From mboxrd@z Thu Jan  1 00:00:00 1970
From: marc.zyngier@arm.com (Marc Zyngier)
Date: Mon, 02 Dec 2013 10:46:34 +0000
Subject: [REPOST PATCH] ARM: sunxi: stop timer from ticking before enabling
 interrupts
In-Reply-To: <529C61A3.8010208@linaro.org>
References: <1385976575-28011-1-git-send-email-marc.zyngier@arm.com>
 <529C61A3.8010208@linaro.org>
Message-ID: <529C650A.7060209@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 02/12/13 10:32, Daniel Lezcano wrote:
> On 12/02/2013 10:29 AM, Marc Zyngier wrote:
>> The sun4i timer can still be ticking when we enable the interrupt.
>> If another timer is actually used (A7 architected timer, for example),
>> odds are that the interrupt will eventually fire with the event_handler
>> pointer being NULL.
>>
>> The obvious fix it to stop the timer before registering the interrupt.
>>
>> Observed and tested on sun7i (cubietruck).
>>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>> Daniel,
>>
>> Maxime asked me to forward this to you directly. Please consider merging
>> it for 3.13.
>>
>> Thanks,
>>
>> 	M.
>>
>>   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 2fb4695..a4f6119 100644
>> --- a/drivers/clocksource/sun4i_timer.c
>> +++ b/drivers/clocksource/sun4i_timer.c
>> @@ -179,6 +179,9 @@ static void __init sun4i_timer_init(struct device_node *node)
>>   	writel(TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
>>   	       timer_base + TIMER_CTL_REG(0));
>>
>> +	/* Make sure timer is stopped before playing with interrupts */
>> +	sun4i_clkevt_time_stop(0);
>> +
> 
> It isn't possible to *not* enable it instead of stopping it ?

Well, it is already enabled by the bootloader.

> In the code before we have:
> 
>          writel(TIMER_CTL_ENABLE | TIMER_CTL_RELOAD |
>                 TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
>                 timer_base + TIMER_CTL_REG(1));
> 
> If we remove the TIMER_CTL_ENABLE flag, wouldn't it fix the issue ?

No. This piece of code enables the clocksource, which is implemented
using timer 1. Timer 0 still needs to be disabled.

	M.
-- 
Jazz is not dead. It just smells funny...