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

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Date:   Thu, 03 Dec 2020 14:58:27 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Keqian Zhu <zhukeqian1@...wei.com>
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

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.

> 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.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...