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/aty/aty128fb.c b/drivers/video/aty/aty128fb.c
index 1fa211c0d7bb..5d8f73b2b66f 100644
--- a/drivers/video/aty/aty128fb.c
+++ b/drivers/video/aty/aty128fb.c
@@ -1807,10 +1807,8 @@ static void aty128_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;
                 __aty128_bl_update_status(info->bl_dev);
-                up(&info->bl_dev->sem);
         }
 
         mutex_unlock(&info->bl_mutex);
@@ -1847,11 +1845,9 @@ static void aty128_bl_init(struct aty128fb_par *par)
                 219 * FB_BACKLIGHT_MAX / MAX_LEVEL);
         mutex_unlock(&info->bl_mutex);
 
-        down(&bd->sem);
         bd->props->brightness = aty128_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);