linux-kernel - RE: [PATCH v6 1/1] PRUSS UIO driver support

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Date:	Tue, 1 Mar 2011 10:53:16 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"TK, Pratheesh Gangadhar" <pratheesh@...com>
cc:	"Hans J. Koch" <hjk@...sjkoch.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"sshtylyov@...sta.com" <sshtylyov@...sta.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"Chatterjee, Amit" <amit.chatterjee@...com>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v6 1/1] PRUSS UIO driver support

On Tue, 1 Mar 2011, TK, Pratheesh Gangadhar wrote:
> > On Tue, Mar 01, 2011 at 02:31:35AM +0530, Pratheesh Gangadhar wrote:
> > > +
> > > +		/* Register PRUSS IRQ lines */
> > > +		p->irq = IRQ_DA8XX_EVTOUT0 + cnt;
> > > +		p->handler = pruss_handler;
> > > +
> > > +		ret = uio_register_device(&dev->dev, p);
> > > +
> > > +		if (ret < 0)
> > > +			goto out_free;
> > > +	}
> > > +
> > > +	spin_lock_init(&lock);
> > 
> > That's too late. uio_register_device() enables the irq, and your spin_lock
> > is not ready at that time.
> 
> This is ok in this context as "modprobe uio_pruss" is pre-requisite for
> running PRUSS firmware and without firmware running PRUSS won't
> generate interrupts. Actually PRUSS INTC is not setup till we start
> user application.

No, it's not. If you enable interrupts you have to be prepared for
getting one whether the device mask is enabled or not. It's that
simple.

Thanks,

	tglx
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