On Tue, Nov 01, 2016 at 01:57:05PM -0700, Vineet Gupta wrote: > Hi Daniel, > > On 11/01/2016 01:42 PM, Daniel Lezcano wrote: > > Please stay consistent with the rest of the Kconfig. > > > > config ARC_TIMER_RTC > > bool "64-bit cycle counter in HS38 cores" if COMPILE_TEST > > select CLKSRC_OF > > help > > This counter provides 64-bit resolution vs. the 32-bit TIMER1. > > It is implemented inside the core thus can't be used in SMP systems. > > > > config ARC_TIMER_GFRC > > bool "64-bit cycle counter in ARConnect block in HS38x cores" if > > COMPILE_TEST > > select CLKSRC_OF > > help > > This counter can be used as clocksource in SMP HS38 SoCs. > > It sits outside the core thus can be used in SMP systems > > > > Yes I did so already :-) Although I also added a default y if ARC to both, > but as > you say that is better done in ARC Kconfig. > > > Then in the ARC's Kconfig you select ARC_TIMER_RTC or ARC_TIMER_GFRC > > depending > > it is SMP or not. > > > > One question: > > > > Why ARC_TIMER_RTC can't be used in a SMP system ? Doesn't have each core its > > own clocksource ? It seems you are assuming a clocksource can be used on SMP > > only if the clocksource is unique and shared across the cores. > > Thats what I thought so far. Thing is, the individual core's counters could > get > out of sync, simply because non masters cores were halted to begin with and > came > up at different points in real time. so a gtod might return different value > depending on what core it landed on. Does clocksource also does ticks > broadcasts > and such to keep things in sync ?
Sounds like it is similar than the TSC. Do you agree to have a try by setting the CONFIG_HAVE_UNSTABLE_SCHED_CLOCK option ? If you can use those per cpu clocksource, performances on your system may improve with the sched_clock(). > Because of the git mv you, diff didn't include bulk of driver code which would > make for bulk of review anyways. So perhaps in v2 I don't do the git mv. OK ? That means I will review and comment existing code. It is not a problem for me if you agree to do the changes. -- Daniel
