linux-kernel - Re: [PATCH 1/2] regulator: ltc3589: make IRQ optional

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Message-ID: <20160121111115.GJ6588@sirena.org.uk>
Date:	Thu, 21 Jan 2016 11:11:15 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Benoît Cousson <bcousson@...libre.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH 1/2] regulator: ltc3589: make IRQ optional

On Thu, Jan 21, 2016 at 11:26:11AM +0100, Lothar Waßmann wrote:
> > On Thu, Jan 21, 2016 at 08:05:24AM +0100, Lothar Waßmann wrote:
> > > > On Wed, Jan 20, 2016 at 01:29:51PM +0100, Lothar Waßmann wrote:

> > > > > This pin is used as IRQ pin for the LTC3589 PMIC on the Ka-Ro
> > > > > electronics TX48 module. Make the IRQ optional in the driver and use a
> > > > > polling routine instead if no IRQ is specified in DT.
> > > > > Otherwise the driver will continuously generate interrupts and make
> > > > > the system unusable.

> > > > How will the driver generate interrupts if there is no interrupt
> > > > physically present in the system?

> > > It's using timer interrupts to poll the LTC3589 state.

> > I know that is what your patch does, my question is why you say in your
> > commit log that "Otherwise the driver will continuously generate
> > interrupts and make the system unusable".

> Because the interrupt is level triggered and the polarity of the
> EXTINT pin is inverted, the interrupt will be constantly active when
> the IRQ pin of the LTC3589 is inactive.

So, to repeat my original question, how will that generate interrupts if
there is no interrupt physically present in the system?

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