linux-kernel - Re: [PATCH 4/4] ARM: dts: qcom: msm8974pro-htc-m8: add touchscreen

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Message-ID: <84d7ab07-4026-4313-8919-b5f9205132c6@oss.qualcomm.com>
Date: Thu, 9 Oct 2025 11:30:01 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Alexandre Messier <alex@...ssier.org>,
        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: Luca Weiss <luca@...aweiss.eu>, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        phone-devel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] ARM: dts: qcom: msm8974pro-htc-m8: add touchscreen

On 10/9/25 7:50 AM, Alexandre Messier wrote:
> On 2025-10-07 06:04, Konrad Dybcio wrote:
>> On 10/7/25 7:55 AM, Alexandre Messier via B4 Relay wrote:
>>> From: Alexandre Messier <alex@...ssier.org>
>>>
>>> Add the touchscreen device node for the HTC One (M8).
>>>
>>> Signed-off-by: Alexandre Messier <alex@...ssier.org>
>>> ---
>>>  arch/arm/boot/dts/qcom/qcom-msm8974pro-htc-m8.dts | 36 +++++++++++++++++++++++
>>>  1 file changed, 36 insertions(+)
>>>
>>> diff --git a/arch/arm/boot/dts/qcom/qcom-msm8974pro-htc-m8.dts b/arch/arm/boot/dts/qcom/qcom-msm8974pro-htc-m8.dts
>>> index 36eb42f0f3d9..040a256f9465 100644
>>> --- a/arch/arm/boot/dts/qcom/qcom-msm8974pro-htc-m8.dts
>>> +++ b/arch/arm/boot/dts/qcom/qcom-msm8974pro-htc-m8.dts
>>> @@ -65,6 +65,35 @@ vreg_vph_pwr: vreg-vph-pwr {
>>>  	};
>>>  };
>>>  
>>> +&blsp1_i2c2 {
>>> +	clock-frequency = <384000>;
>>
>> This is not a valid I2C frequency
>>
>> You're looking for 100/400/1000 kHz
> 
> Hello Konrad,
> 
> This frequency value is used in the vendor kernel [1], hence why I used it.
> 
> I did a test at 400 kHz, and the I2C devices (touchscreen here, and NFC in the
> other patch) are still detected, with basic functions still working.
> 
> Let me know if I should still update to use 400 kHz. I would prefer to keep
> the value from the vendor kernel (and in that case, I will update the commit
> message to add that information).

Hm, I grepped around in old vendor trees, and it seems like there was
a period of horrid wild west wrt this..

I see 355 kHz, 384 kHz, next to "normal" values of 100/400..

Let's just keep it as-is, but please note in the commit message that this
is intended and that's what the downstream sets too

Konrad