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Message-Id: <9ec913b47790e9412d5b71a5fc52794ce4ebafb9.1487702890.git.shorne@gmail.com>
Date: Wed, 22 Feb 2017 04:11:39 +0900
From: Stafford Horne <shorne@...il.com>
To: Jonas Bonn <jonas@...thpole.se>,
Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
Cc: linux@...ck-us.net, openrisc@...ts.librecores.org,
linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Stafford Horne <shorne@...il.com>,
Ingo Molnar <mingo@...hat.com>
Subject: [PATCH v3 10/25] openrisc: add spinlock implementation
From: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
Heavily based on the ARM implementation, this adds
ticket spinlock support for OpenRISC.
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
[shorne@...il.com: fix tabs vs space checkpatch warning]
Signed-off-by: Stafford Horne <shorne@...il.com>
---
arch/openrisc/include/asm/spinlock.h | 232 ++++++++++++++++++++++++++++-
arch/openrisc/include/asm/spinlock_types.h | 28 ++++
2 files changed, 259 insertions(+), 1 deletion(-)
create mode 100644 arch/openrisc/include/asm/spinlock_types.h
diff --git a/arch/openrisc/include/asm/spinlock.h b/arch/openrisc/include/asm/spinlock.h
index fd00a3a..adf62a6 100644
--- a/arch/openrisc/include/asm/spinlock.h
+++ b/arch/openrisc/include/asm/spinlock.h
@@ -9,6 +9,9 @@
* Copyright (C) 2003 Matjaz Breskvar <phoenix@...mi.com>
* Copyright (C) 2010-2011 Jonas Bonn <jonas@...thpole.se>
* et al.
+ * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
+ *
+ * Ticket spinlocks, based on the ARM implementation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -19,6 +22,233 @@
#ifndef __ASM_OPENRISC_SPINLOCK_H
#define __ASM_OPENRISC_SPINLOCK_H
-#error "or32 doesn't do SMP yet"
+#include <asm/spinlock_types.h>
+
+#define arch_spin_unlock_wait(lock) \
+ do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
+
+#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ u32 newval;
+ arch_spinlock_t lockval;
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%2) \n"
+ " l.add %1, %0, %3 \n"
+ " l.swa 0(%2), %1 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ : "=&r" (lockval), "=&r" (newval)
+ : "r" (&lock->slock), "r" (1 << TICKET_SHIFT)
+ : "cc", "memory");
+
+ while (lockval.tickets.next != lockval.tickets.owner)
+ lockval.tickets.owner = ACCESS_ONCE(lock->tickets.owner);
+
+ smp_mb();
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+ unsigned long contended, tmp;
+ u32 slock;
+
+ /* contended = (lock->tickets.owner != lock->tickets.next) */
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%3) \n"
+ " l.srli %1, %0, 16 \n"
+ " l.andi %2, %0, 0xffff \n"
+ " l.sfeq %1, %2 \n"
+ " l.bnf 1f \n"
+ " l.ori %1, r0, 1 \n"
+ " l.add %0, %0, %4 \n"
+ " l.swa 0(%3), %0 \n"
+ " l.bnf 1b \n"
+ " l.ori %1, r0, 0 \n"
+ "1: \n"
+ : "=&r" (slock), "=&r" (contended), "=&r" (tmp)
+ : "r" (&lock->slock), "r" (1 << TICKET_SHIFT)
+ : "cc", "memory");
+
+ if (!contended) {
+ smp_mb();
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+ smp_mb();
+ lock->tickets.owner++;
+}
+
+static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+ return lock.tickets.owner == lock.tickets.next;
+}
+
+static inline int arch_spin_is_locked(arch_spinlock_t *lock)
+{
+ return !arch_spin_value_unlocked(ACCESS_ONCE(*lock));
+}
+
+static inline int arch_spin_is_contended(arch_spinlock_t *lock)
+{
+ struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets);
+
+ return (tickets.next - tickets.owner) > 1;
+}
+#define arch_spin_is_contended arch_spin_is_contended
+
+/*
+ * RWLOCKS
+ *
+ *
+ * Write locks are easy - we just set bit 31. When unlocking, we can
+ * just write zero since the lock is exclusively held.
+ */
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+ unsigned long tmp;
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%1) \n"
+ " l.sfeqi %0, 0 \n"
+ " l.bnf 1f \n"
+ " l.nop \n"
+ " l.swa 0(%1), %2 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ "1: \n"
+ : "=&r" (tmp)
+ : "r" (&rw->lock), "r" (0x80000000)
+ : "cc", "memory");
+
+ smp_mb();
+}
+
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+ unsigned long contended;
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%1) \n"
+ " l.sfeqi %0, 0 \n"
+ " l.bnf 1f \n"
+ " l.nop \n"
+ " l.swa 0(%1), %2 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ "1: \n"
+ : "=&r" (contended)
+ : "r" (&rw->lock), "r" (0x80000000)
+ : "cc", "memory");
+
+ if (!contended) {
+ smp_mb();
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+ smp_mb();
+ rw->lock = 0;
+}
+
+/* write_can_lock - would write_trylock() succeed? */
+#define arch_write_can_lock(x) (ACCESS_ONCE((x)->lock) == 0)
+
+/*
+ * Read locks are a bit more hairy:
+ * - Exclusively load the lock value.
+ * - Increment it.
+ * - Store new lock value if positive, and we still own this location.
+ * If the value is negative, we've already failed.
+ * - If we failed to store the value, we want a negative result.
+ * - If we failed, try again.
+ * Unlocking is similarly hairy. We may have multiple read locks
+ * currently active. However, we know we won't have any write
+ * locks.
+ */
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+ unsigned long tmp;
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%1) \n"
+ " l.sfltsi %0, -1 \n"
+ " l.bf 1b \n"
+ " l.addi %0, %0, 1 \n"
+ " l.swa 0(%1), %0 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ : "=&r" (tmp)
+ : "r" (&rw->lock)
+ : "cc", "memory");
+
+ smp_mb();
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+ unsigned long tmp;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%1) \n"
+ " l.addi %0, %0, -1 \n"
+ " l.swa 0(%1), %0 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ : "=&r" (tmp)
+ : "r" (&rw->lock)
+ : "cc", "memory");
+
+}
+
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+ unsigned long contended;
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%1) \n"
+ " l.sfltsi %0, -1 \n"
+ " l.bf 1f \n"
+ " l.addi %0, %0, 1 \n"
+ " l.swa 0(%1), %0 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ "1: \n"
+ : "=&r" (contended)
+ : "r" (&rw->lock)
+ : "cc", "memory");
+
+ /* If the lock is negative, then it is already held for write. */
+ if (contended < 0x80000000) {
+ smp_mb();
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+/* read_can_lock - would read_trylock() succeed? */
+#define arch_read_can_lock(x) (ACCESS_ONCE((x)->lock) < 0x80000000)
+
+#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
+#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
+
+#define arch_spin_relax(lock) cpu_relax()
+#define arch_read_relax(lock) cpu_relax()
+#define arch_write_relax(lock) cpu_relax()
#endif
diff --git a/arch/openrisc/include/asm/spinlock_types.h b/arch/openrisc/include/asm/spinlock_types.h
new file mode 100644
index 0000000..bc0de48
--- /dev/null
+++ b/arch/openrisc/include/asm/spinlock_types.h
@@ -0,0 +1,28 @@
+#ifndef __ASM_SPINLOCK_TYPES_H
+#define __ASM_SPINLOCK_TYPES_H
+
+#ifndef __LINUX_SPINLOCK_TYPES_H
+# error "please don't include this file directly"
+#endif
+
+#define TICKET_SHIFT 16
+
+typedef struct {
+ union {
+ u32 slock;
+ struct __raw_tickets {
+ u16 next;
+ u16 owner;
+ } tickets;
+ };
+} arch_spinlock_t;
+
+#define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } }
+
+typedef struct {
+ u32 lock;
+} arch_rwlock_t;
+
+#define __ARCH_RW_LOCK_UNLOCKED { 0 }
+
+#endif
--
2.9.3
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