linux-kernel - RE: [PATCH 1/3 v2] GPIO: gpio-dwapb: Enable platform driver binding to MFD driver

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Message-ID: <4656BEB6164FC34F8171C6538F1A595B2E982BFA@SHSMSX101.ccr.corp.intel.com>
Date:	Sat, 6 Sep 2014 10:47:01 +0000
From:	"Chen, Alvin" <alvin.chen@...el.com>
To:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>,
	Arnd Bergmann <arnd@...db.de>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	atull <atull@...nsource.altera.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"Ong, Boon Leong" <boon.leong.ong@...el.com>,
	"Kweh, Hock Leong" <hock.leong.kweh@...el.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	"Westerberg, Mika" <mika.westerberg@...el.com>,
	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
Subject: RE: [PATCH 1/3 v2] GPIO: gpio-dwapb: Enable platform driver binding
 to MFD driver

> > >
> > > -	irq_set_chained_handler(irq, dwapb_irq_handler);
> > > -	irq_set_handler_data(irq, gpio);
> > > +	if (!pp->irq_shared) {
> > > +		irq_set_chained_handler(pp->irq, dwapb_irq_handler);
> > > +		irq_set_handler_data(pp->irq, gpio);
> > > +	} else {
> > > +		/*
> > > +		 * Request a shared IRQ since where MFD would have devices
> > > +		 * using the same irq pin
> > > +		 */
> > > +		err = devm_request_irq(gpio->dev, pp->irq,
> > > +				       dwapb_irq_handler_mfd,
> > > +				       IRQF_SHARED, "gpio-dwapb-mfd", gpio);
> > > +		if (err) {
> > > +			dev_err(gpio->dev, "error requesting IRQ\n");
> > > +			irq_domain_remove(gpio->domain);
> > > +			gpio->domain = NULL;
> > > +			return;
> > > +		}
> > > +	}
> > >
> >
> > I think this need some better documentation. Why is it safe to use
> > devm_request_irq rather than irq_set_chained_handler here?
> 
> Usually it is preferred to use irq_set_chained_handler() for the chained handler
> so the handler does not show up in /proc/interrupts.
> This requires an exclusive non-shared handler which is not the case on the intel
> platform. So they have to use devm_request_irq() instead.
> 
Yes, for Intel Quark, it has a single PCI function exporting a GPIO and I2C controller, and
the irq is shared by GPIO and I2C, so we need shared irq as the comments said.



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