linux-kernel - Re: [PATCH] ARM: dts: qcom: msm8960: expressatt Add PWM vibrator

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Message-ID: <821a7dc3-7b00-40d1-9332-ef57ad22f9ca@oss.qualcomm.com>
Date: Tue, 16 Dec 2025 15:22:30 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: guptarud@...il.com, Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: dts: qcom: msm8960: expressatt Add PWM vibrator

On 12/11/25 11:23 AM, Rudraksha Gupta via B4 Relay wrote:
> From: Rudraksha Gupta <guptarud@...il.com>
> 
> Add a pwm-vibrator to expressatt. Currently this vibrates only at 100%
> 
> Signed-off-by: Rudraksha Gupta <guptarud@...il.com>
> ---
> Add a pwm-vibrator to expressatt. Currently this vibrates only at 100%
> 
> Link:
> - https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/arch/arm/mach-msm/board-express.c#L1767
> - https://github.com/LineageOS/android_kernel_samsung_d2/blob/stable/cm-12.0-YNG4N/drivers/motor/Makefile#L5
> 
> Test:
> =====================
> samsung-expressatt:~$ dmesg | grep vibra
> [   79.892226] input: pwm-vibrator as /devices/platform/vibrator/input/input4
> samsung-expressatt:~$ fftest /dev/input/event4 
> Force feedback test program.
> HOLD FIRMLY YOUR WHEEL OR JOYSTICK TO PREVENT DAMAGES
> 
> Device /dev/input/event4 opened
> Features:
>   * Absolute axes: 
>     [00 00 00 00 00 00 00 00 ]
>   * Relative axes: 
>     [00 00 ]
>   * Force feedback effects types: Periodic, Rumble, Gain, 
>     Force feedback periodic effects: Square, Triangle, Sine, 
>     [00 00 00 00 00 00 00 00 00 00 03 07 01 00 00 00 ]
>   * Number of simultaneous effects: 16
> 
> Setting master gain to 75% ... OK
> Uploading effect #0 (Periodic sinusoidal) ... OK (id 0)
> Uploading effect #1 (Constant) ... Error: Invalid argument
> Uploading effect #2 (Spring) ... Error: Invalid argument
> Uploading effect #3 (Damper) ... Error: Invalid argument

Looks like this is because GP1_CLK does not implement .set_duty_cycle..

The downstream driver you linked to does so in a terribly hacky way
(from the vibrator driver and not the clock driver):

https://github.com/LineageOS/android_kernel_samsung_d2/blob/cm-14.1/drivers/motor/immvibespi.c#L53

Upstream, we have an implementation for clk_rcg*2*_ops, whereas 8960
uses clk_rcg_ops.

They look very similar though, perhaps you can hack it up..

One thing to note is that you're passing GP1_CLK to the clk-pwm (as
you should), but we need to do clk_set_duty_cycle on its parent,
GP1_CLK*_SRC*. The framework will take care of this:

```
--- drivers/clk/clk.c
	if (!core->ops->get_duty_cycle)
		return clk_core_update_duty_cycle_parent_nolock(core);
```

so long as you add CLK_DUTY_CYCLE_PARENT to the child

[...]
> +	/* TODO: Vary the frequency besides being 0% or 100% */
> +	vibrator {
> +		compatible = "pwm-vibrator";
> +		pwms = <&gp1_pwm 0 54347 0>;  /* ~18.4 kHz */
> +		pwm-names = "enable";
> +		enable-gpios = <&pm8921_gpio 4 GPIO_ACTIVE_HIGH>;
> +		vcc-supply = <&vdd_haptics>;
> +
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&vib_pwm_gpio>;

pinctrl-n
pinctrl-names

please, both occurences

> +	};
> +
> +	vdd_haptics: vdd-haptics-regulator {
> +		compatible = "regulator-fixed";
> +		regulator-name = "vdd_haptics";
> +		gpio = <&tlmm 47 GPIO_ACTIVE_HIGH>;
> +		enable-active-high;
> +		regulator-boot-on;
> +
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&haptics_pwr_en>;
> +	};
>  };
>  
>  &gsbi2 {
> @@ -241,6 +270,21 @@ touchkey_i2c_pins: touchkey-i2c-state {
>  		bias-disable;
>  	};
>  
> +	haptics_pwr_en: haptics-pwr-en-state {
> +		pins = "gpio47";
> +		function = "gpio";
> +		drive-strength = <2>;
> +		bias-disable;
> +		output-low;

Drop output-low, the driver should take care of setting the state

Konrad