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

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Date:	Sat, 09 Aug 2014 00:26:25 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Doug Anderson <dianders@...omium.org>
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

Hello Doug,

On 08/08/2014 10:54 PM, Doug Anderson wrote:
> Hi,
>>
>> To fix the issue a variation of patch [0] will be posted that moves the IRQ
>> pinmux setup from .irq_set_type to the .irq_request_resources function handler.
>> That way the pin will be setup as IRQ regardless of the the trigger type [1]
>> when someone calls request_[threaded]_irq().
>>
>> Only the mentioned patch fixes the issue but Tomasz said that even a call to
>> gpio_direction_{input,output} can change the pin configuration so he will post
>> another patch that will add a bit mask to samsung_pin_bank to prevent any pinmux
>> reconfiguration.
> 
> Would just making a device tree change fix this?  AKA for the pin, do:
> 
>   samsung,pin-function = <0xf>;
> 

Yes, when configuring the pin as 0xf (GPIO interrupt) instead of 0x0 (GPIO
input) the issue is not present indeed. So after Nick answer my question about
what I got wrong with the "linux,gpio-keymap" property, I will change the pin
function when re-posing the DTS changes for the atmel touchpad.

> 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?

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.

> -Doug
> 

Best regards,
Javier
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