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SubjectRe: [PATCH 2/3] arm64: dts: uniphier: add CPU clock and OPP table for LD11 SoC
On 19-10-16, 17:33, Masahiro Yamada wrote:
> Hi Viresh,
>
>
> 2016-10-18 20:25 GMT+09:00 Viresh Kumar <viresh.kumar@linaro.org>:
> > On 16-10-16, 23:59, Masahiro Yamada wrote:
> >> + cluster0_opp: opp_table {
> >> + compatible = "operating-points-v2";
> >> + opp-shared;
> >> +
> >> + opp@245000000 {
> >> + opp-hz = /bits/ 64 <245000000>;
> >> + clock-latency-ns = <300>;
> >> + };
> >> + opp@250000000 {
> >> + opp-hz = /bits/ 64 <250000000>;
> >> + clock-latency-ns = <300>;
> >> + };
> >> + opp@490000000 {
> >> + opp-hz = /bits/ 64 <490000000>;
> >> + clock-latency-ns = <300>;
> >> + };
> >> + opp@500000000 {
> >> + opp-hz = /bits/ 64 <500000000>;
> >> + clock-latency-ns = <300>;
> >> + };
> >> + opp@653333333 {
> >
> > Why isn't ^^ matching with below values ? Same in next patch as well.
>
>
>
> When I try to update /sys/devices/system/cpu/cpufreq/policy*/scaling_max_freq,
> it did not work as I had expected.
>
>
> scaling_max_freq is specified by kHz unit,
> on the other hand, clock frequency in the clk driver is specified by Hz.
>
>
>
> If the operating point is 653333kHz, the cpufreq requests
> the clk driver to set 653333000, but it is lower than
> the exact clock, 653333333.
> So, the next lower frequency, 500000000 is selected.
> As a result, the operating point 653333kHz is never enabled.
>
>
> So, the operating point must be equal or a little bit bigger.
>
>
> Do you know a better way to solve this distortion?

I am not sure about how to fix that problem but there is no reason to
have the exact frequency in opp@*** name. Just use what you have used
in opp-hz line and you will have the exact same behavior.

Right now, its a bit confusing if we read the DT.

--
viresh

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