具有pinctrl需要的设备初始化
1. 故事的开始
static int really_probe(struct device *dev, struct device_driver *drv)
{
dev->driver = drv;
/* If using pinctrl, bind pins now before probing */
ret = pinctrl_bind_pins(dev);
if (ret)
goto pinctrl_bind_failed;
if (dev->bus->dma_configure) {
ret = dev->bus->dma_configure(dev);
if (ret)
goto dma_failed;
}
if (driver_sysfs_add(dev)) {
printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
__func__, dev_name(dev));
goto probe_failed;
}
if (dev->pm_domain && dev->pm_domain->activate) {
ret = dev->pm_domain->activate(dev);
if (ret)
goto probe_failed;
}
if (dev->bus->probe) {
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) {
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}
}
在设备的probe函数执行之前，会执行pinctrl相关的引脚初始化和配置。同时从上面的函数我们可以看出：Linux内核会提前处理pinctrl，dma等硬件设备的请求，让驱动开发变得尽量少的直接接触硬件。
2. 故事的概述
这里我去掉了一些不相关或者不重要的函数，重点分析函数执行的核心流程和关键代码
/**
* pinctrl_bind_pins() - called by the device core before probe
* @dev: the device that is just about to probe
*/
int pinctrl_bind_pins(struct device *dev)
{
int ret;
if (dev->of_node_reused)
return 0;
dev->pins = devm_kzalloc(dev, sizeof(*(dev->pins)), GFP_KERNEL);
if (!dev->pins)
return -ENOMEM;
dev->pins->p = devm_pinctrl_get(dev);
if (IS_ERR(dev->pins->p)) {
dev_dbg(dev, "no pinctrl handle\n");
ret = PTR_ERR(dev->pins->p);
goto cleanup_alloc;
}
/* defualt 状态的检查: 一般都采取defualt的配置 */
dev->pins->default_state = pinctrl_lookup_state(dev->pins->p,
PINCTRL_STATE_DEFAULT);
if (IS_ERR(dev->pins->default_state)) {
dev_dbg(dev, "no default pinctrl state\n");
ret = 0;
goto cleanup_get;
}
/* init状态的检查 ：一般没有该设置*/
dev->pins->init_state = pinctrl_lookup_state(dev->pins->p,
PINCTRL_STATE_INIT);
if (IS_ERR(dev->pins->init_state)) {
/* Not supplying this state is perfectly legal */
dev_dbg(dev, "no init pinctrl state\n");
ret = pinctrl_select_state(dev->pins->p, //该函数在定义了default之后会被执行
dev->pins->default_state);
} else {
ret = pinctrl_select_state(dev->pins->p, dev->pins->init_state); //该函数在定义了init属性后会被执行
}
if (ret) {
dev_dbg(dev, "failed to activate initial pinctrl state\n");
goto cleanup_get;
}
/* 这里去掉了功耗相关的代码 */
return 0;
cleanup_get:
devm_pinctrl_put(dev->pins->p);
cleanup_alloc:
devm_kfree(dev, dev->pins);
dev->pins = NULL;
/* Return deferrals */
if (ret == -EPROBE_DEFER)
return ret;
/* Return serious errors */
if (ret == -EINVAL)
return ret;
/* We ignore errors like -ENOENT meaning no pinctrl state */
return 0;
}
这里我总结一下重要的函数在哪，这也是众多解析文章会替到的：
-
devm_get_pinctrl: 检查当前设备是否具有对应的pinctrl; 如果没有，注册一个结构体 -
pinctrl_lookup_state: 查找设备时候具有指定的状态，一般是查找default,idle,init等 -
pinctrl_select_state: 根据状态设置
3. 第一个大片场面
/**
* struct devm_pinctrl_get() - Resource managed pinctrl_get()
* @dev: the device to obtain the handle for
*
* If there is a need to explicitly destroy the returned struct pinctrl,
* devm_pinctrl_put() should be used, rather than plain pinctrl_put().
*/
struct pinctrl *devm_pinctrl_get(struct device *dev)
{
struct pinctrl **ptr, *p;
ptr = devres_alloc(devm_pinctrl_release, sizeof(*ptr), GFP_KERNEL);
if (!ptr)
return ERR_PTR(-ENOMEM);
p = pinctrl_get(dev);
if (!IS_ERR(p)) {
*ptr = p;
devres_add(dev, ptr);
} else {
devres_free(ptr);
}
return p;
}
EXPORT_SYMBOL_GPL(devm_pinctrl_get);
具体的设备获取函数：
/**
* pinctrl_get() - retrieves the pinctrl handle for a device
* @dev: the device to obtain the handle for
*/
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.
*/
p = find_pinctrl(dev);
if (p) {
dev_dbg(dev, "obtain a copy of previously claimed pinctrl\n");
kref_get(&p->users);
return p;
}
return create_pinctrl(dev, NULL);
}
EXPORT_SYMBOL_GPL(pinctrl_get);
pinctrl的查找：在设备驱动中应该是找不到的
static struct pinctrl *find_pinctrl(struct device *dev)
{
struct pinctrl *p;
mutex_lock(&pinctrl_list_mutex);
list_for_each_entry(p, &pinctrl_list, node)
if (p->dev == dev) {
mutex_unlock(&pinctrl_list_mutex);
return p;
}
mutex_unlock(&pinctrl_list_mutex);
return NULL;
}
理论上来说，这里应该是找不到的。所以会调用后面的create_pinctrl函数构造一个。下面便开始解析这个函数是如何够找的。
第二个重要函数点
设备的pinctrl的注册
参数解析：
dev: 设备的dev结构体
pctldev: NULL
static struct pinctrl *create_pinctrl(struct device *dev,
struct pinctrl_dev *pctldev)
{
struct pinctrl *p;
const char *devname;
struct pinctrl_maps *maps_node;
int i;
const struct pinctrl_map *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)
return ERR_PTR(-ENOMEM);
p->dev = dev;
INIT_LIST_HEAD(&p->states);
INIT_LIST_HEAD(&p->dt_maps);
ret = pinctrl_dt_to_map(p, pctldev);
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 */
for_each_maps(maps_node, i, map) {
/* Map must be for this device */
if (strcmp(map->dev_name, devname))
continue;
/*
* If pctldev is not null, we are claiming hog for it,
* that means, setting that is served by pctldev by itself.
*
* Thus we must skip map that is for this device but is served
* by other device.
*/
if (pctldev &&
strcmp(dev_name(pctldev->dev), map->ctrl_dev_name))
continue;
ret = add_setting(p, pctldev, 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 occurred, 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);
list_add_tail(&p->node, &pinctrl_list);
mutex_unlock(&pinctrl_list_mutex);
return p;
}
创建pinctrl的函数
int pinctrl_dt_to_map(struct pinctrl *p, struct pinctrl_dev *pctldev)
{
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++) { //轮询pinctrl-n属性
/* 1. Retrieve the pinctrl-* property ：取回/找回 pinctrl-n的属性*/
propname = kasprintf(GFP_KERNEL, "pinctrl-%d", state);
prop = of_find_property(np, propname, &size);
kfree(propname);
if (!prop) {
if (state == 0) {
of_node_put(np);
return -ENODEV;
}
break;
}
list = prop->value;
size /= sizeof(*list);
/* 2. Determine whether pinctrl-names property names the state
这里取回设备定义的状态信息，state作为一个index指示读取的数据
statename 保存了读取的数据
*/
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 */
statename = prop->name + 8;
}
/* For every referenced pin configuration node in it
* 这里是处理的一个核心所在
*/
for (config = 0; config < size; config++) {
phandle = be32_to_cpup(list++);
/* Look up the pin configuration node: 查找pinctrl配置的节点 */
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 */
ret = dt_to_map_one_config(p, pctldev, statename,
np_config);
of_node_put(np_config); //配置完成后去掉对该节点的引用
if (ret < 0)
goto err;
}
/* No entries in DT? Generate a dummy state table entry */
if (!size) { //size属性错误的处理
ret = dt_remember_dummy_state(p, statename);
if (ret < 0)
goto err;
}
}
return 0;
err:
pinctrl_dt_free_maps(p);
return ret;
}
这里的函数个人认为非常重要，所以会细致的分析该函数的作用和执行流程：
- 轮询
pinctrl-x的属性信息,以及pinctrl-names的状态信息，其中x的值会动态的变化，如果某个pinctrl-x没有的话就会退出 - 根据某个
pinctrl-x中value的的个数依次遍历对应的pinctrl定义 - 更具
phandle值，找到对应的父节点，并开始进行映射处理，映射的处理会调用到驱动程序
下面分析一个映射的实现:
static int dt_to_map_one_config(struct pinctrl *p,
struct pinctrl_dev *hog_pctldev,
const char *statename,
struct device_node *np_config)
{
struct pinctrl_dev *pctldev = NULL;
struct device_node *np_pctldev;
const struct pinctrl_ops *ops;
int ret;
struct pinctrl_map *map;
unsigned num_maps;
bool allow_default = false;
/* Find the pin controller containing np_config */
np_pctldev = of_node_get(np_config);
for (;;) {
if (!allow_default)
allow_default = of_property_read_bool(np_pctldev,
"pinctrl-use-default");
np_pctldev = of_get_next_parent(np_pctldev);
if (!np_pctldev || of_node_is_root(np_pctldev)) {
of_node_put(np_pctldev);
ret = driver_deferred_probe_check_state(p->dev);
/* keep deferring if modules are enabled unless we've timed out */
if (IS_ENABLED(CONFIG_MODULES) && !allow_default && ret == -ENODEV)
ret = -EPROBE_DEFER;
return ret;
}
/* If we're creating a hog we can use the passed pctldev */
if (hog_pctldev && (np_pctldev == p->dev->of_node)) {
pctldev = hog_pctldev;
break;
}
pctldev = get_pinctrl_dev_from_of_node(np_pctldev);
if (pctldev)
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;
if (!ops->dt_node_to_map) {
dev_err(p->dev, "pctldev %s doesn't support DT\n",
dev_name(pctldev->dev));
return -ENODEV;
}
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 */
return dt_remember_or_free_map(p, statename, pctldev, map, num_maps);
}
这里的函数主要具有两个功能
- 查找设备对应的
pinctrl_dev结构体 - 调用该结构体中的
dt_node_to_map函数执行映射的功能
上面的函数先分析到这里，下面的函数更加精彩！
4. 第二个大片场面
1. 状态查找函数
这里会根据状态去查找相应的pinctrl_state结构。
/**
* pinctrl_lookup_state() - retrieves a state handle from a pinctrl handle
* @p: the pinctrl handle to retrieve the state from
* @name: the state name to retrieve
*/
struct pinctrl_state *pinctrl_lookup_state(struct pinctrl *p,
const char *name)
{
struct pinctrl_state *state;
state = find_state(p, name);
if (!state) {
if (pinctrl_dummy_state) {
/* create dummy state */
dev_dbg(p->dev, "using pinctrl dummy state (%s)\n",
name);
state = create_state(p, name);
} else
state = ERR_PTR(-ENODEV);
}
return state;
}
EXPORT_SYMBOL_GPL(pinctrl_lookup_state);
static struct pinctrl_state *find_state(struct pinctrl *p,
const char *name)
{
struct pinctrl_state *state;
list_for_each_entry(state, &p->states, node)
if (!strcmp(state->name, name))
return state;
return NULL;
}
2. 查找到对应的状态后如何初始化
这里先说明：我们的分析是以设备的defualt状态设置来分析的，在具体的设备树中，我们也主要使用defualt这个默认属性
/**
* pinctrl_select_state() - select/activate/program a pinctrl state to HW
* @p: the pinctrl handle for the device that requests configuration
* @state: the state handle to select/activate/program
*/
int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)
{
if (p->state == state)
return 0;
return pinctrl_commit_state(p, state);
}
EXPORT_SYMBOL_GPL(pinctrl_select_state);
下面便是具体执行的流程:
/**
* pinctrl_commit_state() - select/activate/program a pinctrl state to HW
* @p: the pinctrl handle for the device that requests configuration
* @state: the state handle to select/activate/program
*/
static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state)
{
struct pinctrl_setting *setting, *setting2;
struct pinctrl_state *old_state = p->state;
int ret;
if (p->state) {
/*
* For each pinmux setting in the old state, forget SW's record
* of mux owner for that pingroup. Any pingroups which are
* still owned by the new state will be re-acquired by the call
* to pinmux_enable_setting() in the loop below.
*/
list_for_each_entry(setting, &p->state->settings, node) {
if (setting->type != PIN_MAP_TYPE_MUX_GROUP)
continue;
pinmux_disable_setting(setting);
}
}
p->state = NULL;
/* Apply all the settings for the new state */
list_for_each_entry(setting, &state->settings, node) {
switch (setting->type) {
case PIN_MAP_TYPE_MUX_GROUP:
ret = pinmux_enable_setting(setting);
break;
case PIN_MAP_TYPE_CONFIGS_PIN:
case PIN_MAP_TYPE_CONFIGS_GROUP:
ret = pinconf_apply_setting(setting);
break;
default:
ret = -EINVAL;
break;
}
if (ret < 0) {
goto unapply_new_state;
}
}
p->state = state;
return 0;
}
这里我去掉了和错误处理有关的函数，分析其中的核心函数！我们可以看到，这里会根据设置的类型调用不同的函数进行设置处理，下面详细的分析一下这两个函数的执行流程：
int pinmux_enable_setting(const struct pinctrl_setting *setting)
{
struct pinctrl_dev *pctldev = setting->pctldev;
const struct pinctrl_ops *pctlops = pctldev->desc->pctlops;
const struct pinmux_ops *ops = pctldev->desc->pmxops;
int ret = 0;
const unsigned *pins = NULL;
unsigned num_pins = 0;
int i;
struct pin_desc *desc;
if (pctlops->get_group_pins)
ret = pctlops->get_group_pins(pctldev, setting->data.mux.group,
&pins, &num_pins);
if (ret) {
const char *gname;
/* errors only affect debug data, so just warn */
gname = pctlops->get_group_name(pctldev,
setting->data.mux.group);
dev_warn(pctldev->dev,
"could not get pins for group %s\n",
gname);
num_pins = 0;
}
/* Try to allocate all pins in this group, one by one */
for (i = 0; i < num_pins; i++) {
ret = pin_request(pctldev, pins[i], setting->dev_name, NULL);
if (ret) {
const char *gname;
const char *pname;
desc = pin_desc_get(pctldev, pins[i]);
pname = desc ? desc->name : "non-existing";
gname = pctlops->get_group_name(pctldev,
setting->data.mux.group);
dev_err(pctldev->dev,
"could not request pin %d (%s) from group %s "
" on device %s\n",
pins[i], pname, gname,
pinctrl_dev_get_name(pctldev));
goto err_pin_request;
}
}
/* Now that we have acquired the pins, encode the mux setting */
for (i = 0; i < num_pins; i++) {
desc = pin_desc_get(pctldev, pins[i]);
if (desc == NULL) {
dev_warn(pctldev->dev,
"could not get pin desc for pin %d\n",
pins[i]);
continue;
}
desc->mux_setting = &(setting->data.mux);
}
ret = ops->set_mux(pctldev, setting->data.mux.func,
setting->data.mux.group);
if (ret)
goto err_set_mux;
return 0;
err_set_mux:
for (i = 0; i < num_pins; i++) {
desc = pin_desc_get(pctldev, pins[i]);
if (desc)
desc->mux_setting = NULL;
}
err_pin_request:
/* On error release all taken pins */
while (--i >= 0)
pin_free(pctldev, pins[i], NULL);
return ret;
}
int pinconf_apply_setting(const struct pinctrl_setting *setting)
{
struct pinctrl_dev *pctldev = setting->pctldev;
const struct pinconf_ops *ops = pctldev->desc->confops;
int ret;
if (!ops) {
dev_err(pctldev->dev, "missing confops\n");
return -EINVAL;
}
switch (setting->type) {
case PIN_MAP_TYPE_CONFIGS_PIN:
if (!ops->pin_config_set) {
dev_err(pctldev->dev, "missing pin_config_set op\n");
return -EINVAL;
}
ret = ops->pin_config_set(pctldev,
setting->data.configs.group_or_pin,
setting->data.configs.configs,
setting->data.configs.num_configs);
if (ret < 0) {
dev_err(pctldev->dev,
"pin_config_set op failed for pin %d\n",
setting->data.configs.group_or_pin);
return ret;
}
break;
case PIN_MAP_TYPE_CONFIGS_GROUP:
if (!ops->pin_config_group_set) {
dev_err(pctldev->dev,
"missing pin_config_group_set op\n");
return -EINVAL;
}
ret = ops->pin_config_group_set(pctldev,
setting->data.configs.group_or_pin,
setting->data.configs.configs,
setting->data.configs.num_configs);
if (ret < 0) {
dev_err(pctldev->dev,
"pin_config_group_set op failed for group %d\n",
setting->data.configs.group_or_pin);
return ret;
}
break;
default:
return -EINVAL;
}
return 0;
}
到这里设备侧的函数执行流程便已经结束