Re: [PATCH 19/25] hw/timer/cmsdk-apb-dualtimer: Convert to use Clock input

[Luc Michel]

On 21:41 Fri 22 Jan     , Peter Maydell wrote:
> On Fri, 22 Jan 2021 at 20:48, Luc Michel <luc@lmichel.fr> wrote:
> >
> > On 19:06 Thu 21 Jan     , Peter Maydell wrote:
> > > Switch the CMSDK APB dualtimer device over to using its Clock input;
> > > the pclk-frq property is now ignored.
> > >
> > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > > ---
> > >  hw/timer/cmsdk-apb-dualtimer.c | 42 ++++++++++++++++++++++++++++++----
> > >  1 file changed, 37 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/hw/timer/cmsdk-apb-dualtimer.c 
> > > b/hw/timer/cmsdk-apb-dualtimer.c
> > > index 781b496037b..828127b366f 100644
> > > --- a/hw/timer/cmsdk-apb-dualtimer.c
> > > +++ b/hw/timer/cmsdk-apb-dualtimer.c
> > > @@ -106,6 +106,22 @@ static void 
> > > cmsdk_apb_dualtimer_update(CMSDKAPBDualTimer *s)
> > >      qemu_set_irq(s->timerintc, timintc);
> > >  }
> > >
> > > +static int cmsdk_dualtimermod_divisor(CMSDKAPBDualTimerModule *m)
> > > +{
> > > +    /* Return the divisor set by the current CONTROL.PRESCALE value */
> > > +    switch (FIELD_EX32(m->control, CONTROL, PRESCALE)) {
> > > +    case 0:
> > > +        return 1;
> > > +    case 1:
> > > +        return 16;
> > > +    case 2:
> > > +    case 3: /* UNDEFINED, we treat like 2 (and complained when it was 
> > > set) */
> > > +        return 256;
> > > +    default:
> > > +        g_assert_not_reached();
> > > +    }
> > > +}
> > > +
> > >  static void cmsdk_dualtimermod_write_control(CMSDKAPBDualTimerModule *m,
> > >                                               uint32_t newctrl)
> > >  {
> > > @@ -146,7 +162,7 @@ static void 
> > > cmsdk_dualtimermod_write_control(CMSDKAPBDualTimerModule *m,
> > >          default:
> > >              g_assert_not_reached();
> > >          }
> > > -        ptimer_set_freq(m->timer, m->parent->pclk_frq / divisor);
> > > +        ptimer_set_period_from_clock(m->timer, m->parent->timclk, 
> > > divisor);
> >
> > Just a small cosmetic note, maybe you can use your new
> > cmsdk_dualtimermod_divisor function to factor out the switch above?
> > Something like:
> >
> > if (changed & R_CONTROL_PRESCALE_MASK) {
> >     if (FIELD_EX32(newctrl, CONTROL, PRESCALE) == 3) {
> >         qemu_log_mask(LOG_GUEST_ERROR,
> >                       "CMSDK APB dual-timer: CONTROL.PRESCALE==0b11"
> >                       " is undefined behaviour\n");
> >     }
> >
> >     ptimer_set_period_from_clock(m->timer, m->parent->timclk,
> >                                  cmsdk_dualtimermod_divisor(m));
> > }
> 
> Nope, because cmsdk_dualtimermod_divisor() uses the current
> m->control value, and at this point in the code we need the
> divisor from the new control value which isn't in m->control yet.
> I liked the slight duplication better than either having to
> pass m->control in in all the other callsites or trying to
> refactor the control write handling so that m->control is
> updated before this point in the code.

Oops yes I missed that. Sure make sense, forget what I said.

> 
> thanks
> -- PMM

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