linux-kernel - Re: [PATCH] clocksource: mips-gic-timer: fix clocksource counter width

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Message-ID: <alpine.DEB.2.21.1802280955430.1886@nanos.tec.linutronix.de>
Date:   Wed, 28 Feb 2018 09:56:02 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Felix Fietkau <nbd@....name>
cc:     linux-kernel@...r.kernel.org, daniel.lezcano@...aro.org,
        paul.burton@...tec.com
Subject: Re: [PATCH] clocksource: mips-gic-timer: fix clocksource counter
 width

On Wed, 21 Feb 2018, Felix Fietkau wrote:

> This code needs to use ffs instead of fls on the mask to determine the
> shift for reading the GIC_CONFIG_COUNTBITS field.

Why?

Thanks,

	tglx
 
> Fixes: e07127a077c7 ("clocksource: mips-gic-timer: Use new GIC accessor functions")
> Cc: Paul Burton <paul.burton@...tec.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Felix Fietkau <nbd@....name>
> ---
>  drivers/clocksource/mips-gic-timer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
> index a04808a21d4e..bf0eee78c6ef 100644
> --- a/drivers/clocksource/mips-gic-timer.c
> +++ b/drivers/clocksource/mips-gic-timer.c
> @@ -166,7 +166,7 @@ static int __init __gic_clocksource_init(void)
>  
>  	/* Set clocksource mask. */
>  	count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
> -	count_width >>= __fls(GIC_CONFIG_COUNTBITS);
> +	count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
>  	count_width *= 4;
>  	count_width += 32;
>  	gic_clocksource.mask = CLOCKSOURCE_MASK(count_width);
> -- 
> 2.14.2
> 
>