linux-kernel - Re: [PATCH 6/7] arm64: dts: qcom: sc8280xp-x13s: switch to uefi rtc offset

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Message-ID: <0abde047-7f9b-470b-8b16-74e6230a541b@oldschoolsolutions.biz>
Date: Mon, 20 Jan 2025 19:08:14 +0100
From: Jens Glathe <jens.glathe@...schoolsolutions.biz>
To: Johan Hovold <johan+linaro@...nel.org>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Bjorn Andersson <andersson@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>,
 Jonathan Marek <jonathan@...ek.ca>, linux-arm-msm@...r.kernel.org,
 linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] arm64: dts: qcom: sc8280xp-x13s: switch to uefi rtc
 offset

Hi Johan,

On 20.01.25 15:41, Johan Hovold wrote:
> On many Qualcomm platforms the PMIC RTC control and time registers are
> read-only so that the RTC time can not be updated. Instead an offset
> needs be stored in some machine-specific non-volatile memory, which a
> driver can take into account.
>
> Switch to using the Qualcomm specific UEFI variable that is used by the
> UEFI firmware (and Windows) to store the RTC offset.
>
> This specifically means that the RTC time will be synchronised between
> the UEFI firmware setup (or UEFI shell), Windows and Linux.
>
> Note however that Windows stores the RTC time in local time by default,
> while Linux typically uses UTC (i.e. as on X86).
>
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>   .../boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts   | 11 +----------
>   1 file changed, 1 insertion(+), 10 deletions(-)
>
> diff --git a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
> index 38d911992475..66c39765225f 100644
> --- a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
> +++ b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
> @@ -1090,20 +1090,11 @@ &pmk8280_pon_resin {
>   };
>
>   &pmk8280_rtc {
> -	nvmem-cells = <&rtc_offset>;
> -	nvmem-cell-names = "offset";
> +	qcom,uefi-rtc-info;
>
>   	status = "okay";
>   };
>
> -&pmk8280_sdam_6 {
> -	status = "okay";
> -
> -	rtc_offset: rtc-offset@bc {
> -		reg = <0xbc 0x4>;
> -	};
> -};
> -
>   &pmk8280_vadc {
>   	channel@144 {
>   		reg = <PM8350_ADC7_AMUX_THM1_100K_PU(1)>;

Nice. I have it running on my X13s now, looks to work fine. Also ported
to Windows Dev Kit 2023, patch will follow soon after testing it. Thanks!

Tested-by: Jens Glathe <jens.glathe@...schoolsolutions.biz>

with best regards

Jens