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