linux-kernel - Re: [PATCH 1/2] clocksource: arm_arch_timer: Simplify and fix count reader code logic

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Message-ID: <2093b7c1-6ef4-c0ff-e9df-1f493fccdda8@huawei.com>
Date:   Tue, 18 Aug 2020 09:40:56 +0800
From:   zhukeqian <zhukeqian1@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
        Steven Price <steven.price@....com>,
        Andrew Jones <drjones@...hat.com>,
        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: [PATCH 1/2] clocksource: arm_arch_timer: Simplify and fix count
 reader code logic

Hi Marc,

On 2020/8/17 20:52, Marc Zyngier wrote:
> On 2020-08-17 13:24, Keqian Zhu wrote:
>> In commit 0ea415390cd3 (clocksource/arm_arch_timer: Use arch_timer_read_counter
>> to access stable counters), we separate stable and normal count reader. Actually
>> the stable reader can correctly lead us to normal reader if we has no
>> workaround.
> 
> Resulting in an unnecessary overhead on non-broken systems that can run
> without CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND. Not happening.
OK, so I got the purpose of that patch wrong.
> 
>> Besides, in erratum_set_next_event_tval_generic(), we use normal reader, it is
>> obviously wrong, so just revert this commit to solve this problem by the way.
> 
> If you want to fix something, post a patch that does exactly that.
> 
I will.

Thanks,
Keqian
>         M.