linux-kernel - Re: [PATCH 1/5] iio:adc:at91_adc8xx: introduce new atmel adc driver

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Message-ID: <E2C27D1A-1035-4330-AEF3-C72B87C27FEF@jic23.retrosnub.co.uk>
Date:	Wed, 23 Dec 2015 17:21:25 +0000
From:	Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:	Ludovic Desroches <ludovic.desroches@...el.com>,
	Jonathan Cameron <jic23@...nel.org>, nicolas.ferre@...el.com,
	alexandre.belloni@...e-electrons.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	plagnioj@...osoft.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/5] iio:adc:at91_adc8xx: introduce new atmel adc driver



On 23 December 2015 10:48:33 GMT+00:00, Ludovic Desroches <ludovic.desroches@...el.com> wrote:
>On Wed, Dec 23, 2015 at 11:27:00AM +0100, Ludovic Desroches wrote:
>> On Tue, Dec 22, 2015 at 06:34:00PM +0000, Jonathan Cameron wrote:
>> > On 21/12/15 09:24, Ludovic Desroches wrote:
>> > > This driver supports the new version of the Atmel ADC device
>introduced
>> > > with the SAMA5D2 SoC family.
>> > > 
>
>[...]
>
>> > > +static irqreturn_t at91_adc_interrupt(int irq, void *private)
>> > > +{
>> > > +	struct iio_dev *indio = private;
>> > > +	struct at91_adc_state *st = iio_priv(indio);
>> > > +	u32 status = at91_adc_readl(st, ADC_ISR);
>> > > +
>> > > +	status &= at91_adc_readl(st, ADC_IMR);
>> > > +	if (status & 0xFFF) {
>> > > +		st->last_value = at91_adc_readl(st, st->chan->address);
>> > If this is a polled read - is there any reason to read this value
>here
>> > rather than outside the interrupt?
>> 
>> No it can be done outside the interrupt. I have taken some parts from
>the
>> previous driver but it was reading a register used by all the
>channels
>> when it has been designed. So yes there is probably no more reason to
>> read it into the interrupt.
>> 
>
>Thinking about it. Is it really useful to move reading outside the
>interrupt?
It avoids needing to know the channel in here, hence simplifying the code a bit.
>
>By the way this is not a polled read.
I meant that it is an individually requested conversion rather than a free running
 sampling system where the value read might change before it is read out.
>
>> > > +		st->done = true;
>> > > +		wake_up_interruptible(&st->wq_data_available);
>> > > +	}
>> > > +
>> > > +	return IRQ_HANDLED;
>> > > +}
>
>Ludovic
>--
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