ARM: at91: fix hanged boot due to early rtt-interrupt

Make sure the RTT-interrupts are masked at boot by adding a new helper
function to be used at SOC-init.

This fixes hanged boot on all AT91 SOCs with an RTT, for example, if an
RTT-alarm goes off after a non-clean shutdown (e.g. when using RTC
wakeup).

The RTC and RTT-peripherals are powered by backup power (VDDBU) (on all
AT91 SOCs but RM9200) and are not reset on wake-up, user, watchdog or
software reset. This means that their interrupts may be enabled during
early boot if, for example, they where not disabled during a previous
shutdown (e.g. due to a buggy driver or a non-clean shutdown such as a
user reset). Furthermore, an RTC or RTT-alarm may also be active.

The RTC and RTT-interrupts use the shared system-interrupt line, which
is also used by the PIT, and if an interrupt occurs before a handler
(e.g. RTC-driver) has been installed this leads to the system interrupt
being disabled and prevents the system from booting.

Note that when boot hangs due to an early RTC or RTT-interrupt, the only
way to get the system to start again is to remove the backup power (e.g.
battery) or to disable the interrupt manually from the bootloader. In
particular, a user reset is not sufficient.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: stable@vger.kernel.org # 3.11.x

7 files changed, 34 insertions, 0 deletions

diff --git a/arch/arm/mach-at91/at91sam9260.c b/arch/arm/mach-at91/at91sam9260.c
index 5de6074b4f4f..ae10d14de700 100644
--- a/arch/arm/mach-at91/at91sam9260.c
+++ b/arch/arm/mach-at91/at91sam9260.c
@@ -349,6 +349,8 @@ static void __init at91sam9260_initialize(void)
         arm_pm_idle = at91sam9_idle;
         arm_pm_restart = at91sam9_alt_restart;
 
+        at91_sysirq_mask_rtt(AT91SAM9260_BASE_RTT);
+
         /* Register GPIO subsystem */
         at91_gpio_init(at91sam9260_gpio, 3);
 }
diff --git a/arch/arm/mach-at91/at91sam9261.c b/arch/arm/mach-at91/at91sam9261.c
index 0e0793241ab7..e761e74ac64b 100644
--- a/arch/arm/mach-at91/at91sam9261.c
+++ b/arch/arm/mach-at91/at91sam9261.c
@@ -291,6 +291,8 @@ static void __init at91sam9261_initialize(void)
         arm_pm_idle = at91sam9_idle;
         arm_pm_restart = at91sam9_alt_restart;
 
+        at91_sysirq_mask_rtt(AT91SAM9261_BASE_RTT);
+
         /* Register GPIO subsystem */
         at91_gpio_init(at91sam9261_gpio, 3);
 }
diff --git a/arch/arm/mach-at91/at91sam9263.c b/arch/arm/mach-at91/at91sam9263.c
index 6ce7d1850893..e6fed6253a7f 100644
--- a/arch/arm/mach-at91/at91sam9263.c
+++ b/arch/arm/mach-at91/at91sam9263.c
@@ -328,6 +328,9 @@ static void __init at91sam9263_initialize(void)
         arm_pm_idle = at91sam9_idle;
         arm_pm_restart = at91sam9_alt_restart;
 
+        at91_sysirq_mask_rtt(AT91SAM9263_BASE_RTT0);
+        at91_sysirq_mask_rtt(AT91SAM9263_BASE_RTT1);
+
         /* Register GPIO subsystem */
         at91_gpio_init(at91sam9263_gpio, 5);
 }
diff --git a/arch/arm/mach-at91/at91sam9g45.c b/arch/arm/mach-at91/at91sam9g45.c
index ff662af77fee..9f7a97c84c12 100644
--- a/arch/arm/mach-at91/at91sam9g45.c
+++ b/arch/arm/mach-at91/at91sam9g45.c
@@ -378,6 +378,7 @@ static void __init at91sam9g45_initialize(void)
         arm_pm_restart = at91sam9g45_restart;
 
         at91_sysirq_mask_rtc(AT91SAM9G45_BASE_RTC);
+        at91_sysirq_mask_rtt(AT91SAM9G45_BASE_RTT);
 
         /* Register GPIO subsystem */
         at91_gpio_init(at91sam9g45_gpio, 5);
diff --git a/arch/arm/mach-at91/at91sam9rl.c b/arch/arm/mach-at91/at91sam9rl.c
index b5a8c9d81bc8..301e1728d353 100644
--- a/arch/arm/mach-at91/at91sam9rl.c
+++ b/arch/arm/mach-at91/at91sam9rl.c
@@ -295,6 +295,7 @@ static void __init at91sam9rl_initialize(void)
         arm_pm_restart = at91sam9_alt_restart;
 
         at91_sysirq_mask_rtc(AT91SAM9RL_BASE_RTC);
+        at91_sysirq_mask_rtt(AT91SAM9RL_BASE_RTT);
 
         /* Register GPIO subsystem */
         at91_gpio_init(at91sam9rl_gpio, 4);
diff --git a/arch/arm/mach-at91/generic.h b/arch/arm/mach-at91/generic.h
index 80269bda0dd7..26dee3ce9397 100644
--- a/arch/arm/mach-at91/generic.h
+++ b/arch/arm/mach-at91/generic.h
@@ -35,6 +35,7 @@ extern int  __init at91_aic_of_init(struct device_node *node,
 extern int  __init at91_aic5_of_init(struct device_node *node,
                                     struct device_node *parent);
 extern void __init at91_sysirq_mask_rtc(u32 rtc_base);
+extern void __init at91_sysirq_mask_rtt(u32 rtt_base);
 
 
  /* Timer */
diff --git a/arch/arm/mach-at91/sysirq_mask.c b/arch/arm/mach-at91/sysirq_mask.c
index ee3e22c66ce8..2ba694f9626b 100644
--- a/arch/arm/mach-at91/sysirq_mask.c
+++ b/arch/arm/mach-at91/sysirq_mask.c
@@ -21,6 +21,7 @@
  */
 
 #include <linux/io.h>
+#include <mach/at91_rtt.h>
 
 #include "generic.h"
 
@@ -45,3 +46,26 @@ void __init at91_sysirq_mask_rtc(u32 rtc_base)
 
         iounmap(base);
 }
+
+void __init at91_sysirq_mask_rtt(u32 rtt_base)
+{
+        void __iomem *base;
+        void __iomem *reg;
+        u32 mode;
+
+        base = ioremap(rtt_base, 16);
+        if (!base)
+                return;
+
+        reg = base + AT91_RTT_MR;
+
+        mode = readl_relaxed(reg);
+        if (mode & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN)) {
+                pr_info("AT91: Disabling rtt irq\n");
+                mode &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
+                writel_relaxed(mode, reg);
+                (void)readl_relaxed(reg);                       /* flush */
+        }
+
+        iounmap(base);
+}