2 files changed, 35 insertions, 12 deletions

diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index c2c6e9b39bbe..d96a6dba5748 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -158,10 +158,11 @@ and configure pullups/pulldowns appropriately.)
 Spinlock-Safe GPIO access
 -------------------------
 Most GPIO controllers can be accessed with memory read/write instructions.
-That doesn't need to sleep, and can safely be done from inside IRQ handlers.
-(That includes hardirq contexts on RT kernels.)
+Those don't need to sleep, and can safely be done from inside hard
+(nonthreaded) IRQ handlers and similar contexts.
 
-Use these calls to access such GPIOs:
+Use the following calls to access such GPIOs,
+for which gpio_cansleep() will always return false (see below):
 
         /* GPIO INPUT:  return zero or nonzero */
         int gpio_get_value(unsigned gpio);
@@ -210,9 +211,31 @@ To access such GPIOs, a different set of accessors is defined:
         /* GPIO OUTPUT, might sleep */
         void gpio_set_value_cansleep(unsigned gpio, int value);
 
-Other than the fact that these calls might sleep, and will not be ignored
-for GPIOs that can't be accessed from IRQ handlers, these calls act the
-same as the spinlock-safe calls.
+
+Accessing such GPIOs requires a context which may sleep,  for example
+a threaded IRQ handler, and those accessors must be used instead of
+spinlock-safe accessors without the cansleep() name suffix.
+
+Other than the fact that these accessors might sleep, and will work
+on GPIOs that can't be accessed from hardIRQ handlers, these calls act
+the same as the spinlock-safe calls.
+
+  ** IN ADDITION ** calls to setup and configure such GPIOs must be made
+from contexts which may sleep, since they may need to access the GPIO
+controller chip too:  (These setup calls are usually made from board
+setup or driver probe/teardown code, so this is an easy constraint.)
+
+        gpio_direction_input()
+        gpio_direction_output()
+        gpio_request()
+
+##      gpio_request_one()
+##      gpio_request_array()
+##      gpio_free_array()
+
+        gpio_free()
+        gpio_set_debounce()
+
 
 
 Claiming and Releasing GPIOs
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6a6bd569e1f8..1a8c18cbf201 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1272,7 +1272,7 @@ void gpio_free(unsigned gpio)
         if (chip && test_bit(FLAG_REQUESTED, &desc->flags)) {
                 if (chip->free) {
                         spin_unlock_irqrestore(&gpio_lock, flags);
-                        might_sleep_if(extra_checks && chip->can_sleep);
+                        might_sleep_if(chip->can_sleep);
                         chip->free(chip, gpio - chip->base);
                         spin_lock_irqsave(&gpio_lock, flags);
                 }
@@ -1410,7 +1410,7 @@ int gpio_direction_input(unsigned gpio)
 
         spin_unlock_irqrestore(&gpio_lock, flags);
 
-        might_sleep_if(extra_checks && chip->can_sleep);
+        might_sleep_if(chip->can_sleep);
 
         if (status) {
                 status = chip->request(chip, gpio);
@@ -1463,7 +1463,7 @@ int gpio_direction_output(unsigned gpio, int value)
 
         spin_unlock_irqrestore(&gpio_lock, flags);
 
-        might_sleep_if(extra_checks && chip->can_sleep);
+        might_sleep_if(chip->can_sleep);
 
         if (status) {
                 status = chip->request(chip, gpio);
@@ -1521,7 +1521,7 @@ int gpio_set_debounce(unsigned gpio, unsigned debounce)
 
         spin_unlock_irqrestore(&gpio_lock, flags);
 
-        might_sleep_if(extra_checks && chip->can_sleep);
+        might_sleep_if(chip->can_sleep);
 
         return chip->set_debounce(chip, gpio, debounce);
 
@@ -1571,7 +1571,7 @@ int __gpio_get_value(unsigned gpio)
         struct gpio_chip        *chip;
 
         chip = gpio_to_chip(gpio);
-        WARN_ON(extra_checks && chip->can_sleep);
+        WARN_ON(chip->can_sleep);
         return chip->get ? chip->get(chip, gpio - chip->base) : 0;
 }
 EXPORT_SYMBOL_GPL(__gpio_get_value);
@@ -1590,7 +1590,7 @@ void __gpio_set_value(unsigned gpio, int value)
         struct gpio_chip        *chip;
 
         chip = gpio_to_chip(gpio);
-        WARN_ON(extra_checks && chip->can_sleep);
+        WARN_ON(chip->can_sleep);
         chip->set(chip, gpio - chip->base, value);
 }
 EXPORT_SYMBOL_GPL(__gpio_set_value);