gpiolib: request/free hooks

Add a new internal mechanism to gpiolib to support low power
operations by letting gpio_chip instances see when their GPIOs
are in use.  When no GPIOs are active, chips may be able to
enter lower powered runtime states by disabling clocks and/or
power domains.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: "Magnus Damm" <magnus.damm@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 78 insertions, 13 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 29a7e6b1be5d..9112830107a5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -67,17 +67,28 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
  * when setting direction, and otherwise illegal.  Until board setup code
  * and drivers use explicit requests everywhere (which won't happen when
  * those calls have no teeth) we can't avoid autorequesting.  This nag
- * message should motivate switching to explicit requests...
+ * message should motivate switching to explicit requests... so should
+ * the weaker cleanup after faults, compared to gpio_request().
  */
-static void gpio_ensure_requested(struct gpio_desc *desc)
+static int gpio_ensure_requested(struct gpio_desc *desc, unsigned offset)
 {
         if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
-                pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
+                struct gpio_chip *chip = desc->chip;
+                int gpio = chip->base + offset;
+
+                if (!try_module_get(chip->owner)) {
+                        pr_err("GPIO-%d: module can't be gotten \n", gpio);
+                        clear_bit(FLAG_REQUESTED, &desc->flags);
+                        /* lose */
+                        return -EIO;
+                }
+                pr_warning("GPIO-%d autorequested\n", gpio);
                 desc_set_label(desc, "[auto]");
-                if (!try_module_get(desc->chip->owner))
-                        pr_err("GPIO-%d: module can't be gotten \n",
-                                        (int)(desc - gpio_desc));
+                /* caller must chip->request() w/o spinlock */
+                if (chip->request)
+                        return 1;
         }
+        return 0;
 }
 
 /* caller holds gpio_lock *OR* gpio is marked as requested */
@@ -752,6 +763,7 @@ EXPORT_SYMBOL_GPL(gpiochip_remove);
 int gpio_request(unsigned gpio, const char *label)
 {
         struct gpio_desc        *desc;
+        struct gpio_chip        *chip;
         int                     status = -EINVAL;
         unsigned long           flags;
 
@@ -760,14 +772,15 @@ int gpio_request(unsigned gpio, const char *label)
         if (!gpio_is_valid(gpio))
                 goto done;
         desc = &gpio_desc[gpio];
-        if (desc->chip == NULL)
+        chip = desc->chip;
+        if (chip == NULL)
                 goto done;
 
-        if (!try_module_get(desc->chip->owner))
+        if (!try_module_get(chip->owner))
                 goto done;
 
         /* NOTE:  gpio_request() can be called in early boot,
-         * before IRQs are enabled.
+         * before IRQs are enabled, for non-sleeping (SOC) GPIOs.
          */
 
         if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
@@ -775,7 +788,20 @@ int gpio_request(unsigned gpio, const char *label)
                 status = 0;
         } else {
                 status = -EBUSY;
-                module_put(desc->chip->owner);
+                module_put(chip->owner);
+        }
+
+        if (chip->request) {
+                /* chip->request may sleep */
+                spin_unlock_irqrestore(&gpio_lock, flags);
+                status = chip->request(chip, gpio - chip->base);
+                spin_lock_irqsave(&gpio_lock, flags);
+
+                if (status < 0) {
+                        desc_set_label(desc, NULL);
+                        module_put(chip->owner);
+                        clear_bit(FLAG_REQUESTED, &desc->flags);
+                }
         }
 
 done:
@@ -791,6 +817,7 @@ void gpio_free(unsigned gpio)
 {
         unsigned long           flags;
         struct gpio_desc        *desc;
+        struct gpio_chip        *chip;
 
         might_sleep();
 
@@ -804,9 +831,17 @@ void gpio_free(unsigned gpio)
         spin_lock_irqsave(&gpio_lock, flags);
 
         desc = &gpio_desc[gpio];
-        if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
+        chip = desc->chip;
+        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);
+                        chip->free(chip, gpio - chip->base);
+                        spin_lock_irqsave(&gpio_lock, flags);
+                }
                 desc_set_label(desc, NULL);
                 module_put(desc->chip->owner);
+                clear_bit(FLAG_REQUESTED, &desc->flags);
         } else
                 WARN_ON(extra_checks);
 
@@ -871,7 +906,9 @@ int gpio_direction_input(unsigned gpio)
         gpio -= chip->base;
         if (gpio >= chip->ngpio)
                 goto fail;
-        gpio_ensure_requested(desc);
+        status = gpio_ensure_requested(desc, gpio);
+        if (status < 0)
+                goto fail;
 
         /* now we know the gpio is valid and chip won't vanish */
 
@@ -879,9 +916,22 @@ int gpio_direction_input(unsigned gpio)
 
         might_sleep_if(extra_checks && chip->can_sleep);
 
+        if (status) {
+                status = chip->request(chip, gpio);
+                if (status < 0) {
+                        pr_debug("GPIO-%d: chip request fail, %d\n",
+                                chip->base + gpio, status);
+                        /* and it's not available to anyone else ...
+                         * gpio_request() is the fully clean solution.
+                         */
+                        goto lose;
+                }
+        }
+
         status = chip->direction_input(chip, gpio);
         if (status == 0)
                 clear_bit(FLAG_IS_OUT, &desc->flags);
+lose:
         return status;
 fail:
         spin_unlock_irqrestore(&gpio_lock, flags);
@@ -909,7 +959,9 @@ int gpio_direction_output(unsigned gpio, int value)
         gpio -= chip->base;
         if (gpio >= chip->ngpio)
                 goto fail;
-        gpio_ensure_requested(desc);
+        status = gpio_ensure_requested(desc, gpio);
+        if (status < 0)
+                goto fail;
 
         /* now we know the gpio is valid and chip won't vanish */
 
@@ -917,9 +969,22 @@ int gpio_direction_output(unsigned gpio, int value)
 
         might_sleep_if(extra_checks && chip->can_sleep);
 
+        if (status) {
+                status = chip->request(chip, gpio);
+                if (status < 0) {
+                        pr_debug("GPIO-%d: chip request fail, %d\n",
+                                chip->base + gpio, status);
+                        /* and it's not available to anyone else ...
+                         * gpio_request() is the fully clean solution.
+                         */
+                        goto lose;
+                }
+        }
+
         status = chip->direction_output(chip, gpio, value);
         if (status == 0)
                 set_bit(FLAG_IS_OUT, &desc->flags);
+lose:
         return status;
 fail:
         spin_unlock_irqrestore(&gpio_lock, flags);