From: Marc Zyngier <maz@kernel.org>
To: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Nianyao Tang <tangnianyao@huawei.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: arch_timer: Ensure timer is enabled before using istatus
Date: Fri, 24 Jul 2020 11:22:18 +0100 [thread overview]
Message-ID: <fec2a9020d1ad34cbfe951122697c225@kernel.org> (raw)
In-Reply-To: <1595584037-6877-1-git-send-email-zhangshaokun@hisilicon.com>
On 2020-07-24 10:47, Shaokun Zhang wrote:
> From: Nianyao Tang <tangnianyao@huawei.com>
>
> In Arm ARM spec, there is a description for timer control register,
> when
> the value of the ENABLE bit is 0, the ISTATUS field is UNKNOWN. We
> shall
> only read and use ISTATUS when ENABLE is 1, otherwise ISTATUS may be
> invalid.
>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Signed-off-by: Nianyao Tang <tangnianyao@huawei.com>
> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
> ---
> drivers/clocksource/arm_arch_timer.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c
> b/drivers/clocksource/arm_arch_timer.c
> index 6c3e84180146..0bbc2715de79 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -641,7 +641,8 @@ static __always_inline irqreturn_t
> timer_handler(const int access,
> unsigned long ctrl;
>
> ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, evt);
> - if (ctrl & ARCH_TIMER_CTRL_IT_STAT) {
> + if ((ctrl & ARCH_TIMER_CTRL_ENABLE) &&
> + (ctrl & ARCH_TIMER_CTRL_IT_STAT)) {
> ctrl |= ARCH_TIMER_CTRL_IT_MASK;
> arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, evt);
> evt->event_handler(evt);
Interesting. A question for you though:
How do you think we made it in the interrupt handler if the timer
was disabled?
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-07-24 10:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-24 9:47 [PATCH] arm64: arch_timer: Ensure timer is enabled before using istatus Shaokun Zhang
2020-07-24 10:22 ` Marc Zyngier [this message]
2020-07-25 8:49 ` Shaokun Zhang
2020-07-25 9:23 ` Marc Zyngier
2020-07-28 2:18 ` Shaokun Zhang
2020-07-28 7:59 ` Marc Zyngier
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