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, 2 insertions, 6 deletions

diff --git a/drivers/video/chipsfb.c b/drivers/video/chipsfb.c
index 73cb426bf2d7..9a656bc6295c 100644
--- a/drivers/video/chipsfb.c
+++ b/drivers/video/chipsfb.c
@@ -153,13 +153,11 @@ static int chipsfb_blank(int blank, struct fb_info *info)
                  * useful at blank = 1 too (saves battery, extends backlight
                  * life)
                  */
-                down(&pmac_backlight->sem);
                 if (blank)
                         pmac_backlight->props->power = FB_BLANK_POWERDOWN;
                 else
                         pmac_backlight->props->power = FB_BLANK_UNBLANK;
-                pmac_backlight->props->update_status(pmac_backlight);
-                up(&pmac_backlight->sem);
+                backlight_update_status(pmac_backlight);
         }
 
         mutex_unlock(&pmac_backlight_mutex);
@@ -415,10 +413,8 @@ chipsfb_pci_init(struct pci_dev *dp, const struct pci_device_id *ent)
         /* turn on the backlight */
         mutex_lock(&pmac_backlight_mutex);
         if (pmac_backlight) {
-                down(&pmac_backlight->sem);
                 pmac_backlight->props->power = FB_BLANK_UNBLANK;
-                pmac_backlight->props->update_status(pmac_backlight);
-                up(&pmac_backlight->sem);
+                backlight_update_status(pmac_backlight);
         }
         mutex_unlock(&pmac_backlight_mutex);
 #endif /* CONFIG_PMAC_BACKLIGHT */