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, 08 Aug 2014 20:29:32 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Nick Dyer <nick.dyer@...ev.co.uk>
CC:	Stephen Warren <swarren@...dia.com>,
	Yufeng Shen <miletus@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Tomasz Figa <tomasz.figa@...il.com>,
	linux-input@...r.kernel.org, devicetree@...r.kernel.org,
	linux-samsung-soc@...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,

On 08/08/2014 06:38 PM, Javier Martinez Canillas wrote:
> 
> 
> It seems as if the first call to exynos_irq_set_type() that is made by OF is a
> no-op while the second call is the one that actually setups the hw correctly.
> Does this make any sense? Maybe is related to the pin not being muxed in the
> correct function when the "interrupts" property is parsed by OF?
> 

So after a conversation with Tomasz Figa over IRC the problem was after all that
the pin was reconfigured. The IRQ trigger type resulted to be just a red herring
and not a direct cause.

The pinctrl-eyxnos driver does the IRQ pinmux setup in the .irq_set_type
function handler. So what happened was that OF parsed the "interrupts" property
and called exynos_irq_set_type() which did the pinmux setup.

But after that, due a DTS pinctrl configuration the pin function was changed as
a GPIO input and that happened before the atmel driver was probed. So when the
driver called request_threaded_irq(), the correct flags were used but the pin
was not configured as an IRQ anymore so IRQ were not fired.

Setting a trigger type just had the side effect of calling exynos_irq_set_type()
which again setup the pin as an IRQ.

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.

Thanks a lot and best regards,
Javier

[0]: http://thread.gmane.org/gmane.linux.kernel.samsung-soc/34259/focus=34261
[1]: http://lxr.free-electrons.com/source/kernel/irq/manage.c#L1162

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