Re: [PATCH v3 7/7] clocksource: mips-gic-timer: Set limitations on clocksource/sched-clocks usage

[Daniel Lezcano]

On Thu, May 07, 2020 at 12:41:07AM +0300, Serge Semin wrote:
> Currently neither clocksource nor scheduler clock kernel framework
> support the clocks with variable frequency. Needless to say how many
> problems may cause the sudden base clocks frequency change. In a
> simplest case the system time will either slow down or speed up.
> Since on CM2.5 and earlier MIPS GIC timer is synchronously clocked
> with CPU we must set some limitations on using it for these frameworks
> if CPU frequency may change. First of all it's not safe to have the
> MIPS GIC used for scheduler timings. So we shouldn't proceed with
> the clocks registration in the sched-subsystem. Secondly we must
> significantly decrease the MIPS GIC clocksource rating. This will let
> the system to use it only as a last resort.
>
> Note CM3.x-based systems may also experience the problems with MIPS GIC
> if the CPU-frequency change is activated for the whole CPU cluster
> instead of using the individual CPC core clocks divider.

May be there is no alternative but the code looks a bit hacksih. Isn't possible
to do something with the sched_mark_unstable?

Or just not use the timer at all ?