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
diff --git a/arch/arm/mach-at91/at91sam9rl.c b/arch/arm/mach-at91/at91sam9rl.c
index b5a8c9d..301e172 100644
--- a/arch/arm/mach-at91/at91sam9rl.c
+++ b/arch/arm/mach-at91/at91sam9rl.c
@@ -295,6 +295,7 @@
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);