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![Ohad Ben-Cohen](/assets/img/avatar_default.png)
Hardware Spinlock devices usually contain numerous locks (known devices today support between 32 to 256 locks). Originally hwspinlock core required drivers to register (and later, when needed, unregister) each lock separately. That worked, but required hwspinlocks drivers to do a bit extra work when they were probed/removed. This patch changes hwspin_lock_{un}register() to allow a bank of hwspinlocks to be {un}registered in a single invocation. A new 'struct hwspinlock_device', which contains an array of 'struct hwspinlock's is now being passed to the core upon registration (so instead of wrapping each struct hwspinlock, a priv member has been added to allow drivers to piggyback their private data with each hwspinlock). While at it, several per-lock members were moved to be per-device: 1. struct device *dev 2. struct hwspinlock_ops *ops In addition, now that the array of locks is handled by the core, there's no reason to maintain a per-lock 'int id' member: the id of the lock anyway equals to its index in the bank's array plus the bank's base_id. Remove this per-lock id member too, and instead use a simple pointers arithmetic to derive it. As a result of this change, hwspinlocks drivers are now simpler and smaller (about %20 code reduction) and the memory footprint of the hwspinlock framework is reduced. Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
598 lines
18 KiB
C
598 lines
18 KiB
C
/*
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* Hardware spinlock framework
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*
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* Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
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*
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* Contact: Ohad Ben-Cohen <ohad@wizery.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#define pr_fmt(fmt) "%s: " fmt, __func__
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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#include <linux/err.h>
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#include <linux/jiffies.h>
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#include <linux/radix-tree.h>
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#include <linux/hwspinlock.h>
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#include <linux/pm_runtime.h>
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#include <linux/mutex.h>
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#include "hwspinlock_internal.h"
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/* radix tree tags */
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#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */
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/*
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* A radix tree is used to maintain the available hwspinlock instances.
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* The tree associates hwspinlock pointers with their integer key id,
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* and provides easy-to-use API which makes the hwspinlock core code simple
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* and easy to read.
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*
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* Radix trees are quick on lookups, and reasonably efficient in terms of
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* storage, especially with high density usages such as this framework
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* requires (a continuous range of integer keys, beginning with zero, is
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* used as the ID's of the hwspinlock instances).
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*
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* The radix tree API supports tagging items in the tree, which this
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* framework uses to mark unused hwspinlock instances (see the
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* HWSPINLOCK_UNUSED tag above). As a result, the process of querying the
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* tree, looking for an unused hwspinlock instance, is now reduced to a
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* single radix tree API call.
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*/
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static RADIX_TREE(hwspinlock_tree, GFP_KERNEL);
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/*
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* Synchronization of access to the tree is achieved using this mutex,
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* as the radix-tree API requires that users provide all synchronisation.
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* A mutex is needed because we're using non-atomic radix tree allocations.
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*/
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static DEFINE_MUTEX(hwspinlock_tree_lock);
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/**
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* __hwspin_trylock() - attempt to lock a specific hwspinlock
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* @hwlock: an hwspinlock which we want to trylock
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* @mode: controls whether local interrupts are disabled or not
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* @flags: a pointer where the caller's interrupt state will be saved at (if
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* requested)
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*
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* This function attempts to lock an hwspinlock, and will immediately
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* fail if the hwspinlock is already taken.
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*
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* Upon a successful return from this function, preemption (and possibly
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* interrupts) is disabled, so the caller must not sleep, and is advised to
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* release the hwspinlock as soon as possible. This is required in order to
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* minimize remote cores polling on the hardware interconnect.
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*
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* The user decides whether local interrupts are disabled or not, and if yes,
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* whether he wants their previous state to be saved. It is up to the user
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* to choose the appropriate @mode of operation, exactly the same way users
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* should decide between spin_trylock, spin_trylock_irq and
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* spin_trylock_irqsave.
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*
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* Returns 0 if we successfully locked the hwspinlock or -EBUSY if
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* the hwspinlock was already taken.
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* This function will never sleep.
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*/
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int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
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{
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int ret;
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BUG_ON(!hwlock);
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BUG_ON(!flags && mode == HWLOCK_IRQSTATE);
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/*
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* This spin_lock{_irq, _irqsave} serves three purposes:
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*
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* 1. Disable preemption, in order to minimize the period of time
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* in which the hwspinlock is taken. This is important in order
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* to minimize the possible polling on the hardware interconnect
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* by a remote user of this lock.
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* 2. Make the hwspinlock SMP-safe (so we can take it from
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* additional contexts on the local host).
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* 3. Ensure that in_atomic/might_sleep checks catch potential
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* problems with hwspinlock usage (e.g. scheduler checks like
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* 'scheduling while atomic' etc.)
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*/
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if (mode == HWLOCK_IRQSTATE)
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ret = spin_trylock_irqsave(&hwlock->lock, *flags);
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else if (mode == HWLOCK_IRQ)
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ret = spin_trylock_irq(&hwlock->lock);
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else
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ret = spin_trylock(&hwlock->lock);
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/* is lock already taken by another context on the local cpu ? */
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if (!ret)
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return -EBUSY;
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/* try to take the hwspinlock device */
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ret = hwlock->bank->ops->trylock(hwlock);
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/* if hwlock is already taken, undo spin_trylock_* and exit */
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if (!ret) {
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if (mode == HWLOCK_IRQSTATE)
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spin_unlock_irqrestore(&hwlock->lock, *flags);
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else if (mode == HWLOCK_IRQ)
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spin_unlock_irq(&hwlock->lock);
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else
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spin_unlock(&hwlock->lock);
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return -EBUSY;
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}
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/*
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* We can be sure the other core's memory operations
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* are observable to us only _after_ we successfully take
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* the hwspinlock, and we must make sure that subsequent memory
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* operations (both reads and writes) will not be reordered before
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* we actually took the hwspinlock.
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*
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* Note: the implicit memory barrier of the spinlock above is too
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* early, so we need this additional explicit memory barrier.
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*/
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mb();
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return 0;
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}
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EXPORT_SYMBOL_GPL(__hwspin_trylock);
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/**
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* __hwspin_lock_timeout() - lock an hwspinlock with timeout limit
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* @hwlock: the hwspinlock to be locked
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* @timeout: timeout value in msecs
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* @mode: mode which controls whether local interrupts are disabled or not
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* @flags: a pointer to where the caller's interrupt state will be saved at (if
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* requested)
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*
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* This function locks the given @hwlock. If the @hwlock
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* is already taken, the function will busy loop waiting for it to
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* be released, but give up after @timeout msecs have elapsed.
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*
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* Upon a successful return from this function, preemption is disabled
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* (and possibly local interrupts, too), so the caller must not sleep,
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* and is advised to release the hwspinlock as soon as possible.
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* This is required in order to minimize remote cores polling on the
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* hardware interconnect.
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*
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* The user decides whether local interrupts are disabled or not, and if yes,
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* whether he wants their previous state to be saved. It is up to the user
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* to choose the appropriate @mode of operation, exactly the same way users
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* should decide between spin_lock, spin_lock_irq and spin_lock_irqsave.
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*
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* Returns 0 when the @hwlock was successfully taken, and an appropriate
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* error code otherwise (most notably -ETIMEDOUT if the @hwlock is still
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* busy after @timeout msecs). The function will never sleep.
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*/
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int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
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int mode, unsigned long *flags)
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{
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int ret;
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unsigned long expire;
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expire = msecs_to_jiffies(to) + jiffies;
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for (;;) {
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/* Try to take the hwspinlock */
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ret = __hwspin_trylock(hwlock, mode, flags);
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if (ret != -EBUSY)
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break;
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/*
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* The lock is already taken, let's check if the user wants
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* us to try again
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*/
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if (time_is_before_eq_jiffies(expire))
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return -ETIMEDOUT;
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/*
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* Allow platform-specific relax handlers to prevent
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* hogging the interconnect (no sleeping, though)
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*/
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if (hwlock->bank->ops->relax)
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hwlock->bank->ops->relax(hwlock);
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}
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return ret;
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}
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EXPORT_SYMBOL_GPL(__hwspin_lock_timeout);
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/**
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* __hwspin_unlock() - unlock a specific hwspinlock
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* @hwlock: a previously-acquired hwspinlock which we want to unlock
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* @mode: controls whether local interrupts needs to be restored or not
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* @flags: previous caller's interrupt state to restore (if requested)
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*
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* This function will unlock a specific hwspinlock, enable preemption and
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* (possibly) enable interrupts or restore their previous state.
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* @hwlock must be already locked before calling this function: it is a bug
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* to call unlock on a @hwlock that is already unlocked.
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*
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* The user decides whether local interrupts should be enabled or not, and
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* if yes, whether he wants their previous state to be restored. It is up
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* to the user to choose the appropriate @mode of operation, exactly the
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* same way users decide between spin_unlock, spin_unlock_irq and
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* spin_unlock_irqrestore.
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*
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* The function will never sleep.
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*/
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void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
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{
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BUG_ON(!hwlock);
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BUG_ON(!flags && mode == HWLOCK_IRQSTATE);
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/*
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* We must make sure that memory operations (both reads and writes),
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* done before unlocking the hwspinlock, will not be reordered
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* after the lock is released.
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*
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* That's the purpose of this explicit memory barrier.
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*
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* Note: the memory barrier induced by the spin_unlock below is too
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* late; the other core is going to access memory soon after it will
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* take the hwspinlock, and by then we want to be sure our memory
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* operations are already observable.
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*/
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mb();
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hwlock->bank->ops->unlock(hwlock);
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/* Undo the spin_trylock{_irq, _irqsave} called while locking */
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if (mode == HWLOCK_IRQSTATE)
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spin_unlock_irqrestore(&hwlock->lock, *flags);
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else if (mode == HWLOCK_IRQ)
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spin_unlock_irq(&hwlock->lock);
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else
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spin_unlock(&hwlock->lock);
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}
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EXPORT_SYMBOL_GPL(__hwspin_unlock);
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static int hwspin_lock_register_single(struct hwspinlock *hwlock, int id)
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{
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struct hwspinlock *tmp;
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int ret;
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mutex_lock(&hwspinlock_tree_lock);
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ret = radix_tree_insert(&hwspinlock_tree, id, hwlock);
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if (ret) {
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if (ret == -EEXIST)
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pr_err("hwspinlock id %d already exists!\n", id);
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goto out;
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}
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/* mark this hwspinlock as available */
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tmp = radix_tree_tag_set(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
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/* self-sanity check which should never fail */
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WARN_ON(tmp != hwlock);
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out:
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mutex_unlock(&hwspinlock_tree_lock);
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return 0;
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}
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static struct hwspinlock *hwspin_lock_unregister_single(unsigned int id)
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{
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struct hwspinlock *hwlock = NULL;
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int ret;
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mutex_lock(&hwspinlock_tree_lock);
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/* make sure the hwspinlock is not in use (tag is set) */
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ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
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if (ret == 0) {
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pr_err("hwspinlock %d still in use (or not present)\n", id);
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goto out;
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}
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hwlock = radix_tree_delete(&hwspinlock_tree, id);
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if (!hwlock) {
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pr_err("failed to delete hwspinlock %d\n", id);
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goto out;
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}
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out:
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mutex_unlock(&hwspinlock_tree_lock);
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return hwlock;
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}
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/**
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* hwspin_lock_register() - register a new hw spinlock device
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* @bank: the hwspinlock device, which usually provides numerous hw locks
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* @dev: the backing device
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* @ops: hwspinlock handlers for this device
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* @base_id: id of the first hardware spinlock in this bank
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* @num_locks: number of hwspinlocks provided by this device
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*
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* This function should be called from the underlying platform-specific
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* implementation, to register a new hwspinlock device instance.
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*
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* Should be called from a process context (might sleep)
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*
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* Returns 0 on success, or an appropriate error code on failure
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*/
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int hwspin_lock_register(struct hwspinlock_device *bank, struct device *dev,
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const struct hwspinlock_ops *ops, int base_id, int num_locks)
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{
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struct hwspinlock *hwlock;
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int ret = 0, i;
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if (!bank || !ops || !dev || !num_locks || !ops->trylock ||
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!ops->unlock) {
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pr_err("invalid parameters\n");
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return -EINVAL;
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}
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bank->dev = dev;
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bank->ops = ops;
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bank->base_id = base_id;
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bank->num_locks = num_locks;
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for (i = 0; i < num_locks; i++) {
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hwlock = &bank->lock[i];
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spin_lock_init(&hwlock->lock);
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hwlock->bank = bank;
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ret = hwspin_lock_register_single(hwlock, i);
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if (ret)
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goto reg_failed;
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}
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return 0;
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reg_failed:
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while (--i >= 0)
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hwspin_lock_unregister_single(i);
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return ret;
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}
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EXPORT_SYMBOL_GPL(hwspin_lock_register);
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/**
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* hwspin_lock_unregister() - unregister an hw spinlock device
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* @bank: the hwspinlock device, which usually provides numerous hw locks
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*
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* This function should be called from the underlying platform-specific
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* implementation, to unregister an existing (and unused) hwspinlock.
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*
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* Should be called from a process context (might sleep)
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*
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* Returns 0 on success, or an appropriate error code on failure
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*/
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int hwspin_lock_unregister(struct hwspinlock_device *bank)
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{
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struct hwspinlock *hwlock, *tmp;
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int i;
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for (i = 0; i < bank->num_locks; i++) {
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hwlock = &bank->lock[i];
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tmp = hwspin_lock_unregister_single(bank->base_id + i);
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if (!tmp)
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return -EBUSY;
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/* self-sanity check that should never fail */
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WARN_ON(tmp != hwlock);
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(hwspin_lock_unregister);
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/**
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* __hwspin_lock_request() - tag an hwspinlock as used and power it up
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*
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* This is an internal function that prepares an hwspinlock instance
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* before it is given to the user. The function assumes that
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* hwspinlock_tree_lock is taken.
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*
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* Returns 0 or positive to indicate success, and a negative value to
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* indicate an error (with the appropriate error code)
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*/
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static int __hwspin_lock_request(struct hwspinlock *hwlock)
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{
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struct device *dev = hwlock->bank->dev;
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struct hwspinlock *tmp;
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int ret;
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/* prevent underlying implementation from being removed */
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if (!try_module_get(dev->driver->owner)) {
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dev_err(dev, "%s: can't get owner\n", __func__);
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return -EINVAL;
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}
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/* notify PM core that power is now needed */
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ret = pm_runtime_get_sync(dev);
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if (ret < 0) {
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dev_err(dev, "%s: can't power on device\n", __func__);
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return ret;
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}
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/* mark hwspinlock as used, should not fail */
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tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock),
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HWSPINLOCK_UNUSED);
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/* self-sanity check that should never fail */
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WARN_ON(tmp != hwlock);
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return ret;
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}
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/**
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* hwspin_lock_get_id() - retrieve id number of a given hwspinlock
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* @hwlock: a valid hwspinlock instance
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*
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* Returns the id number of a given @hwlock, or -EINVAL if @hwlock is invalid.
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*/
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int hwspin_lock_get_id(struct hwspinlock *hwlock)
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{
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if (!hwlock) {
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pr_err("invalid hwlock\n");
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return -EINVAL;
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}
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return hwlock_to_id(hwlock);
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}
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EXPORT_SYMBOL_GPL(hwspin_lock_get_id);
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/**
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* hwspin_lock_request() - request an hwspinlock
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*
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* This function should be called by users of the hwspinlock device,
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* in order to dynamically assign them an unused hwspinlock.
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* Usually the user of this lock will then have to communicate the lock's id
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* to the remote core before it can be used for synchronization (to get the
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* id of a given hwlock, use hwspin_lock_get_id()).
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*
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* Should be called from a process context (might sleep)
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*
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* Returns the address of the assigned hwspinlock, or NULL on error
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*/
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struct hwspinlock *hwspin_lock_request(void)
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{
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struct hwspinlock *hwlock;
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int ret;
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mutex_lock(&hwspinlock_tree_lock);
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/* look for an unused lock */
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ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock,
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0, 1, HWSPINLOCK_UNUSED);
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if (ret == 0) {
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pr_warn("a free hwspinlock is not available\n");
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hwlock = NULL;
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goto out;
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}
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/* sanity check that should never fail */
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WARN_ON(ret > 1);
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/* mark as used and power up */
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ret = __hwspin_lock_request(hwlock);
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if (ret < 0)
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hwlock = NULL;
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out:
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mutex_unlock(&hwspinlock_tree_lock);
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return hwlock;
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}
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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.
|
|
*
|
|
* Should be called from a process context (might sleep)
|
|
*
|
|
* 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;
|
|
|
|
mutex_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_to_id(hwlock) != 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:
|
|
mutex_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}.
|
|
*
|
|
* Should be called from a process context (might sleep)
|
|
*
|
|
* Returns 0 on success, or an appropriate error code on failure
|
|
*/
|
|
int hwspin_lock_free(struct hwspinlock *hwlock)
|
|
{
|
|
struct device *dev = hwlock->bank->dev;
|
|
struct hwspinlock *tmp;
|
|
int ret;
|
|
|
|
if (!hwlock) {
|
|
pr_err("invalid hwlock\n");
|
|
return -EINVAL;
|
|
}
|
|
|
|
mutex_lock(&hwspinlock_tree_lock);
|
|
|
|
/* make sure the hwspinlock is used */
|
|
ret = radix_tree_tag_get(&hwspinlock_tree, hwlock_to_id(hwlock),
|
|
HWSPINLOCK_UNUSED);
|
|
if (ret == 1) {
|
|
dev_err(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(dev);
|
|
if (ret < 0)
|
|
goto out;
|
|
|
|
/* mark this hwspinlock as available */
|
|
tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock),
|
|
HWSPINLOCK_UNUSED);
|
|
|
|
/* sanity check (this shouldn't happen) */
|
|
WARN_ON(tmp != hwlock);
|
|
|
|
module_put(dev->driver->owner);
|
|
|
|
out:
|
|
mutex_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 <ohad@wizery.com>");
|