8 files changed, 1216 insertions, 0 deletions

diff --git a/Documentation/hwspinlock.txt b/Documentation/hwspinlock.txt
new file mode 100644
index 000000000000..7dcd1a4e726c
--- /dev/null
+++ b/Documentation/hwspinlock.txt
@@ -0,0 +1,293 @@
+Hardware Spinlock Framework
+
+1. Introduction
+
+Hardware spinlock modules provide hardware assistance for synchronization
+and mutual exclusion between heterogeneous processors and those not operating
+under a single, shared operating system.
+
+For example, OMAP4 has dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP,
+each of which is running a different Operating System (the master, A9,
+is usually running Linux and the slave processors, the M3 and the DSP,
+are running some flavor of RTOS).
+
+A generic hwspinlock framework allows platform-independent drivers to use
+the hwspinlock device in order to access data structures that are shared
+between remote processors, that otherwise have no alternative mechanism
+to accomplish synchronization and mutual exclusion operations.
+
+This is necessary, for example, for Inter-processor communications:
+on OMAP4, cpu-intensive multimedia tasks are offloaded by the host to the
+remote M3 and/or C64x+ slave processors (by an IPC subsystem called Syslink).
+
+To achieve fast message-based communications, a minimal kernel support
+is needed to deliver messages arriving from a remote processor to the
+appropriate user process.
+
+This communication is based on simple data structures that is shared between
+the remote processors, and access to it is synchronized using the hwspinlock
+module (remote processor directly places new messages in this shared data
+structure).
+
+A common hwspinlock interface makes it possible to have generic, platform-
+independent, drivers.
+
+2. User API
+
+  struct hwspinlock *hwspin_lock_request(void);
+   - dynamically assign an hwspinlock and return its address, or NULL
+     in case an unused hwspinlock isn't available. Users of this
+     API will usually want to communicate the lock's id to the remote core
+     before it can be used to achieve synchronization.
+     Can be called from an atomic context (this function will not sleep) but
+     not from within interrupt context.
+
+  struct hwspinlock *hwspin_lock_request_specific(unsigned int id);
+   - assign a specific hwspinlock id and return its address, or NULL
+     if that hwspinlock is already in use. Usually board code will
+     be calling this function in order to reserve specific hwspinlock
+     ids for predefined purposes.
+     Can be called from an atomic context (this function will not sleep) but
+     not from within interrupt context.
+
+  int hwspin_lock_free(struct hwspinlock *hwlock);
+   - free a previously-assigned hwspinlock; returns 0 on success, or an
+     appropriate error code on failure (e.g. -EINVAL if the hwspinlock
+     is already free).
+     Can be called from an atomic context (this function will not sleep) but
+     not from within interrupt context.
+
+  int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int timeout);
+   - lock a previously-assigned hwspinlock with a timeout limit (specified in
+     msecs). If the hwspinlock is already taken, the function will busy loop
+     waiting for it to be released, but give up when the timeout elapses.
+     Upon a successful return from this function, preemption is disabled so
+     the caller must not sleep, and is advised to release the hwspinlock as
+     soon as possible, in order to minimize remote cores polling on the
+     hardware interconnect.
+     Returns 0 when successful and an appropriate error code otherwise (most
+     notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
+     The function will never sleep.
+
+  int hwspin_lock_timeout_irq(struct hwspinlock *hwlock, unsigned int timeout);
+   - lock a previously-assigned hwspinlock with a timeout limit (specified in
+     msecs). If the hwspinlock is already taken, the function will busy loop
+     waiting for it to be released, but give up when the timeout elapses.
+     Upon a successful return from this function, preemption and the local
+     interrupts are disabled, so the caller must not sleep, and is advised to
+     release the hwspinlock as soon as possible.
+     Returns 0 when successful and an appropriate error code otherwise (most
+     notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
+     The function will never sleep.
+
+  int hwspin_lock_timeout_irqsave(struct hwspinlock *hwlock, unsigned int to,
+                                                        unsigned long *flags);
+   - lock a previously-assigned hwspinlock with a timeout limit (specified in
+     msecs). If the hwspinlock is already taken, the function will busy loop
+     waiting for it to be released, but give up when the timeout elapses.
+     Upon a successful return from this function, preemption is disabled,
+     local interrupts are disabled and their previous state is saved at the
+     given flags placeholder. The caller must not sleep, and is advised to
+     release the hwspinlock as soon as possible.
+     Returns 0 when successful and an appropriate error code otherwise (most
+     notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
+     The function will never sleep.
+
+  int hwspin_trylock(struct hwspinlock *hwlock);
+   - attempt to lock a previously-assigned hwspinlock, but immediately fail if
+     it is already taken.
+     Upon a successful return from this function, preemption is disabled so
+     caller must not sleep, and is advised to release the hwspinlock as soon as
+     possible, in order to minimize remote cores polling on the hardware
+     interconnect.
+     Returns 0 on success and an appropriate error code otherwise (most
+     notably -EBUSY if the hwspinlock was already taken).
+     The function will never sleep.
+
+  int hwspin_trylock_irq(struct hwspinlock *hwlock);
+   - attempt to lock a previously-assigned hwspinlock, but immediately fail if
+     it is already taken.
+     Upon a successful return from this function, preemption and the local
+     interrupts are disabled so caller must not sleep, and is advised to
+     release the hwspinlock as soon as possible.
+     Returns 0 on success and an appropriate error code otherwise (most
+     notably -EBUSY if the hwspinlock was already taken).
+     The function will never sleep.
+
+  int hwspin_trylock_irqsave(struct hwspinlock *hwlock, unsigned long *flags);
+   - attempt to lock a previously-assigned hwspinlock, but immediately fail if
+     it is already taken.
+     Upon a successful return from this function, preemption is disabled,
+     the local interrupts are disabled and their previous state is saved
+     at the given flags placeholder. The caller must not sleep, and is advised
+     to release the hwspinlock as soon as possible.
+     Returns 0 on success and an appropriate error code otherwise (most
+     notably -EBUSY if the hwspinlock was already taken).
+     The function will never sleep.
+
+  void hwspin_unlock(struct hwspinlock *hwlock);
+   - unlock a previously-locked hwspinlock. Always succeed, and can be called
+     from any context (the function never sleeps). Note: code should _never_
+     unlock an hwspinlock which is already unlocked (there is no protection
+     against this).
+
+  void hwspin_unlock_irq(struct hwspinlock *hwlock);
+   - unlock a previously-locked hwspinlock and enable local interrupts.
+     The caller should _never_ unlock an hwspinlock which is already unlocked.
+     Doing so is considered a bug (there is no protection against this).
+     Upon a successful return from this function, preemption and local
+     interrupts are enabled. This function will never sleep.
+
+  void
+  hwspin_unlock_irqrestore(struct hwspinlock *hwlock, unsigned long *flags);
+   - unlock a previously-locked hwspinlock.
+     The caller should _never_ unlock an hwspinlock which is already unlocked.
+     Doing so is considered a bug (there is no protection against this).
+     Upon a successful return from this function, preemption is reenabled,
+     and the state of the local interrupts is restored to the state saved at
+     the given flags. This function will never sleep.
+
+  int hwspin_lock_get_id(struct hwspinlock *hwlock);
+   - retrieve id number of a given hwspinlock. This is needed when an
+     hwspinlock is dynamically assigned: before it can be used to achieve
+     mutual exclusion with a remote cpu, the id number should be communicated
+     to the remote task with which we want to synchronize.
+     Returns the hwspinlock id number, or -EINVAL if hwlock is null.
+
+3. Typical usage
+
+#include <linux/hwspinlock.h>
+#include <linux/err.h>
+
+int hwspinlock_example1(void)
+{
+        struct hwspinlock *hwlock;
+        int ret;
+
+        /* dynamically assign a hwspinlock */
+        hwlock = hwspin_lock_request();
+        if (!hwlock)
+                ...
+
+        id = hwspin_lock_get_id(hwlock);
+        /* probably need to communicate id to a remote processor now */
+
+        /* take the lock, spin for 1 sec if it's already taken */
+        ret = hwspin_lock_timeout(hwlock, 1000);
+        if (ret)
+                ...
+
+        /*
+         * we took the lock, do our thing now, but do NOT sleep
+         */
+
+        /* release the lock */
+        hwspin_unlock(hwlock);
+
+        /* free the lock */
+        ret = hwspin_lock_free(hwlock);
+        if (ret)
+                ...
+
+        return ret;
+}
+
+int hwspinlock_example2(void)
+{
+        struct hwspinlock *hwlock;
+        int ret;
+
+        /*
+         * assign a specific hwspinlock id - this should be called early
+         * by board init code.
+         */
+        hwlock = hwspin_lock_request_specific(PREDEFINED_LOCK_ID);
+        if (!hwlock)
+                ...
+
+        /* try to take it, but don't spin on it */
+        ret = hwspin_trylock(hwlock);
+        if (!ret) {
+                pr_info("lock is already taken\n");
+                return -EBUSY;
+        }
+
+        /*
+         * we took the lock, do our thing now, but do NOT sleep
+         */
+
+        /* release the lock */
+        hwspin_unlock(hwlock);
+
+        /* free the lock */
+        ret = hwspin_lock_free(hwlock);
+        if (ret)
+                ...
+
+        return ret;
+}
+
+
+4. API for implementors
+
+  int hwspin_lock_register(struct hwspinlock *hwlock);
+   - to be called from the underlying platform-specific implementation, in
+     order to register a new hwspinlock instance. Can be called from an atomic
+     context (this function will not sleep) but not from within interrupt
+     context. Returns 0 on success, or appropriate error code on failure.
+
+  struct hwspinlock *hwspin_lock_unregister(unsigned int id);
+   - to be called from the underlying vendor-specific implementation, in order
+     to unregister an existing (and unused) hwspinlock instance.
+     Can be called from an atomic context (will not sleep) but not from
+     within interrupt context.
+     Returns the address of hwspinlock on success, or NULL on error (e.g.
+     if the hwspinlock is sill in use).
+
+5. struct hwspinlock
+
+This struct represents an hwspinlock instance. It is registered by the
+underlying hwspinlock implementation using the hwspin_lock_register() API.
+
+/**
+ * struct hwspinlock - vendor-specific hwspinlock implementation
+ *
+ * @dev: underlying device, will be used with runtime PM api
+ * @ops: vendor-specific hwspinlock handlers
+ * @id: a global, unique, system-wide, index of the lock.
+ * @lock: initialized and used by hwspinlock core
+ * @owner: underlying implementation module, used to maintain module ref count
+ */
+struct hwspinlock {
+        struct device *dev;
+        const struct hwspinlock_ops *ops;
+        int id;
+        spinlock_t lock;
+        struct module *owner;
+};
+
+The underlying implementation is responsible to assign the dev, ops, id and
+owner members. The lock member, OTOH, is initialized and used by the hwspinlock
+core.
+
+6. Implementation callbacks
+
+There are three possible callbacks defined in 'struct hwspinlock_ops':
+
+struct hwspinlock_ops {
+        int (*trylock)(struct hwspinlock *lock);
+        void (*unlock)(struct hwspinlock *lock);
+        void (*relax)(struct hwspinlock *lock);
+};
+
+The first two callbacks are mandatory:
+
+The ->trylock() callback should make a single attempt to take the lock, and
+return 0 on failure and 1 on success. This callback may _not_ sleep.
+
+The ->unlock() callback releases the lock. It always succeed, and it, too,
+may _not_ sleep.
+
+The ->relax() callback is optional. It is called by hwspinlock core while
+spinning on a lock, and can be used by the underlying implementation to force
+a delay between two successive invocations of ->trylock(). It may _not_ sleep.
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 9bfb71ff3a6a..177c7d156933 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -117,4 +117,6 @@ source "drivers/staging/Kconfig"
 source "drivers/platform/Kconfig"
 
 source "drivers/clk/Kconfig"
+
+source "drivers/hwspinlock/Kconfig"
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index b423bb16c3a8..3f135b6fb014 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -117,3 +117,5 @@ obj-y				+= platform/
 obj-y                           += ieee802154/
 #common clk code
 obj-y                           += clk/
+
+obj-$(CONFIG_HWSPINLOCK)        += hwspinlock/
diff --git a/drivers/hwspinlock/Kconfig b/drivers/hwspinlock/Kconfig
new file mode 100644
index 000000000000..9dd8db46606b
--- /dev/null
+++ b/drivers/hwspinlock/Kconfig
@@ -0,0 +1,13 @@
+#
+# Generic HWSPINLOCK framework
+#
+
+config HWSPINLOCK
+        tristate "Generic Hardware Spinlock framework"
+        help
+          Say y here to support the generic hardware spinlock framework.
+          You only need to enable this if you have hardware spinlock module
+          on your system (usually only relevant if your system has remote slave
+          coprocessors).
+
+          If unsure, say N.
diff --git a/drivers/hwspinlock/Makefile b/drivers/hwspinlock/Makefile
new file mode 100644
index 000000000000..b9d2b9f40491
--- /dev/null
+++ b/drivers/hwspinlock/Makefile
@@ -0,0 +1,5 @@
+#
+# Generic Hardware Spinlock framework
+#
+
+obj-$(CONFIG_HWSPINLOCK)                += hwspinlock_core.o
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 <ohad@wizery.com>
+ *
+ * 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 <ohad@wizery.com>");
diff --git a/drivers/hwspinlock/hwspinlock_internal.h b/drivers/hwspinlock/hwspinlock_internal.h
new file mode 100644
index 000000000000..69935e6b93e5
--- /dev/null
+++ b/drivers/hwspinlock/hwspinlock_internal.h
@@ -0,0 +1,61 @@
+/*
+ * Hardware spinlocks internal header
+ *
+ * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
+ *
+ * Contact: Ohad Ben-Cohen <ohad@wizery.com>
+ *
+ * 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.
+ */
+
+#ifndef __HWSPINLOCK_HWSPINLOCK_H
+#define __HWSPINLOCK_HWSPINLOCK_H
+
+#include <linux/spinlock.h>
+#include <linux/device.h>
+
+/**
+ * struct hwspinlock_ops - platform-specific hwspinlock handlers
+ *
+ * @trylock: make a single attempt to take the lock. returns 0 on
+ *           failure and true on success. may _not_ sleep.
+ * @unlock:  release the lock. always succeed. may _not_ sleep.
+ * @relax:   optional, platform-specific relax handler, called by hwspinlock
+ *           core while spinning on a lock, between two successive
+ *           invocations of @trylock. may _not_ sleep.
+ */
+struct hwspinlock_ops {
+        int (*trylock)(struct hwspinlock *lock);
+        void (*unlock)(struct hwspinlock *lock);
+        void (*relax)(struct hwspinlock *lock);
+};
+
+/**
+ * struct hwspinlock - this struct represents a single hwspinlock instance
+ *
+ * @dev: underlying device, will be used to invoke runtime PM api
+ * @ops: platform-specific hwspinlock handlers
+ * @id: a global, unique, system-wide, index of the lock.
+ * @lock: initialized and used by hwspinlock core
+ * @owner: underlying implementation module, used to maintain module ref count
+ *
+ * Note: currently simplicity was opted for, but later we can squeeze some
+ * memory bytes by grouping the dev, ops and owner members in a single
+ * per-platform struct, and have all hwspinlocks point at it.
+ */
+struct hwspinlock {
+        struct device *dev;
+        const struct hwspinlock_ops *ops;
+        int id;
+        spinlock_t lock;
+        struct module *owner;
+};
+
+#endif /* __HWSPINLOCK_HWSPINLOCK_H */
diff --git a/include/linux/hwspinlock.h b/include/linux/hwspinlock.h
new file mode 100644
index 000000000000..8390efc457eb
--- /dev/null
+++ b/include/linux/hwspinlock.h
@@ -0,0 +1,292 @@
+/*
+ * Hardware spinlock public header
+ *
+ * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
+ *
+ * Contact: Ohad Ben-Cohen <ohad@wizery.com>
+ *
+ * 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.
+ */
+
+#ifndef __LINUX_HWSPINLOCK_H
+#define __LINUX_HWSPINLOCK_H
+
+#include <linux/err.h>
+#include <linux/sched.h>
+
+/* hwspinlock mode argument */
+#define HWLOCK_IRQSTATE 0x01    /* Disable interrupts, save state */
+#define HWLOCK_IRQ      0x02    /* Disable interrupts, don't save state */
+
+struct hwspinlock;
+
+#if defined(CONFIG_HWSPINLOCK) || defined(CONFIG_HWSPINLOCK_MODULE)
+
+int hwspin_lock_register(struct hwspinlock *lock);
+struct hwspinlock *hwspin_lock_unregister(unsigned int id);
+struct hwspinlock *hwspin_lock_request(void);
+struct hwspinlock *hwspin_lock_request_specific(unsigned int id);
+int hwspin_lock_free(struct hwspinlock *hwlock);
+int hwspin_lock_get_id(struct hwspinlock *hwlock);
+int __hwspin_lock_timeout(struct hwspinlock *, unsigned int, int,
+                                                        unsigned long *);
+int __hwspin_trylock(struct hwspinlock *, int, unsigned long *);
+void __hwspin_unlock(struct hwspinlock *, int, unsigned long *);
+
+#else /* !CONFIG_HWSPINLOCK */
+
+/*
+ * We don't want these functions to fail if CONFIG_HWSPINLOCK is not
+ * enabled. We prefer to silently succeed in this case, and let the
+ * code path get compiled away. This way, if CONFIG_HWSPINLOCK is not
+ * required on a given setup, users will still work.
+ *
+ * The only exception is hwspin_lock_register/hwspin_lock_unregister, with which
+ * we _do_ want users to fail (no point in registering hwspinlock instances if
+ * the framework is not available).
+ *
+ * Note: ERR_PTR(-ENODEV) will still be considered a success for NULL-checking
+ * users. Others, which care, can still check this with IS_ERR.
+ */
+static inline struct hwspinlock *hwspin_lock_request(void)
+{
+        return ERR_PTR(-ENODEV);
+}
+
+static inline struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
+{
+        return ERR_PTR(-ENODEV);
+}
+
+static inline int hwspin_lock_free(struct hwspinlock *hwlock)
+{
+        return 0;
+}
+
+static inline
+int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
+                                        int mode, unsigned long *flags)
+{
+        return 0;
+}
+
+static inline
+int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
+{
+        return 0;
+}
+
+static inline
+void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
+{
+        return 0;
+}
+
+static inline int hwspin_lock_get_id(struct hwspinlock *hwlock)
+{
+        return 0;
+}
+
+static inline int hwspin_lock_register(struct hwspinlock *hwlock)
+{
+        return -ENODEV;
+}
+
+static inline struct hwspinlock *hwspin_lock_unregister(unsigned int id)
+{
+        return NULL;
+}
+
+#endif /* !CONFIG_HWSPINLOCK */
+
+/**
+ * hwspin_trylock_irqsave() - try to lock an hwspinlock, disable interrupts
+ * @hwlock: an hwspinlock which we want to trylock
+ * @flags: a pointer to where the caller's interrupt state will be saved at
+ *
+ * This function attempts to lock the underlying hwspinlock, and will
+ * immediately fail if the hwspinlock is already locked.
+ *
+ * Upon a successful return from this function, preemption and local
+ * interrupts are disabled (previous interrupts state is saved at @flags),
+ * so the caller must not sleep, and is advised to release the hwspinlock
+ * as soon as possible.
+ *
+ * Returns 0 if we successfully locked the hwspinlock, -EBUSY if
+ * the hwspinlock was already taken, and -EINVAL if @hwlock is invalid.
+ */
+static inline
+int hwspin_trylock_irqsave(struct hwspinlock *hwlock, unsigned long *flags)
+{
+        return __hwspin_trylock(hwlock, HWLOCK_IRQSTATE, flags);
+}
+
+/**
+ * hwspin_trylock_irq() - try to lock an hwspinlock, disable interrupts
+ * @hwlock: an hwspinlock which we want to trylock
+ *
+ * This function attempts to lock the underlying hwspinlock, and will
+ * immediately fail if the hwspinlock is already locked.
+ *
+ * Upon a successful return from this function, preemption and local
+ * interrupts are disabled, so the caller must not sleep, and is advised
+ * to release the hwspinlock as soon as possible.
+ *
+ * Returns 0 if we successfully locked the hwspinlock, -EBUSY if
+ * the hwspinlock was already taken, and -EINVAL if @hwlock is invalid.
+ */
+static inline int hwspin_trylock_irq(struct hwspinlock *hwlock)
+{
+        return __hwspin_trylock(hwlock, HWLOCK_IRQ, NULL);
+}
+
+/**
+ * hwspin_trylock() - attempt to lock a specific hwspinlock
+ * @hwlock: an hwspinlock which we want to trylock
+ *
+ * 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 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.
+ *
+ * Returns 0 if we successfully locked the hwspinlock, -EBUSY if
+ * the hwspinlock was already taken, and -EINVAL if @hwlock is invalid.
+ */
+static inline int hwspin_trylock(struct hwspinlock *hwlock)
+{
+        return __hwspin_trylock(hwlock, 0, NULL);
+}
+
+/**
+ * hwspin_lock_timeout_irqsave() - lock hwspinlock, with timeout, disable irqs
+ * @hwlock: the hwspinlock to be locked
+ * @to: timeout value in msecs
+ * @flags: a pointer to where the caller's interrupt state will be saved at
+ *
+ * This function locks the underlying @hwlock. If the @hwlock
+ * is already taken, the function will busy loop waiting for it to
+ * be released, but give up when @timeout msecs have elapsed.
+ *
+ * Upon a successful return from this function, preemption and local interrupts
+ * are disabled (plus previous interrupt state is saved), so the caller must
+ * not sleep, and is advised to release the hwspinlock as soon as possible.
+ *
+ * Returns 0 when the @hwlock was successfully taken, and an appropriate
+ * error code otherwise (most notably an -ETIMEDOUT if the @hwlock is still
+ * busy after @timeout msecs). The function will never sleep.
+ */
+static inline int hwspin_lock_timeout_irqsave(struct hwspinlock *hwlock,
+                                unsigned int to, unsigned long *flags)
+{
+        return __hwspin_lock_timeout(hwlock, to, HWLOCK_IRQSTATE, flags);
+}
+
+/**
+ * hwspin_lock_timeout_irq() - lock hwspinlock, with timeout, disable irqs
+ * @hwlock: the hwspinlock to be locked
+ * @to: timeout value in msecs
+ *
+ * This function locks the underlying @hwlock. If the @hwlock
+ * is already taken, the function will busy loop waiting for it to
+ * be released, but give up when @timeout msecs have elapsed.
+ *
+ * Upon a successful return from this function, preemption and local interrupts
+ * are disabled so the caller must not sleep, and is advised to release the
+ * hwspinlock as soon as possible.
+ *
+ * Returns 0 when the @hwlock was successfully taken, and an appropriate
+ * error code otherwise (most notably an -ETIMEDOUT if the @hwlock is still
+ * busy after @timeout msecs). The function will never sleep.
+ */
+static inline
+int hwspin_lock_timeout_irq(struct hwspinlock *hwlock, unsigned int to)
+{
+        return __hwspin_lock_timeout(hwlock, to, HWLOCK_IRQ, NULL);
+}
+
+/**
+ * hwspin_lock_timeout() - lock an hwspinlock with timeout limit
+ * @hwlock: the hwspinlock to be locked
+ * @to: timeout value in msecs
+ *
+ * This function locks the underlying @hwlock. If the @hwlock
+ * is already taken, the function will busy loop waiting for it to
+ * be released, but give up when @timeout msecs have elapsed.
+ *
+ * Upon a successful return from this function, preemption 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.
+ *
+ * Returns 0 when the @hwlock was successfully taken, and an appropriate
+ * error code otherwise (most notably an -ETIMEDOUT if the @hwlock is still
+ * busy after @timeout msecs). The function will never sleep.
+ */
+static inline
+int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to)
+{
+        return __hwspin_lock_timeout(hwlock, to, 0, NULL);
+}
+
+/**
+ * hwspin_unlock_irqrestore() - unlock hwspinlock, restore irq state
+ * @hwlock: a previously-acquired hwspinlock which we want to unlock
+ * @flags: previous caller's interrupt state to restore
+ *
+ * This function will unlock a specific hwspinlock, enable preemption and
+ * restore the previous state of the local interrupts. It should be used
+ * to undo, e.g., hwspin_trylock_irqsave().
+ *
+ * @hwlock must be already locked before calling this function: it is a bug
+ * to call unlock on a @hwlock that is already unlocked.
+ */
+static inline void hwspin_unlock_irqrestore(struct hwspinlock *hwlock,
+                                                        unsigned long *flags)
+{
+        __hwspin_unlock(hwlock, HWLOCK_IRQSTATE, flags);
+}
+
+/**
+ * hwspin_unlock_irq() - unlock hwspinlock, enable interrupts
+ * @hwlock: a previously-acquired hwspinlock which we want to unlock
+ *
+ * This function will unlock a specific hwspinlock, enable preemption and
+ * enable local interrupts. Should be used to undo hwspin_lock_irq().
+ *
+ * @hwlock must be already locked (e.g. by hwspin_trylock_irq()) before
+ * calling this function: it is a bug to call unlock on a @hwlock that is
+ * already unlocked.
+ */
+static inline void hwspin_unlock_irq(struct hwspinlock *hwlock)
+{
+        __hwspin_unlock(hwlock, HWLOCK_IRQ, NULL);
+}
+
+/**
+ * hwspin_unlock() - unlock hwspinlock
+ * @hwlock: a previously-acquired hwspinlock which we want to unlock
+ *
+ * This function will unlock a specific hwspinlock and enable preemption
+ * back.
+ *
+ * @hwlock must be already locked (e.g. by hwspin_trylock()) before calling
+ * this function: it is a bug to call unlock on a @hwlock that is already
+ * unlocked.
+ */
+static inline void hwspin_unlock(struct hwspinlock *hwlock)
+{
+        __hwspin_unlock(hwlock, 0, NULL);
+}
+
+#endif /* __LINUX_HWSPINLOCK_H */