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

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

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@gmail.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.

Also, there is clear_penirq() platform method that is called to clean
penirq state, if needed.


> 
> By grep the tsc2007_platform_data in kernel, I see most of the most of
> the tsc2007 platforms are using GPIO line as tsc2007 IRQ ine. So this
> should be a general problem.
> 
> Following is patch with updated log and comments.
> 
> Thanks,
> Feng
> 
> -----------------
> 
> From 16585020d27a066d2908959e370ea4f8905a0d34 Mon Sep 17 00:00:00 2001
> From: Feng Tang <feng.tang@intel.com>
> Date: Tue, 29 Nov 2011 15:48:42 +0800
> Subject: [PATCH 1/2] Input: tsc2007 - Disable irq when the irq thread is handling data
> 
> The TSC2007 data sheet say in some case the HW may fire some false
> interrrupt, which I also met during integrating one TSC2007 device.
> Most of the tsc2007 platforms including ours are using a gpio line as
> tsc2007's irq line, so calling disable_irq_nosync() to actually
> prevent the gpio controller from firing IRQ for tsc2007 in such case.
> 
> Signed-off-by: Feng Tang <feng.tang@intel.com>
> ---
>  drivers/input/touchscreen/tsc2007.c |   13 +++++++++++++
>  1 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/tsc2007.c b/drivers/input/touchscreen/tsc2007.c
> index 1f674cb..03c1961 100644
> --- a/drivers/input/touchscreen/tsc2007.c
> +++ b/drivers/input/touchscreen/tsc2007.c
> @@ -171,6 +171,18 @@ static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
>  	struct ts_event tc;
>  	u32 rt;
>  
> +	/*
> +	 * Disable the irq, as it may fire several other IRQs during
> +	 * this thread is handling data, as suggested by the TSC2007
> +	 * datasheet, p19, "Touch Detect" chapter.
> +	 *
> +	 * Most of the tsc2007 platforms are using a gpio line as
> +	 * tsc2007's irq line, so calling disable_irq_nosync() will
> +	 * actually prevent the gpio controller from firing IRQ for
> +	 * this tsc2007 line in such case.
> +	 */
> +	disable_irq_nosync(irq);
> +
>  	while (!ts->stopped && tsc2007_is_pen_down(ts)) {
>  
>  		/* pen is down, continue with the measurement */
> @@ -221,6 +233,7 @@ static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
>  	if (ts->clear_penirq)
>  		ts->clear_penirq();
>  
> +	enable_irq(irq);
>  	return IRQ_HANDLED;
>  }
>  
> -- 
> 1.7.1
> > 
> > Thanks.
> > 
> > > 
> > > Signed-off-by: Feng Tang <feng.tang@intel.com>
> > > ---
> > >  drivers/input/touchscreen/tsc2007.c |    8 ++++++++
> > >  1 files changed, 8 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/drivers/input/touchscreen/tsc2007.c
> > > b/drivers/input/touchscreen/tsc2007.c index 1f674cb..789f216 100644
> > > --- a/drivers/input/touchscreen/tsc2007.c
> > > +++ b/drivers/input/touchscreen/tsc2007.c
> > > @@ -171,6 +171,13 @@ static irqreturn_t tsc2007_soft_irq(int irq,
> > > void *handle) struct ts_event tc;
> > >  	u32 rt;
> > >  
> > > +	/*
> > > +	 * Disable the irq, as it may fire several other IRQs
> > > during
> > > +	 * this thread is handling data, as suggested by the
> > > TSC2007
> > > +	 * datasheet, p19, "Touch Detect" chapter
> > > +	 */
> > > +	disable_irq_nosync(irq);
> > > +
> > >  	while (!ts->stopped && tsc2007_is_pen_down(ts)) {
> > >  
> > >  		/* pen is down, continue with the measurement */
> > > @@ -221,6 +228,7 @@ static irqreturn_t tsc2007_soft_irq(int irq,
> > > void *handle) if (ts->clear_penirq)
> > >  		ts->clear_penirq();
> > >  
> > > +	enable_irq(irq);
> > >  	return IRQ_HANDLED;
> > >  }
> > >  
> > > -- 
> > > 1.7.1
> > > 
> > > 
> > 

-- 
Dmitry