linux-kernel - Re: [PATCH V3 3/3] mfd: stmpe: Update DT support in stmpe driver

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Message-ID: <20121127084007.GA7897@gmail.com>
Date:	Tue, 27 Nov 2012 08:40:07 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Grant Likely <grant.likely@...retlab.ca>, sameo@...ux.intel.com,
	devicetree-discuss@...ts.ozlabs.org, spear-devel@...t.st.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 3/3] mfd: stmpe: Update DT support in stmpe driver

On Tue, 27 Nov 2012, Viresh Kumar wrote:

> On 27 November 2012 08:10, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > On 27 November 2012 00:10, Grant Likely <grant.likely@...retlab.ca> wrote:
> >> It would actually be good to ask the interrupt controller driver what
> >> kind of interrupt signal it expects for a given interrupt line. That
> >> should also solve the problem and I think it would be more useful to
> >> other devices. Can you investigate whether or not
> >> irqd_get_trigger_type() returns the information you need?
> >
> > That's a pretty cool function to use. :)
> >
> > Will check it out :)
> 
> I was thinking about this logic in my earlier mail, don't know what stopped me
> from thinking it is wrong. :(
> 
> Problem is with invert polarity, which the interrupt controller is not aware of.
> For example, suppose interrupt controller needs Rising edge interrupt, but
> the board has inverted the line between stmpe and IC. So, we will get
> Rising high from the routine you mentioned, but we need to generate
> opposite of that to make it rising high.

Surely that would be a hardware design error/quirk?

Can you give an example where this has happened?

> And so interrupt polarity field is still required.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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