Messages in this thread | | | From | Wesley Terpstra <> | Date | Mon, 15 Oct 2018 16:19:20 -0700 | Subject | Re: [RFC 1/4] pwm: sifive: Add DT documentation for SiFive PWM Controller. |
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On Mon, Oct 15, 2018 at 3:57 PM Atish Patra <atish.patra@wdc.com> wrote: > >> +SiFive PWM controller > >> + > >> +Unlike most other PWM controllers, the SiFive PWM controller currently only > >> +supports one period for all channels in the PWM. This is set globally in DTS. > >> +The period also has significant restrictions on the values it can achieve, > >> +which the driver rounds to the nearest achievable frequency. > > > > What restrictions are these? If "nearest achievable" is too far off the > > target period it might be preferable to error out. > > > > @Wes: Any comments?
When I last looked at this driver and hardware, I briefly considered throwing up my hands and pretending that this PWM device had no period control at all, only duty-cycle. There are several examples of PWM controllers in linux already that behave that way.
Most of the uses of this PWM are only going to care about the duty-cycle, not the period. So failing when the period is unachievable seems worse to me than just completely eliminating access to period control.
> I think yes. Since fu540 is the first Linux capable RISC-V core, SiFive > Guys decided mark it as version 0. > > @Wesly: Please correct me if I am wrong.
Correct.
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