diff --git a/target/linux/adm5120/files/arch/mips/adm5120/boards/mikrotik.c b/target/linux/adm5120/files/arch/mips/adm5120/boards/mikrotik.c
index 1ed420e0c..855ec3afb 100644
--- a/target/linux/adm5120/files/arch/mips/adm5120/boards/mikrotik.c
+++ b/target/linux/adm5120/files/arch/mips/adm5120/boards/mikrotik.c
@@ -140,6 +140,7 @@ static unsigned char rb133c_vlans[6] __initdata = {
 static unsigned char rb15x_vlans[6] __initdata = {
 	/* FIXME: untested */
 	0x41, 0x42, 0x44, 0x48, 0x50, 0x00
+};
 
 static unsigned char rb192_vlans[6] __initdata = {
 	/* FIXME: untested */
@@ -261,6 +262,8 @@ static void __init rb150_setup(void)
 	adm5120_nand_data.ctrl.cmd_ctrl = rb150_nand_cmd_ctrl;
 	adm5120_nand_data.ctrl.dev_ready = rb150_nand_ready;
 
+	adm5120_flash0_data.window_size = 512*1024;
+
 	rb1xx_flash_setup();
 	rb1xx_mac_setup();
 }
diff --git a/target/linux/adm5120/files/drivers/mtd/maps/adm5120-flash.c b/target/linux/adm5120/files/drivers/mtd/maps/adm5120-flash.c
index e07fb96d2..20f67d625 100644
--- a/target/linux/adm5120/files/drivers/mtd/maps/adm5120-flash.c
+++ b/target/linux/adm5120/files/drivers/mtd/maps/adm5120-flash.c
@@ -244,7 +244,7 @@ static int adm5120_flash_initinfo(struct adm5120_flash_info *info,
 	struct map_info *map = &info->amap.map;
 	struct adm5120_flash_platform_data *pdata = dev->dev.platform_data;
 	struct flash_desc *fdesc;
-	u32 t;
+	u32 t = 0;
 
 	map->name = dev->dev.bus_id;
 
@@ -255,12 +255,18 @@ static int adm5120_flash_initinfo(struct adm5120_flash_info *info,
 
 	fdesc = &flash_descs[dev->id];
 
-	/* get memory window size */
-	t = SW_READ_REG(MEMCTRL) >> fdesc->srs_shift;
-	t &= MEMCTRL_SRS_MASK;
-	info->amap.window_size = flash_sizes[t];
+	if (pdata)
+		info->amap.window_size = pdata->window_size;
+
 	if (info->amap.window_size == 0) {
-		MAP_ERR(map, "invalid flash size detected\n");
+		/* get memory window size */
+		t = SW_READ_REG(MEMCTRL) >> fdesc->srs_shift;
+		t &= MEMCTRL_SRS_MASK;
+		info->amap.window_size = flash_sizes[t];
+	}
+
+	if (info->amap.window_size == 0) {
+		MAP_ERR(map, "unable to determine window size\n");
 		goto err_out;
 	}
 
diff --git a/target/linux/adm5120/files/include/asm-mips/mach-adm5120/adm5120_platform.h b/target/linux/adm5120/files/include/asm-mips/mach-adm5120/adm5120_platform.h
index b20c483b8..f47b10b78 100644
--- a/target/linux/adm5120/files/include/asm-mips/mach-adm5120/adm5120_platform.h
+++ b/target/linux/adm5120/files/include/asm-mips/mach-adm5120/adm5120_platform.h
@@ -39,6 +39,7 @@
 struct adm5120_flash_platform_data {
 	void			(*set_vpp)(struct map_info *, int);
 	void			(*switch_bank)(unsigned);
+	u32			window_size;
 #ifdef CONFIG_MTD_PARTITIONS
 	unsigned int		nr_parts;
 	struct mtd_partition	*parts;