OMAP: DSS2: OMAPFB: Make lockdep happy

When more than one memory region needs to be lockd at the same time use
the memory region id to fix the order in which the locks are taken. Also
one needs to use the _nested() versions of the locking primitives. The
memory region id can serve as the lock class there as well.

Signed-off-by: Ville Syrjälä <ville.syrjala@nokia.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>

3 files changed, 36 insertions, 13 deletions

diff --git a/drivers/video/omap2/omapfb/omapfb-ioctl.c b/drivers/video/omap2/omapfb/omapfb-ioctl.c
index 3a10146dc120..7975a99c33f9 100644
--- a/drivers/video/omap2/omapfb/omapfb-ioctl.c
+++ b/drivers/video/omap2/omapfb/omapfb-ioctl.c
@@ -55,7 +55,7 @@ static struct omapfb2_mem_region *get_mem_region(struct omapfb_info *ofbi,
         if (mem_idx >= fbdev->num_fbs)
                 return NULL;
 
-        return omapfb_get_mem_region(&fbdev->regions[mem_idx]);
+        return &fbdev->regions[mem_idx];
 }
 
 static int omapfb_setup_plane(struct fb_info *fbi, struct omapfb_plane_info *pi)
@@ -77,20 +77,30 @@ static int omapfb_setup_plane(struct fb_info *fbi, struct omapfb_plane_info *pi)
         /* XXX uses only the first overlay */
         ovl = ofbi->overlays[0];
 
-        old_rg = omapfb_get_mem_region(ofbi->region);
+        old_rg = ofbi->region;
         new_rg = get_mem_region(ofbi, pi->mem_idx);
         if (!new_rg) {
                 r = -EINVAL;
-                goto put_old;
+                goto out;
         }
 
+        /* Take the locks in a specific order to keep lockdep happy */
+        if (old_rg->id < new_rg->id) {
+                omapfb_get_mem_region(old_rg);
+                omapfb_get_mem_region(new_rg);
+        } else if (new_rg->id < old_rg->id) {
+                omapfb_get_mem_region(new_rg);
+                omapfb_get_mem_region(old_rg);
+        } else
+                omapfb_get_mem_region(old_rg);
+
         if (pi->enabled && !new_rg->size) {
                 /*
                  * This plane's memory was freed, can't enable it
                  * until it's reallocated.
                  */
                 r = -EINVAL;
-                goto put_new;
+                goto put_mem;
         }
 
         ovl->get_overlay_info(ovl, &old_info);
@@ -135,8 +145,15 @@ static int omapfb_setup_plane(struct fb_info *fbi, struct omapfb_plane_info *pi)
         if (ovl->manager)
                 ovl->manager->apply(ovl->manager);
 
-        omapfb_put_mem_region(new_rg);
-        omapfb_put_mem_region(old_rg);
+        /* Release the locks in a specific order to keep lockdep happy */
+        if (old_rg->id > new_rg->id) {
+                omapfb_put_mem_region(old_rg);
+                omapfb_put_mem_region(new_rg);
+        } else if (new_rg->id > old_rg->id) {
+                omapfb_put_mem_region(new_rg);
+                omapfb_put_mem_region(old_rg);
+        } else
+                omapfb_put_mem_region(old_rg);
 
         return 0;
 
@@ -147,10 +164,16 @@ static int omapfb_setup_plane(struct fb_info *fbi, struct omapfb_plane_info *pi)
         }
 
         ovl->set_overlay_info(ovl, &old_info);
- put_new:
-        omapfb_put_mem_region(new_rg);
- put_old:
-        omapfb_put_mem_region(old_rg);
+ put_mem:
+        /* Release the locks in a specific order to keep lockdep happy */
+        if (old_rg->id > new_rg->id) {
+                omapfb_put_mem_region(old_rg);
+                omapfb_put_mem_region(new_rg);
+        } else if (new_rg->id > old_rg->id) {
+                omapfb_put_mem_region(new_rg);
+                omapfb_put_mem_region(old_rg);
+        } else
+                omapfb_put_mem_region(old_rg);
  out:
         dev_err(fbdev->dev, "setup_plane failed\n");
 
@@ -198,7 +221,7 @@ static int omapfb_setup_mem(struct fb_info *fbi, struct omapfb_mem_info *mi)
 
         rg = ofbi->region;
 
-        down_write(&rg->lock);
+        down_write_nested(&rg->lock, rg->id);
 
         if (atomic_read(&rg->map_count)) {
                 r = -EBUSY;
diff --git a/drivers/video/omap2/omapfb/omapfb-sysfs.c b/drivers/video/omap2/omapfb/omapfb-sysfs.c
index 724b760404f2..1e714bb48d39 100644
--- a/drivers/video/omap2/omapfb/omapfb-sysfs.c
+++ b/drivers/video/omap2/omapfb/omapfb-sysfs.c
@@ -452,7 +452,7 @@ static ssize_t store_size(struct device *dev, struct device_attribute *attr,
 
         rg = ofbi->region;
 
-        down_write(&rg->lock);
+        down_write_nested(&rg->lock, rg->id);
 
         if (atomic_read(&rg->map_count)) {
                 r = -EBUSY;
diff --git a/drivers/video/omap2/omapfb/omapfb.h b/drivers/video/omap2/omapfb/omapfb.h
index 195a760eef54..676b55d98941 100644
--- a/drivers/video/omap2/omapfb/omapfb.h
+++ b/drivers/video/omap2/omapfb/omapfb.h
@@ -165,7 +165,7 @@ static inline int omapfb_overlay_enable(struct omap_overlay *ovl,
 static inline struct omapfb2_mem_region *
 omapfb_get_mem_region(struct omapfb2_mem_region *rg)
 {
-        down_read(&rg->lock);
+        down_read_nested(&rg->lock, rg->id);
         return rg;
 }