Re: [PATCH] arm64: dts: qcom: mahua-t14s: store the RTC offset in SDAM

[Konrad Dybcio]

On 10/17/26 1:25 AM, Luke Macken wrote:
> The PMIC RTC registers on the Lenovo ThinkPad T14s Gen 7 are read-only,
> so an offset needs to be stored in machine-specific non-volatile memory
> which the RTC driver can take into account when reading or updating the
> time.
> 
> The firmware on this machine does not provide the RTCInfo UEFI variable
> that other Glymur based machines use for this purpose, so, as on
> sc8280xp-crd and the QCS8550 boards, reserve four bytes in one of the
> PMIC SDAM blocks to hold the RTC offset. SDAM 2 on PMK8850 is 128 bytes
> and its last word is not used by the firmware.

Bold claim, there's a lot of firmware!

On Glymur machines, the RTC is coordinated through SoCCP. We're working
on providing an interface to that.

[...]


> Note for reviewers: Qualcomm's "rtc: Add Qualcomm PMIC RTC-GLINK support
> for Glymur" (August 2026) would move the RTC behind the charger firmware
> on these machines, but it has not been resubmitted and needs firmware
> that at least the ThinkPad does not ship yet. This patch uses the
> existing rtc-pm8xxx nvmem offset mechanism in the meantime and does not
> conflict with that work.

There's another access mechanism to pmic-glink that may unblock this.

Konrad