brcm47xx: added dual image support to flashmap driver

some CFE versions (i.e. WRT54G3Gv2-VF) expect two separate firmware
images which each consume half of the available flash space.
these changes check for the TRX header version and set the partition
size correctly.
Tested on G3Gv2-VF and Asus WL-500GP

SVN-Revision: 22019

target/linux/brcm47xx/files/drivers/mtd/maps/bcm47xx-flash.c

@@ -222,6 +222,37 @@ static int erase_write (struct mtd_info *mtd, unsigned long pos,
 }
 
 
+static int __init
+find_dual_image_off (struct mtd_info *mtd, size_t size)
+{
+	struct trx_header trx;
+	int off, blocksize;
+	size_t len;
+
+	blocksize = mtd->erasesize;
+	if (blocksize < 0x10000)
+		blocksize = 0x10000;
+
+	for (off = (128*1024); off < size; off += blocksize) {
+		memset(&trx, 0xe5, sizeof(trx));
+		/*
+		* Read into buffer 
+		*/
+		if (mtd->read(mtd, off, sizeof(trx), &len, (char *) &trx) ||
+		    len != sizeof(trx))
+			continue;
+		/* found last TRX header */
+		if (le32_to_cpu(trx.magic) == TRX_MAGIC){ 
+			if (le32_to_cpu(trx.flag_version >> 16)==2){
+				printk("dual image TRX header found\n");
+				return size/2;
+			} else {
+				return 0;
+			}
+		}
+	}
+	return 0;
+}
 
 
 static int __init
@@ -232,7 +263,6 @@ find_root(struct mtd_info *mtd, size_t size, struct mtd_partition *part)
 	int off, blocksize;
 	u32 i, crc = ~0;
 	size_t len;
-	struct squashfs_super_block *sb = (struct squashfs_super_block *) buf;
 
 	blocksize = mtd->erasesize;
 	if (blocksize < 0x10000)
@@ -318,6 +348,7 @@ struct mtd_partition * __init
 init_mtd_partitions(struct mtd_info *mtd, size_t size)
 {
 	int cfe_size;
+	int dual_image_offset = 0;
 
 	if ((cfe_size = find_cfe_size(mtd,size)) < 0)
 		return NULL;
@@ -336,10 +367,13 @@ init_mtd_partitions(struct mtd_info *mtd, size_t size)
 		bcm47xx_parts[3].size   = ROUNDUP(NVRAM_SPACE, mtd->erasesize);
 	}
 
+	/* dual image offset*/
+	printk("Looking for dual image\n");
+	dual_image_offset=find_dual_image_off(mtd,size);
 	/* linux (kernel and rootfs) */
 	if (cfe_size != 384 * 1024) {
 		bcm47xx_parts[1].offset = bcm47xx_parts[0].size;
-		bcm47xx_parts[1].size   = bcm47xx_parts[3].offset - 
+		bcm47xx_parts[1].size   = bcm47xx_parts[3].offset - dual_image_offset -
 			bcm47xx_parts[1].offset;
 	} else {
 		/* do not count the elf loader, which is on one block */
@@ -353,7 +387,7 @@ init_mtd_partitions(struct mtd_info *mtd, size_t size)
 
 	/* find and size rootfs */
 	find_root(mtd,size,&bcm47xx_parts[2]);
-	bcm47xx_parts[2].size = size - bcm47xx_parts[2].offset - bcm47xx_parts[3].size;
+	bcm47xx_parts[2].size = size - dual_image_offset - bcm47xx_parts[2].offset - bcm47xx_parts[3].size;
 
 	return bcm47xx_parts;
 }