Date: Tue, 28 Feb 2006 16:57:47 -0800 From: Nate Lawson <nate@root.org> To: Marcus Alves Grando <mnag@FreeBSD.org> Cc: FreeBSD Stable <freebsd-stable@FreeBSD.org> Subject: Re: sysctl: dev.cpu.0.freq: Device busy (cpufreq p4tcc / RELENG_6) Message-ID: <4404F18B.7090006@root.org> In-Reply-To: <4404EF3F.8050006@FreeBSD.org> References: <4404E852.80908@FreeBSD.org> <4404EC20.8030500@root.org> <4404EF3F.8050006@FreeBSD.org>
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I'll approve a commit if you send me a patch. Add something like this to the SYSCTL VARIABLES section: The frequency cannot be changed if TSC is in use as the timecounter. This is because the timecounter system needs to use a source that has a constant rate. The timecounter source can be changed with the kern.timecounter.hardware sysctl. Marcus Alves Grando wrote: > Well, works. Thanks. It's possible to printf some message about this if > kern.timecounter.hardware != ACPI-fast? Or add message in cpufreq(4)? > > Thanks > > Nate Lawson wrote: >> Marcus Alves Grando wrote: >>> I have problems in cpufreq in RELENG_6 (today). >>> >>> I try to set another frequency in my laptop and get this error: >>> >>> # sysctl dev.cpu.0.freq=250 >>> dev.cpu.0.freq: 2000 >>> sysctl: dev.cpu.0.freq: Device busy >>> >>> Timecounter "TSC" frequency 1995011972 Hz quality 800 >>> Timecounters tick every 1.000 msec >> >> Try setting your timecounter to acpi or i8254 (not TSC): >> >> sysctl kern.timecounter.hardware="acpi" >> >> Without complicated recalibration code (which no one has written yet), >> we can't base our system time off the TSC counter when cpufreq is >> changing it. >> > -- Nate
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