From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:56436 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726225AbeIYC1e (ORCPT ); Mon, 24 Sep 2018 22:27:34 -0400 Date: Mon, 24 Sep 2018 21:23:33 +0100 From: Jonathan Cameron To: Eugen Hristev Cc: , , , , , Maxime Ripard Subject: Re: [PATCH v2 1/2] iio: adc: at91: fix acking DRDY irq on simple conversions Message-ID: <20180924212333.797439dd@archlinux> In-Reply-To: <1537775504-7981-1-git-send-email-eugen.hristev@microchip.com> References: <1537775504-7981-1-git-send-email-eugen.hristev@microchip.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On Mon, 24 Sep 2018 10:51:43 +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 > Signed-off-by: Eugen Hristev > --- > Hello Jonathan, > > I moved this LCDR read/acknowledge into the IRQ handler after the conversion > value is being read. Ah.. This all makes more sense now. I'd misunderstood originally and thought we were looking at a read raw that wasn't using the interrupt at all. Sorry about that. However, mostly by coincidence (given I misread the code) I think this is a neater way to do this than the previous option as it puts it near the actual read. Given Maxime is the author of this one though I'd like to leave it on the list a little longer before applying. At this stage in the cycle I'll probably just queue it up for the next merge window anyway (marked for stable). It's not exactly a new bug after all. Thanks, Jonathan > Sorry about the noise to stable@vger, 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); > }