linux-kernel - Re: [PATCH 2/2] Input: tsc2007 - Add a z1_low

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Date:	Thu, 1 Dec 2011 17:04:55 +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>,
	"Clark, Joel" <joel.clark@...el.com>
Subject: Re: [PATCH 2/2] Input: tsc2007 - Add a z1_low_threshhold platform
 data parameter

Hi Dmitry,


On Thu, 1 Dec 2011 16:45:24 +0800
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:


> > > 
> > > Even if we add the pressure threshold would not that noise cause
> > > endless stream of interrupts?
> > 
> > No, there is no endless interrupts for tsc2007. Without the z1
> > threshold, the while circle in tsc2007_soft_irq will run endlessly
> > as the noise data will be seen as a valid data:
> > 
> > 		rt = tsc2007_calculate_pressure(ts, &tc);
> > 		if (rt == 0 && !ts->get_pendown_state) {
> > 			/*
> > 			 * If pressure reported is 0 and we don't
> > have
> > 			 * callback to check pendown state, we have
> > to
> > 			 * assume that pen was lifted up.
> > 			 */
> > 			break;
> > 		}
> > 
> > With the z1 threshold check, the rt will be 0 for noise data, and
> > the code flow broke out.
> 
> What I meant is with the threshold check we'll break out of the ISR
> but why won't IRQ be raised again?

The IRQ will be fired again after we exist the tsc2007_soft_irq in my
test, as I re-enable the irq before existing the code.

> 
> > 
> > > 
> > > Also, what kind of z2 is reported with low z1? And do you
> > > implement get_pendown_state()?
> > 
> > z2 seems normal as some data between 3000-4000. We don't have a
> > get_pendown_state().
> 
> OK, there is max_rt platform parameter. I think we should employ it
> instead and break out if we get several incorrect samples in a row.
> Too bad you do not have a dedicate method.
> 
No, the max_rt won't help here, if the rt > max_rt, it won't break the
while loop, but just issue a warning message

		if (rt <= ts->max_rt) {
			.......

		} else {
			/*
			 * Sample found inconsistent by debouncing or pressure is
			 * beyond the maximum. Don't report it to user space,
			 * repeat at least once more the measurement.
			 */
			dev_dbg(&ts->client->dev, "ignored pressure %d\n", rt);
		}

Thanks,
Feng
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