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, 4 insertions, 2 deletions

diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index 6d3d40036d1b..75476b3d87da 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -33,6 +33,7 @@ struct pinctrl_gpio_range;
  * @p: result of pinctrl_get() for this device
  * @hog_default: default state for pins hogged by this device
  * @hog_sleep: sleep state for pins hogged by this device
+ * @mutex: mutex taken on each pin controller specific action
  * @device_root: debugfs root for this device
  */
 struct pinctrl_dev {
@@ -46,6 +47,7 @@ struct pinctrl_dev {
         struct pinctrl *p;
         struct pinctrl_state *hog_default;
         struct pinctrl_state *hog_sleep;
+        struct mutex mutex;
 #ifdef CONFIG_DEBUG_FS
         struct dentry *device_root;
 #endif
@@ -168,6 +170,7 @@ struct pinctrl_maps {
 };
 
 struct pinctrl_dev *get_pinctrl_dev_from_devname(const char *dev_name);
+struct pinctrl_dev *get_pinctrl_dev_from_of_node(struct device_node *np);
 int pin_get_from_name(struct pinctrl_dev *pctldev, const char *name);
 const char *pin_get_name(struct pinctrl_dev *pctldev, const unsigned pin);
 int pinctrl_get_group_selector(struct pinctrl_dev *pctldev,
@@ -186,8 +189,7 @@ void pinctrl_unregister_map(struct pinctrl_map const *map);
 extern int pinctrl_force_sleep(struct pinctrl_dev *pctldev);
 extern int pinctrl_force_default(struct pinctrl_dev *pctldev);
 
-extern struct mutex pinctrl_mutex;
-extern struct list_head pinctrldev_list;
+extern struct mutex pinctrl_maps_mutex;
 extern struct list_head pinctrl_maps;
 
 #define for_each_maps(_maps_node_, _i_, _map_) \