Re: [PATCH] cpufreq: qoriq: optimize the CPU frequency switching time

From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Yuantian.Tang@freescale.com, linux-pm@vger.kernel.org,
	cpufreq@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] cpufreq: qoriq: optimize the CPU frequency switching time
Date: Tue, 16 Jun 2015 01:46:16 +0200	[thread overview]
Message-ID: <1528534.foUvvcDHWW@vostro.rjw.lan> (raw)
In-Reply-To: <20150604063636.GH11325@linux>

On Thursday, June 04, 2015 12:06:36 PM Viresh Kumar wrote:
> On 04-06-15, 14:25, Yuantian.Tang@freescale.com wrote:
> > From: Tang Yuantian <Yuantian.Tang@freescale.com>
> > 
> > Each time the CPU switches its frequency, the clock nodes in
> > DTS are walked through to find proper clock source. This is
> > very time-consuming, for example, it is up to 500+ us on T4240.
> > Besides, switching time varies from clock to clock.
> > To optimize this, each input clock of CPU is buffered, so that
> > it can be picked up instantly when needed.
> > 
> > Since for each CPU each input clock is stored in a pointer
> > which takes 4 or 8 bytes memory and normally there are several
> > input clocks per CPU, that will not take much memory as well.
> 
> Not sure how it got included in this form in the first place. :)
> 
> > Signed-off-by: Tang Yuantian <Yuantian.Tang@freescale.com>
> > ---
> >  drivers/cpufreq/qoriq-cpufreq.c | 32 +++++++++++++++++++++-----------
> >  1 file changed, 21 insertions(+), 11 deletions(-)
> 
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Queued up for 4.2, thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.