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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20111201170021.3556aac3@feng-i7>
Date:	Thu, 1 Dec 2011 17:00:21 +0800
From:	Feng Tang <feng.tang@...el.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.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

Hi Dmitry

On Thu, 1 Dec 2011 16:48:18 +0800
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:

> 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.

My understanding is, if the GPIO line used by tsc2007 is not disabled
in GPIO controller level, the GPIOC will always be triggered by tsc2007
to fire those extra interrupts.

Actually I did try the old version driver (no threaded irq version), which
will see the extra interrupts if the disable_irq/enable_irq is removed.

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

I'm now using the falling edge trigger, but I tried the level trigger
which will have more interrupts storm.

Thanks,
Feng

> 
> > 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.
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/