tridentfb: preserve memory type settings

Do not overwrite bits which contain memory type settings.  It removes
noise pixels ("snow") on Blade3D and 3DImage chips.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/video/tridentfb.c b/drivers/video/tridentfb.c
index 62701c5570fd..26bc4d75d4fd 100644
--- a/drivers/video/tridentfb.c
+++ b/drivers/video/tridentfb.c
@@ -1095,7 +1095,10 @@ static int tridentfb_set_par(struct fb_info *info)
         vga_mm_wseq(par->io_virt, 4, 0x0E); /* memory mode enable bitmaps ?? */
 
         /* divide clock by 2 if 32bpp chain4 mode display and CPU path */
-        write3CE(par, MiscExtFunc, (bpp == 32) ? 0x1A : 0x12);
+        tmp = read3CE(par, MiscExtFunc) & 0xF0;
+        if (bpp == 32)
+                tmp |= 8;
+        write3CE(par, MiscExtFunc, tmp | 0x12);
         write3CE(par, 0x5, 0x40);       /* no CGA compat, allow 256 col */
         write3CE(par, 0x6, 0x05);       /* graphics mode */
         write3CE(par, 0x7, 0x0F);       /* planes? */