linux-kernel - Re: [PATCH] ARM: dts: add support for gpio buttons for exynos5422-odroidxu3

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Date:	Tue, 23 Feb 2016 17:47:31 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Anand Moon <linux.amoon@...il.com>, Kukjin Kim <kgene@...nel.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: add support for gpio buttons for
 exynos5422-odroidxu3

On 23.02.2016 17:33, Krzysztof Kozlowski wrote:
> On 23.02.2016 17:21, Krzysztof Kozlowski wrote:
>> On 23.02.2016 17:01, Anand Moon wrote:
>>> Add support for gpio-based button on Odroid-XU3 boards
>>> for reboot/poweroff feature.
>>>
>>> Signed-off-by: Anand Moon <linux.amoon@...il.com>
>>> ---
>>> changes rebase based on linux next-20160222.
>>>
>>> Tested on Odroid-XU4
>>>
>>> dmesg output.
>>> [    3.286068] of_get_named_gpiod_flags: parsed 'gpios' property of node '/gpio_keys/power_key[0]' - status (0)
>>> [    3.286206] gpio-11 (power key): gpiod_set_debounce: missing set() or set_debounce() operations
>>> [    3.286600] input: gpio_keys as /devices/platform/gpio_keys/input/input0
>>> ---
>>>  arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi | 22 ++++++++++++++++++++++
>>>  1 file changed, 22 insertions(+)
>>>
>>> diff --git a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
>>> index 1bd507b..db9770b 100644
>>> --- a/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
>>> +++ b/arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi
>>> @@ -11,6 +11,7 @@
>>>  */
>>>  
>>>  #include <dt-bindings/clock/samsung,s2mps11.h>
>>> +#include <dt-bindings/input/input.h>
>>>  #include <dt-bindings/interrupt-controller/irq.h>
>>>  #include <dt-bindings/gpio/gpio.h>
>>>  #include <dt-bindings/sound/samsung-i2s.h>
>>> @@ -54,6 +55,22 @@
>>>  		#cooling-cells = <2>;
>>>  		cooling-levels = <0 130 170 230>;
>>>  	};
>>> +
>>> +	gpio_keys {
>>> +		compatible = "gpio-keys";
>>> +		pinctrl-names = "default";
>>> +		pinctrl-0 = <&gpio_power_key>;
>>> +
>>> +		power_key {
>>> +			interrupt-parent = <&gpx0>;
>>> +			interrupts = <3 IRQ_TYPE_NONE>;
>>
>> Hmmm.... why you specify the interrupts?
>>
>>> +			gpios = <&gpx0 3 GPIO_ACTIVE_LOW>;
> 
> Please, explain it to me. The SW2 key is connected to PWRON of PMIC.
> However you are adding a GPIO key for external interrupt source 3
> (XE.INT3)... which comes from PMIC's ONOB.
> 
> It's interesting.... how does it work? The PMIC will generate ONOB
> interrupt on PWRON low->high change (when PWRHOLD is high)?

Hmmm... This is not well documented but apparently that is the case. The
PMIC will generate ONOB interrupt (with 16 ms de-bounce for PWRON) on
each PWRON flip.

This looks kind of hacky or indirect usage. Using a GPIO key not for
GPIO itself but for an interrupt generated by PMIC on a key press...

Best regards,
Krzysztof