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Documentation/hwspinlock.txt

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		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.

MAINTAINERS

+10 −0

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		@@ -4496,6 +4496,16 @@ L: linux-omap@vger.kernel.org
		S: Maintained
		F: arch/arm/omap/pm

		OMAP POWERDOMAIN/CLOCKDOMAIN SOC ADAPTATION LAYER SUPPORT
		M: Rajendra Nayak <rnayak@ti.com>
		M: Paul Walmsley <paul@pwsan.com>
		L: linux-omap@vger.kernel.org
		S: Maintained
		F: arch/arm/mach-omap2/powerdomain2xxx_3xxx.c
		F: arch/arm/mach-omap2/powerdomain44xx.c
		F: arch/arm/mach-omap2/clockdomain2xxx_3xxx.c
		F: arch/arm/mach-omap2/clockdomain44xx.c

		OMAP AUDIO SUPPORT
		M: Jarkko Nikula <jhnikula@gmail.com>
		L: alsa-devel@alsa-project.org (subscribers-only)

arch/arm/configs/omap2plus_defconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -58,6 +58,7 @@ CONFIG_ARM_ERRATA_411920=y
		CONFIG_NO_HZ=y
		CONFIG_HIGH_RES_TIMERS=y
		CONFIG_SMP=y
		CONFIG_NR_CPUS=2
		# CONFIG_LOCAL_TIMERS is not set
		CONFIG_AEABI=y
		CONFIG_LEDS=y

arch/arm/mach-omap1/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -4,7 +4,7 @@

		# Common support
		obj-y := io.o id.o sram.o time.o irq.o mux.o flash.o serial.o devices.o dma.o
		obj-y += clock.o clock_data.o opp_data.o
		obj-y += clock.o clock_data.o opp_data.o reset.o

		obj-$(CONFIG_OMAP_MCBSP) += mcbsp.o

arch/arm/mach-omap1/board-ams-delta.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -165,7 +165,7 @@ static struct map_desc ams_delta_io_desc[] __initdata = {
		}
		};

		static struct omap_lcd_config ams_delta_lcd_config __initdata = {
		static struct omap_lcd_config ams_delta_lcd_config = {
		.ctrl_name = "internal",
		};

		@@ -175,7 +175,7 @@ static struct omap_usb_config ams_delta_usb_config __initdata = {
		.pins[0] = 2,
		};

		static struct omap_board_config_kernel ams_delta_config[] = {
		static struct omap_board_config_kernel ams_delta_config[] __initdata = {
		{ OMAP_TAG_LCD, &ams_delta_lcd_config },
		};

		@@ -208,14 +208,14 @@ static const struct matrix_keymap_data ams_delta_keymap_data = {
		.keymap_size = ARRAY_SIZE(ams_delta_keymap),
		};

		static struct omap_kp_platform_data ams_delta_kp_data = {
		static struct omap_kp_platform_data ams_delta_kp_data __initdata = {
		.rows = 8,
		.cols = 8,
		.keymap_data = &ams_delta_keymap_data,
		.delay = 9,
		};

		static struct platform_device ams_delta_kp_device = {
		static struct platform_device ams_delta_kp_device __initdata = {
		.name = "omap-keypad",
		.id = -1,
		.dev = {
		@@ -225,12 +225,12 @@ static struct platform_device ams_delta_kp_device = {
		.resource = ams_delta_kp_resources,
		};

		static struct platform_device ams_delta_lcd_device = {
		static struct platform_device ams_delta_lcd_device __initdata = {
		.name = "lcd_ams_delta",
		.id = -1,
		};

		static struct platform_device ams_delta_led_device = {
		static struct platform_device ams_delta_led_device __initdata = {
		.name = "ams-delta-led",
		.id = -1
		};
		@@ -259,7 +259,7 @@ static int ams_delta_camera_power(struct device *dev, int power)
		#define ams_delta_camera_power NULL
		#endif

		static struct soc_camera_link __initdata ams_delta_iclink = {
		static struct soc_camera_link ams_delta_iclink = {
		.bus_id = 0, /* OMAP1 SoC camera bus */
		.i2c_adapter_id = 1,
		.board_info = &ams_delta_camera_board_info[0],
		@@ -267,7 +267,7 @@ static struct soc_camera_link __initdata ams_delta_iclink = {
		.power = ams_delta_camera_power,
		};

		static struct platform_device ams_delta_camera_device = {
		static struct platform_device ams_delta_camera_device __initdata = {
		.name = "soc-camera-pdrv",
		.id = 0,
		.dev = {

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