From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mirror2.csie.ntu.edu.tw ([140.112.30.76]:47528 "EHLO wens.csie.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750995AbcHOFxD (ORCPT ); Mon, 15 Aug 2016 01:53:03 -0400 From: Chen-Yu Tsai To: Daniel Lezcano , Thomas Gleixner , Maxime Ripard Cc: Chen-Yu Tsai , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2] clocksource: sun4i: Clear interrupts after stopping timer in probe function Date: Mon, 15 Aug 2016 12:57:04 +0800 Message-Id: <1471237024-16655-1-git-send-email-wens@csie.org> Sender: stable-owner@vger.kernel.org List-ID: 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@vger.kernel.org Signed-off-by: Chen-Yu Tsai --- 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