diff options
Diffstat (limited to 'target/linux/ubicom32/files/arch/ubicom32/include/asm/spinlock.h')
-rw-r--r-- | target/linux/ubicom32/files/arch/ubicom32/include/asm/spinlock.h | 296 |
1 files changed, 296 insertions, 0 deletions
diff --git a/target/linux/ubicom32/files/arch/ubicom32/include/asm/spinlock.h b/target/linux/ubicom32/files/arch/ubicom32/include/asm/spinlock.h new file mode 100644 index 0000000000..40080584c0 --- /dev/null +++ b/target/linux/ubicom32/files/arch/ubicom32/include/asm/spinlock.h @@ -0,0 +1,296 @@ +/* + * arch/ubicom32/include/asm/spinlock.h + * Spinlock related definitions for Ubicom32 architecture. + * + * (C) Copyright 2009, Ubicom, Inc. + * + * This file is part of the Ubicom32 Linux Kernel Port. + * + * The Ubicom32 Linux Kernel Port is free software: you can redistribute + * it and/or modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, either version 2 of the + * License, or (at your option) any later version. + * + * The Ubicom32 Linux Kernel Port 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. + * + * You should have received a copy of the GNU General Public License + * along with the Ubicom32 Linux Kernel Port. If not, + * see <http://www.gnu.org/licenses/>. + * + * Ubicom32 implementation derived from (with many thanks): + * arch/m68knommu + * arch/blackfin + * arch/parisc + */ +#ifndef _ASM_UBICOM32_SPINLOCK_H +#define _ASM_UBICOM32_SPINLOCK_H + +#include <asm/system.h> +#include <asm/processor.h> +#include <asm/spinlock_types.h> + +/* + * __raw_spin_lock() + * Lock the lock. + */ +static inline void __raw_spin_lock(raw_spinlock_t *x) +{ + asm volatile ( + "1: bset %0, %0, #0 \n\t" + " jmpne.f 1b \n\t" + : "+U4" (x->lock) + : + : "memory", "cc" + ); +} + +/* + * __raw_spin_unlock() + * Unlock the lock. + */ +static inline void __raw_spin_unlock(raw_spinlock_t *x) +{ + asm volatile ( + " bclr %0, %0, #0 \n\t" + : "+U4" (x->lock) + : + : "memory", "cc" + ); +} + +/* + * __raw_spin_is_locked() + * Test if the lock is locked. + */ +static inline int __raw_spin_is_locked(raw_spinlock_t *x) +{ + return x->lock; +} + +/* + * __raw_spin_unlock_wait() + * Wait for the lock to be unlocked. + * + * Note: the caller has not guarantee that the lock will not + * be acquired before they get to it. + */ +static inline void __raw_spin_unlock_wait(raw_spinlock_t *x) +{ + do { + cpu_relax(); + } while (__raw_spin_is_locked(x)); +} + +/* + * __raw_spin_trylock() + * Try the lock, return 0 on failure, 1 on success. + */ +static inline int __raw_spin_trylock(raw_spinlock_t *x) +{ + int ret = 0; + + asm volatile ( + " bset %1, %1, #0 \n\t" + " jmpne.f 1f \n\t" + " move.4 %0, #1 \n\t" + "1: \n\t" + : "+r" (ret), "+U4" (x->lock) + : + : "memory", "cc" + ); + + return ret; +} + +/* + * __raw_spin_lock_flags() + * Spin waiting for the lock (enabling IRQ(s)) + */ +static inline void __raw_spin_lock_flags(raw_spinlock_t *x, unsigned long flags) +{ + mb(); + while (!__raw_spin_trylock(x)) { + /* + * If the flags from the IRQ are set, interrupts are disabled and we + * need to re-enable them. + */ + if (!flags) { + cpu_relax(); + } else { + raw_local_irq_enable(); + cpu_relax(); + raw_local_irq_disable(); + } + } + mb(); +} + +/* + * Read-write spinlocks, allowing multiple readers but only one writer. + * Linux rwlocks are unfair to writers; they can be starved for an indefinite + * time by readers. With care, they can also be taken in interrupt context. + * + * In Ubicom32 architecture implementation, we have a spinlock and a counter. + * Readers use the lock to serialise their access to the counter (which + * records how many readers currently hold the lock). + * Writers hold the spinlock, preventing any readers or other writers from + * grabbing the rwlock. + */ + +/* + * __raw_read_lock() + * Increment the counter in the rwlock. + * + * Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to grab the same read lock + */ +static inline void __raw_read_lock(raw_rwlock_t *rw) +{ + unsigned long flags; + raw_local_irq_save(flags); + __raw_spin_lock_flags(&rw->lock, flags); + rw->counter++; + __raw_spin_unlock(&rw->lock); + raw_local_irq_restore(flags); +} + +/* + * __raw_read_unlock() + * Decrement the counter. + * + * Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to grab the same read lock + */ +static inline void __raw_read_unlock(raw_rwlock_t *rw) +{ + unsigned long flags; + raw_local_irq_save(flags); + __raw_spin_lock_flags(&rw->lock, flags); + rw->counter--; + __raw_spin_unlock(&rw->lock); + raw_local_irq_restore(flags); +} + +/* + * __raw_read_trylock() + * Increment the counter if we can. + * + * Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to grab the same read lock + */ +static inline int __raw_read_trylock(raw_rwlock_t *rw) +{ + unsigned long flags; + retry: + raw_local_irq_save(flags); + if (__raw_spin_trylock(&rw->lock)) { + rw->counter++; + __raw_spin_unlock(&rw->lock); + raw_local_irq_restore(flags); + return 1; + } + + raw_local_irq_restore(flags); + + /* + * If write-locked, we fail to acquire the lock + */ + if (rw->counter < 0) { + return 0; + } + + /* + * Wait until we have a realistic chance at the lock + */ + while (__raw_spin_is_locked(&rw->lock) && rw->counter >= 0) { + cpu_relax(); + } + + goto retry; +} + +/* + * __raw_write_lock() + * + * Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to read_trylock() this lock + */ +static inline void __raw_write_lock(raw_rwlock_t *rw) +{ + unsigned long flags; +retry: + raw_local_irq_save(flags); + __raw_spin_lock_flags(&rw->lock, flags); + + if (rw->counter != 0) { + __raw_spin_unlock(&rw->lock); + raw_local_irq_restore(flags); + + while (rw->counter != 0) + cpu_relax(); + + goto retry; + } + + rw->counter = -1; /* mark as write-locked */ + mb(); + raw_local_irq_restore(flags); +} + +static inline void __raw_write_unlock(raw_rwlock_t *rw) +{ + rw->counter = 0; + __raw_spin_unlock(&rw->lock); +} + +/* Note that we have to ensure interrupts are disabled in case we're + * interrupted by some other code that wants to read_trylock() this lock */ +static inline int __raw_write_trylock(raw_rwlock_t *rw) +{ + unsigned long flags; + int result = 0; + + raw_local_irq_save(flags); + if (__raw_spin_trylock(&rw->lock)) { + if (rw->counter == 0) { + rw->counter = -1; + result = 1; + } else { + /* Read-locked. Oh well. */ + __raw_spin_unlock(&rw->lock); + } + } + raw_local_irq_restore(flags); + + return result; +} + +/* + * read_can_lock - would read_trylock() succeed? + * @lock: the rwlock in question. + */ +static inline int __raw_read_can_lock(raw_rwlock_t *rw) +{ + return rw->counter >= 0; +} + +/* + * write_can_lock - would write_trylock() succeed? + * @lock: the rwlock in question. + */ +static inline int __raw_write_can_lock(raw_rwlock_t *rw) +{ + return !rw->counter; +} + +#define __raw_read_lock_flags(lock, flags) __raw_read_lock(lock) +#define __raw_write_lock_flags(lock, flags) __raw_write_lock(lock) + +#define _raw_spin_relax(lock) cpu_relax() +#define _raw_read_relax(lock) cpu_relax() +#define _raw_write_relax(lock) cpu_relax() + +#endif /* _ASM_UBICOM32_SPINLOCK_H */ |