Re: [PATCH v3] clocksource: sun4i: Clear interrupts after stopping timer in probe function

From: Maxime Ripard
Date: Thu Aug 25 2016 - 04:14:51 EST

On Thu, Aug 25, 2016 at 02:26:59PM +0800, Chen-Yu Tsai wrote:
> 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>

Acked-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>


Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering

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