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linux-sg2042/drivers/gpio/gpiolib.c

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#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <asm/gpio.h>
/* Optional implementation infrastructure for GPIO interfaces.
*
* Platforms may want to use this if they tend to use very many GPIOs
* that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
*
* When kernel footprint or instruction count is an issue, simpler
* implementations may be preferred. The GPIO programming interface
* allows for inlining speed-critical get/set operations for common
* cases, so that access to SOC-integrated GPIOs can sometimes cost
* only an instruction or two per bit.
*/
/* When debugging, extend minimal trust to callers and platform code.
* Also emit diagnostic messages that may help initial bringup, when
* board setup or driver bugs are most common.
*
* Otherwise, minimize overhead in what may be bitbanging codepaths.
*/
#ifdef DEBUG
#define extra_checks 1
#else
#define extra_checks 0
#endif
/* gpio_lock prevents conflicts during gpio_desc[] table updates.
* While any GPIO is requested, its gpio_chip is not removable;
* each GPIO's "requested" flag serves as a lock and refcount.
*/
static DEFINE_SPINLOCK(gpio_lock);
struct gpio_desc {
struct gpio_chip *chip;
unsigned long flags;
/* flag symbols are bit numbers */
#define FLAG_REQUESTED 0
#define FLAG_IS_OUT 1
#define FLAG_RESERVED 2
#ifdef CONFIG_DEBUG_FS
const char *label;
#endif
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
static inline void desc_set_label(struct gpio_desc *d, const char *label)
{
#ifdef CONFIG_DEBUG_FS
d->label = label;
#endif
}
/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
* 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...
*/
static void gpio_ensure_requested(struct gpio_desc *desc)
{
if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
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 holds gpio_lock *OR* gpio is marked as requested */
static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
{
return gpio_desc[gpio].chip;
}
/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
static int gpiochip_find_base(int ngpio)
{
int i;
int spare = 0;
int base = -ENOSPC;
for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
struct gpio_desc *desc = &gpio_desc[i];
struct gpio_chip *chip = desc->chip;
if (!chip && !test_bit(FLAG_RESERVED, &desc->flags)) {
spare++;
if (spare == ngpio) {
base = i;
break;
}
} else {
spare = 0;
if (chip)
i -= chip->ngpio - 1;
}
}
if (gpio_is_valid(base))
pr_debug("%s: found new base at %d\n", __func__, base);
return base;
}
/**
* gpiochip_reserve() - reserve range of gpios to use with platform code only
* @start: starting gpio number
* @ngpio: number of gpios to reserve
* Context: platform init, potentially before irqs or kmalloc will work
*
* Returns a negative errno if any gpio within the range is already reserved
* or registered, else returns zero as a success code. Use this function
* to mark a range of gpios as unavailable for dynamic gpio number allocation,
* for example because its driver support is not yet loaded.
*/
int __init gpiochip_reserve(int start, int ngpio)
{
int ret = 0;
unsigned long flags;
int i;
if (!gpio_is_valid(start) || !gpio_is_valid(start + ngpio))
return -EINVAL;
spin_lock_irqsave(&gpio_lock, flags);
for (i = start; i < start + ngpio; i++) {
struct gpio_desc *desc = &gpio_desc[i];
if (desc->chip || test_bit(FLAG_RESERVED, &desc->flags)) {
ret = -EBUSY;
goto err;
}
set_bit(FLAG_RESERVED, &desc->flags);
}
pr_debug("%s: reserved gpios from %d to %d\n",
__func__, start, start + ngpio - 1);
err:
spin_unlock_irqrestore(&gpio_lock, flags);
return ret;
}
/**
* gpiochip_add() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
* Context: potentially before irqs or kmalloc will work
*
* Returns a negative errno if the chip can't be registered, such as
* because the chip->base is invalid or already associated with a
* different chip. Otherwise it returns zero as a success code.
*
* If chip->base is negative, this requests dynamic assignment of
* a range of valid GPIOs.
*/
int gpiochip_add(struct gpio_chip *chip)
{
unsigned long flags;
int status = 0;
unsigned id;
int base = chip->base;
if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio))
&& base >= 0) {
status = -EINVAL;
goto fail;
}
spin_lock_irqsave(&gpio_lock, flags);
if (base < 0) {
base = gpiochip_find_base(chip->ngpio);
if (base < 0) {
status = base;
goto fail_unlock;
}
chip->base = base;
}
/* these GPIO numbers must not be managed by another gpio_chip */
for (id = base; id < base + chip->ngpio; id++) {
if (gpio_desc[id].chip != NULL) {
status = -EBUSY;
break;
}
}
if (status == 0) {
for (id = base; id < base + chip->ngpio; id++) {
gpio_desc[id].chip = chip;
gpio_desc[id].flags = 0;
}
}
fail_unlock:
spin_unlock_irqrestore(&gpio_lock, flags);
fail:
/* failures here can mean systems won't boot... */
if (status)
pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
chip->base, chip->base + chip->ngpio,
chip->label ? : "generic");
return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add);
/**
* gpiochip_remove() - unregister a gpio_chip
* @chip: the chip to unregister
*
* A gpio_chip with any GPIOs still requested may not be removed.
*/
int gpiochip_remove(struct gpio_chip *chip)
{
unsigned long flags;
int status = 0;
unsigned id;
spin_lock_irqsave(&gpio_lock, flags);
for (id = chip->base; id < chip->base + chip->ngpio; id++) {
if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
status = -EBUSY;
break;
}
}
if (status == 0) {
for (id = chip->base; id < chip->base + chip->ngpio; id++)
gpio_desc[id].chip = NULL;
}
spin_unlock_irqrestore(&gpio_lock, flags);
return status;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);
/* These "optional" allocation calls help prevent drivers from stomping
* on each other, and help provide better diagnostics in debugfs.
* They're called even less than the "set direction" calls.
*/
int gpio_request(unsigned gpio, const char *label)
{
struct gpio_desc *desc;
int status = -EINVAL;
unsigned long flags;
spin_lock_irqsave(&gpio_lock, flags);
if (!gpio_is_valid(gpio))
goto done;
desc = &gpio_desc[gpio];
if (desc->chip == NULL)
goto done;
if (!try_module_get(desc->chip->owner))
goto done;
/* NOTE: gpio_request() can be called in early boot,
* before IRQs are enabled.
*/
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);
}
done:
if (status)
pr_debug("gpio_request: gpio-%d (%s) status %d\n",
gpio, label ? : "?", status);
spin_unlock_irqrestore(&gpio_lock, flags);
return status;
}
EXPORT_SYMBOL_GPL(gpio_request);
void gpio_free(unsigned gpio)
{
unsigned long flags;
struct gpio_desc *desc;
if (!gpio_is_valid(gpio)) {
WARN_ON(extra_checks);
return;
}
spin_lock_irqsave(&gpio_lock, flags);
desc = &gpio_desc[gpio];
if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
desc_set_label(desc, NULL);
module_put(desc->chip->owner);
} else
WARN_ON(extra_checks);
spin_unlock_irqrestore(&gpio_lock, flags);
}
EXPORT_SYMBOL_GPL(gpio_free);
/**
* gpiochip_is_requested - return string iff signal was requested
* @chip: controller managing the signal
* @offset: of signal within controller's 0..(ngpio - 1) range
*
* Returns NULL if the GPIO is not currently requested, else a string.
* If debugfs support is enabled, the string returned is the label passed
* to gpio_request(); otherwise it is a meaningless constant.
*
* This function is for use by GPIO controller drivers. The label can
* help with diagnostics, and knowing that the signal is used as a GPIO
* can help avoid accidentally multiplexing it to another controller.
*/
const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
{
unsigned gpio = chip->base + offset;
if (!gpio_is_valid(gpio) || gpio_desc[gpio].chip != chip)
return NULL;
if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
return NULL;
#ifdef CONFIG_DEBUG_FS
return gpio_desc[gpio].label;
#else
return "?";
#endif
}
EXPORT_SYMBOL_GPL(gpiochip_is_requested);
/* Drivers MUST set GPIO direction before making get/set calls. In
* some cases this is done in early boot, before IRQs are enabled.
*
* As a rule these aren't called more than once (except for drivers
* using the open-drain emulation idiom) so these are natural places
* to accumulate extra debugging checks. Note that we can't (yet)
* rely on gpio_request() having been called beforehand.
*/
int gpio_direction_input(unsigned gpio)
{
unsigned long flags;
struct gpio_chip *chip;
struct gpio_desc *desc = &gpio_desc[gpio];
int status = -EINVAL;
spin_lock_irqsave(&gpio_lock, flags);
if (!gpio_is_valid(gpio))
goto fail;
chip = desc->chip;
if (!chip || !chip->get || !chip->direction_input)
goto fail;
gpio -= chip->base;
if (gpio >= chip->ngpio)
goto fail;
gpio_ensure_requested(desc);
/* now we know the gpio is valid and chip won't vanish */
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(extra_checks && chip->can_sleep);
status = chip->direction_input(chip, gpio);
if (status == 0)
clear_bit(FLAG_IS_OUT, &desc->flags);
return status;
fail:
spin_unlock_irqrestore(&gpio_lock, flags);
if (status)
pr_debug("%s: gpio-%d status %d\n",
__func__, gpio, status);
return status;
}
EXPORT_SYMBOL_GPL(gpio_direction_input);
int gpio_direction_output(unsigned gpio, int value)
{
unsigned long flags;
struct gpio_chip *chip;
struct gpio_desc *desc = &gpio_desc[gpio];
int status = -EINVAL;
spin_lock_irqsave(&gpio_lock, flags);
if (!gpio_is_valid(gpio))
goto fail;
chip = desc->chip;
if (!chip || !chip->set || !chip->direction_output)
goto fail;
gpio -= chip->base;
if (gpio >= chip->ngpio)
goto fail;
gpio_ensure_requested(desc);
/* now we know the gpio is valid and chip won't vanish */
spin_unlock_irqrestore(&gpio_lock, flags);
might_sleep_if(extra_checks && chip->can_sleep);
status = chip->direction_output(chip, gpio, value);
if (status == 0)
set_bit(FLAG_IS_OUT, &desc->flags);
return status;
fail:
spin_unlock_irqrestore(&gpio_lock, flags);
if (status)
pr_debug("%s: gpio-%d status %d\n",
__func__, gpio, status);
return status;
}
EXPORT_SYMBOL_GPL(gpio_direction_output);
/* I/O calls are only valid after configuration completed; the relevant
* "is this a valid GPIO" error checks should already have been done.
*
* "Get" operations are often inlinable as reading a pin value register,
* and masking the relevant bit in that register.
*
* When "set" operations are inlinable, they involve writing that mask to
* one register to set a low value, or a different register to set it high.
* Otherwise locking is needed, so there may be little value to inlining.
*
*------------------------------------------------------------------------
*
* IMPORTANT!!! The hot paths -- get/set value -- assume that callers
* have requested the GPIO. That can include implicit requesting by
* a direction setting call. Marking a gpio as requested locks its chip
* in memory, guaranteeing that these table lookups need no more locking
* and that gpiochip_remove() will fail.
*
* REVISIT when debugging, consider adding some instrumentation to ensure
* that the GPIO was actually requested.
*/
/**
* __gpio_get_value() - return a gpio's value
* @gpio: gpio whose value will be returned
* Context: any
*
* This is used directly or indirectly to implement gpio_get_value().
* It returns the zero or nonzero value provided by the associated
* gpio_chip.get() method; or zero if no such method is provided.
*/
int __gpio_get_value(unsigned gpio)
{
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(extra_checks && chip->can_sleep);
return chip->get ? chip->get(chip, gpio - chip->base) : 0;
}
EXPORT_SYMBOL_GPL(__gpio_get_value);
/**
* __gpio_set_value() - assign a gpio's value
* @gpio: gpio whose value will be assigned
* @value: value to assign
* Context: any
*
* This is used directly or indirectly to implement gpio_set_value().
* It invokes the associated gpio_chip.set() method.
*/
void __gpio_set_value(unsigned gpio, int value)
{
struct gpio_chip *chip;
chip = gpio_to_chip(gpio);
WARN_ON(extra_checks && chip->can_sleep);
chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(__gpio_set_value);
/**
* __gpio_cansleep() - report whether gpio value access will sleep
* @gpio: gpio in question
* Context: any
*
* This is used directly or indirectly to implement gpio_cansleep(). It
* returns nonzero if access reading or writing the GPIO value can sleep.
*/
int __gpio_cansleep(unsigned gpio)
{
struct gpio_chip *chip;
/* only call this on GPIOs that are valid! */
chip = gpio_to_chip(gpio);
return chip->can_sleep;
}
EXPORT_SYMBOL_GPL(__gpio_cansleep);
/* There's no value in making it easy to inline GPIO calls that may sleep.
* Common examples include ones connected to I2C or SPI chips.
*/
int gpio_get_value_cansleep(unsigned gpio)
{
struct gpio_chip *chip;
might_sleep_if(extra_checks);
chip = gpio_to_chip(gpio);
return chip->get(chip, gpio - chip->base);
}
EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);
void gpio_set_value_cansleep(unsigned gpio, int value)
{
struct gpio_chip *chip;
might_sleep_if(extra_checks);
chip = gpio_to_chip(gpio);
chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#include <linux/seq_file.h>
static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
unsigned i;
unsigned gpio = chip->base;
struct gpio_desc *gdesc = &gpio_desc[gpio];
int is_out;
for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
continue;
is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
seq_printf(s, " gpio-%-3d (%-12s) %s %s",
gpio, gdesc->label,
is_out ? "out" : "in ",
chip->get
? (chip->get(chip, i) ? "hi" : "lo")
: "? ");
if (!is_out) {
int irq = gpio_to_irq(gpio);
struct irq_desc *desc = irq_desc + irq;
/* This races with request_irq(), set_irq_type(),
* and set_irq_wake() ... but those are "rare".
*
* More significantly, trigger type flags aren't
* currently maintained by genirq.
*/
if (irq >= 0 && desc->action) {
char *trigger;
switch (desc->status & IRQ_TYPE_SENSE_MASK) {
case IRQ_TYPE_NONE:
trigger = "(default)";
break;
case IRQ_TYPE_EDGE_FALLING:
trigger = "edge-falling";
break;
case IRQ_TYPE_EDGE_RISING:
trigger = "edge-rising";
break;
case IRQ_TYPE_EDGE_BOTH:
trigger = "edge-both";
break;
case IRQ_TYPE_LEVEL_HIGH:
trigger = "level-high";
break;
case IRQ_TYPE_LEVEL_LOW:
trigger = "level-low";
break;
default:
trigger = "?trigger?";
break;
}
seq_printf(s, " irq-%d %s%s",
irq, trigger,
(desc->status & IRQ_WAKEUP)
? " wakeup" : "");
}
}
seq_printf(s, "\n");
}
}
static int gpiolib_show(struct seq_file *s, void *unused)
{
struct gpio_chip *chip = NULL;
unsigned gpio;
int started = 0;
/* REVISIT this isn't locked against gpio_chip removal ... */
for (gpio = 0; gpio_is_valid(gpio); gpio++) {
if (chip == gpio_desc[gpio].chip)
continue;
chip = gpio_desc[gpio].chip;
if (!chip)
continue;
seq_printf(s, "%sGPIOs %d-%d, %s%s:\n",
started ? "\n" : "",
chip->base, chip->base + chip->ngpio - 1,
chip->label ? : "generic",
chip->can_sleep ? ", can sleep" : "");
started = 1;
if (chip->dbg_show)
chip->dbg_show(s, chip);
else
gpiolib_dbg_show(s, chip);
}
return 0;
}
static int gpiolib_open(struct inode *inode, struct file *file)
{
return single_open(file, gpiolib_show, NULL);
}
static struct file_operations gpiolib_operations = {
.open = gpiolib_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int __init gpiolib_debugfs_init(void)
{
/* /sys/kernel/debug/gpio */
(void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
NULL, NULL, &gpiolib_operations);
return 0;
}
subsys_initcall(gpiolib_debugfs_init);
#endif /* DEBUG_FS */
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