linux-kernel - Re: [PATCH v2 1/2] clocksource: arm_arch_timer: Use stable count reader in erratum sne

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Date:   Fri, 4 Dec 2020 15:35:39 +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 v2 1/2] clocksource: arm_arch_timer: Use stable count
 reader in erratum sne

Hi Marc,

On 2020/12/3 22:58, Marc Zyngier wrote:
> On 2020-08-18 04:28, 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 to omit
>> unnecessary overhead on systems that have no timer erratum.
>>
>> However, in erratum_set_next_event_tval_generic(), count reader becomes normal
>> reader. This converts it to stable reader.
>>
>> Fixes: 0ea415390cd3 ("clocksource/arm_arch_timer: Use
>>        arch_timer_read_counter to access stable counters")
> 
> On a single line.
Addressed. Thanks.

> 
>> Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
>> ---
>>  drivers/clocksource/arm_arch_timer.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/clocksource/arm_arch_timer.c
>> b/drivers/clocksource/arm_arch_timer.c
>> index 6c3e841..777d38c 100644
>> --- a/drivers/clocksource/arm_arch_timer.c
>> +++ b/drivers/clocksource/arm_arch_timer.c
>> @@ -396,10 +396,10 @@ static void
>> erratum_set_next_event_tval_generic(const int access, unsigned long
>>      ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;
>>
>>      if (access == ARCH_TIMER_PHYS_ACCESS) {
>> -        cval = evt + arch_counter_get_cntpct();
>> +        cval = evt + arch_counter_get_cntpct_stable();
>>          write_sysreg(cval, cntp_cval_el0);
>>      } else {
>> -        cval = evt + arch_counter_get_cntvct();
>> +        cval = evt + arch_counter_get_cntvct_stable();
>>          write_sysreg(cval, cntv_cval_el0);
>>      }
> 
> With that fixed:
> 
> Acked-by: Marc Zyngier <maz@...nel.org>
> 
> This should go via the clocksource tree.
Added Cc to it's maintainers, thanks.

> 
> Thanks,
> 
>         M.
Cheers,
Keqian