[PATCH v2] ARM: dts: qcom: msm8960: expressatt: Add coreriver,tc360-touchkey

[PATCH v2] ARM: dts: qcom: msm8960: expressatt: Add coreriver,tc360-touchkey

[Rudraksha Gupta via B4 Relay]

From: Rudraksha Gupta <guptarud@gmail.com>

Add the tc360 touchkey. It's unknown if this is the actual model of the
touchkey, as downstream doesn't mention a variant, but this works.

Link:
https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/input/keyboard/cypress_touchkey_236/Makefile#L5

Assisted-by: Claude:claude-opus-4.6
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
---
Add the tc360 touchkey. It's unknown if this is the actual model of the
touchkey, as downstream doesn't mention a variant, but this works.

Link:
https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/input/keyboard/cypress_touchkey_236/Makefile#L5

Test:
=============
- LEDs:
samsung-expressatt:/sys/class/leds/tm2-touchkey$ echo heartbeat > trigger
// Flashes LEDs :)

- Touching buttons:
samsung-expressatt:/sys/class/leds/tm2-touchkey$ evtest
No device specified, trying to scan all of /dev/input/event*
Not running as root, no devices may be available.
Available devices:
/dev/input/event0:      pmic8xxx_pwrkey
/dev/input/event1:      gpio-keys
/dev/input/event2:      tm2-touchkey
/dev/input/event3:      Atmel maXTouch Touchscreen
Select the device event number [0-3]: 2
Input driver version is 1.0.1
Input device ID: bus 0x18 vendor 0x0 product 0x0 version 0x0
Input device name: "tm2-touchkey"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 139 (KEY_MENU)
    Event code 158 (KEY_BACK)
  Event type 4 (EV_MSC)
    Event code 4 (MSC_SCAN)
Properties:
Testing ... (interrupt to exit)
Event: time 1761059686.899755, type 4 (EV_MSC), code 4 (MSC_SCAN), value 00
Event: time 1761059686.899755, type 1 (EV_KEY), code 139 (KEY_MENU), value 1
Event: time 1761059686.899755, -------------- SYN_REPORT ------------
Event: time 1761059687.113489, type 4 (EV_MSC), code 4 (MSC_SCAN), value 00
Event: time 1761059687.113489, type 1 (EV_KEY), code 139 (KEY_MENU), value 0
Event: time 1761059687.113489, -------------- SYN_REPORT ------------
Event: time 1761059688.764757, type 4 (EV_MSC), code 4 (MSC_SCAN), value 01
Event: time 1761059688.764757, type 1 (EV_KEY), code 158 (KEY_BACK), value 1
Event: time 1761059688.764757, -------------- SYN_REPORT ------------
Event: time 1761059688.817516, type 4 (EV_MSC), code 4 (MSC_SCAN), value 01
Event: time 1761059688.817516, type 1 (EV_KEY), code 158 (KEY_BACK), value 0
Event: time 1761059688.817516, -------------- SYN_REPORT ------------
---
Changes in v2:
- drop status = okay
- reorder pinctrl-{n,names}
- Resend of v1: https://lore.kernel.org/all/20260503-expressatt-touchkey-v1-1-f7dd5db64e0d@gmail.com/
- Link to v1: https://lore.kernel.org/r/20251205-expressatt-touchkey-v1-1-1444b927c9f3@gmail.com
---
 .../dts/qcom/qcom-msm8960-samsung-expressatt.dts   | 54 ++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
index 5a39abd6f3ce..5a3d88e31cf5 100644
--- a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
+++ b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
@@ -52,6 +52,40 @@ key-volume-down {
 			linux,code = <KEY_VOLUMEDOWN>;
 		};
 	};
+
+	touchkey_enable: touchkey-enable {
+		compatible = "regulator-fixed";
+		regulator-name = "touchkey_enable";
+		gpio = <&tlmm 51 GPIO_ACTIVE_HIGH>;
+		enable-active-high;
+		regulator-boot-on;
+	};
+
+	i2c-gpio-touchkey {
+		compatible = "i2c-gpio";
+		#address-cells = <1>;
+		#size-cells = <0>;
+		sda-gpios = <&tlmm 71 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
+		scl-gpios = <&tlmm 72 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
+		pinctrl-0 = <&touchkey_i2c_pins>;
+		pinctrl-names = "default";
+		i2c-gpio,delay-us = <2>;
+
+		touchkey@20 {
+			compatible = "coreriver,tc360-touchkey";
+			reg = <0x20>;
+
+			interrupts-extended = <&tlmm 52 IRQ_TYPE_EDGE_FALLING>;
+			pinctrl-0 = <&touchkey_irq_pin>;
+			pinctrl-names = "default";
+
+			vddio-supply = <&touchkey_enable>;
+			vdd-supply = <&pm8921_l29>;
+			vcc-supply = <&pm8921_l29>;
+
+			linux,keycodes = <KEY_MENU KEY_BACK>;
+		};
+	};
 };
 
 &gsbi2 {
@@ -198,6 +232,20 @@ firmware-pins {
 			bias-disable;
 		};
 	};
+
+	touchkey_i2c_pins: touchkey-i2c-state {
+		pins = "gpio71", "gpio72";
+		function = "gpio";
+		drive-strength = <2>;
+		bias-disable;
+	};
+
+	touchkey_irq_pin: touchkey-irq-state {
+		pins = "gpio52";
+		function = "gpio";
+		drive-strength = <2>;
+		bias-disable;
+	};
 };
 
 &pm8921 {
@@ -420,6 +468,12 @@ pm8921_l25: l25 {
 			bias-pull-down;
 		};
 
+		pm8921_l29: l29 {
+			regulator-min-microvolt = <1800000>;
+			regulator-max-microvolt = <3300000>;
+			bias-pull-down;
+		};
+
 		/* Low Voltage Switch */
 		pm8921_lvs1: lvs1 {
 			bias-pull-down;

---
base-commit: 3131ff5a117498bb4b9db3a238bb311cbf8383ce
change-id: 20251205-expressatt-touchkey-1747c503a2f3

Best regards,
-- 
Rudraksha Gupta <guptarud@gmail.com>

Re: [PATCH v2] ARM: dts: qcom: msm8960: expressatt: Add coreriver,tc360-touchkey

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] The `pm8921_l29` regulator provides a wide voltage range instead of a fixed voltage, which is incompatible with the `tc360-touchkey` driver that expects a fixed regulator.
- [Low] The newly added nodes `i2c-gpio-touchkey` and `touchkey-enable` violate standard devicetree node naming schemas and will trigger `dtbs_check` warnings.
--

commit df1b82e005a06f9e0f91c39a21c42b56f537d34d
Author: Rudraksha Gupta <guptarud@gmail.com>

ARM: dts: qcom: msm8960: expressatt: Add coreriver,tc360-touchkey

This commit adds the tc360 touchkey using an i2c-gpio bus for the msm8960
samsung expressatt device. It includes the necessary pin configurations,
regulators, and interrupt mappings.

Link: https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/input/keyboard/cypress_touchkey_236/Makefile#L5

> diff --git a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
> --- a/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
> +++ b/arch/arm/boot/dts/qcom/qcom-msm8960-samsung-expressatt.dts
> @@ -52,6 +52,40 @@ key-volume-down {
>  			linux,code = <KEY_VOLUMEDOWN>;
>  		};
>  	};
> +
> +	touchkey_enable: touchkey-enable {

[Severity: Low]
Will this node name trigger dtbs_check warnings? The fixed regulator schema
typically requires nodes to match the regular expression
^regulator(-[0-9]+v[0-9]+|-[0-9a-z-]+)?$. Would renaming this to something
like regulator-touchkey be more compliant?

> +		compatible = "regulator-fixed";
> +		regulator-name = "touchkey_enable";
> +		gpio = <&tlmm 51 GPIO_ACTIVE_HIGH>;
> +		enable-active-high;
> +		regulator-boot-on;
> +	};
> +
> +	i2c-gpio-touchkey {

[Severity: Low]
Does this node name violate the standard I2C controller schema? The standard
schema expects the bus node to match the regular expression ^i2c(@.*)?$.
Should this be named just i2c instead?

> +		compatible = "i2c-gpio";
> +		#address-cells = <1>;
> +		#size-cells = <0>;

[ ... ]

> @@ -420,6 +468,12 @@ pm8921_l25: l25 {
>  			bias-pull-down;
>  		};
>  
> +		pm8921_l29: l29 {
> +			regulator-min-microvolt = <1800000>;
> +			regulator-max-microvolt = <3300000>;

[Severity: High]
Will the wide voltage range here cause the touchkey to fail?

The tc360-touchkey driver is configured as a fixed regulator and only enables
it without calling regulator_set_voltage(). If the core regulator framework
enables this at the minimum voltage of 1.8V, will it be below the typical
voltage expected by the hardware? 

Should the min and max microvolts be constrained to the exact required fixed
voltage?

> +			bias-pull-down;
> +		};
> +

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260527-expressatt-touchkey-v2-1-049dca41fc3a@gmail.com?part=1