[PATCH 0/5] Switch to the DT cpufreq policy on the Integrator

[Rafael J. Wysocki]

On Wednesday, October 19, 2016 11:59:09 AM 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.
> 
> Linus Walleij (5):
>   cpufreq: enable the DT cpufreq driver on the Integrators
>   ARM: dts: Add Integrator/AP cpus node and operating points
>   ARM: dts: Add Integrator/CP cpus node and operating points
>   ARM: defconfig: turn on the DT cpufreq for Integrator
>   cpufreq: retire the Integrator cpufreq driver

The cpufreq changes look good to me, but Viresh is the expert for the DT stuff.

Thanks,
Rafael