OMAP: DSS2: DSI: change DSI bus_lock to semaphore

Physical DSI bus is protected by a mutex. This patch changed the mutex to
a semaphore, so that we can lock and unlock the bus_lock from different
threads.

This is needed as the update process is started by user space program, and
thus the lock is acquired in that context, but the lock can be released in
different context, a work thread via irq.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>

drivers/video/omap2/dss/dsi.c

@@ -27,6 +27,7 @@
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
+#include <linux/semaphore.h>
 #include <linux/seq_file.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
@@ -227,7 +228,7 @@ static struct
 	} vc[4];
 
 	struct mutex lock;
-	struct mutex bus_lock;
+	struct semaphore bus_lock;
 
 	unsigned pll_locked;
 
@@ -298,19 +299,19 @@ void dsi_restore_context(void)
 
 void dsi_bus_lock(void)
 {
-	mutex_lock(&dsi.bus_lock);
+	down(&dsi.bus_lock);
 }
 EXPORT_SYMBOL(dsi_bus_lock);
 
 void dsi_bus_unlock(void)
 {
-	mutex_unlock(&dsi.bus_lock);
+	up(&dsi.bus_lock);
 }
 EXPORT_SYMBOL(dsi_bus_unlock);
 
 static bool dsi_bus_is_locked(void)
 {
-	return mutex_is_locked(&dsi.bus_lock);
+	return dsi.bus_lock.count == 0;
 }
 
 static inline int wait_for_bit_change(const struct dsi_reg idx, int bitnum,
@@ -3002,8 +3003,6 @@ static int dsi_update_thread(void *data)
 	u16 x, y, w, h;
 
 	while (1) {
-		bool sched;
-
 		wait_event_interruptible(dsi.waitqueue,
 				dsi.update_mode == OMAP_DSS_UPDATE_AUTO ||
 				(dsi.update_mode == OMAP_DSS_UPDATE_MANUAL &&
@@ -3089,16 +3088,9 @@ static int dsi_update_thread(void *data)
 			dsi_perf_show("L4");
 		}
 
-		sched = atomic_read(&dsi.bus_lock.count) < 0;
-
 		complete_all(&dsi.update_completion);
 
 		dsi_bus_unlock();
-
-		/* XXX We need to give others chance to get the bus lock. Is
-		 * there a better way for this? */
-		if (dsi.update_mode == OMAP_DSS_UPDATE_AUTO && sched)
-			schedule_timeout_interruptible(1);
 	}
 
 	DSSDBG("update thread exiting\n");
@@ -3798,7 +3790,7 @@ int dsi_init(struct platform_device *pdev)
 	spin_lock_init(&dsi.update_lock);
 
 	mutex_init(&dsi.lock);
-	mutex_init(&dsi.bus_lock);
+	sema_init(&dsi.bus_lock, 1);
 
 #ifdef DSI_CATCH_MISSING_TE
 	init_timer(&dsi.te_timer);