linux-kernel - Re: [PATCH v2 1/1] Input: atmel_mxt_ts - Get IRQ edge/level flags on DT booting

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Date:	Fri, 8 Aug 2014 16:58:49 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Nick Dyer <nick.dyer@...ev.co.uk>,
	Stephen Warren <swarren@...dia.com>,
	Yufeng Shen <miletus@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Tomasz Figa <tomasz.figa@...il.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Abraham <thomas.ab@...sung.com>
Subject: Re: [PATCH v2 1/1] Input: atmel_mxt_ts - Get IRQ edge/level flags on
 DT booting

Javier,

On Fri, Aug 8, 2014 at 3:26 PM, Javier Martinez Canillas
<javier.martinez@...labora.co.uk> wrote:
>> I have some vague recollection that I set interrupts to pin-function
>> "0" by default for some reason (assuming they would go to 0xf when
>> interrupts were enabled).  ...but I can't for the life of me remember
>> if it was a good reason or just seemed like the right thing to do.
>>
>
> It would be great to know if there is a good reason. I see indeed that all
> pinctrl setup in the Peach Pit/Pi and Snow DTS that involves interrupts are
> using 0x0 as the pin function. Since as Tomasz explained Samsung SoC makes a
> difference between GPIO-IRQ and GPIO input I guess that it's better to change
> those to 0xf instead. What do you think?

I think it's worth trying out.  If there are no problems with it then
let's do it.

My vague recollection is that I was worried that pinctrl would take
effect right at driver probe time (maybe this used to happen? or maybe
I imagined it?) and that configuring to 0xf at this point in time
would cause a spurious interrupt.  I can't remember ever testing it so
it was probably just something I imagined.  Even if it was configured
as 0xf I'd imagine that the interrupt would be masked anyway so there
should be no spurious interrupt, right?


> Regardless of this though I think that both the patch to move the IRQ
> pinmux setup from .irq_set_type to the .irq_request_resources and the patch to
> to prevent any pinmux reconfiguration are good improvements to avoid future
> issues like the one we found here.

OK.  I'll let you, Tomasz, and Linus figure out what's best here since
I haven't done extensive thinking on it.  ;)

-Doug
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