linux-kernel - Re: [PATCH v2 1/2] iio: adc: at91: fix acking DRDY irq on simple conversions

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Date:   Sat, 29 Sep 2018 12:31:07 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Ludovic Desroches <ludovic.desroches@...rochip.com>
Cc:     Eugen Hristev <eugen.hristev@...rochip.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <nicolas.ferre@...rochip.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>
Subject: Re: [PATCH v2 1/2] iio: adc: at91: fix acking DRDY irq on simple
 conversions

On Tue, 25 Sep 2018 15:17:39 +0200
Ludovic Desroches <ludovic.desroches@...rochip.com> wrote:

> On Mon, Sep 24, 2018 at 10:51:43AM +0300, Eugen Hristev wrote:
> > When doing simple conversions, the driver did not acknowledge the DRDY irq.
> > If this irq status is not acked, it will be left pending, and as soon as a
> > trigger is enabled, the irq handler will be called, it doesn't know why
> > this status has occurred because no channel is pending, and then it will go
> > int a irq loop and board will hang.
> > To avoid this situation, read the LCDR after a raw conversion is done.
> > 
> > Fixes 0e589d5fb ("ARM: AT91: IIO: Add AT91 ADC driver.")
> > Cc: Maxime Ripard <maxime.ripard@...tlin.com>
> > Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>  
> Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com> 
Applied to the togreg branch of iio.git and marked for stable.

It's been broken long enough that I think it can wait for the merge window
coming in a few weeks time.

Thanks,

Jonathan

> 
> > ---
> > Hello Jonathan,
> > 
> > I moved this LCDR read/acknowledge into the IRQ handler after the conversion
> > value is being read.
> > Sorry about the noise to stable@...r, removed from message.
> > 
> > Thanks,
> > Eugen
> > 
> >  drivers/iio/adc/at91_adc.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
> > index 44b5168..e3be88e 100644
> > --- a/drivers/iio/adc/at91_adc.c
> > +++ b/drivers/iio/adc/at91_adc.c
> > @@ -279,6 +279,8 @@ static void handle_adc_eoc_trigger(int irq, struct iio_dev *idev)
> >  		iio_trigger_poll(idev->trig);
> >  	} else {
> >  		st->last_value = at91_adc_readl(st, AT91_ADC_CHAN(st, st->chnb));
> > +		/* Needed to ACK the DRDY interruption */
> > +		at91_adc_readl(st, AT91_ADC_LCDR);
> >  		st->done = true;
> >  		wake_up_interruptible(&st->wq_data_avail);
> >  	}
> > -- 
> > 2.7.4
> >