linux-kernel - Re: A question about Cortex-A73 erratum 858921

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Message-ID: <7f9bc4fb-67f5-5989-21ba-0833bd3cdd78@huawei.com>
Date:   Tue, 13 Sep 2022 18:52:09 +0800
From:   Kunkun Jiang <jiangkunkun@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Mark Rutland <mark.rutland@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "wanghaibin.wang@...wei.com" <wanghaibin.wang@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: A question about Cortex-A73 erratum 858921

Hi Marc,

Thank you for your reply, I've sent a fix.
https://lore.kernel.org/all/20220913104723.332-1-jiangkunkun@huawei.com/

Thanks,
Kunkun Jiang

On 2022/9/9 20:23, Marc Zyngier wrote:
> On Fri, 09 Sep 2022 08:31:43 +0100,
> Kunkun Jiang <jiangkunkun@...wei.com> wrote:
>> Hi all,
>>
>> Recently I am learning the code related to Arm arch timer. I found that the
>> Cortex-A73 erratum 858921 does not set the corresponding callback functions:
>> set_next_event_phys and set_next_event_virt like other erratums. Won't it
>> get the wrong value when reading the counter during setting next event?
> Yup, you're correct.
>
> This is a regression introduced by a38b71b0833e
> ("clocksource/drivers/arm_arch_timer: Move system register timer
> programming over to CVAL"). We used to use the TVAL accessor which
> doesn't need a read of the counter, while the switch to CVAL needs
> one. Obviously, I didn't enough pay attention to the A73 erratum.
>
> Please send in a fix for this.
>
> Thanks,
>
> 	M.
>