linux-kernel - Re: [PATCH 1/2] Input: tsc2007 - Disable irq when the irq thread is handling data

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Message-ID: <20111201084818.GC31610@core.coreip.homeip.net>
Date:	Thu, 1 Dec 2011 00:48:18 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Feng Tang <feng.tang@...el.com>
Cc:	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kwlee@...kvision.com" <kwlee@...kvision.com>,
	"Clark, Joel" <joel.clark@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/2] Input: tsc2007 - Disable irq when the irq thread is
 handling data

On Thu, Dec 01, 2011 at 02:30:12PM +0800, Feng Tang wrote:
> Hi Dmitry,
> 
> On Thu, 1 Dec 2011 14:10:15 +0800
> Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> 
> > On Wed, Nov 30, 2011 at 10:08:24AM +0800, Feng Tang wrote:
> > > Hi Dmitry,
> > > 
> > > Thanks for the review.
> > > 
> > > On Tue, 29 Nov 2011 17:22:08 +0800
> > > Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > 
> > > > Hi Feng,
> > > > 
> > > > On Tue, Nov 29, 2011 at 04:12:57PM +0800, Feng Tang wrote:
> > > > > The TSC2007 data sheet say in some case the HW may fire some
> > > > > false interrrupt, which I also met during integrating one
> > > > > TSC2007 device. So add the disable_irq/enable_irq protection
> > > > > around data handling.
> > > > 
> > > > IRQF_ONESHOT should prevent IRQ from firing again while thread is
> > > > servicing it. Did you actually observe it not working?
> > > 
> > > You are right, the tsc's threaded IRQ function is not re-entered,
> > > and the driver is working actually. My bad not stating the problem
> > > clearly. The real problem I want solve is, many platforms including
> > > ours use a GPIO line as the tsc2007's IRQ line, and when these
> > > extra tsc2007 IRQ is triggered on the gpio line, that GPIO
> > > controller will fire up extra noise IRQ accordingly, causing its
> > > ISR to be called. And my patch is trying to let the GPIO controller
> > > driver disable that specific IRQ pin from tsc2007. As disable_irq
> > > will call GPIO irq_chip's irq_disable() or mask() hook.
> > 
> > But ONESHOT interrupt handler will not unmask interrupt until thead
> > finishes servicing it so we should not be seeing these extra IRQs.
> > I'm adding Thomas in case I misunderstand how it threaded IRQ
> > supposed to work.
> 
> I did see these extra IRQs. As the tsc2007 datasheet says, the PENIRQ may
> be falsely triggered, and that signal is passed to the GPIO controller, if
> the tsc2007 specific pin is not disabled in GPIOC level, then the GPIOC HW
> will send out a IRQ anyway. 
> 
> While calling the disable_irq(), it will call the irq_chip's (implemented by
> GPIO controller) irq_disable() or irq_mask() hook to disable that specific
> line for tsc2007.
> 
> I did check the original tsc2007 driver, which used the disable_irq/enable_irq
> too, which means this problem is a general one and has been seen before.
> 

No, the original had disable/enable IRQ because it was the only way to
stop interrupt storm with combination of hard IRQ + workqueue or thread.

BTW, do you have it configured as level or edge interrupt?

> Or should we have a another flag in tsc2007 platform data, to let each platform
> chose whether or not to use the disable/enable_irq according to their platform
> need.
> 
> > 
> > Also, there is clear_penirq() platform method that is called to clean
> > penirq state, if needed.
> 
> Sadly we don't have a way to clear the irq from TSC2007 on our platform :(
>

Thanks.

-- 
Dmitry
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