linux-kernel - Re: PROBLEM: Kernel BUG in mfgpt_tick (cs5535-clockevt.c) on ALIX 2c3

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Date:   Thu, 12 Oct 2017 14:47:47 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     David Kozub <zub@...ux.fjfi.cvut.cz>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: PROBLEM: Kernel BUG in mfgpt_tick (cs5535-clockevt.c) on ALIX 2c3
 - null call

On 11/10/2017 22:48, David Kozub wrote:

[ ... ]

>>
>> +       disable_timer(timer);
>> +       cs5535_mfgpt_write(timer, MFGPT_REG_COUNTER, 0);
>> +
>>        /* Set up the IRQ on the MFGPT side */
>>        if (cs5535_mfgpt_setup_irq(timer, MFGPT_CMP2, &timer_irq)) {
>>                printk(KERN_ERR DRV_NAME ": Could not set up IRQ %d\n",
> 
> I tried that and the handler is still called. So I did some more random
> experiments and I found out that if I call disable_timer(timer) twice,
> then the issue is resolved (the handler is not called before the
> registration is finished.) And I don't have to set MFGPT_REG_COUNTER to 0.

Aha! we are close to a fix.

> I have no idea why do I have to call disable_timer twice.

For testing purpose, can you try by adding mmiowb() and/or wmb() after
disable_timer()?




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