| Message ID | 20230126142057.25715-25-johan+linaro@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | rtc: pm8xxx: add support for setting time using nvmem | expand |
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 db406f7774de..6e88e0bb6871 100644 --- a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts +++ b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts @@ -683,6 +683,21 @@ &pmk8280_pon_resin { status = "okay"; }; +&pmk8280_rtc { + nvmem-cells = <&rtc_offset>; + nvmem-cell-names = "offset"; + + status = "okay"; +}; + +&pmk8280_sdam_6 { + status = "okay"; + + rtc_offset: rtc-offset@bc { + reg = <0xbc 0x4>; + }; +}; + &pmk8280_vadc { status = "okay";
The Lenovo X13s firmware does not implement the UEFI time runtime services so the RTC in the PM8280K PMIC needs to be accessed directly. To complicate things further, the RTC control and time registers are read-only on this platform so an offset must be stored in some other machine-specific non-volatile memory which an RTC driver can take into account when reading or updating the time. The UEFI firmware (and Windows) use a UEFI variable for this: 882f8c2b-9646-435f-8de5-f208ff80c1bd-RTCInfo but the offset can only be accessed via the Qualcomm UEFI Secure Application residing in the TEE as the firmware does not implement the variable runtime services either. While it is possible to access this UEFI variable from Linux on the X13s, this requires using a fairly complex and reverse-engineered firmware interface. As the only benefit of doing so is to make sure that the UEFI (Windows) and Linux time never gets out of sync, it seems preferable to use the PMIC scratch registers for storing an offset instead. This also avoids flash wear in case of RTC drift, etc. So instead of using the UEFI RTC offset, reserve four bytes in one of the PMIC SDAM blocks to hold the RTC offset. Signed-off-by: Johan Hovold <johan+linaro@kernel.org> --- .../dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 15 +++++++++++++++ 1 file changed, 15 insertions(+)