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

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Message-ID: <20151223104833.GE2789@odux.rfo.atmel.com>
Date:	Wed, 23 Dec 2015 11:48:33 +0100
From:	Ludovic Desroches <ludovic.desroches@...el.com>
To:	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 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?

By the way this is not a polled read.

> > > +		st->done = true;
> > > +		wake_up_interruptible(&st->wq_data_available);
> > > +	}
> > > +
> > > +	return IRQ_HANDLED;
> > > +}

Ludovic
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