[PATCH 1/3] i2c: append hardware lock with bus lock

[Haojian Zhuang <haojian.zhuang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Both AP and CP are contained in Marvell PXA910 silicon. These two ARM
cores are sharing one pair of I2C pins.

In order to keep I2C transaction operated with atomic, hardware lock
(RIPC) is required. Because of this, bus lock in AP side can't afford
this requirement. Now hardware lock is appended.

Signed-off-by: Haojian Zhuang <haojian.zhuang-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>
Cc: Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
---
 drivers/i2c/i2c-core.c |   22 ++++++++++++++++++----
 include/linux/i2c.h    |    3 +++
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 045ba6e..412c7a5 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -448,8 +448,11 @@ void i2c_lock_adapter(struct i2c_adapter *adapter)
 
 	if (parent)
 		i2c_lock_adapter(parent);
-	else
+	else {
 		rt_mutex_lock(&adapter->bus_lock);
+		if (adapter->hardware_lock)
+			adapter->hardware_lock();
+	}
 }
 EXPORT_SYMBOL_GPL(i2c_lock_adapter);
 
@@ -460,11 +463,19 @@ EXPORT_SYMBOL_GPL(i2c_lock_adapter);
 static int i2c_trylock_adapter(struct i2c_adapter *adapter)
 {
 	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
+	int ret = 0;
 
 	if (parent)
 		return i2c_trylock_adapter(parent);
-	else
-		return rt_mutex_trylock(&adapter->bus_lock);
+	else {
+		ret = rt_mutex_trylock(&adapter->bus_lock);
+		if (ret && adapter->hardware_trylock) {
+			ret = adapter->hardware_trylock();
+			if (!ret)
+				i2c_unlock_adapter(adapter);
+		}
+		return ret;
+	}
 }
 
 /**
@@ -477,8 +488,11 @@ void i2c_unlock_adapter(struct i2c_adapter *adapter)
 
 	if (parent)
 		i2c_unlock_adapter(parent);
-	else
+	else {
+		if (adapter->hardware_unlock)
+			adapter->hardware_unlock();
 		rt_mutex_unlock(&adapter->bus_lock);
+	}
 }
 EXPORT_SYMBOL_GPL(i2c_unlock_adapter);
 
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 06a8d9c..b283b4e 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -361,6 +361,9 @@ struct i2c_adapter {
 
 	/* data fields that are valid for all devices	*/
 	struct rt_mutex bus_lock;
+	void (*hardware_lock)(void);
+	void (*hardware_unlock)(void);
+	int (*hardware_trylock)(void);
 
 	int timeout;			/* in jiffies */
 	int retries;
-- 
1.7.1