[ARM] Kirkwood: support L2 writeback mode

This patch allows booting Kirkwood with the L2 in writeback mode,
by reading the WT override bit from the L2 config register and
passing that into the Feroceon L2 init routine, instead of assuming
that the WT override bit will always be set

Signed-off-by: Saeed Bishara <saeed@marvell.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
diff --git a/arch/arm/mach-kirkwood/common.c b/arch/arm/mach-kirkwood/common.c
index e73384f..5938a3b 100644
--- a/arch/arm/mach-kirkwood/common.c
+++ b/arch/arm/mach-kirkwood/common.c
@@ -313,6 +313,11 @@
 	return "unknown 88F6000 variant";
 }
 
+static int __init is_l2_writethrough(void)
+{
+	return !!(readl(L2_CONFIG_REG) & L2_WRITETHROUGH);
+}
+
 void __init kirkwood_init(void)
 {
 	printk(KERN_INFO "Kirkwood: %s, TCLK=%d.\n",
@@ -321,6 +326,6 @@
 	kirkwood_setup_cpu_mbus();
 
 #ifdef CONFIG_CACHE_FEROCEON_L2
-	feroceon_l2_init(1);
+	feroceon_l2_init(is_l2_writethrough());
 #endif
 }