Hi Thierry,
> Sent: Monday, June 29, 2015 6:12 PM
>
> On Mon, Jun 15, 2015 at 05:48:00AM +0000, Yoshihiro Shimoda wrote:
> [...]
> > > > +static void rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div,
> > > > + int duty_ns, int period_ns)
> > > > +{
> > > > + unsigned long long one_cycle, tmp; /* 0.01 nanoseconds */
> > > > + unsigned long clk_rate = clk_get_rate(rp->clk);
> > > > + u32 cyc, ph;
> > > > +
> > > > + one_cycle = (unsigned long long)NSEC_PER_SEC * 100ULL * (1 << div);
> > > > + do_div(one_cycle, clk_rate);
> > > > +
> > > > + tmp = period_ns * 100ULL;
> > > > + do_div(tmp, one_cycle);
> > > > + cyc = (tmp << RCAR_PWMCNT_CYC0_SHIFT) & RCAR_PWMCNT_CYC0_MASK;
> > > > +
> > > > + tmp = duty_ns * 100ULL;
> > > > + do_div(tmp, one_cycle);
> > > > + ph = tmp & RCAR_PWMCNT_PH0_MASK;
> > > > +
> > > > + /* Avoid prohibited setting */
> > > > + if (cyc && ph)
> > > > + rcar_pwm_write(rp, cyc | ph, RCAR_PWMCNT);
> > >
> > > So if a period and duty-cycle are passed in that yield the prohibited
> > > setting the operation will simply be silently ignored?
> >
> > Yes, to update values of pwm->duty_cycle and ->period by pwm_config(),
> > this code will be silently ignored.
>
> That's not right. If someone passes in invalid values you should report
> an error.
Thank you for the comment.
After I sent the previous email, I was also confusing this behavior.
So, I fixed it in v5 patch.
(In other words, if the PWM is enabled and a user input invalid values,
this driver will report an error.)
I'm sorry, I should have explained that in this email thread.
> Also, are you sure the check is correct? The current check:
>
> if (cyc && ph)
>
> is the same as
>
> if (cyc != 0 && ph != 0)
>
> which means that you will never be able to set a zero duty cycle. Is
> that really what you want here?
Yes, I really want to avoid to set a zero duty cycle because
the PWM doesn't accept it.
(According to the datasheet, it said "Setting H'000 is prohibited.")
Best regards,
Yoshihiro Shimoda
> Thierry
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