metag: Atomics, locks and bitops

Add header files to implement Meta hardware thread locks (used by some
other atomic operations), atomics, spinlocks, and bitops.

There are 2 main types of atomic primitives for metag (in addition to
IRQs off on UP):
 - LOCK instructions provide locking between hardware threads.
 - LNKGET/LNKSET instructions provide load-linked/store-conditional
   operations allowing for lighter weight atomics on Meta2

LOCK instructions allow for hardware threads to acquire voluntary or
exclusive hardware thread locks:
 - LOCK0 releases exclusive and voluntary lock from the running hardware
   thread.
 - LOCK1 acquires the voluntary hardware lock, blocking until it becomes
   available.
 - LOCK2 implies LOCK1, and additionally acquires the exclusive hardware
   lock, blocking all other hardware threads from executing.

Signed-off-by: James Hogan <james.hogan@imgtec.com>

1 files changed, 249 insertions, 0 deletions

diff --git a/arch/metag/include/asm/spinlock_lnkget.h b/arch/metag/include/asm/spinlock_lnkget.h
new file mode 100644
index 000000000000..ad8436feed8d
--- /dev/null
+++ b/arch/metag/include/asm/spinlock_lnkget.h
@@ -0,0 +1,249 @@
+#ifndef __ASM_SPINLOCK_LNKGET_H
+#define __ASM_SPINLOCK_LNKGET_H
+
+/*
+ * None of these asm statements clobber memory as LNKSET writes around
+ * the cache so the memory it modifies cannot safely be read by any means
+ * other than these accessors.
+ */
+
+static inline int arch_spin_is_locked(arch_spinlock_t *lock)
+{
+	int ret;
+
+	asm volatile ("LNKGETD	%0, [%1]\n"
+		      "TST	%0, #1\n"
+		      "MOV	%0, #1\n"
+		      "XORZ      %0, %0, %0\n"
+		      : "=&d" (ret)
+		      : "da" (&lock->lock)
+		      : "cc");
+	return ret;
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+	int tmp;
+
+	asm volatile ("1:     LNKGETD %0,[%1]\n"
+		      "       TST     %0, #1\n"
+		      "       ADD     %0, %0, #1\n"
+		      "       LNKSETDZ [%1], %0\n"
+		      "       BNZ     1b\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       BNZ     1b\n"
+		      : "=&d" (tmp)
+		      : "da" (&lock->lock)
+		      : "cc");
+
+	smp_mb();
+}
+
+/* Returns 0 if failed to acquire lock */
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+	int tmp;
+
+	asm volatile ("       LNKGETD %0,[%1]\n"
+		      "       TST     %0, #1\n"
+		      "       ADD     %0, %0, #1\n"
+		      "       LNKSETDZ [%1], %0\n"
+		      "       BNZ     1f\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       MOV     %0, #1\n"
+		      "1:     XORNZ   %0, %0, %0\n"
+		      : "=&d" (tmp)
+		      : "da" (&lock->lock)
+		      : "cc");
+
+	smp_mb();
+
+	return tmp;
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+	smp_mb();
+
+	asm volatile ("       SETD    [%0], %1\n"
+		      :
+		      : "da" (&lock->lock), "da" (0)
+		      : "memory");
+}
+
+/*
+ * 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)
+{
+	int tmp;
+
+	asm volatile ("1:     LNKGETD %0,[%1]\n"
+		      "       CMP     %0, #0\n"
+		      "       ADD     %0, %0, %2\n"
+		      "       LNKSETDZ [%1], %0\n"
+		      "       BNZ     1b\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       BNZ     1b\n"
+		      : "=&d" (tmp)
+		      : "da" (&rw->lock), "bd" (0x80000000)
+		      : "cc");
+
+	smp_mb();
+}
+
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+	int tmp;
+
+	asm volatile ("       LNKGETD %0,[%1]\n"
+		      "       CMP     %0, #0\n"
+		      "       ADD     %0, %0, %2\n"
+		      "       LNKSETDZ [%1], %0\n"
+		      "       BNZ     1f\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       MOV     %0,#1\n"
+		      "1:     XORNZ   %0, %0, %0\n"
+		      : "=&d" (tmp)
+		      : "da" (&rw->lock), "bd" (0x80000000)
+		      : "cc");
+
+	smp_mb();
+
+	return tmp;
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+	smp_mb();
+
+	asm volatile ("       SETD    [%0], %1\n"
+		      :
+		      : "da" (&rw->lock), "da" (0)
+		      : "memory");
+}
+
+/* write_can_lock - would write_trylock() succeed? */
+static inline int arch_write_can_lock(arch_rwlock_t *rw)
+{
+	int ret;
+
+	asm volatile ("LNKGETD	%0, [%1]\n"
+		      "CMP	%0, #0\n"
+		      "MOV	%0, #1\n"
+		      "XORNZ     %0, %0, %0\n"
+		      : "=&d" (ret)
+		      : "da" (&rw->lock)
+		      : "cc");
+	return ret;
+}
+
+/*
+ * 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)
+{
+	int tmp;
+
+	asm volatile ("1:     LNKGETD %0,[%1]\n"
+		      "       ADDS    %0, %0, #1\n"
+		      "       LNKSETDPL [%1], %0\n"
+		      "       BMI     1b\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       BNZ     1b\n"
+		      : "=&d" (tmp)
+		      : "da" (&rw->lock)
+		      : "cc");
+
+	smp_mb();
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+	int tmp;
+
+	smp_mb();
+
+	asm volatile ("1:     LNKGETD %0,[%1]\n"
+		      "       SUB     %0, %0, #1\n"
+		      "       LNKSETD [%1], %0\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       BNZ     1b\n"
+		      : "=&d" (tmp)
+		      : "da" (&rw->lock)
+		      : "cc", "memory");
+}
+
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+	int tmp;
+
+	asm volatile ("       LNKGETD %0,[%1]\n"
+		      "       ADDS    %0, %0, #1\n"
+		      "       LNKSETDPL [%1], %0\n"
+		      "       BMI     1f\n"
+		      "       DEFR    %0, TXSTAT\n"
+		      "       ANDT    %0, %0, #HI(0x3f000000)\n"
+		      "       CMPT    %0, #HI(0x02000000)\n"
+		      "       MOV     %0,#1\n"
+		      "       BZ      2f\n"
+		      "1:     MOV     %0,#0\n"
+		      "2:\n"
+		      : "=&d" (tmp)
+		      : "da" (&rw->lock)
+		      : "cc");
+
+	smp_mb();
+
+	return tmp;
+}
+
+/* read_can_lock - would read_trylock() succeed? */
+static inline int arch_read_can_lock(arch_rwlock_t *rw)
+{
+	int tmp;
+
+	asm volatile ("LNKGETD	%0, [%1]\n"
+		      "CMP	%0, %2\n"
+		      "MOV	%0, #1\n"
+		      "XORZ	%0, %0, %0\n"
+		      : "=&d" (tmp)
+		      : "da" (&rw->lock), "bd" (0x80000000)
+		      : "cc");
+	return tmp;
+}
+
+#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 /* __ASM_SPINLOCK_LNKGET_H */