linux-kernel - Re: [PATCH 4/5] arm64: dts: qcom: r0q: enable hardware clocks

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Message-ID: <c21a408b-ec4f-4de8-a9b6-ca25410ace6a@oss.qualcomm.com>
Date: Mon, 6 Oct 2025 14:31:42 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Eric Gonçalves <ghatto404@...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: devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] arm64: dts: qcom: r0q: enable hardware clocks

On 10/5/25 5:50 AM, Eric Gonçalves wrote:
> 
> 
> On September 25, 2025 10:09:48 AM GMT-03:00, Konrad Dybcio <konrad.dybcio@....qualcomm.com> wrote:
>> On 9/20/25 3:46 AM, Eric Gonçalves wrote:
>>> Enable the real-time clocks found in R0Q board.
>>>
>>> Signed-off-by: Eric Gonçalves <ghatto404@...il.com>
>>> ---
>>>  arch/arm64/boot/dts/qcom/sm8450-samsung-r0q.dts | 15 +++++++++++++++
>>>  1 file changed, 15 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/sm8450-samsung-r0q.dts b/arch/arm64/boot/dts/qcom/sm8450-samsung-r0q.dts
>>> index c1b0b21c0ec5..c088f1acf6ea 100644
>>> --- a/arch/arm64/boot/dts/qcom/sm8450-samsung-r0q.dts
>>> +++ b/arch/arm64/boot/dts/qcom/sm8450-samsung-r0q.dts
>>> @@ -225,6 +225,21 @@ vol_up_n: vol-up-n-state {
>>>  	};
>>>  };
>>>  
>>> +&pmk8350_rtc {
>>> +	nvmem-cells = <&rtc_offset>;
>>> +	nvmem-cell-names = "offset";
>>> +
>>> +	status = "okay";
>>> +};
>>> +
>>> +&pmk8350_sdam_2 {
>>> +	status = "okay";
>>> +
>>> +	rtc_offset: rtc-offset@bc {
>>
>> Is this an offset you took from somewhere downstream?
>>
>> Generally you *really don't want to* poke at random SDAM cells,
>> as they contain a lot of important settings (incl. battery/charging)
> From another sm8450 device, I'm sure it's okay.

That as an argument alone doesn't sound convincing to me, since vendors
also sometimes repurpose unused-by-Qualcomm SDAM cells

I actually found a data source internally and this cell you're trying
to use is reserved for PBS (see drivers/soc/qcom/qcom-pbs.c), meaning
you already fell into this trap..

Konrad