Quoting Geert Uytterhoeven (2021-03-26 05:00:53)

        Hi Mike, Stephen,

This patch series improves the accuracy of the CPU clock rate on R-Car
Gen3 SoCs, and adds support for CPU boost modes (marked "turbo-mode" in
the operating points table in DT).
As usual, it is preceded by a few small cleanups.

The easiest way to test this is by enabling
CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE, and writing the requested clock
rate to /sys/devices/system/cpu/cpufreq/policy$n/scaling_setspeed
(n=0 for the first cluster, n=2 or 4 for the second cluster).
Note that you need to do

    echo 1 > /sys/devices/system/cpu/cpufreq/boost

before you can enable boost modes.

The PLL rates and CPU clock rates and voltages can be monitored in
/sys/kernel/debug/{clk/{z,z2,.pll[024]}/clk_rate,reg*/dvfs/cpu*/*uV}.
The DVFS voltage measured by the on-board max9611 can be monitored
remotely using iio-monitor.

This series has been tested on Salvator-(X)S (with R-Car H3 ES1.0, H3
ES2.0, M3-W, and M3-N) and Ebisu-4D (R-Car E3).

As boost modes may be unstable without increasing the CPU core voltage,
this series depends on "[PATCH 0/2] arm64: dts: renesas: Add cpu-supply
properties for DVFS"[1].  Hence I think it is better to postpone this to
v5.14.

Thanks for your comments!

Acked-by: Stephen Boyd <sboyd@kernel.org>