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>

1 files changed, 15 insertions, 7 deletions

diff --git a/drivers/video/stifb.c b/drivers/video/stifb.c
index e7c8db2eb49b..f98be301140c 100644
--- a/drivers/video/stifb.c
+++ b/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);
 }