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

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Message-ID: <458ba722-ab52-4b30-b020-30039102ce57@me.ssier.org>
Date: Sun, 12 Oct 2025 02:06:55 -0400
From: Alexandre Messier <alex@...ssier.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.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: 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 2025-10-09 05:30, Konrad Dybcio wrote:
> 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

Got it, for V2, I will add a note in the commit message, for this patch and the
other one (for the NFC support).

> 
> Konrad