pinctrl: move subsystem mutex to pinctrl_dev struct

This mutex avoids deadlock in case of use of multiple pin
controllers. Before this modification, by using a global
mutex, deadlock appeared when, for example, a call to
pinctrl_pins_show() locked the pinctrl_mutex, called the
ops->pin_dbg_show of a particular pin controller. If this
pin controller needs I2C access to retrieve configuration
information and I2C driver is using pinctrl to drive its
pins, a call to pinctrl_select_state() try to lock again
pinctrl_mutex which leads to a deadlock.

Notice that the mutex grab from the two direction functions
was moved into pinctrl_gpio_direction().

For several cases, we can't replace pinctrl_mutex by
pctldev->mutex, because at this stage, pctldev is
not accessible :
	- pinctrl_get()/pinctrl_put()
	- pinctrl_register_maps()

So add respectively pinctrl_list_mutex and
pinctrl_maps_mutex in order to protect
pinctrl_list and pinctrl_maps list instead.

Reintroduce pinctrldev_list_mutex in
find_pinctrl_by_of_node(),
pinctrl_find_and_add_gpio_range()
pinctrl_request_gpio(), pinctrl_free_gpio(),
pinctrl_gpio_direction(), pinctrl_devices_show(),
pinctrl_register() and pinctrl_unregister() to
protect pinctrldev_list.

Changes v2->v3:
- Fix a missing EXPORT_SYMBOL_GPL() for pinctrl_select_state().

Changes v1->v2:
- pinctrl_select_state_locked() is removed, all lock mechanism
  is located inside pinctrl_select_state(). When parsing
  the state->setting list, take the per-pin-controller driver
  lock. (Patrice).
- Introduce pinctrldev_list_mutex to protect pinctrldev_list
  in all functions which parse or modify pictrldev_list.
  (Patrice).
- move find_pinctrl_by_of_node() from pinctrl/devicetree.c to
  pinctrl/core.c in order to protect pinctrldev_list.
  (Patrice).
- Sink mutex:es into some functions and remove some _locked
  variants down to where the lists are actually accessed to
  make things simpler. (Linus)
- Drop *all* mutexes completely from pinctrl_lookup_state()
  and pinctrl_select_state() - no relevant mutex was taken
  and it was unclear what this was protecting against. (Linus)

Reported by : Seraphin Bonnaffe <seraphin.bonnaffe@stericsson.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 24 insertions, 22 deletions

diff --git a/drivers/pinctrl/pinconf.c b/drivers/pinctrl/pinconf.c
index 32f96808202a..c67c37e23dd7 100644
--- a/drivers/pinctrl/pinconf.c
+++ b/drivers/pinctrl/pinconf.c
@@ -89,14 +89,14 @@ int pin_config_get(const char *dev_name, const char *name,
         struct pinctrl_dev *pctldev;
         int pin;
 
-        mutex_lock(&pinctrl_mutex);
-
         pctldev = get_pinctrl_dev_from_devname(dev_name);
         if (!pctldev) {
                 pin = -EINVAL;
-                goto unlock;
+                return pin;
         }
 
+        mutex_lock(&pctldev->mutex);
+
         pin = pin_get_from_name(pctldev, name);
         if (pin < 0)
                 goto unlock;
@@ -104,7 +104,7 @@ int pin_config_get(const char *dev_name, const char *name,
         pin = pin_config_get_for_pin(pctldev, pin, config);
 
 unlock:
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pctldev->mutex);
         return pin;
 }
 EXPORT_SYMBOL(pin_config_get);
@@ -145,14 +145,14 @@ int pin_config_set(const char *dev_name, const char *name,
         struct pinctrl_dev *pctldev;
         int pin, ret;
 
-        mutex_lock(&pinctrl_mutex);
-
         pctldev = get_pinctrl_dev_from_devname(dev_name);
         if (!pctldev) {
                 ret = -EINVAL;
-                goto unlock;
+                return ret;
         }
 
+        mutex_lock(&pctldev->mutex);
+
         pin = pin_get_from_name(pctldev, name);
         if (pin < 0) {
                 ret = pin;
@@ -162,7 +162,7 @@ int pin_config_set(const char *dev_name, const char *name,
         ret = pin_config_set_for_pin(pctldev, pin, config);
 
 unlock:
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pctldev->mutex);
         return ret;
 }
 EXPORT_SYMBOL(pin_config_set);
@@ -174,13 +174,14 @@ int pin_config_group_get(const char *dev_name, const char *pin_group,
         const struct pinconf_ops *ops;
         int selector, ret;
 
-        mutex_lock(&pinctrl_mutex);
-
         pctldev = get_pinctrl_dev_from_devname(dev_name);
         if (!pctldev) {
                 ret = -EINVAL;
-                goto unlock;
+                return ret;
         }
+
+        mutex_lock(&pctldev->mutex);
+
         ops = pctldev->desc->confops;
 
         if (!ops || !ops->pin_config_group_get) {
@@ -200,7 +201,7 @@ int pin_config_group_get(const char *dev_name, const char *pin_group,
         ret = ops->pin_config_group_get(pctldev, selector, config);
 
 unlock:
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pctldev->mutex);
         return ret;
 }
 EXPORT_SYMBOL(pin_config_group_get);
@@ -217,13 +218,14 @@ int pin_config_group_set(const char *dev_name, const char *pin_group,
         int ret;
         int i;
 
-        mutex_lock(&pinctrl_mutex);
-
         pctldev = get_pinctrl_dev_from_devname(dev_name);
         if (!pctldev) {
                 ret = -EINVAL;
-                goto unlock;
+                return ret;
         }
+
+        mutex_lock(&pctldev->mutex);
+
         ops = pctldev->desc->confops;
         pctlops = pctldev->desc->pctlops;
 
@@ -279,7 +281,7 @@ int pin_config_group_set(const char *dev_name, const char *pin_group,
         ret = 0;
 
 unlock:
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pctldev->mutex);
 
         return ret;
 }
@@ -487,7 +489,7 @@ static int pinconf_pins_show(struct seq_file *s, void *what)
         seq_puts(s, "Pin config settings per pin\n");
         seq_puts(s, "Format: pin (name): configs\n");
 
-        mutex_lock(&pinctrl_mutex);
+        mutex_lock(&pctldev->mutex);
 
         /* The pin number can be retrived from the pin controller descriptor */
         for (i = 0; i < pctldev->desc->npins; i++) {
@@ -507,7 +509,7 @@ static int pinconf_pins_show(struct seq_file *s, void *what)
                 seq_printf(s, "\n");
         }
 
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pctldev->mutex);
 
         return 0;
 }
@@ -608,7 +610,7 @@ static int pinconf_dbg_config_print(struct seq_file *s, void *d)
         bool found = false;
         unsigned long config;
 
-        mutex_lock(&pinctrl_mutex);
+        mutex_lock(&pctldev->mutex);
 
         /* Parse the pinctrl map and look for the elected pin/state */
         for_each_maps(maps_node, i, map) {
@@ -657,7 +659,7 @@ static int pinconf_dbg_config_print(struct seq_file *s, void *d)
                 confops->pin_config_config_dbg_show(pctldev, s, config);
 
 exit:
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pctldev->mutex);
 
         return 0;
 }
@@ -747,7 +749,7 @@ static int pinconf_dbg_config_write(struct file *file,
                 return -EINVAL;
         strncpy(config, token, MAX_NAME_LEN);
 
-        mutex_lock(&pinctrl_mutex);
+        mutex_lock(&pinctrl_maps_mutex);
 
         /* Parse the pinctrl map and look for the selected dev/state/pin */
         for_each_maps(maps_node, i, map) {
@@ -785,7 +787,7 @@ static int pinconf_dbg_config_write(struct file *file,
         }
 
 exit:
-        mutex_unlock(&pinctrl_mutex);
+        mutex_unlock(&pinctrl_maps_mutex);
 
         return count;
 }