On 16/05/2020 14:16, Serge Semin wrote:

Hello Daniel,

Thanks for your comment. My response is below.

On Fri, May 15, 2020 at 07:10:04PM +0200, Daniel Lezcano wrote:

quoted

On Thu, May 07, 2020 at 12:41:07AM +0300, Serge Semin wrote:

quoted

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 ?

Not using the timer might be better, but not that good alternative either
especially in our case due to very slow external timer. Me and Thomas
Bogendoerfer discussed the similar commit I've provided to the csrc-r4k driver
available on MIPS:
https://lkml.org/lkml/2020/5/11/576

To cut it short, you are right. The solution with using clocksource_mark_unstable()
is better alternative spied up in x86 tsc implementation. I'll use a similar
approach here and submit the updated patch in v3.

Could you please proceed with the rest of the series review? I'd like to send
the next version with as many comments taken into account as possible. The
patchset has been submitted a while ago, but except Rob noone have had any
comments.(

For me other patches are ok.

I can apply patches 1, 2, 4, 5, 6

Will remain patches 3 et 7


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