diff options
Diffstat (limited to 'drivers/gpio/gpiolib.c')
| -rw-r--r-- | drivers/gpio/gpiolib.c | 567 |
1 files changed, 567 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c new file mode 100644 index 0000000..d8db2f8 --- /dev/null +++ b/drivers/gpio/gpiolib.c @@ -0,0 +1,567 @@ +#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 + +#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]"); + } +} + +/* 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; +} + +/** + * 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. + */ +int gpiochip_add(struct gpio_chip *chip) +{ + unsigned long flags; + int status = 0; + unsigned id; + + /* NOTE chip->base negative is reserved to mean a request for + * dynamic allocation. We don't currently support that. + */ + + if (chip->base < 0 || (chip->base + chip->ngpio) >= ARCH_NR_GPIOS) { + status = -EINVAL; + goto fail; + } + + spin_lock_irqsave(&gpio_lock, flags); + + /* these GPIO numbers must not be managed by another gpio_chip */ + for (id = chip->base; id < chip->base + chip->ngpio; id++) { + if (gpio_desc[id].chip != NULL) { + status = -EBUSY; + break; + } + } + if (status == 0) { + for (id = chip->base; id < chip->base + chip->ngpio; id++) { + gpio_desc[id].chip = chip; + gpio_desc[id].flags = 0; + } + } + + 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 >= ARCH_NR_GPIOS) + goto done; + desc = &gpio_desc[gpio]; + if (desc->chip == NULL) + 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; + +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 >= ARCH_NR_GPIOS) { + 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); + 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 >= ARCH_NR_GPIOS || 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 >= ARCH_NR_GPIOS) + 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", + __FUNCTION__, 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 >= ARCH_NR_GPIOS) + 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", + __FUNCTION__, 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 < ARCH_NR_GPIOS; 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 */ |