diff options
Diffstat (limited to 'drivers/gpio/gpiolib-shared.c')
| -rw-r--r-- | drivers/gpio/gpiolib-shared.c | 797 |
1 files changed, 797 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c new file mode 100644 index 000000000..495bd3d0d --- /dev/null +++ b/drivers/gpio/gpiolib-shared.c @@ -0,0 +1,797 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 Linaro Ltd. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/auxiliary_bus.h> +#include <linux/cleanup.h> +#include <linux/device.h> +#include <linux/fwnode.h> +#include <linux/gpio/consumer.h> +#include <linux/gpio/machine.h> +#include <linux/idr.h> +#include <linux/kref.h> +#include <linux/list.h> +#include <linux/lockdep.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/of.h> +#include <linux/overflow.h> +#include <linux/printk.h> +#include <linux/property.h> +#include <linux/slab.h> +#include <linux/string.h> + +#include "gpiolib.h" +#include "gpiolib-shared.h" + +/* Represents a single reference to a GPIO pin. */ +struct gpio_shared_ref { + struct list_head list; + /* Firmware node associated with this GPIO's consumer. */ + struct fwnode_handle *fwnode; + /* GPIO flags this consumer uses for the request. */ + enum gpiod_flags flags; + char *con_id; + int dev_id; + /* Protects the auxiliary device struct and the lookup table. */ + struct mutex lock; + struct lock_class_key lock_key; + struct auxiliary_device adev; + struct gpiod_lookup_table *lookup; + bool is_reset_gpio; +}; + +/* Represents a single GPIO pin. */ +struct gpio_shared_entry { + struct list_head list; + /* Firmware node associated with the GPIO controller. */ + struct fwnode_handle *fwnode; + /* Hardware offset of the GPIO within its chip. */ + unsigned int offset; + /* Index in the property value array. */ + size_t index; + /* Synchronizes the modification of shared_desc and offset. */ + struct mutex lock; + struct gpio_shared_desc *shared_desc; + struct kref ref; + struct list_head refs; +}; + +static LIST_HEAD(gpio_shared_list); +static DEFINE_IDA(gpio_shared_ida); + +#if IS_ENABLED(CONFIG_OF) +static struct gpio_shared_entry * +gpio_shared_find_entry(struct fwnode_handle *controller_node, + unsigned int offset) +{ + struct gpio_shared_entry *entry; + + list_for_each_entry(entry, &gpio_shared_list, list) { + if (entry->fwnode == controller_node && entry->offset == offset) + return entry; + } + + return NULL; +} + +static struct gpio_shared_ref *gpio_shared_make_ref(struct fwnode_handle *fwnode, + const char *con_id, + enum gpiod_flags flags) +{ + char *con_id_cpy __free(kfree) = NULL; + + struct gpio_shared_ref *ref __free(kfree) = kzalloc_obj(*ref); + if (!ref) + return NULL; + + if (con_id) { + con_id_cpy = kstrdup(con_id, GFP_KERNEL); + if (!con_id_cpy) + return NULL; + } + + ref->dev_id = ida_alloc(&gpio_shared_ida, GFP_KERNEL); + if (ref->dev_id < 0) + return NULL; + + ref->flags = flags; + ref->con_id = no_free_ptr(con_id_cpy); + ref->fwnode = fwnode; + lockdep_register_key(&ref->lock_key); + mutex_init_with_key(&ref->lock, &ref->lock_key); + + return no_free_ptr(ref); +} + +static int gpio_shared_setup_reset_proxy(struct gpio_shared_entry *entry, + enum gpiod_flags flags) +{ + struct gpio_shared_ref *ref; + + list_for_each_entry(ref, &entry->refs, list) { + if (ref->is_reset_gpio) + /* Already set-up. */ + return 0; + } + + ref = gpio_shared_make_ref(NULL, "reset", flags); + if (!ref) + return -ENOMEM; + + ref->is_reset_gpio = true; + + list_add_tail(&ref->list, &entry->refs); + + pr_debug("Created a secondary shared GPIO reference for potential reset-gpio device for GPIO %u at %s\n", + entry->offset, fwnode_get_name(entry->fwnode)); + + return 0; +} + +/* Handle all special nodes that we should ignore. */ +static bool gpio_shared_of_node_ignore(struct device_node *node) +{ + /* Ignore disabled devices. */ + if (!of_device_is_available(node)) + return true; + + /* + * __symbols__ is a special, internal node and should not be considered + * when scanning for shared GPIOs. + */ + if (of_node_name_eq(node, "__symbols__")) + return true; + + /* + * GPIO hogs have a "gpios" property which is not a phandle and can't + * possibly refer to a shared GPIO. + */ + if (of_property_present(node, "gpio-hog")) + return true; + + return false; +} + +static int gpio_shared_of_traverse(struct device_node *curr) +{ + struct gpio_shared_entry *entry; + size_t con_id_len, suffix_len; + struct fwnode_handle *fwnode; + struct of_phandle_args args; + struct gpio_shared_ref *ref; + struct property *prop; + unsigned int offset; + const char *suffix; + int ret, count, i; + + if (gpio_shared_of_node_ignore(curr)) + return 0; + + for_each_property_of_node(curr, prop) { + /* + * The standard name for a GPIO property is "foo-gpios" + * or "foo-gpio". Some bindings also use "gpios" or "gpio". + * There are some legacy device-trees which have a different + * naming convention and for which we have rename quirks in + * place in gpiolib-of.c. I don't think any of them require + * support for shared GPIOs so for now let's just ignore + * them. We can always just export the quirk list and + * iterate over it here. + */ + if (!strends(prop->name, "-gpios") && + !strends(prop->name, "-gpio") && + strcmp(prop->name, "gpios") != 0 && + strcmp(prop->name, "gpio") != 0) + continue; + + count = of_count_phandle_with_args(curr, prop->name, + "#gpio-cells"); + if (count <= 0) + continue; + + for (i = 0; i < count; i++) { + struct device_node *np __free(device_node) = NULL; + char *con_id __free(kfree) = NULL; + + ret = of_parse_phandle_with_args(curr, prop->name, + "#gpio-cells", i, + &args); + if (ret) + continue; + + np = args.np; + + if (!of_property_present(np, "gpio-controller")) + continue; + + /* + * We support 1, 2 and 3 cell GPIO bindings in the + * kernel currently. There's only one old MIPS dts that + * has a one-cell binding but there's no associated + * consumer so it may as well be an error. There don't + * seem to be any 3-cell users of non-exclusive GPIOs, + * so we can skip this as well. Let's occupy ourselves + * with the predominant 2-cell binding with the first + * cell indicating the hardware offset of the GPIO and + * the second defining the GPIO flags of the request. + */ + if (args.args_count != 2) + continue; + + fwnode = of_fwnode_handle(args.np); + offset = args.args[0]; + + entry = gpio_shared_find_entry(fwnode, offset); + if (!entry) { + entry = kzalloc_obj(*entry); + if (!entry) + return -ENOMEM; + + entry->fwnode = fwnode_handle_get(fwnode); + entry->offset = offset; + entry->index = count; + INIT_LIST_HEAD(&entry->refs); + mutex_init(&entry->lock); + + list_add_tail(&entry->list, &gpio_shared_list); + } + + if (strends(prop->name, "gpios")) + suffix = "-gpios"; + else if (strends(prop->name, "gpio")) + suffix = "-gpio"; + else + suffix = NULL; + if (!suffix) + continue; + + /* We only set con_id if there's actually one. */ + if (strcmp(prop->name, "gpios") && strcmp(prop->name, "gpio")) { + con_id = kstrdup(prop->name, GFP_KERNEL); + if (!con_id) + return -ENOMEM; + + con_id_len = strlen(con_id); + suffix_len = strlen(suffix); + + con_id[con_id_len - suffix_len] = '\0'; + } + + ref = gpio_shared_make_ref(fwnode_handle_get(of_fwnode_handle(curr)), + con_id, args.args[1]); + if (!ref) + return -ENOMEM; + + if (!list_empty(&entry->refs)) + pr_debug("GPIO %u at %s is shared by multiple firmware nodes\n", + entry->offset, fwnode_get_name(entry->fwnode)); + + list_add_tail(&ref->list, &entry->refs); + + if (strcmp(prop->name, "reset-gpios") == 0) { + ret = gpio_shared_setup_reset_proxy(entry, args.args[1]); + if (ret) + return ret; + } + } + } + + for_each_child_of_node_scoped(curr, child) { + ret = gpio_shared_of_traverse(child); + if (ret) + return ret; + } + + return 0; +} + +static int gpio_shared_of_scan(void) +{ + if (of_root) + return gpio_shared_of_traverse(of_root); + + return 0; +} +#else +static int gpio_shared_of_scan(void) +{ + return 0; +} +#endif /* CONFIG_OF */ + +static void gpio_shared_adev_release(struct device *dev) +{ + +} + +static int gpio_shared_make_adev(struct gpio_device *gdev, + struct gpio_shared_entry *entry, + struct gpio_shared_ref *ref) +{ + struct auxiliary_device *adev = &ref->adev; + int ret; + + guard(mutex)(&ref->lock); + + memset(adev, 0, sizeof(*adev)); + + adev->id = ref->dev_id; + adev->name = "proxy"; + adev->dev.parent = gdev->dev.parent; + adev->dev.platform_data = entry; + adev->dev.release = gpio_shared_adev_release; + + ret = auxiliary_device_init(adev); + if (ret) + return ret; + + ret = auxiliary_device_add(adev); + if (ret) { + auxiliary_device_uninit(adev); + return ret; + } + + pr_debug("Created an auxiliary GPIO proxy %s for GPIO device %s\n", + dev_name(&adev->dev), gpio_device_get_label(gdev)); + + return 0; +} + +#if IS_ENABLED(CONFIG_RESET_GPIO) +/* + * Special case: reset-gpio is an auxiliary device that's created dynamically + * and put in between the GPIO controller and consumers of shared GPIOs + * referred to by the "reset-gpios" property. + * + * If the supposed consumer of a shared GPIO didn't match any of the mappings + * we created when scanning the firmware nodes, it's still possible that it's + * the reset-gpio device which didn't exist at the time of the scan. + * + * This function verifies it an return true if it's the case. + */ +static bool gpio_shared_dev_is_reset_gpio(struct device *consumer, + struct gpio_shared_entry *entry, + struct gpio_shared_ref *ref) +{ + struct fwnode_handle *reset_fwnode = dev_fwnode(consumer); + struct fwnode_reference_args ref_args, aux_args; + struct device *parent = consumer->parent; + struct gpio_shared_ref *real_ref; + bool match; + int ret; + + lockdep_assert_held(&ref->lock); + + /* The reset-gpio device must have a parent AND a firmware node. */ + if (!parent || !reset_fwnode) + return false; + + /* + * Parent of the reset-gpio auxiliary device is the GPIO chip whose + * fwnode we stored in the entry structure. + */ + if (!device_match_fwnode(parent, entry->fwnode)) + return false; + + /* + * Now we need to find the actual pin we want to assign to this + * reset-gpio device. To that end: iterate over the list of references + * of this entry and see if there's one, whose reset-gpios property's + * arguments match the ones from this consumer's node. + */ + list_for_each_entry(real_ref, &entry->refs, list) { + if (real_ref == ref) + continue; + + guard(mutex)(&real_ref->lock); + + if (!real_ref->fwnode) + continue; + + /* + * The device associated with the shared reference's firmware + * node is the consumer of the reset control exposed by the + * reset-gpio device. It must have a "reset-gpios" property + * that's referencing the entry's firmware node. + * + * The reference args must agree between the real consumer and + * the auxiliary reset-gpio device. + */ + ret = fwnode_property_get_reference_args(real_ref->fwnode, + "reset-gpios", + NULL, 2, 0, &ref_args); + if (ret) + continue; + + ret = fwnode_property_get_reference_args(reset_fwnode, "reset-gpios", + NULL, 2, 0, &aux_args); + if (ret) { + fwnode_handle_put(ref_args.fwnode); + continue; + } + + match = ((ref_args.fwnode == entry->fwnode) && + (aux_args.fwnode == entry->fwnode) && + (ref_args.args[0] == aux_args.args[0])); + + fwnode_handle_put(ref_args.fwnode); + fwnode_handle_put(aux_args.fwnode); + + if (!match) + continue; + + /* + * Reuse the fwnode of the real device, next time we'll use it + * in the normal path. + */ + ref->fwnode = fwnode_handle_get(reset_fwnode); + return true; + } + + return false; +} +#else +static bool gpio_shared_dev_is_reset_gpio(struct device *consumer, + struct gpio_shared_entry *entry, + struct gpio_shared_ref *ref) +{ + return false; +} +#endif /* CONFIG_RESET_GPIO */ + +int gpio_shared_add_proxy_lookup(struct device *consumer, struct fwnode_handle *fwnode, + const char *con_id, unsigned long lflags) +{ + const char *dev_id = dev_name(consumer); + struct gpiod_lookup_table *lookup; + struct gpio_shared_entry *entry; + struct gpio_shared_ref *ref; + + list_for_each_entry(entry, &gpio_shared_list, list) { + list_for_each_entry(ref, &entry->refs, list) { + guard(mutex)(&ref->lock); + + if (!ref->fwnode && device_is_compatible(consumer, "reset-gpio")) { + if (!gpio_shared_dev_is_reset_gpio(consumer, entry, ref)) + continue; + } else if (fwnode != ref->fwnode) { + continue; + } + + if ((!con_id && ref->con_id) || (con_id && !ref->con_id) || + (con_id && ref->con_id && strcmp(con_id, ref->con_id) != 0)) + continue; + + /* We've already done that on a previous request. */ + if (ref->lookup) + return 0; + + char *key __free(kfree) = + kasprintf(GFP_KERNEL, + KBUILD_MODNAME ".proxy.%u", + ref->adev.id); + if (!key) + return -ENOMEM; + + lookup = kzalloc_flex(*lookup, table, 2); + if (!lookup) + return -ENOMEM; + + pr_debug("Adding machine lookup entry for a shared GPIO for consumer %s, with key '%s' and con_id '%s'\n", + dev_id, key, ref->con_id ?: "none"); + + lookup->dev_id = dev_id; + lookup->table[0] = GPIO_LOOKUP(no_free_ptr(key), 0, + ref->con_id, lflags); + + ref->lookup = lookup; + gpiod_add_lookup_table(ref->lookup); + + return 0; + } + } + + /* We warn here because this can only happen if the programmer borked. */ + WARN_ON(1); + return -ENOENT; +} + +static void gpio_shared_remove_adev(struct auxiliary_device *adev) +{ + auxiliary_device_delete(adev); + auxiliary_device_uninit(adev); +} + +int gpiochip_setup_shared(struct gpio_chip *gc) +{ + struct gpio_device *gdev = gc->gpiodev; + struct gpio_shared_entry *entry; + struct gpio_shared_ref *ref; + struct gpio_desc *desc; + int ret; + + list_for_each_entry(entry, &gpio_shared_list, list) { + list_for_each_entry(ref, &entry->refs, list) { + if (gdev->dev.parent == &ref->adev.dev) { + /* + * This is a shared GPIO proxy. Mark its + * descriptor as such and return here. + */ + __set_bit(GPIOD_FLAG_SHARED_PROXY, + &gdev->descs[0].flags); + return 0; + } + } + } + + /* + * This is not a shared GPIO proxy but it still may be the device + * exposing shared pins. Find them and create the proxy devices. + */ + list_for_each_entry(entry, &gpio_shared_list, list) { + if (!device_match_fwnode(&gdev->dev, entry->fwnode)) + continue; + + if (list_count_nodes(&entry->refs) <= 1) + continue; + + scoped_guard(mutex, &entry->lock) { +#if IS_ENABLED(CONFIG_OF) + if (is_of_node(entry->fwnode) && gc->of_xlate) { + /* + * This is the earliest that we can tranlate the + * devicetree offset to the chip offset. + */ + struct of_phandle_args gpiospec = { }; + + gpiospec.np = to_of_node(entry->fwnode); + gpiospec.args_count = 2; + gpiospec.args[0] = entry->offset; + + ret = gc->of_xlate(gc, &gpiospec, NULL); + if (ret < 0) + return ret; + + entry->offset = ret; + } +#endif /* CONFIG_OF */ + + desc = &gdev->descs[entry->offset]; + + __set_bit(GPIOD_FLAG_SHARED, &desc->flags); + /* + * Shared GPIOs are not requested via the normal path. Make + * them inaccessible to anyone even before we register the + * chip. + */ + ret = gpiod_request_commit(desc, "shared"); + if (ret) + return ret; + + pr_debug("GPIO %u owned by %s is shared by multiple consumers\n", + entry->offset, gpio_device_get_label(gdev)); + } + + list_for_each_entry(ref, &entry->refs, list) { + pr_debug("Setting up a shared GPIO entry for %s (con_id: '%s')\n", + fwnode_get_name(ref->fwnode) ?: "(no fwnode)", + ref->con_id ?: "(none)"); + + ret = gpio_shared_make_adev(gdev, entry, ref); + if (ret) { + gpiod_free_commit(desc); + return ret; + } + } + } + + return 0; +} + +void gpio_device_teardown_shared(struct gpio_device *gdev) +{ + struct gpio_shared_entry *entry; + struct gpio_shared_ref *ref; + + list_for_each_entry(entry, &gpio_shared_list, list) { + if (!device_match_fwnode(&gdev->dev, entry->fwnode)) + continue; + + scoped_guard(mutex, &entry->lock) + gpiod_free_commit(&gdev->descs[entry->offset]); + + list_for_each_entry(ref, &entry->refs, list) { + if (ref->lookup) { + gpiod_remove_lookup_table(ref->lookup); + kfree(ref->lookup->table[0].key); + kfree(ref->lookup); + ref->lookup = NULL; + } + + gpio_shared_remove_adev(&ref->adev); + } + } +} + +static void gpio_shared_release(struct kref *kref) +{ + struct gpio_shared_entry *entry = + container_of(kref, struct gpio_shared_entry, ref); + struct gpio_shared_desc *shared_desc; + + guard(mutex)(&entry->lock); + + shared_desc = entry->shared_desc; + gpio_device_put(shared_desc->desc->gdev); + mutex_destroy(&shared_desc->mutex); + kfree(shared_desc); + entry->shared_desc = NULL; +} + +static void gpiod_shared_put(void *data) +{ + struct gpio_shared_entry *entry = data; + + kref_put(&entry->ref, gpio_shared_release); +} + +static struct gpio_shared_desc * +gpiod_shared_desc_create(struct gpio_shared_entry *entry) +{ + struct gpio_shared_desc *shared_desc; + struct gpio_device *gdev; + + lockdep_assert_held(&entry->lock); + + shared_desc = kzalloc_obj(*shared_desc); + if (!shared_desc) + return ERR_PTR(-ENOMEM); + + gdev = gpio_device_find_by_fwnode(entry->fwnode); + if (!gdev) { + kfree(shared_desc); + return ERR_PTR(-EPROBE_DEFER); + } + + shared_desc->desc = &gdev->descs[entry->offset]; + mutex_init(&shared_desc->mutex); + + return shared_desc; +} + +struct gpio_shared_desc *devm_gpiod_shared_get(struct device *dev) +{ + struct gpio_shared_desc *shared_desc; + struct gpio_shared_entry *entry; + int ret; + + entry = dev_get_platdata(dev); + if (WARN_ON(!entry)) + /* Programmer bug */ + return ERR_PTR(-ENOENT); + + scoped_guard(mutex, &entry->lock) { + if (entry->shared_desc) { + kref_get(&entry->ref); + shared_desc = entry->shared_desc; + } else { + shared_desc = gpiod_shared_desc_create(entry); + if (IS_ERR(shared_desc)) + return ERR_CAST(shared_desc); + + kref_init(&entry->ref); + entry->shared_desc = shared_desc; + } + + pr_debug("Device %s acquired a reference to the shared GPIO %u owned by %s\n", + dev_name(dev), gpiod_hwgpio(shared_desc->desc), + gpio_device_get_label(shared_desc->desc->gdev)); + } + + ret = devm_add_action_or_reset(dev, gpiod_shared_put, entry); + if (ret) + return ERR_PTR(ret); + + return shared_desc; +} +EXPORT_SYMBOL_GPL(devm_gpiod_shared_get); + +static void gpio_shared_drop_ref(struct gpio_shared_ref *ref) +{ + list_del(&ref->list); + mutex_destroy(&ref->lock); + lockdep_unregister_key(&ref->lock_key); + kfree(ref->con_id); + ida_free(&gpio_shared_ida, ref->dev_id); + fwnode_handle_put(ref->fwnode); + kfree(ref); +} + +static void gpio_shared_drop_entry(struct gpio_shared_entry *entry) +{ + list_del(&entry->list); + mutex_destroy(&entry->lock); + fwnode_handle_put(entry->fwnode); + kfree(entry); +} + +/* + * This is only called if gpio_shared_init() fails so it's in fact __init and + * not __exit. + */ +static void __init gpio_shared_teardown(void) +{ + struct gpio_shared_entry *entry, *epos; + struct gpio_shared_ref *ref, *rpos; + + list_for_each_entry_safe(entry, epos, &gpio_shared_list, list) { + list_for_each_entry_safe(ref, rpos, &entry->refs, list) + gpio_shared_drop_ref(ref); + + gpio_shared_drop_entry(entry); + } +} + +static bool gpio_shared_entry_is_really_shared(struct gpio_shared_entry *entry) +{ + size_t num_nodes = list_count_nodes(&entry->refs); + struct gpio_shared_ref *ref; + + if (num_nodes <= 1) + return false; + + if (num_nodes > 2) + return true; + + /* Exactly two references: */ + list_for_each_entry(ref, &entry->refs, list) { + /* + * Corner-case: the second reference comes from the potential + * reset-gpio instance. However, this pin is not really shared + * as it would have three references in this case. Avoid + * creating unnecessary proxies. + */ + if (ref->is_reset_gpio) + return false; + } + + return true; +} + +static void gpio_shared_free_exclusive(void) +{ + struct gpio_shared_entry *entry, *epos; + struct gpio_shared_ref *ref, *rpos; + + list_for_each_entry_safe(entry, epos, &gpio_shared_list, list) { + if (gpio_shared_entry_is_really_shared(entry)) + continue; + + list_for_each_entry_safe(ref, rpos, &entry->refs, list) + gpio_shared_drop_ref(ref); + gpio_shared_drop_entry(entry); + } +} + +static int __init gpio_shared_init(void) +{ + int ret; + + /* Right now, we only support OF-based systems. */ + ret = gpio_shared_of_scan(); + if (ret) { + gpio_shared_teardown(); + pr_err("Failed to scan OF nodes for shared GPIOs: %d\n", ret); + return ret; + } + + gpio_shared_free_exclusive(); + + pr_debug("Finished scanning firmware nodes for shared GPIOs\n"); + return 0; +} +postcore_initcall(gpio_shared_init); |