[PATCH] MIPS: lantiq: allow WDT to read reset cause bit from the RCU registers

[John Crispin <blogic@openwrt.org>]

The watchdog needs to know if the last reset cause was the watchdog itself.
This patch adds a function to easily read the relevant bits form the RCU
registers.

Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: Ralph Hempel <ralph.hempel@lantiq.com>
Cc: linux-mips@linux-mips.org
---
 arch/mips/include/asm/mach-lantiq/lantiq.h |    4 ++++
 arch/mips/lantiq/xway/reset.c              |   12 ++++++++++++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/arch/mips/include/asm/mach-lantiq/lantiq.h 
b/arch/mips/include/asm/mach-lantiq/lantiq.h
index 1a705b4..ce2f029 100644
--- a/arch/mips/include/asm/mach-lantiq/lantiq.h
+++ b/arch/mips/include/asm/mach-lantiq/lantiq.h
@@ -49,6 +49,10 @@ extern void ltq_disable_irq(struct irq_data *data);
 extern void ltq_mask_and_ack_irq(struct irq_data *data);
 extern void ltq_enable_irq(struct irq_data *data);
 
+/* find out what caused the last cpu reset */
+extern int ltq_reset_cause(void);
+#define LTQ_RST_CAUSE_WDTRST   0x20
+
 #define IOPORT_RESOURCE_START  0x10000000
 #define IOPORT_RESOURCE_END    0xffffffff
 #define IOMEM_RESOURCE_START   0x10000000
diff --git a/arch/mips/lantiq/xway/reset.c b/arch/mips/lantiq/xway/reset.c
index e3ec635..a1be36d 100644
--- a/arch/mips/lantiq/xway/reset.c
+++ b/arch/mips/lantiq/xway/reset.c
@@ -10,6 +10,7 @@
 #include <linux/io.h>
 #include <linux/ioport.h>
 #include <linux/pm.h>
+#include <linux/module.h>
 #include <asm/reboot.h>
 
 #include <lantiq_soc.h>
@@ -21,6 +22,9 @@
 #define LTQ_RCU_RST            0x0010
 #define LTQ_RCU_RST_ALL                0x40000000
 
+#define LTQ_RCU_RST_STAT       0x0014
+#define LTQ_RCU_STAT_SHIFT     26
+
 static struct resource ltq_rcu_resource = {
        .name   = "rcu",
        .start  = LTQ_RCU_BASE_ADDR,
@@ -31,6 +35,14 @@ static struct resource ltq_rcu_resource = {
 /* remapped base addr of the reset control unit */
 static void __iomem *ltq_rcu_membase;
 
+/* This function is used by the watchdog driver */
+int ltq_reset_cause(void)
+{
+       u32 val = ltq_rcu_r32(LTQ_RCU_RST_STAT);
+       return val >> LTQ_RCU_STAT_SHIFT;
+}
+EXPORT_SYMBOL_GPL(ltq_reset_cause);
+
 static void ltq_machine_restart(char *command)
 {
        pr_notice("System restart\n");
-- 
1.7.2.3