diff options
Diffstat (limited to 'drivers/hwspinlock/hwspinlock_core.c')
| -rw-r--r-- | drivers/hwspinlock/hwspinlock_core.c | 548 |
1 files changed, 548 insertions, 0 deletions
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c new file mode 100644 index 000000000000..43a62714b4fb --- /dev/null +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -0,0 +1,548 @@ +/* + * Hardware spinlock framework + * + * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com + * + * Contact: Ohad Ben-Cohen <[email protected]> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published + * by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#define pr_fmt(fmt) "%s: " fmt, __func__ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/spinlock.h> +#include <linux/types.h> +#include <linux/err.h> +#include <linux/jiffies.h> +#include <linux/radix-tree.h> +#include <linux/hwspinlock.h> +#include <linux/pm_runtime.h> + +#include "hwspinlock_internal.h" + +/* radix tree tags */ +#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */ + +/* + * A radix tree is used to maintain the available hwspinlock instances. + * The tree associates hwspinlock pointers with their integer key id, + * and provides easy-to-use API which makes the hwspinlock core code simple + * and easy to read. + * + * Radix trees are quick on lookups, and reasonably efficient in terms of + * storage, especially with high density usages such as this framework + * requires (a continuous range of integer keys, beginning with zero, is + * used as the ID's of the hwspinlock instances). + * + * The radix tree API supports tagging items in the tree, which this + * framework uses to mark unused hwspinlock instances (see the + * HWSPINLOCK_UNUSED tag above). As a result, the process of querying the + * tree, looking for an unused hwspinlock instance, is now reduced to a + * single radix tree API call. + */ +static RADIX_TREE(hwspinlock_tree, GFP_KERNEL); + +/* + * Synchronization of access to the tree is achieved using this spinlock, + * as the radix-tree API requires that users provide all synchronisation. + */ +static DEFINE_SPINLOCK(hwspinlock_tree_lock); + +/** + * __hwspin_trylock() - attempt to lock a specific hwspinlock + * @hwlock: an hwspinlock which we want to trylock + * @mode: controls whether local interrupts are disabled or not + * @flags: a pointer where the caller's interrupt state will be saved at (if + * requested) + * + * This function attempts to lock an hwspinlock, and will immediately + * fail if the hwspinlock is already taken. + * + * Upon a successful return from this function, preemption (and possibly + * interrupts) is disabled, so the caller must not sleep, and is advised to + * release the hwspinlock as soon as possible. This is required in order to + * minimize remote cores polling on the hardware interconnect. + * + * The user decides whether local interrupts are disabled or not, and if yes, + * whether he wants their previous state to be saved. It is up to the user + * to choose the appropriate @mode of operation, exactly the same way users + * should decide between spin_trylock, spin_trylock_irq and + * spin_trylock_irqsave. + * + * Returns 0 if we successfully locked the hwspinlock or -EBUSY if + * the hwspinlock was already taken. + * This function will never sleep. + */ +int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags) +{ + int ret; + + BUG_ON(!hwlock); + BUG_ON(!flags && mode == HWLOCK_IRQSTATE); + + /* + * This spin_lock{_irq, _irqsave} serves three purposes: + * + * 1. Disable preemption, in order to minimize the period of time + * in which the hwspinlock is taken. This is important in order + * to minimize the possible polling on the hardware interconnect + * by a remote user of this lock. + * 2. Make the hwspinlock SMP-safe (so we can take it from + * additional contexts on the local host). + * 3. Ensure that in_atomic/might_sleep checks catch potential + * problems with hwspinlock usage (e.g. scheduler checks like + * 'scheduling while atomic' etc.) + */ + if (mode == HWLOCK_IRQSTATE) + ret = spin_trylock_irqsave(&hwlock->lock, *flags); + else if (mode == HWLOCK_IRQ) + ret = spin_trylock_irq(&hwlock->lock); + else + ret = spin_trylock(&hwlock->lock); + + /* is lock already taken by another context on the local cpu ? */ + if (!ret) + return -EBUSY; + + /* try to take the hwspinlock device */ + ret = hwlock->ops->trylock(hwlock); + + /* if hwlock is already taken, undo spin_trylock_* and exit */ + if (!ret) { + if (mode == HWLOCK_IRQSTATE) + spin_unlock_irqrestore(&hwlock->lock, *flags); + else if (mode == HWLOCK_IRQ) + spin_unlock_irq(&hwlock->lock); + else + spin_unlock(&hwlock->lock); + + return -EBUSY; + } + + /* + * We can be sure the other core's memory operations + * are observable to us only _after_ we successfully take + * the hwspinlock, and we must make sure that subsequent memory + * operations (both reads and writes) will not be reordered before + * we actually took the hwspinlock. + * + * Note: the implicit memory barrier of the spinlock above is too + * early, so we need this additional explicit memory barrier. + */ + mb(); + + return 0; +} +EXPORT_SYMBOL_GPL(__hwspin_trylock); + +/** + * __hwspin_lock_timeout() - lock an hwspinlock with timeout limit + * @hwlock: the hwspinlock to be locked + * @timeout: timeout value in msecs + * @mode: mode which controls whether local interrupts are disabled or not + * @flags: a pointer to where the caller's interrupt state will be saved at (if + * requested) + * + * This function locks the given @hwlock. If the @hwlock + * is already taken, the function will busy loop waiting for it to + * be released, but give up after @timeout msecs have elapsed. + * + * Upon a successful return from this function, preemption is disabled + * (and possibly local interrupts, too), so the caller must not sleep, + * and is advised to release the hwspinlock as soon as possible. + * This is required in order to minimize remote cores polling on the + * hardware interconnect. + * + * The user decides whether local interrupts are disabled or not, and if yes, + * whether he wants their previous state to be saved. It is up to the user + * to choose the appropriate @mode of operation, exactly the same way users + * should decide between spin_lock, spin_lock_irq and spin_lock_irqsave. + * + * Returns 0 when the @hwlock was successfully taken, and an appropriate + * error code otherwise (most notably -ETIMEDOUT if the @hwlock is still + * busy after @timeout msecs). The function will never sleep. + */ +int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to, + int mode, unsigned long *flags) +{ + int ret; + unsigned long expire; + + expire = msecs_to_jiffies(to) + jiffies; + + for (;;) { + /* Try to take the hwspinlock */ + ret = __hwspin_trylock(hwlock, mode, flags); + if (ret != -EBUSY) + break; + + /* + * The lock is already taken, let's check if the user wants + * us to try again + */ + if (time_is_before_eq_jiffies(expire)) + return -ETIMEDOUT; + + /* + * Allow platform-specific relax handlers to prevent + * hogging the interconnect (no sleeping, though) + */ + if (hwlock->ops->relax) + hwlock->ops->relax(hwlock); + } + + return ret; +} +EXPORT_SYMBOL_GPL(__hwspin_lock_timeout); + +/** + * __hwspin_unlock() - unlock a specific hwspinlock + * @hwlock: a previously-acquired hwspinlock which we want to unlock + * @mode: controls whether local interrupts needs to be restored or not + * @flags: previous caller's interrupt state to restore (if requested) + * + * This function will unlock a specific hwspinlock, enable preemption and + * (possibly) enable interrupts or restore their previous state. + * @hwlock must be already locked before calling this function: it is a bug + * to call unlock on a @hwlock that is already unlocked. + * + * The user decides whether local interrupts should be enabled or not, and + * if yes, whether he wants their previous state to be restored. It is up + * to the user to choose the appropriate @mode of operation, exactly the + * same way users decide between spin_unlock, spin_unlock_irq and + * spin_unlock_irqrestore. + * + * The function will never sleep. + */ +void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags) +{ + BUG_ON(!hwlock); + BUG_ON(!flags && mode == HWLOCK_IRQSTATE); + + /* + * We must make sure that memory operations (both reads and writes), + * done before unlocking the hwspinlock, will not be reordered + * after the lock is released. + * + * That's the purpose of this explicit memory barrier. + * + * Note: the memory barrier induced by the spin_unlock below is too + * late; the other core is going to access memory soon after it will + * take the hwspinlock, and by then we want to be sure our memory + * operations are already observable. + */ + mb(); + + hwlock->ops->unlock(hwlock); + + /* Undo the spin_trylock{_irq, _irqsave} called while locking */ + if (mode == HWLOCK_IRQSTATE) + spin_unlock_irqrestore(&hwlock->lock, *flags); + else if (mode == HWLOCK_IRQ) + spin_unlock_irq(&hwlock->lock); + else + spin_unlock(&hwlock->lock); +} +EXPORT_SYMBOL_GPL(__hwspin_unlock); + +/** + * hwspin_lock_register() - register a new hw spinlock + * @hwlock: hwspinlock to register. + * + * This function should be called from the underlying platform-specific + * implementation, to register a new hwspinlock instance. + * + * Can be called from an atomic context (will not sleep) but not from + * within interrupt context. + * + * Returns 0 on success, or an appropriate error code on failure + */ +int hwspin_lock_register(struct hwspinlock *hwlock) +{ + struct hwspinlock *tmp; + int ret; + + if (!hwlock || !hwlock->ops || + !hwlock->ops->trylock || !hwlock->ops->unlock) { + pr_err("invalid parameters\n"); + return -EINVAL; + } + + spin_lock_init(&hwlock->lock); + + spin_lock(&hwspinlock_tree_lock); + + ret = radix_tree_insert(&hwspinlock_tree, hwlock->id, hwlock); + if (ret) + goto out; + + /* mark this hwspinlock as available */ + tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock->id, + HWSPINLOCK_UNUSED); + + /* self-sanity check which should never fail */ + WARN_ON(tmp != hwlock); + +out: + spin_unlock(&hwspinlock_tree_lock); + return ret; +} +EXPORT_SYMBOL_GPL(hwspin_lock_register); + +/** + * hwspin_lock_unregister() - unregister an hw spinlock + * @id: index of the specific hwspinlock to unregister + * + * This function should be called from the underlying platform-specific + * implementation, to unregister an existing (and unused) hwspinlock. + * + * Can be called from an atomic context (will not sleep) but not from + * within interrupt context. + * + * Returns the address of hwspinlock @id on success, or NULL on failure + */ +struct hwspinlock *hwspin_lock_unregister(unsigned int id) +{ + struct hwspinlock *hwlock = NULL; + int ret; + + spin_lock(&hwspinlock_tree_lock); + + /* make sure the hwspinlock is not in use (tag is set) */ + ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); + if (ret == 0) { + pr_err("hwspinlock %d still in use (or not present)\n", id); + goto out; + } + + hwlock = radix_tree_delete(&hwspinlock_tree, id); + if (!hwlock) { + pr_err("failed to delete hwspinlock %d\n", id); + goto out; + } + +out: + spin_unlock(&hwspinlock_tree_lock); + return hwlock; +} +EXPORT_SYMBOL_GPL(hwspin_lock_unregister); + +/** + * __hwspin_lock_request() - tag an hwspinlock as used and power it up + * + * This is an internal function that prepares an hwspinlock instance + * before it is given to the user. The function assumes that + * hwspinlock_tree_lock is taken. + * + * Returns 0 or positive to indicate success, and a negative value to + * indicate an error (with the appropriate error code) + */ +static int __hwspin_lock_request(struct hwspinlock *hwlock) +{ + struct hwspinlock *tmp; + int ret; + + /* prevent underlying implementation from being removed */ + if (!try_module_get(hwlock->owner)) { + dev_err(hwlock->dev, "%s: can't get owner\n", __func__); + return -EINVAL; + } + + /* notify PM core that power is now needed */ + ret = pm_runtime_get_sync(hwlock->dev); + if (ret < 0) { + dev_err(hwlock->dev, "%s: can't power on device\n", __func__); + return ret; + } + + /* mark hwspinlock as used, should not fail */ + tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock->id, + HWSPINLOCK_UNUSED); + + /* self-sanity check that should never fail */ + WARN_ON(tmp != hwlock); + + return ret; +} + +/** + * hwspin_lock_get_id() - retrieve id number of a given hwspinlock + * @hwlock: a valid hwspinlock instance + * + * Returns the id number of a given @hwlock, or -EINVAL if @hwlock is invalid. + */ +int hwspin_lock_get_id(struct hwspinlock *hwlock) +{ + if (!hwlock) { + pr_err("invalid hwlock\n"); + return -EINVAL; + } + + return hwlock->id; +} +EXPORT_SYMBOL_GPL(hwspin_lock_get_id); + +/** + * hwspin_lock_request() - request an hwspinlock + * + * This function should be called by users of the hwspinlock device, + * in order to dynamically assign them an unused hwspinlock. + * Usually the user of this lock will then have to communicate the lock's id + * to the remote core before it can be used for synchronization (to get the + * id of a given hwlock, use hwspin_lock_get_id()). + * + * Can be called from an atomic context (will not sleep) but not from + * within interrupt context (simply because there is no use case for + * that yet). + * + * Returns the address of the assigned hwspinlock, or NULL on error + */ +struct hwspinlock *hwspin_lock_request(void) +{ + struct hwspinlock *hwlock; + int ret; + + spin_lock(&hwspinlock_tree_lock); + + /* look for an unused lock */ + ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock, + 0, 1, HWSPINLOCK_UNUSED); + if (ret == 0) { + pr_warn("a free hwspinlock is not available\n"); + hwlock = NULL; + goto out; + } + + /* sanity check that should never fail */ + WARN_ON(ret > 1); + + /* mark as used and power up */ + ret = __hwspin_lock_request(hwlock); + if (ret < 0) + hwlock = NULL; + +out: + spin_unlock(&hwspinlock_tree_lock); + return hwlock; +} +EXPORT_SYMBOL_GPL(hwspin_lock_request); + +/** + * hwspin_lock_request_specific() - request for a specific hwspinlock + * @id: index of the specific hwspinlock that is requested + * + * This function should be called by users of the hwspinlock module, + * in order to assign them a specific hwspinlock. + * Usually early board code will be calling this function in order to + * reserve specific hwspinlock ids for predefined purposes. + * + * Can be called from an atomic context (will not sleep) but not from + * within interrupt context (simply because there is no use case for + * that yet). + * + * Returns the address of the assigned hwspinlock, or NULL on error + */ +struct hwspinlock *hwspin_lock_request_specific(unsigned int id) +{ + struct hwspinlock *hwlock; + int ret; + + spin_lock(&hwspinlock_tree_lock); + + /* make sure this hwspinlock exists */ + hwlock = radix_tree_lookup(&hwspinlock_tree, id); + if (!hwlock) { + pr_warn("hwspinlock %u does not exist\n", id); + goto out; + } + + /* sanity check (this shouldn't happen) */ + WARN_ON(hwlock->id != id); + + /* make sure this hwspinlock is unused */ + ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); + if (ret == 0) { + pr_warn("hwspinlock %u is already in use\n", id); + hwlock = NULL; + goto out; + } + + /* mark as used and power up */ + ret = __hwspin_lock_request(hwlock); + if (ret < 0) + hwlock = NULL; + +out: + spin_unlock(&hwspinlock_tree_lock); + return hwlock; +} +EXPORT_SYMBOL_GPL(hwspin_lock_request_specific); + +/** + * hwspin_lock_free() - free a specific hwspinlock + * @hwlock: the specific hwspinlock to free + * + * This function mark @hwlock as free again. + * Should only be called with an @hwlock that was retrieved from + * an earlier call to omap_hwspin_lock_request{_specific}. + * + * Can be called from an atomic context (will not sleep) but not from + * within interrupt context (simply because there is no use case for + * that yet). + * + * Returns 0 on success, or an appropriate error code on failure + */ +int hwspin_lock_free(struct hwspinlock *hwlock) +{ + struct hwspinlock *tmp; + int ret; + + if (!hwlock) { + pr_err("invalid hwlock\n"); + return -EINVAL; + } + + spin_lock(&hwspinlock_tree_lock); + + /* make sure the hwspinlock is used */ + ret = radix_tree_tag_get(&hwspinlock_tree, hwlock->id, + HWSPINLOCK_UNUSED); + if (ret == 1) { + dev_err(hwlock->dev, "%s: hwlock is already free\n", __func__); + dump_stack(); + ret = -EINVAL; + goto out; + } + + /* notify the underlying device that power is not needed */ + ret = pm_runtime_put(hwlock->dev); + if (ret < 0) + goto out; + + /* mark this hwspinlock as available */ + tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock->id, + HWSPINLOCK_UNUSED); + + /* sanity check (this shouldn't happen) */ + WARN_ON(tmp != hwlock); + + module_put(hwlock->owner); + +out: + spin_unlock(&hwspinlock_tree_lock); + return ret; +} +EXPORT_SYMBOL_GPL(hwspin_lock_free); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("Hardware spinlock interface"); +MODULE_AUTHOR("Ohad Ben-Cohen <[email protected]>"); |