From: Felix Fietkau <nbd@nbd.name>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, daniel.lezcano@linaro.org,
paul.burton@imgtec.com
Subject: Re: [PATCH] clocksource: mips-gic-timer: fix clocksource counter width
Date: Wed, 28 Feb 2018 10:19:25 +0100 [thread overview]
Message-ID: <207b6722-a506-1e6a-c81c-a530e772dfa6@nbd.name> (raw)
In-Reply-To: <alpine.DEB.2.21.1802280955430.1886@nanos.tec.linutronix.de>
On 2018-02-28 09:56, Thomas Gleixner wrote:
> 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?
>> count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
>> - count_width >>= __fls(GIC_CONFIG_COUNTBITS);
>> + count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
This code is trying to extract the GIC_CONFIG_COUNTBITS field from
read_gic_config(), so it needs to shift count_width right by the index
of the least significant bit (__ffs) instead of the most significant bit
(__fls) of the field mask.
- Felix
next prev parent reply other threads:[~2018-02-28 9:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-21 12:47 Felix Fietkau
2018-02-28 8:56 ` Thomas Gleixner
2018-02-28 9:19 ` Felix Fietkau [this message]
2018-02-28 9:27 ` Thomas Gleixner
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