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Date:      Tue, 17 Aug 2004 00:05:16 -0700
From:      Colin Percival <colin.percival@wadham.ox.ac.uk>
To:        Arne Schwabe <arne@rfc2549.org>
Cc:        freebsd-mobile@freebsd.org
Subject:   Re: Enhanced SpeedStep driver available
Message-ID:  <6.1.0.6.1.20040817000124.03faa468@popserver.sfu.ca>
In-Reply-To: <86zn4uwr82.fsf@kamino.rfc1149.org>
References:  <6.1.0.6.1.20040816074348.03f99338@popserver.sfu.ca> <86zn4uwr82.fsf@kamino.rfc1149.org>

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At 17:19 16/08/2004, Arne Schwabe wrote:
>Colin Percival <colin.percival@wadham.ox.ac.uk> writes:
>>   Thanks to everyone who has been sending me data about their
>> processors (and in particular, the 90nm versions), I now have
>> a first draft of a Enhanced SpeedStep driver available.  [...]
>
>[2:14]arne@kamino:~/tmp/estctrl% sudo sysctl hw.est_curfreq=1600
>hw.est_curfreq: 600 -> 600
>[2:14]arne@kamino:~/tmp/estctrl% sudo sysctl hw.est_curfreq=1600
>hw.est_curfreq: 1600 -> 1600
>
>For some reason, the message when I set cpu freq higher does not work

I think I know what cases this: It takes a few microseconds for the
processor to change frequencies, and sysctl(8) is checking the new
value too soon.  I've added a small delay before returning from the
sysctl handler; this should make it impossible for this race to occur.

I've put an updated version online; could you try it and tell me if
this problem goes away?

Colin Percival




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