[PATCH] FB: Get the Geode GX frambuffer size from the BIOS

Use the Geode GX BIOS virtual registers to get the actual size of the
framebuffer.

Signed-off-by: Jordan Crouse <jordan.crouse@amd.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Acked-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/video/geode/display_gx.c

@@ -21,10 +21,19 @@
 #include "geodefb.h"
 #include "display_gx.h"
 
-int gx_frame_buffer_size(void)
+unsigned int gx_frame_buffer_size(void)
 {
-	/* Assuming 16 MiB. */
-	return 16*1024*1024;
+	unsigned int val;
+
+	/* FB size is reported by a virtual register */
+	/* Virtual register class = 0x02 */
+	/* VG_MEM_SIZE(512Kb units) = 0x00 */
+
+	outw(0xFC53, 0xAC1C);
+	outw(0x0200, 0xAC1C);
+
+	val = (unsigned int)(inw(0xAC1E)) & 0xFFl;
+	return (val << 19);
 }
 
 int gx_line_delta(int xres, int bpp)