linux-kernel - Re: [RESEND PATCH] drivers: arm arch timer: Correct fault programming of CNTKCTL

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Message-ID: <b3d2fe2f-a64b-af37-dea0-fa76a14ac2bc@huawei.com>
Date:   Tue, 28 Jul 2020 15:39:40 +0800
From:   zhukeqian <zhukeqian1@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>
CC:     Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        James Morse <james.morse@....com>,
        "Suzuki K Poulose" <suzuki.poulose@....com>,
        <wanghaibin.wang@...wei.com>
Subject: Re: [RESEND PATCH] drivers: arm arch timer: Correct fault programming
 of CNTKCTL_EL1.EVNTI

Friendly ping.
Is this an effective bugfix?

On 2020/7/17 17:21, Keqian Zhu wrote:
> ARM virtual counter supports event stream. It can only trigger an event
> when the trigger bit of CNTVCT_EL0 changes from 0 to 1 (or from 1 to 0),
> so the actual period of event stream is 2 ^ (cntkctl_evnti + 1). For
> example, when the trigger bit is 0, then it triggers an event for every
> two cycles.
> 
> Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
> ---
>  drivers/clocksource/arm_arch_timer.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index ecf7b7db2d05..06d99a4b1b9b 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -799,10 +799,20 @@ static void __arch_timer_setup(unsigned type,
>  static void arch_timer_evtstrm_enable(int divider)
>  {
>  	u32 cntkctl = arch_timer_get_cntkctl();
> +	int cntkctl_evnti;
> +
> +	/*
> +	 * Note that it can only trigger an event when the trigger bit
> +	 * of CNTVCT_EL0 changes from 1 to 0 (or from 0 to 1), so the
> +	 * actual period of event stream is 2 ^ (cntkctl_evnti + 1).
> +	 */
> +	cntkctl_evnti = divider - 1;
> +	cntkctl_evnti = min(cntkctl_evnti, 15);
> +	cntkctl_evnti = max(cntkctl_evnti, 0);
>  
>  	cntkctl &= ~ARCH_TIMER_EVT_TRIGGER_MASK;
>  	/* Set the divider and enable virtual event stream */
> -	cntkctl |= (divider << ARCH_TIMER_EVT_TRIGGER_SHIFT)
> +	cntkctl |= (cntkctl_evnti << ARCH_TIMER_EVT_TRIGGER_SHIFT)
>  			| ARCH_TIMER_VIRT_EVT_EN;
>  	arch_timer_set_cntkctl(cntkctl);
>  	arch_timer_set_evtstrm_feature();
> @@ -816,10 +826,11 @@ static void arch_timer_configure_evtstream(void)
>  	/* Find the closest power of two to the divisor */
>  	evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
>  	pos = fls(evt_stream_div);
> -	if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
> +	if ((pos == 1) || (pos > 1 && !(evt_stream_div & (1 << (pos - 2)))))
>  		pos--;
> +
>  	/* enable event stream */
> -	arch_timer_evtstrm_enable(min(pos, 15));
> +	arch_timer_evtstrm_enable(pos);
>  }
>  
>  static void arch_counter_set_user_access(void)
>