From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [Openpxa-users] Linux udelay() is way off
Date: Thu, 20 Jan 2011 19:30:13 +0000 [thread overview]
Message-ID: <20110120193013.GL6335@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <AANLkTin8UR_1kU=+Dw-O9zHahquGJvBC560nByO=F6YV@mail.gmail.com>
On Thu, Jan 20, 2011 at 08:18:10PM +0100, Bj?rn Forsman wrote:
> [ 11.425363] cpufreq-core: saving 518144 as reference value for
> loops_per_jiffy; freq is 312000 kHz
> [ 11.425523] cpufreq-core: scaling loops_per_jiffy to 1036288 for
> frequency 624000 kHz
So despite scaling lpj by a factor of two for the doubling in clock
frequency, we see a 30% error in it?
Is it possible to boot at 624MHz and report the resulting lpj?
Alternatively, call calibrate_delay() after the cpufreq switch to
624MHz, disabling the 'printed' stuff and see what it reports.
I wonder if this is a case where it scales according to
new_lpj = ref_lpj * (new_freq / ref_freq) + some_offset
rather than just
new_lpj = ref_lpj * (new_freq / ref_freq)
next prev parent reply other threads:[~2011-01-20 19:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AANLkTin_cCzNWhJnD=A2h1qiKpeUrnPrSZPs_Kmfjjd1@mail.gmail.com>
2011-01-20 17:00 ` [Openpxa-users] Linux udelay() is way off Marek Vasut
2011-01-20 17:55 ` Russell King - ARM Linux
2011-01-20 19:18 ` Bjørn Forsman
2011-01-20 19:30 ` Russell King - ARM Linux [this message]
2011-01-20 20:25 ` Bjørn Forsman
2011-01-20 22:10 ` Russell King - ARM Linux
2011-01-21 0:02 ` Bjørn Forsman
2011-01-21 17:46 ` Bjørn Forsman
2011-01-21 18:11 ` Marek Vasut
2011-01-21 18:55 ` Bjørn Forsman
2011-01-23 10:35 ` Marek Vasut
2011-01-25 17:45 ` Bjørn Forsman
2011-01-25 20:18 ` Marek Vasut
2011-01-21 7:29 ` Saravana Kannan
2011-01-21 17:56 ` Bjørn Forsman
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