xtensa: add s32c1i-based spinlock implementations

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/include/asm/spinlock.h

@@ -11,6 +11,192 @@
 #ifndef _XTENSA_SPINLOCK_H
 #define _XTENSA_SPINLOCK_H
 
-#include <linux/spinlock.h>
+/*
+ * spinlock
+ *
+ * There is at most one owner of a spinlock.  There are not different
+ * types of spinlock owners like there are for rwlocks (see below).
+ *
+ * When trying to obtain a spinlock, the function "spins" forever, or busy-
+ * waits, until the lock is obtained.  When spinning, presumably some other
+ * owner will soon give up the spinlock making it available to others.  Use
+ * the trylock functions to avoid spinning forever.
+ *
+ * possible values:
+ *
+ *    0         nobody owns the spinlock
+ *    1         somebody owns the spinlock
+ */
+
+#define __raw_spin_is_locked(x) ((x)->slock != 0)
+#define __raw_spin_unlock_wait(lock) \
+	do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
+
+#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
+
+static inline void __raw_spin_lock(raw_spinlock_t *lock)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       movi    %0, 0\n"
+			"       wsr     %0, scompare1\n"
+			"1:     movi    %0, 1\n"
+			"       s32c1i  %0, %1, 0\n"
+			"       bnez    %0, 1b\n"
+			: "=&a" (tmp)
+			: "a" (&lock->slock)
+			: "memory");
+}
+
+/* Returns 1 if the lock is obtained, 0 otherwise. */
+
+static inline int __raw_spin_trylock(raw_spinlock_t *lock)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       movi    %0, 0\n"
+			"       wsr     %0, scompare1\n"
+			"       movi    %0, 1\n"
+			"       s32c1i  %0, %1, 0\n"
+			: "=&a" (tmp)
+			: "a" (&lock->slock)
+			: "memory");
+
+	return tmp == 0 ? 1 : 0;
+}
+
+static inline void __raw_spin_unlock(raw_spinlock_t *lock)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       movi    %0, 0\n"
+			"       s32ri   %0, %1, 0\n"
+			: "=&a" (tmp)
+			: "a" (&lock->slock)
+			: "memory");
+}
+
+/*
+ * rwlock
+ *
+ * Read-write locks are really a more flexible spinlock.  They allow
+ * multiple readers but only one writer.  Write ownership is exclusive
+ * (i.e., all other readers and writers are blocked from ownership while
+ * there is a write owner).  These rwlocks are unfair to writers.  Writers
+ * can be starved for an indefinite time by readers.
+ *
+ * possible values:
+ *
+ *   0          nobody owns the rwlock
+ *  >0          one or more readers own the rwlock
+ *                (the positive value is the actual number of readers)
+ *  0x80000000  one writer owns the rwlock, no other writers, no readers
+ */
+
+#define __raw_write_can_lock(x)  ((x)->lock == 0)
+
+static inline void __raw_write_lock(raw_rwlock_t *rw)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       movi    %0, 0\n"
+			"       wsr     %0, scompare1\n"
+			"1:     movi    %0, 1\n"
+			"       slli    %0, %0, 31\n"
+			"       s32c1i  %0, %1, 0\n"
+			"       bnez    %0, 1b\n"
+			: "=&a" (tmp)
+			: "a" (&rw->lock)
+			: "memory");
+}
+
+/* Returns 1 if the lock is obtained, 0 otherwise. */
+
+static inline int __raw_write_trylock(raw_rwlock_t *rw)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       movi    %0, 0\n"
+			"       wsr     %0, scompare1\n"
+			"       movi    %0, 1\n"
+			"       slli    %0, %0, 31\n"
+			"       s32c1i  %0, %1, 0\n"
+			: "=&a" (tmp)
+			: "a" (&rw->lock)
+			: "memory");
+
+	return tmp == 0 ? 1 : 0;
+}
+
+static inline void __raw_write_unlock(raw_rwlock_t *rw)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       movi    %0, 0\n"
+			"       s32ri   %0, %1, 0\n"
+			: "=&a" (tmp)
+			: "a" (&rw->lock)
+			: "memory");
+}
+
+static inline void __raw_read_lock(raw_rwlock_t *rw)
+{
+	unsigned long tmp;
+	unsigned long result;
+
+	__asm__ __volatile__(
+			"1:     l32i    %1, %2, 0\n"
+			"       bltz    %1, 1b\n"
+			"       wsr     %1, scompare1\n"
+			"       addi    %0, %1, 1\n"
+			"       s32c1i  %0, %2, 0\n"
+			"       bne     %0, %1, 1b\n"
+			: "=&a" (result), "=&a" (tmp)
+			: "a" (&rw->lock)
+			: "memory");
+}
+
+/* Returns 1 if the lock is obtained, 0 otherwise. */
+
+static inline int __raw_read_trylock(raw_rwlock_t *rw)
+{
+	unsigned long result;
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+			"       l32i    %1, %2, 0\n"
+			"       addi    %0, %1, 1\n"
+			"       bltz    %0, 1f\n"
+			"       wsr     %1, scompare1\n"
+			"       s32c1i  %0, %2, 0\n"
+			"       sub     %0, %0, %1\n"
+			"1:\n"
+			: "=&a" (result), "=&a" (tmp)
+			: "a" (&rw->lock)
+			: "memory");
+
+	return result == 0;
+}
+
+static inline void __raw_read_unlock(raw_rwlock_t *rw)
+{
+	unsigned long tmp1, tmp2;
+
+	__asm__ __volatile__(
+			"1:     l32i    %1, %2, 0\n"
+			"       addi    %0, %1, -1\n"
+			"       wsr     %1, scompare1\n"
+			"       s32c1i  %0, %2, 0\n"
+			"       bne     %0, %1, 1b\n"
+			: "=&a" (tmp1), "=&a" (tmp2)
+			: "a" (&rw->lock)
+			: "memory");
+}
 
 #endif	/* _XTENSA_SPINLOCK_H */