From mboxrd@z Thu Jan  1 00:00:00 1970
From: viresh.kumar@linaro.org (Viresh Kumar)
Date: Thu, 20 Oct 2016 10:17:42 +0530
Subject: [PATCH 0/5] Switch to the DT cpufreq policy on the Integrator
In-Reply-To: <20161020042012.GI11766@vireshk-i7>
References: <1476871154-32243-1-git-send-email-linus.walleij@linaro.org>
 <20161020042012.GI11766@vireshk-i7>
Message-ID: <20161020044742.GK11766@vireshk-i7>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 20-10-16, 09:50, Viresh Kumar wrote:
> On 19-10-16, 11:59, Linus Walleij wrote:
> > This switches the ARM Integrator/AP and Integrator/CP to use the
> > Device Tree cpufreq policy with its definition of operating points
> > using the generic OPP library.
> > 
> > The Integrators does not need to control a regulator to switch
> > frequency, only a clock. This clock and its device tree bindings
> > have been defined in the device tree and merged upstream for v4.9.
> > 
> > This approach provides a little better granularity on the
> > Integrator/AP where I defined a few operating points: before
> > this change the Integrator would just switch between min speed
> > (12 MHz) and max speed (71 MHz). Now it can switch between a
> > few arbitrarily chosen OPPs as in the examples below:
> > 
> > The following tests were made on the Integrator/AP:
> > 
> > /sys/devices/system/cpu/cpufreq/policy0 echo ondemand > scaling_governor
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 71000000 Hz --> 24000000 Hz
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 24000000 Hz --> 12000000 Hz
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 12000000 Hz --> 24000000 Hz
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 24000000 Hz --> 12000000 Hz
> > 
> > The switch from 12 to 24 MHz is triggered by as little as using the
> > command line with the ondemand governor. If we do this:
> > 
> > yes > /dev/null &
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 12000000 Hz --> 36000000 Hz
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 36000000 Hz --> 71000000 Hz
> > pkill yes
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 71000000 Hz --> 12000000 Hz
> > 
> > So the algorithm is indeed using all the OPPs.
> > 
> > Also as a confirmation test to make sure performance is affected by the
> > speed changes, we set the performance governor and:
> > 
> > echo 12000 > scaling_max_freq
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 71000000 Hz --> 12000000 Hz
> > time find /sys|sort|uniq > /dev/null
> > real    0m 45.51s
> > user    0m 11.15s
> > sys     0m 26.74s
> > 
> > echo 71000 > scaling_max_freq
> > cpu cpu0: dev_pm_opp_set_rate: switching OPP: 12000000 Hz --> 71000000 Hz
> > time find /sys|sort|uniq
> >  > /dev/null
> > real    0m 9.13s
> > user    0m 2.35s
> > sys     0m 5.50s
> > 
> > So it is working.
> > 
> > If people are happy with this approach and approve of the patches
> > I'd like an ACK from the cpufreq people and then merge the whole set
> > through ARM SoC.
> 
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Integrator is an UP, right? Otherwise you may want to use operating-points-v2
bindings instead.

-- 
viresh