From: marek.vasut@gmail.com (Marek Vasut)
To: linux-arm-kernel@lists.infradead.org
Subject: [Openpxa-users] Linux udelay() is way off
Date: Thu, 20 Jan 2011 18:00:04 +0100 [thread overview]
Message-ID: <201101201800.04289.marek.vasut@gmail.com> (raw)
In-Reply-To: <AANLkTin_cCzNWhJnD=A2h1qiKpeUrnPrSZPs_Kmfjjd1@mail.gmail.com>
On Thursday 20 January 2011 17:09:00 Bj?rn Forsman wrote:
> Hi,
>
> On my Colibri PXA310, I see that Linux udelay() is only 30 % of the
> length it's supposed to. This is way off and cause problems (e.g.
> 1-Wire device driver breaks). I'm running OpenPXA bootloaders (OBM2 +
> U-Boot) and mainline Linux 2.6.36.
>
> Any ideas how to fix this?
>
> Could it be that U-Boot sets up the system clock to something
> different than what Linux "expects" so that loops_per_jiffy becomes
> wrong? I see some clock setup in <u-boot-pxa>/arch/arm/cpu/pxa/start.S
> but I'm not sure what to do with it (yet). I'd like to try out
> different clock speeds to see if it helps. Any pointers?
>
> I also have a workaround in mind: Try out different lpj= settings on
> the kernel command line until a udelay(1000) actually is 1000 us. Is
> this a sane thing to do?
CCing relevant people.
And no, linux kernel should derive it's timing properly so it's a kernel bug.
Cheers
>
> Best regards,
> Bj?rn Forsman
>
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next parent reply other threads:[~2011-01-20 17:00 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 ` Marek Vasut [this message]
2011-01-20 17:55 ` [Openpxa-users] Linux udelay() is way off Russell King - ARM Linux
2011-01-20 19:18 ` Bjørn Forsman
2011-01-20 19:30 ` Russell King - ARM Linux
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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