1 files changed, 101 insertions, 0 deletions
diff --git a/include/linux/remote_spinlock.h b/include/linux/remote_spinlock.h
new file mode 100644
index 000000000000..591c1b24df9c
--- /dev/null
+++ b/include/linux/remote_spinlock.h
@@ -0,0 +1,101 @@
+/* Copyright (c) 2008-2009, 2011, 2013-2015 The Linux Foundation.
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program 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.
+ *
+ */
+#ifndef __LINUX_REMOTE_SPINLOCK_H
+#define __LINUX_REMOTE_SPINLOCK_H
+
+#include <linux/spinlock.h>
+#include <linux/msm_remote_spinlock.h>
+
+/* Grabbing a local spin lock before going for a remote lock has several
+ * advantages:
+ * 1. Get calls to preempt enable/disable and IRQ save/restore for free.
+ * 2. For UP kernel, there is no overhead.
+ * 3. Reduces the possibility of executing the remote spin lock code. This is
+ *    especially useful when the remote CPUs' mutual exclusion instructions
+ *    don't work with the local CPUs' instructions. In such cases, one has to
+ *    use software based mutex algorithms (e.g. Lamport's bakery algorithm)
+ *    which could get expensive when the no. of contending CPUs is high.
+ * 4. In the case of software based mutex algorithm the exection time will be
+ *    smaller since the no. of contending CPUs is reduced by having just one
+ *    contender for all the local CPUs.
+ * 5. Get most of the spin lock debug features for free.
+ * 6. The code will continue to work "gracefully" even when the remote spin
+ *    lock code is stubbed out for debug purposes or when there is no remote
+ *    CPU in some board/machine types.
+ */
+typedef struct {
+	spinlock_t local;
+	_remote_spinlock_t remote;
+} remote_spinlock_t;
+
+#define remote_spin_lock_init(lock, id) \
+	({ \
+		spin_lock_init(&((lock)->local)); \
+		_remote_spin_lock_init(id, &((lock)->remote)); \
+	})
+#define remote_spin_lock(lock) \
+	do { \
+		spin_lock(&((lock)->local)); \
+		_remote_spin_lock(&((lock)->remote)); \
+	} while (0)
+#define remote_spin_unlock(lock) \
+	do { \
+		_remote_spin_unlock(&((lock)->remote)); \
+		spin_unlock(&((lock)->local)); \
+	} while (0)
+#define remote_spin_lock_irqsave(lock, flags) \
+	do { \
+		spin_lock_irqsave(&((lock)->local), flags); \
+		_remote_spin_lock(&((lock)->remote)); \
+	} while (0)
+#define remote_spin_unlock_irqrestore(lock, flags) \
+	do { \
+		_remote_spin_unlock(&((lock)->remote)); \
+		spin_unlock_irqrestore(&((lock)->local), flags); \
+	} while (0)
+#define remote_spin_trylock(lock) \
+	({ \
+		spin_trylock(&((lock)->local)) \
+		? _remote_spin_trylock(&((lock)->remote)) \
+			? 1 \
+			: ({ spin_unlock(&((lock)->local)); 0; }) \
+		: 0; \
+	})
+#define remote_spin_trylock_irqsave(lock, flags) \
+	({ \
+		spin_trylock_irqsave(&((lock)->local), flags) \
+		? _remote_spin_trylock(&((lock)->remote)) \
+			? 1 \
+			: ({ spin_unlock_irqrestore(&((lock)->local), flags); \
+				0; }) \
+		: 0; \
+	})
+#define remote_spin_lock_rlock_id(lock, tid) \
+	_remote_spin_lock_rlock_id(&((lock)->remote), tid)
+
+#define remote_spin_unlock_rlock(lock) \
+	_remote_spin_unlock_rlock(&((lock)->remote))
+
+#define remote_spin_release(lock, pid) \
+	_remote_spin_release(&((lock)->remote), pid)
+
+#define remote_spin_release_all(pid) \
+	_remote_spin_release_all(pid)
+
+#define remote_spin_owner(lock) \
+	_remote_spin_owner(&((lock)->remote))
+
+#define remote_spin_get_hw_spinlocks_element(lock) \
+	_remote_spin_get_hw_spinlocks_element(&((lock)->remote))
+#endif