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: >> 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 ? > > 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 -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
