Hi Thomas Gleixner, Thanks for the feedback. > Subject: RE: [PATCH 0/6] Add RZ/V2M Compare-Match Timer (TIM) support > > Biju! > > On Wed, Dec 07 2022 at 07:52, Biju Das wrote: > >> On Tue, Dec 06 2022 at 09:40, Geert Uytterhoeven wrote: > >> > When multiple clocksources are registered, the clocksource > >> > subsystems picks the best one anyway, right? > >> > >> As it does for the clock event devices. If there is an architected > >> timer then that should be always preferred. > >> > >> No idea why there is a need for the extra hardware and the drivers > >> which are both never utilized. > > > > I got feedback from BSP team for the actual usage of this timer. > > > > Basically, this HW timer is used for measuring the processing time of > > DRP-AI accurately compared to the CPU timer normally we use. > > How is a slow to access timer with a lower clock frequency more accurate? But our tick frequency for arm64 defconfig is CONFIG_HZ_250=y. So we get timer interrupt at every 4 msec. How do we get timer event interrupt, eg: for 1 microsec? > > > The example use cases, > > Timer in FREERUN mode, Check the timer value after the restart(1usec)" > > Timer in FREERUN mode, Check the timer value after the > restart(10000000usec)" > > > > What is the model to be used for this kind of HW usage? Counter or > Timer? > > > > I can think of one possible HW usage by using Counter model. > > Not sure how timer model can be used for this kind of HW usage?? > > > > Eg: we can set ceiling values 1usec and 10000000usec using counter > framework > > And that will trigger interrupt events corresponding to the ceiling > values > > to user space and user space app can accurately measure the DRP-AI > processing time. > > > > Also counter model exposes count values to user space from the counter > HW. > > Counter subsystem != clocksource/event subsystem. > > We are debating a clocksource/clockevent driver and not a counter driver, > right? Yes, Rob pointed out we should not misuse the compatibles as I have both Timer and counter bindings for a given HW timer. Timer, It can be used as broadcast and highres timer for RT. Counter, It can be used as measuring the processing time of DRP-AI. What is the best way to use this hardware to take care of all this use cases? So far all the Renesas timers used timer model. But for RZ/V2M the HW usage is different. The customer BSP mainly uses this timer for measuring the processing time of DRP-AI, so the expectation is we should at least have support for this use case. Cheers, Biju
