On 07/06/2017 at 16:17:35 +0200, Daniel Lezcano wrote: > > > > This driver uses regmap and syscon to be able to probe early in the boot > > > > and avoid having to switch on the TCB clocksource later. Using regmap > > > > also > > > > means that unused TCB channels may be used by other drivers (PWM for > > > > example). > > > > > > Can you give more details, I fail to understand how regmap and syscon > > > help to > > > probe sooner than timer_init()? > > > > > > Because before that, the tcb driver relied on atmel_tclib to share the > > TCBs and it happened way too late, at arch_initcall() time. > > So is it still necesary to use regmap? I would like to take the opportunity to > move the init routine to the common init routine if possible: > > https://patchwork.kernel.org/patch/9768845/ >
It is still necessary because we want to be able to share the timer between multiple drivers. For example, you can have the clocksource on channel 0, clockevent on channel 1 and a pwm on channel 2 > > > Can you explain why we have two clocks here? > > > > > > > Each channel have its clock, I can add a comment if you want. > > I don't understand. Why do we have two clocks? > > One channel is driven by one clock and the second one takes the overflow > signal > from the first one, so no second clock is involved there, no? > Those are the peripheral clocks, they are not used by the counters but used to be able to read/write the registers. -- Alexandre Belloni, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
