Re: [PATCH v1 1/1] iio: adc: tsc2046: rework the trigger state machine

Jonathan Cameron
2022-01-15T18:08:25Z

...

> > >
> > > -static enum hrtimer_restart tsc2046_adc_trig_more(struct hrtimer *hrtimer)
> > > +static enum hrtimer_restart tsc2046_adc_timer(struct hrtimer *hrtimer)
> > > {
> > > struct tsc2046_adc_priv *priv = container_of(hrtimer,
> > > struct tsc2046_adc_priv,
> > > trig_timer);
> > > unsigned long flags;
> > >
> > > - spin_lock_irqsave(&priv->trig_lock, flags);
> > > -
> > > - disable_irq_nosync(priv->spi->irq);
> > > -
> > > - priv->trig_more_count++;
> > > - iio_trigger_poll(priv->trig);
> > > -
> > > - spin_unlock_irqrestore(&priv->trig_lock, flags);
> > > + spin_lock_irqsave(&priv->state_lock, flags);
> > > + switch (priv->state) {
> > > + case TSC2046_STATE_ENABLE_IRQ_POLL:
> > > + /*
> > > + * IRQ handler called iio_trigger_poll() to sample ADC.
> > > + * Here we
> > > + * - re-enable IRQs
> > > + * - start hrtimer for timeout if no IRQ will occur
> > > + */
> > > + priv->state = TSC2046_STATE_POLL;
> > > + enable_irq(priv->spi->irq);
> >
> > I comment on this below, but I'm not sure why you don't move the enable_irq()
> > here out of this timer function and then have the first entry of the timer
> > go directly to TSC2046_STATE_POLL after a longer initial wait.
>
> Hm... yes. You are right.
>
> > It's been a long time since I looked at this, so perhaps I'm missing the
> > point. What you have here works as far as I can see, it just seems to push
> > more than necessary into the state machine.
>
> The IRQ line is a level shifter connected to one of channels muxed to the core
> ADC. If we switch internal muxer to different channel, the IRQ line will
> change the state.
>
> So, we need a trigger which:
> - do not triggers if we do ADC readings.
> - keeps triggering as long as we have some state changes on the IRQ line
> - trigger only with specific rate
> - still triggers for some amount of time after last interrupt event was
> detected. Current implementation is doing only one extra read.
Ah.. Good explanation, I get the point now :)

Jonathan