omapfb: Condition mutex acquisition

This fixes a bug introduced by this commit ID:

  commit 537a1bf0
  Author: Krzysztof Helt <krzysztof.h1@wp.pl>
  Date:   Tue Jun 30 11:41:29 2009 -0700

    fbdev: add mutex for fb_mmap locking

In which a mutex was added when changing smem_start and smem_len fields,
so the mutex inside the fb_mmap() call is actually used.

The problem was that set_fb_fix, which modifies the above 2 fields,
was called before and after registering the framebuffer,
which when used before registration, lead to a failed attempt to
use an uninitialized mutex.

Solution: Don't use mutex before framebuffer registration.
Signed-off-by: Sergio Aguirre <saaguirre@ti.com>
Acked-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>
Acked-by: Imre Deak <imre.deak@nokia.com>
Tested-by: Cory Maccarrone <darkstar6262@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/video/omap/omapfb_main.c

@@ -393,7 +393,7 @@ static void omapfb_sync(struct fb_info *fbi)
  * Set fb_info.fix fields and also updates fbdev.
  * When calling this fb_info.var must be set up already.
  */
-static void set_fb_fix(struct fb_info *fbi)
+static void set_fb_fix(struct fb_info *fbi, int from_init)
 {
 	struct fb_fix_screeninfo *fix = &fbi->fix;
 	struct fb_var_screeninfo *var = &fbi->var;
@@ -403,10 +403,16 @@ static void set_fb_fix(struct fb_info *fbi)
 
 	rg = &plane->fbdev->mem_desc.region[plane->idx];
 	fbi->screen_base	= rg->vaddr;
-	mutex_lock(&fbi->mm_lock);
-	fix->smem_start		= rg->paddr;
-	fix->smem_len		= rg->size;
-	mutex_unlock(&fbi->mm_lock);
+
+	if (!from_init) {
+		mutex_lock(&fbi->mm_lock);
+		fix->smem_start		= rg->paddr;
+		fix->smem_len		= rg->size;
+		mutex_unlock(&fbi->mm_lock);
+	} else {
+		fix->smem_start		= rg->paddr;
+		fix->smem_len		= rg->size;
+	}
 
 	fix->type = FB_TYPE_PACKED_PIXELS;
 	bpp = var->bits_per_pixel;
@@ -704,7 +710,7 @@ static int omapfb_set_par(struct fb_info *fbi)
 	int r = 0;
 
 	omapfb_rqueue_lock(fbdev);
-	set_fb_fix(fbi);
+	set_fb_fix(fbi, 0);
 	r = ctrl_change_mode(fbi);
 	omapfb_rqueue_unlock(fbdev);
 
@@ -904,7 +910,7 @@ static int omapfb_setup_mem(struct fb_info *fbi, struct omapfb_mem_info *mi)
 		if (old_size != size) {
 			if (size) {
 				memcpy(&fbi->var, new_var, sizeof(fbi->var));
-				set_fb_fix(fbi);
+				set_fb_fix(fbi, 0);
 			} else {
 				/*
 				 * Set these explicitly to indicate that the
@@ -1504,7 +1510,7 @@ static int fbinfo_init(struct omapfb_device *fbdev, struct fb_info *info)
 	var->bits_per_pixel = fbdev->panel->bpp;
 
 	set_fb_var(info, var);
-	set_fb_fix(info);
+	set_fb_fix(info, 1);
 
 	r = fb_alloc_cmap(&info->cmap, 16, 0);
 	if (r != 0)