The bootloader (U-boot) sometimes uses this timer for various delays. It uses it as a ongoing counter, and does comparisons on the current counter value. The timer counter is never stopped. In some cases when the user interacts with the bootloader, or lets it idle for some time before loading Linux, the timer may expire, and an interrupt will be pending. This results in an unexpected interrupt when the timer interrupt is enabled by the kernel, at which point the event_handler isn't set yet. This results in a NULL pointer dereference exception, panic, and no way to reboot. Clear any pending interrupts after we stop the timer in the probe function to avoid this. Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx> --- Changes since v1: - Add stable kernel to Cc. --- drivers/clocksource/sun4i_timer.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/clocksource/sun4i_timer.c b/drivers/clocksource/sun4i_timer.c index 97669ee4df2a..7ab69b36f744 100644 --- a/drivers/clocksource/sun4i_timer.c +++ b/drivers/clocksource/sun4i_timer.c @@ -208,6 +208,9 @@ static int __init sun4i_timer_init(struct device_node *node) /* Make sure timer is stopped before playing with interrupts */ sun4i_clkevt_time_stop(0); + /* clear timer0 interrupt */ + writel(0x1, timer_base + TIMER_IRQ_ST_REG); + sun4i_clockevent.cpumask = cpu_possible_mask; sun4i_clockevent.irq = irq; -- 2.8.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html