linux-kernel - Re: [PATCH 1/4] dt-bindings: rtc: qcom-pm8xxx: add uefi-variable offset

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Message-ID: <174681048159.3790603.652832218930596449.robh@kernel.org>
Date: Fri, 9 May 2025 12:08:02 -0500
From: "Rob Herring (Arm)" <robh@...nel.org>
To: Johan Hovold <johan+linaro@...nel.org>
Cc: Konrad Dybcio <konradybcio@...nel.org>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Bjorn Andersson <andersson@...nel.org>, linux-rtc@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: rtc: qcom-pm8xxx: add uefi-variable
 offset


On Wed, 23 Apr 2025 09:51:40 +0200, 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.
> 
> On platforms where the offset is stored in a Qualcomm specific UEFI
> variable the variables are also accessed in a non-standard way, which
> means that the OS cannot assume that the variable service is available
> by the time the RTC driver probes.
> 
> Add a 'qcom,uefi-rtc-info' boolean flag to indicate that the RTC offset
> is stored in a Qualcomm specific UEFI variable so that the OS can
> determine whether to wait for it to become available.
> 
> The UEFI variable is
> 
> 	882f8c2b-9646-435f-8de5-f208ff80c1bd-RTCInfo
> 
> and holds a 12-byte structure where the first four bytes is a GPS time
> offset in little-endian byte order.
> 
> Link: https://lore.kernel.org/all/aAecIkgmTTlThKEZ@hovoldconsulting.com/
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  Documentation/devicetree/bindings/rtc/qcom-pm8xxx-rtc.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Acked-by: Rob Herring (Arm) <robh@...nel.org>