linux-kernel - Re: [PATCH] arm64: dts: qcom: sc8280xp-blackrock: switch to uefi rtc offset

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Message-ID: <70614c91-326e-47ee-80da-12f829d13459@oss.qualcomm.com>
Date: Mon, 27 Jan 2025 11:24:10 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: jens.glathe@...schoolsolutions.biz,
        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: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH] arm64: dts: qcom: sc8280xp-blackrock: switch to uefi rtc
 offset

On 22.01.2025 7:41 AM, Jens Glathe via B4 Relay wrote:
> From: Jens Glathe <jens.glathe@...schoolsolutions.biz>
> 
> 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).
> 
> Based on a patch by Johan Hovold. [1]
> 
> Link: https://lore.kernel.org/all/20250120144152.11949-7-johan+linaro@kernel.org/ # [1]
> Signed-off-by: Jens Glathe <jens.glathe@...schoolsolutions.biz>
> ---

Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>

Konrad