stifb: fix crash A1439A CRX (Rattler) graphics card

Fix kernel crash when stifb driver is used with a A1439A CRX (Rattler)
graphics card.  (Reference:
http://thread.gmane.org/gmane.linux.ports.hppa/1834)

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/stifb.c

@@ -505,16 +505,24 @@ ngleSetupAttrPlanes(struct stifb_info *fb, int BufferNumber)
 static void
 rattlerSetupPlanes(struct stifb_info *fb)
 {
+	int saved_id, y;
+
+ 	/* Write RAMDAC pixel read mask register so all overlay
+	 * planes are display-enabled.  (CRX24 uses Bt462 pixel
+	 * read mask register for overlay planes, not image planes).
+	 */
 	CRX24_SETUP_RAMDAC(fb);
 
-	/* replacement for: SETUP_FB(fb, CRX24_OVERLAY_PLANES); */
-	WRITE_WORD(0x83000300, fb, REG_14);
-	SETUP_HW(fb);
-	WRITE_BYTE(1, fb, REG_16b1);
+	/* change fb->id temporarily to fool SETUP_FB() */
+	saved_id = fb->id;
+	fb->id = CRX24_OVERLAY_PLANES;
+	SETUP_FB(fb);
+	fb->id = saved_id;
+
+	for (y = 0; y < fb->info.var.yres; ++y)
+		memset(fb->info.screen_base + y * fb->info.fix.line_length,
+			0xff, fb->info.var.xres * fb->info.var.bits_per_pixel/8);
 
-	fb_memset((void*)fb->info.fix.smem_start, 0xff,
-		fb->info.var.yres*fb->info.fix.line_length);
-
 	CRX24_SET_OVLY_MASK(fb);
 	SETUP_FB(fb);
 }