From: "Kasagar, Srinidhi" <srinidhi.kasagar@intel.com>
To: Len Brown <lenb@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Viresh Kumar <viresh.kumar@linaro.org>,
Linux PM list <linux-pm@vger.kernel.org>,
vishwesh.m.rudramuni@intel.com, "Brown,
Len" <len.brown@intel.com>,
srinidhi.kasagar@intel.com
Subject: Re: [PATCH v4] cpufreq: Add SFI based cpufreq driver support
Date: Tue, 18 Nov 2014 11:09:58 +0530 [thread overview]
Message-ID: <20141118053958.GA28487@intel-desktop> (raw)
In-Reply-To: <CAJvTdKkHsRh1rp4FREn6R+3bOqpXqVD2q8fUG8id75kBsNEHCA@mail.gmail.com>
On Mon, Nov 10, 2014 at 02:10:44PM -0500, Len Brown wrote:
> > Not sure if in understood correctly. Do you mean I should not
> > even read from PERF_CTL in get_cur_freq_on_cpu, rather just
> > return the cached last requested frequency? I'm not sure
> > of the behavior in case if we offline and online a cpu.
>
> Best to simply cache the last written value in software,
> that way it can be read quickly w/o even switching to
> a processor to do the local MSR read.
But it will be wrong after offline-online sequence. I have
sent v5 version of the patch. Please check.
>
> The cpufreq get-current-frequency interface is somewhat bogus.
> It generally doesn't make sense on a lot of modern hardware for the
> driver to actually know the current frequency -- as the driver is only making
> a request and does not have total control over the frequency...
> But we need to answer something b/c there are people still
> using the legacy cpufreq sysfs interface, and they expect a number.
Agree.
Srinidhi
prev parent reply other threads:[~2014-11-18 5:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-04 17:00 [PATCH v4] cpufreq: Add SFI based cpufreq driver support Srinidhi Kasagar
2014-11-07 6:18 ` Len Brown
2014-11-10 10:56 ` Kasagar, Srinidhi
2014-11-10 19:10 ` Len Brown
2014-11-18 5:39 ` Kasagar, Srinidhi [this message]
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