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Merge branch 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/k…
…ernel/git/tmlind/linux-omap-2.6 * 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6: (258 commits) omap: zoom: host should not pull up wl1271's irq line arm: plat-omap: iommu: fix request_mem_region() error path OMAP2+: Common CPU DIE ID reading code reads wrong registers for OMAP4430 omap4: mux: Remove duplicate mux modes omap: iovmm: don't check 'da' to set IOVMF_DA_FIXED flag omap: iovmm: disallow mapping NULL address when IOVMF_DA_ANON is set omap2+: mux: Fix compile when CONFIG_OMAP_MUX is not selected omap4: board-omap4panda: Initialise the serial pads omap3: board-3430sdp: Initialise the serial pads omap4: board-4430sdp: Initialise the serial pads omap2+: mux: Add macro for configuring static with omap_hwmod_mux_init omap2+: mux: Remove the use of IDLE flag omap2+: Add separate list for dynamic pads to mux perf: add OMAP support for the new power events OMAP4: Add IVA OPP enteries. OMAP4: Update Voltage Rail Values for MPU, IVA and CORE OMAP4: Enable 800 MHz and 1 GHz MPU-OPP OMAP3+: OPP: Replace voltage values with Macros OMAP3: wdtimer: Fix CORE idle transition Watchdog: omap_wdt: add fine grain runtime-pm ... Fix up various conflicts in - arch/arm/mach-omap2/board-omap3evm.c - arch/arm/mach-omap2/clock3xxx_data.c - arch/arm/mach-omap2/usb-musb.c - arch/arm/plat-omap/include/plat/usb.h - drivers/usb/musb/musb_core.h
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Hardware Spinlock Framework | ||
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1. Introduction | ||
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Hardware spinlock modules provide hardware assistance for synchronization | ||
and mutual exclusion between heterogeneous processors and those not operating | ||
under a single, shared operating system. | ||
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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). | ||
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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. | ||
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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). | ||
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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. | ||
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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). | ||
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A common hwspinlock interface makes it possible to have generic, platform- | ||
independent, drivers. | ||
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2. User API | ||
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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. | ||
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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. | ||
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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. | ||
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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. | ||
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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. | ||
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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. | ||
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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. | ||
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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. | ||
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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. | ||
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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). | ||
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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. | ||
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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. | ||
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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. | ||
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3. Typical usage | ||
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#include <linux/hwspinlock.h> | ||
#include <linux/err.h> | ||
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int hwspinlock_example1(void) | ||
{ | ||
struct hwspinlock *hwlock; | ||
int ret; | ||
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/* dynamically assign a hwspinlock */ | ||
hwlock = hwspin_lock_request(); | ||
if (!hwlock) | ||
... | ||
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id = hwspin_lock_get_id(hwlock); | ||
/* probably need to communicate id to a remote processor now */ | ||
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/* take the lock, spin for 1 sec if it's already taken */ | ||
ret = hwspin_lock_timeout(hwlock, 1000); | ||
if (ret) | ||
... | ||
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/* | ||
* we took the lock, do our thing now, but do NOT sleep | ||
*/ | ||
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/* release the lock */ | ||
hwspin_unlock(hwlock); | ||
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/* free the lock */ | ||
ret = hwspin_lock_free(hwlock); | ||
if (ret) | ||
... | ||
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return ret; | ||
} | ||
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int hwspinlock_example2(void) | ||
{ | ||
struct hwspinlock *hwlock; | ||
int ret; | ||
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/* | ||
* assign a specific hwspinlock id - this should be called early | ||
* by board init code. | ||
*/ | ||
hwlock = hwspin_lock_request_specific(PREDEFINED_LOCK_ID); | ||
if (!hwlock) | ||
... | ||
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/* 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; | ||
} | ||
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/* | ||
* we took the lock, do our thing now, but do NOT sleep | ||
*/ | ||
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/* release the lock */ | ||
hwspin_unlock(hwlock); | ||
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/* free the lock */ | ||
ret = hwspin_lock_free(hwlock); | ||
if (ret) | ||
... | ||
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return ret; | ||
} | ||
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4. API for implementors | ||
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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. | ||
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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). | ||
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5. struct hwspinlock | ||
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This struct represents an hwspinlock instance. It is registered by the | ||
underlying hwspinlock implementation using the hwspin_lock_register() API. | ||
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/** | ||
* 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; | ||
}; | ||
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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. | ||
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6. Implementation callbacks | ||
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There are three possible callbacks defined in 'struct hwspinlock_ops': | ||
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struct hwspinlock_ops { | ||
int (*trylock)(struct hwspinlock *lock); | ||
void (*unlock)(struct hwspinlock *lock); | ||
void (*relax)(struct hwspinlock *lock); | ||
}; | ||
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The first two callbacks are mandatory: | ||
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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. | ||
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The ->unlock() callback releases the lock. It always succeed, and it, too, | ||
may _not_ sleep. | ||
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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. |
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