From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3354A3AA9CA; Mon, 22 Jun 2026 12:43:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782132211; cv=none; b=PKyaQROAaNuqjN+dDN9O5/+D6YnQfWvC0zXKberJ7Rhi6RoccM8vTFUBqQqg0+r2+t7R4+EinPw70Ia3xfVA1LSywWvLIHLH4zvRQKAQn0ZYXvjDGexCSxRkbUujWqz0rRnZuLw11xIb89SJUlRBHmt84Xs23dWZH1p5cWdB6Zw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782132211; c=relaxed/simple; bh=VPXhLYolPJky/bmGpOtL6BCFAOJr/UlWCP4UfZnTxp8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Slnvc7OMlrnLqC9ueUVwuism51DrCj9rTAQjbBc8x6OmH2Ma7eJ4KD2rX9Lbr9CF7tpf4v9y2b7pA542Cy/BcytKGXbhbvvEElE1YJtN0AICBSNkpT5+wtCvIvvdCmDmtoNlfm6J4+9n0b7cHHuhOEDjs08SvmZ51AJ5lCNR7Z4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kQT0Aggv; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kQT0Aggv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4CD1C1F000E9; Mon, 22 Jun 2026 12:43:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782132209; bh=Ktd9L/8eCw8OPrie6XpyZ7GE0rbforFgxl4XSZd21ws=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=kQT0AggvrEXH6OftsFjazJW5HMf41Rhn5Le5gxrewHnXg4ai1wdugrZtcgwDsoIj+ LLZINGnsyZfY0UEkSWtbUjPSkRgUf8e/njZj82VUQ7ft4hdKj49iqfQmpTGKwJlpcD P8QgijVElsLhtKOhKh8C8e/80xgKCyaJdS5FD3VV9DAFyti4v6uFHEcnGx7agWTiZi Na6JbnHQmlPxhwW+HRzMmiLUHAxIPL96+1QWqT5VgNjkGKWzPUKK/CpJoFoHAxF/ah JfJmkGaQGwPfP4Q91b3bueyBERIbk0rOc9YLIQ2RKHUJKF9RBrskWLdWxkIl5Ag6kf vDpKU5gXBxwZg== Message-ID: <17e73192-85a6-472b-b3ce-7b64712b85fa@kernel.org> Date: Mon, 22 Jun 2026 14:43:21 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] dt-bindings: input: Add binding for Qualcomm SPMI PMIC haptics To: Fenglin Wu Cc: linux-arm-msm@vger.kernel.org, Dmitry Torokhov , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Lee Jones , Stephen Boyd , Bjorn Andersson , Konrad Dybcio , David Collins , Subbaraman Narayanamurthy , Kamal Wadhwa , kernel@oss.qualcomm.com, linux-input@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260616-qcom-spmi-haptics-v1-0-d24e422de6b4@oss.qualcomm.com> <20260616-qcom-spmi-haptics-v1-1-d24e422de6b4@oss.qualcomm.com> <20260617-wakeful-gorilla-of-feminism-75287c@quoll> <44778bec-68c5-426d-bc05-b4013630b3ee@kernel.org> <20fa15e1-316b-44fa-b59d-99cb7fe78bb0@oss.qualcomm.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 22/06/2026 04:28, Fenglin Wu wrote: > > On 6/19/2026 12:18 PM, Krzysztof Kozlowski wrote: >> On 17/06/2026 13:02, Fenglin Wu wrote: >>> On 6/17/2026 6:35 PM, Krzysztof Kozlowski wrote: >>>> On Tue, Jun 16, 2026 at 03:08:24AM -0700, Fenglin Wu wrote: >>>>> .... >>>>> + >>>>> + qcom,lra-period-us: >>>>> + description: >>>>> + LRA actuator initial resonance period in microseconds >>>>> + (1,000,000 / resonant_freq_hz). Used to configure T_LRA-based play >>>>> + rates and the auto-resonance zero-crossing window. >>>> This does not feel like static characteristic. Isn't period depending on >>>> intensity of vibration you want to have? Why would that be fixed per >>>> board? >>> This period is specifically used for playbacks that require >>> auto-resonance to be enabled, which I referred to as "T_LRA-based" and >>> "auto-resonance zero-crossing window." It plays a key role in the >>> "DIRECT_PLAY" mode, which produces a constant vibration effect. To >>> adjust the vibration intensity during this constant effect, the hardware >>> does it by scaling the peak voltage of the driver signals, rather than >>> changing the frequency. >> But maybe changing frequency runtime still would be useful? > It could be, but the LRA F0 (resonant frequency) still needs to be the > starting point. You can control vibration intensity by driving the LRA > slightly off resonance by a given percentage—for example, to reach 50% > vibration, you could probably drive it 10% off resonant frequency, and > that mapping also depends on the LRA characteristic. Keep in mind that > LRA is a spring-mass resonant system, so its output is not linear with > driving frequency; it is a High_Q system, and its output actually shows > a sharp peak at the resonance point. By contrast, the relationship > between driving voltage and its output is much more linear, so scaling > vibration intensity by adjusting the driving voltage is easier to > control. Qcom haptics HW scales vibration intensity in DIRECT_PLAY mode > (for constant vibration effect) by scaling the driving voltage instead. > That said, the HW can also change the driving waveform frequency by > updating the T-LRA registers, and this property has to be specified as > an initial value; otherwise, you won't have a baseline to achieve that. > OK, property is fine. Best regards, Krzysztof