl_register注册时pctlops里的dt_node_to_map回调函数了
	if (!ops->dt_node_to_map) {
		dev_err(p->dev, "pctldev %s doesn't support DT\n",
			dev_name(pctldev->dev));
		return -ENODEV;
	}
    //调用它,靠它来解析出这个配置节点,毕竟格式只有对应的pinctrl driver最清楚
	ret = ops->dt_node_to_map(pctldev, np_config, &map, &num_maps);
	if (ret < 0)
		return ret;

	/* Stash the mapping table chunk away for later use */
    //将解析出来的设置添加到pctldev的dt_maps中,也会加到全局的maps中啦,这里就不再深入分析了,自己都觉得太啰嗦了
	return dt_remember_or_free_map(p, statename, pctldev, map, num_maps);
}

继续看add_setting:

static int add_setting(struct pinctrl *p, struct pinctrl_map const *map)
{
	struct pinctrl_state *state;
	struct pinctrl_setting *setting;
	int ret;
	//前面只是解析出了所有的设置,这里就将所有的设置按状态归类起来,如果状态还没创建,就创建一个
	state = find_state(p, map->name);
	if (!state)
		state = create_state(p, map->name);
	if (IS_ERR(state))
		return PTR_ERR(state);

	if (map->type == PIN_MAP_TYPE_DUMMY_STATE)
		return 0;

	//分配一个设置数据结构
	setting = kzalloc(sizeof(*setting), GFP_KERNEL);
	if (setting == NULL) {
		dev_err(p->dev,
			"failed to alloc struct pinctrl_setting\n");
		return -ENOMEM;
	}

	//设置的类型
	setting->type = map->type;

	//设置所属的pctldev
	setting->pctldev = get_pinctrl_dev_from_devname(map->ctrl_dev_name);
	if (setting->pctldev == NULL) {
		kfree(setting);
		/* Do not defer probing of hogs (circular loop) */
		if (!strcmp(map->ctrl_dev_name, map->dev_name))
			return -ENODEV;
		/*
		 * OK let us guess that the driver is not there yet, and
		 * let's defer obtaining this pinctrl handle to later...
		 */
		dev_info(p->dev, "unknown pinctrl device %s in map entry, deferring probe",
			map->ctrl_dev_name);
		return -EPROBE_DEFER;
	}

	//设置名字
	setting->dev_name = map->dev_name;

	switch (map->type) {//根据设置的类型处理设置,因为设置可以表示mux功能,也可以表示conf功能
	case PIN_MAP_TYPE_MUX_GROUP://如果是mux功能的设置,调用mux模块处理
		ret = pinmux_map_to_setting(map, setting);
		break;
	case PIN_MAP_TYPE_CONFIGS_PIN:
	case PIN_MAP_TYPE_CONFIGS_GROUP://如果是mux功能的设置,调用conf模块处理
		ret = pinconf_map_to_setting(map, setting);
		break;
	default:
		ret = -EINVAL;
		break;
	}
	if (ret < 0) {
		kfree(setting);
		return ret;
	}

	//将设置放入状态链表归类
	list_add_tail(&setting->node, &state->settings);

	return 0;
}

下面分别分析pinmux_map_to_settingpinconf_map_to_setting,先pinmux_map_to_setting,它是和pinmux相关,对应pinmux.c文件,里面也会用到pinmux_ops

int pinmux_map_to_setting(struct pinctrl_map const *map,
			  struct pinctrl_setting *setting)
{
	struct pinctrl_dev *pctldev = setting->pctldev;
	const struct pinmux_ops *pmxops = pctldev->desc->pmxops;
	char const * const *groups;
	unsigned num_groups;
	int ret;
	const char *group;
	int i;
	//如果在register的时候没有指定pinmux_ops,那么该函数什么都不做,出错返回
	if (!pmxops) {
		dev_err(pctldev->dev, "does not support mux function\n");
		return -EINVAL;
	}
	//现在就是pinmux_ops作用的时候啦!里面会以从0开始的索引不停的调用
    //pinmux_ops里的get_function_name来获取对应的名字,然后和前面解析设备树过程解析出来的名字做匹配
    //直到找到或到末尾,返回该索引。这个索引与功能之间的关系由pinctrl bsp实现者负责
	ret = pinmux_func_name_to_selector(pctldev, map->data.mux.function);
	if (ret < 0) {
		dev_err(pctldev->dev, "invalid function %s in map table\n",
			map->data.mux.function);
		return ret;
	}
    //保存该索引
	setting->data.mux.func = ret;

	//调用pmxops的get_function_groups获取该索引对应的组(可能存在多个,前面已经说过,一个功能可以由多个组实现,同一时间只能选一个组)
	ret = pmxops->get_function_groups(pctldev, setting->data.mux.func,
					  &groups, &num_groups);
	if (ret < 0) {
		dev_err(pctldev->dev, "can't query groups for function %s\n",
			map->data.mux.function);
		return ret;
	}
	if (!num_groups) {
		dev_err(pctldev->dev,
			"function %s can't be selected on any group\n",
			map->data.mux.function);
		return -EINVAL;
	}
    //如果设备树里有直接指定组,那么就会以指定的组为默认选择
	if (map->data.mux.group) {
		bool found = false;
		group = map->data.mux.group;
        //当然,也还是要校验下,组是否有效
		for (i = 0; i < num_groups; i++) {
			if (!strcmp(group, groups[i])) {
				found = true;
				break;
			}
		}
		if (!found) {
			dev_err(pctldev->dev,
				"invalid group \"%s\" for function \"%s\"\n",
				group, map->data.mux.function);
			return -EINVAL;
		}
	} else {
    	//如果没有指定,那么就用第一个组咯
		group = groups[0];
	}

	//根据选定的组,获取该组的信息,返回的是该组对应的索引,这里会调用pmxops的get_group_name,操作
    //过程和前面的pinmux_func_name_to_selector类似
	ret = pinctrl_get_group_selector(pctldev, group);
	if (ret < 0) {
		dev_err(pctldev->dev, "invalid group %s in map table\n",
			map->data.mux.group);
		return ret;
	}
    //保存该组索引
	setting->data.mux.group = ret;

	return 0;
}

继续pinconf_map_to_setting吧,它是和pinconf相关,对应pinconf.c文件,但里面还没用pinconf_ops,后面才会用到:

int pinconf_map_to_setting(struct pinctrl_map const *map,
			  struct pinctrl_setting *setting)
{
	struct pinctrl_dev *pctldev = setting->pctldev;
	int pin;

	switch (setting->type) {//该设置到底是什么类型,是pinctrl driver回调dt_node_to_map里解析的
    //配置有两种类型,一种是一个pin一个pin的配置,一种是将一些pin的配置组合为一个组,指定某个组就会采用那个组里的所有的pin的配置
	case PIN_MAP_TYPE_CONFIGS_PIN:
    	//根据设备树里指定的pin名字获取它对应的pin号
		pin = pin_get_from_name(pctldev,
					map->data.configs.group_or_pin);
		if (pin < 0) {
			dev_err(pctldev->dev, "could not map pin config for \"%s\"",
				map->data.configs.group_or_pin);
			return pin;
		}
        //将该设置对应的pin号保存起来
		setting->data.configs.group_or_pin = pin;
		break;
	case PIN_MAP_TYPE_CONFIGS_GROUP:
    	//根据设备树指定的pin组获取它对应的group号
		pin = pinctrl_get_group_selector(pctldev,
					 map->data.configs.group_or_pin);
		if (pin < 0) {
			dev_err(pctldev->dev, "could not map group config for \"%s\"",
				map->data.configs.group_or_pin);
			return pin;
		}
        //将该设置对应的group号保存起来
		setting->data.configs.group_or_pin = pin;
		break;
	default:
		return -EINVAL;
	}
	
    //保存所有其他用于配置的信息
	setting->data.configs.num_configs = map->data.configs.num_configs;
	setting->data.configs.configs = map->data.configs.configs;

	return 0;
}

现在都仅仅是分析了pinmux_map_to_settingpinconf_map_to_setting,具体它们的作用我们在后面才能看的出来,所以继续分析吧!到这里pinctrl_get分析完了,执行完pinctrl_get,就意味着该设备的所有和pin相关的设备树信息已经解析完成,并生成了用于管理、配置的数据结构,为以后的其他api提供了支持。其他驱动一般不会直接调用pinctrl_get,而是调用它的变体devm_pinctrl_get或者pinctrl_get_select来初始化设备。devm_pinctrl_get就不用说了啦,pinctrl_get_select类似与pinctrl_register调用pinctrl_get及它后的那段代码的结合,不仅调用了pinctrl_get,还根据输入参数让设备处于指定的状态。通过pinctrl_select_state来让设备处于指定的状态,下面开始分析它,通过分析它,应该就清楚了前面各种填充的作用啦!

int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)
{
	struct pinctrl_setting *setting, *setting2;
	struct pinctrl_state *old_state = p->state;
	int ret;
	//如果当前就是该状态,直接返回成功
	if (p->state == state)
		return 0;

	//如果之前有设置过状态,那需要做一些额外处理
	if (p->state) {
		/*
		 * The set of groups with a mux configuration in the old state
		 * may not be identical to the set of groups with a mux setting
		 * in the new state. While this might be unusual, it's entirely
		 * possible for the "user"-supplied mapping table to be written
		 * that way. For each group that was configured in the old state
		 * but not in the new state, this code puts that group into a
		 * safe/disabled state.
		 */
		list_for_each_entry(setting, &p->state->settings, node) {
			bool found = false;
			if (setting->type != PIN_MAP_TYPE_MUX_GROUP)
				continue;
			list_for_each_entry(setting2, &state->settings, node) {
				if (setting2->type != PIN_MAP_TYPE_MUX_GROUP)
					continue;
				if (setting2->data.mux.group ==
						setting->data.mux.group) {
					found = true;
					break;
				}
			}
			if (!found)
				pinmux_disable_setting(setting);
		}
	}

	p->state = NULL;

	/* Apply all the settings for the new state */
    //
	list_for_each_entry(setting, &state->settings, node) {
    //遍历该设备的该状态下的所有设置,一个个设置上去
		switch (setting->type) {
		case PIN_MAP_TYPE_MUX_GROUP://如果该设置是mux设置,那么调用pinmux_enable_setting,这里面
        	//就用到了前面填充的信息
			ret = pinmux_enable_setting(setting);
			break;
		case PIN_MAP_TYPE_CONFIGS_PIN:
		case PIN_MAP_TYPE_CONFIGS_GROUP://如果该设置是conf设置,那么调用pinconf_apply_setting,
        	//这里面就用到了前面填充的信息
			ret = pinconf_apply_setting(setting);
			break;
		default:
			ret = -EINVAL;
			break;
		}

		if (ret < 0) {
			goto unapply_new_state;
		}
	}

	p->state = state;

	return 0;

unapply_new_state:
	dev_err(p->dev, "Error applying setting, reverse things back\n");

	list_for_each_entry(setting2, &state->settings, node) {
		if (&setting2->node == &setting->node)
			break;
		/*
		 * All we can do here is pinmux_disable_setting.
		 * That means that some pins are muxed differently now
		 * than they were before applying the setting (We can't
		 * "unmux a pin"!), but it's not a big deal since the pins
		 * are free to be muxed by another apply_setting.
		 */
		if (setting2->type == PIN_MAP_TYPE_MUX_GROUP)
			pinmux_disable_setting(setting2);
	}

	/* There's no infinite recursive loop here because p->state is NULL */
	if (old_state)
		pinctrl_select_state(p, old_state);

	return ret;
}

pinmux_enable_setting当然处于pinmux.c中,根据前面填充的setting->data.mux.group获取该组的pin信息,然后以pin号为参数循环回调ops->request,最后回调ops->enable。

pinconf_apply_setting当然处于pinconf.c中,根据前面填充的group_or_pinconfigsnum_configs以及type分别回调pin_config_setpin_config_group_set

最后补充下,本文描述的都是基于设备树方式的pinctrl处理,其实也可以通过pinctrl_register_mappings调用静态添加所有的设置,只是不常用该方式而已。

未完,待续!
2015年7月

posted @ 2017-10-14 10:18  rongpmcu  阅读(1506)  评论(0编辑  收藏