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Message-Id: <200809241508.11091.david-b@pacbell.net>
Date: Wed, 24 Sep 2008 15:08:10 -0700
From: David Brownell <david-b@...bell.net>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: lkml <linux-kernel@...r.kernel.org>
Subject: [patch 2.6.27-rc7] gpiolib: request/free hooks
From: David Brownell <dbrownell@...rs.sourceforge.net>
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@...rs.sourceforge.net>
---
Documentation/gpio.txt | 4 ++++
drivers/gpio/gpiolib.c | 42 ++++++++++++++++++++++++++++++------------
include/asm-generic/gpio.h | 9 +++++++++
3 files changed, 43 insertions(+), 12 deletions(-)
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -240,6 +240,10 @@ signal, or (b) something wrongly believe
needed to manage a signal that's in active use. That is, requesting a
GPIO can serve as a kind of lock.
+Some platforms may also use knowledge about what GPIOs are active for
+power management, such as by powering down unused chip sectors and, more
+easily, gating off unused clocks.
+
These two calls are optional because not not all current Linux platforms
offer such functionality in their GPIO support; a valid implementation
could return success for all gpio_request() calls. Unlike the other calls,
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -69,14 +69,18 @@ static inline void desc_set_label(struct
* those calls have no teeth) we can't avoid autorequesting. This nag
* message should motivate switching to explicit requests...
*/
-static void gpio_ensure_requested(struct gpio_desc *desc)
+static void 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;
+
+ 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));
+ if (!try_module_get(chip->owner))
+ pr_err("GPIO-%d: module can't be gotten \n", gpio);
+ if (chip->request)
+ chip->request(chip, offset);
}
}
@@ -781,6 +785,7 @@ 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;
@@ -789,22 +794,31 @@ int gpio_request(unsigned gpio, const ch
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 (chip->request) {
+ status = chip->request(chip, gpio - chip->base);
+ if (status < 0) {
+ module_put(chip->owner);
+ goto done;
+ }
+ }
+
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
desc_set_label(desc, label ? : "?");
status = 0;
} else {
status = -EBUSY;
- module_put(desc->chip->owner);
+ module_put(chip->owner);
}
done:
@@ -820,6 +834,7 @@ void gpio_free(unsigned gpio)
{
unsigned long flags;
struct gpio_desc *desc;
+ struct gpio_chip *chip;
if (!gpio_is_valid(gpio)) {
WARN_ON(extra_checks);
@@ -831,8 +846,11 @@ 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_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
desc_set_label(desc, NULL);
+ if (chip->free)
+ chip->free(chip, gpio - chip->base);
module_put(desc->chip->owner);
} else
WARN_ON(extra_checks);
@@ -898,7 +916,7 @@ int gpio_direction_input(unsigned gpio)
gpio -= chip->base;
if (gpio >= chip->ngpio)
goto fail;
- gpio_ensure_requested(desc);
+ gpio_ensure_requested(desc, gpio);
/* now we know the gpio is valid and chip won't vanish */
@@ -936,7 +954,7 @@ int gpio_direction_output(unsigned gpio,
gpio -= chip->base;
if (gpio >= chip->ngpio)
goto fail;
- gpio_ensure_requested(desc);
+ gpio_ensure_requested(desc, gpio);
/* now we know the gpio is valid and chip won't vanish */
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -35,6 +35,10 @@ struct module;
* @label: for diagnostics
* @dev: optional device providing the GPIOs
* @owner: helps prevent removal of modules exporting active GPIOs
+ * @request: optional hook for chip-specific activation, such as
+ * enabling module power and clock; may sleep
+ * @free: optional hook for chip-specific deactivation, such as
+ * disabling module power and clock; may sleep
* @direction_input: configures signal "offset" as input, or returns error
* @get: returns value for signal "offset"; for output signals this
* returns either the value actually sensed, or zero
@@ -67,6 +71,11 @@ struct gpio_chip {
struct device *dev;
struct module *owner;
+ int (*request)(struct gpio_chip *chip,
+ unsigned offset);
+ void (*free)(struct gpio_chip *chip,
+ unsigned offset);
+
int (*direction_input)(struct gpio_chip *chip,
unsigned offset);
int (*get)(struct gpio_chip *chip,
--
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