On 21/10/2019 10:58, claudiu.bez...@microchip.com wrote: > Hi Daniel, > > On 18.10.2019 23:24, Daniel Lezcano wrote: >> Hi Claudiu, >> >> On 15/10/2019 11:23, claudiu.bez...@microchip.com wrote: >> >> [ ... ] >> >>> The timer clock source could be divided by MR.PRES + 1. >>> >>> So, I used the clock-frequency DT binding to let user choose the timer's >>> frequency. Based on the value provided via this DT binding the best clock >>> source and prescaler is chosen via mchp_pit64b_pres_prepare() function. >> >> I'm willing to take the driver but I doubt the purpose of the >> clock-frequency is to let the user choose the frequency. >> > > I found this approach in the following already integrated drivers: > drivers/clocksource/armv7m_systick.c > drivers/clocksource/bcm2835_timer.c > drivers/clocksource/bcm_kona_timer.c > drivers/clocksource/mips-gic-timer.c > drivers/clocksource/mps2-timer.c > drivers/clocksource/timer-qcom.c > drivers/clocksource/arm_arch_timer.c > > Looking through the documentation of these, most of them document this DT > property as the frequency of the clock that drivers the timer, but none of > them seems to have some IP internal dividers so that the timer to tick at > different frequency than the clock that feeds the IP. From the > documentation of the above drivers; > drivers/clocksource/armv7m_systick.c > - clock-frequency : The rate in HZ in input of the ARM SysTick > > drivers/clocksource/bcm2835_timer.c > - clock-frequency : The frequency of the clock that drives the counter, > in > Hz. > drivers/clocksource/bcm_kona_timer.c > - clock-frequency: frequency that the clock operates > > drivers/clocksource/mips-gic-timer.c > clock-frequency : Clock frequency at which the GIC timers operate. > drivers/clocksource/mps2-timer.c > - clock-frequency : The rate in HZ in input of the ARM MPS2 timer > > drivers/clocksource/timer-qcom.c > - clock-frequency : The frequency of the debug timer and the general > purpose > timer(s) in Hz in that order. > > > This is why I also chose this DT bindings. > > If you want I can stick to a fixed frequency hard coded in the driver. > Please let me know if this would be OK for you.
Yes, the clock-frequency is used to specify the frequency when the information can not be retrieved from the clock. The goal is not to specify a frequency and compute from there a prescalar value. Hardcoding the frequency is fine or hardcode the divider and compute the frequency from the clock rate. -- <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
