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, 4 deletions

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index bd83c8b01cd..88cc5095d0c 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -506,7 +506,7 @@ static int pinmux_functions_show(struct seq_file *s, void *what)
 	if (!pmxops)
 		return 0;
 
-	mutex_lock(&pinctrl_mutex);
+	mutex_lock(&pctldev->mutex);
 	nfuncs = pmxops->get_functions_count(pctldev);
 	while (func_selector < nfuncs) {
 		const char *func = pmxops->get_function_name(pctldev,
@@ -530,7 +530,7 @@ static int pinmux_functions_show(struct seq_file *s, void *what)
 		func_selector++;
 	}
 
-	mutex_unlock(&pinctrl_mutex);
+	mutex_unlock(&pctldev->mutex);
 
 	return 0;
 }
@@ -548,7 +548,7 @@ static int pinmux_pins_show(struct seq_file *s, void *what)
 	seq_puts(s, "Pinmux settings per pin\n");
 	seq_puts(s, "Format: pin (name): mux_owner gpio_owner hog?\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++) {
@@ -583,7 +583,7 @@ static int pinmux_pins_show(struct seq_file *s, void *what)
 			seq_printf(s, "\n");
 	}
 
-	mutex_unlock(&pinctrl_mutex);
+	mutex_unlock(&pctldev->mutex);
 
 	return 0;
 }