backlight: Fix external uses of backlight internal semaphore

backlight_device->sem has a very specific use as documented in the
header file. The external users of this are using it for a different
reason, to serialise access to the update_status() method.

backlight users were supposed to implement their own internal
serialisation of update_status() if needed but everyone is doing
things differently and incorrectly. Therefore add a global mutex to
take care of serialisation for everyone, once and for all.

Locking for get_brightness remains optional since most users don't
need it.

Also update the lcd class in a similar way.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>

1 files changed, 1 insertions, 5 deletions

diff --git a/drivers/video/nvidia/nv_backlight.c b/drivers/video/nvidia/nv_backlight.c
index 4254c090dc4b..f5e42d0bd0da 100644
--- a/drivers/video/nvidia/nv_backlight.c
+++ b/drivers/video/nvidia/nv_backlight.c
@@ -114,10 +114,8 @@ void nvidia_bl_set_power(struct fb_info *info, int power)
         mutex_lock(&info->bl_mutex);
 
         if (info->bl_dev) {
-                down(&info->bl_dev->sem);
                 info->bl_dev->props->power = power;
                 __nvidia_bl_update_status(info->bl_dev);
-                up(&info->bl_dev->sem);
         }
 
         mutex_unlock(&info->bl_mutex);
@@ -154,11 +152,9 @@ void nvidia_bl_init(struct nvidia_par *par)
                 0x534 * FB_BACKLIGHT_MAX / MAX_LEVEL);
         mutex_unlock(&info->bl_mutex);
 
-        down(&bd->sem);
         bd->props->brightness = nvidia_bl_data.max_brightness;
         bd->props->power = FB_BLANK_UNBLANK;
-        bd->props->update_status(bd);
-        up(&bd->sem);
+        backlight_update_status(bd);
 
 #ifdef CONFIG_PMAC_BACKLIGHT
         mutex_lock(&pmac_backlight_mutex);