This series adds support for utilising the UEFI firmware RTC offset to the Qualcomm PMIC RTC driver and uses that to enable the RTC on all X Elite machines. Included is also a patch to switch the Lenovo ThinkPad X13s over to using the UEFI offset. The RTCs in many Qualcomm devices are effectively broken due to the time registers being read-only. Instead some other non-volatile memory can be used to store an offset which a driver can take into account. On Windows on Arm laptops, the UEFI firmware (and Windows) use a UEFI variable for storing such an offset. When RTC support for the X13s was added two years ago we did not yet have UEFI variable support for these machines in mainline and there were also some concerns regarding flash wear. [1] As not all Qualcomm platforms have UEFI firmware anyway, we instead opted to use a PMIC scratch register for storing the offset. [2] On the UEFI machines in question this is however arguable not correct as it means that the RTC time can differ between the UEFI firmware (and Windows) and Linux. Now that the (reverse engineered) UEFI variable implementation has been merged and thoroughly tested, let's switch to using that to store the RTC offset also on Linux. The flash wear concerns can be mitigated by deferring writes due to clock drift until shutdown. Note that this also avoids having to wait for months for Qualcomm to provide a free PMIC SDAM scratch register for X1E and future platforms, and specifically allows us to enable the RTC on X1E laptops today. Rob had some concerns about adding a DT property for indicating that a machine uses UEFI for storing the offset and suggested that the driver should probe for this instead. Unfortunately, this is easier said than done given that UEFI variable support itself is probed for and may not be available until after the RTC driver probes. Hopefully this all goes away (for future platforms) once Qualcomm fix their UEFI implementation so that the UEFI time (and variable) services can be used directly. Johan Changes since UEFI offset RFC [1]: - clarify that UEFI variable format is not arbitrary (Alexandre) - add missing use_uefi kernel doc - use dev_dbg() instead of dev_err() (Alexandre) - rename epoch define RTC_TIMESTAMP_EPOCH_GPS (Alexandre) - mitigate flash wear by deferring writes due to clock drift until shutdown Changes since Jonathan's X1E series v3 [3]: - tweak qcom,no-alarm binding update (and drop Krystzof's Reviewed-by tag) - drop no-alarm flag and restructure probe() to clear feature flag before registering RTC - use UEFI variable offset on X1E [1] https://lore.kernel.org/lkml/20230126142057.25715-1-johan+linaro@xxxxxxxxxx/ [2] https://lore.kernel.org/lkml/20230202155448.6715-1-johan+linaro@xxxxxxxxxx/ [3] https://lore.kernel.org/lkml/20241015004945.3676-1-jonathan@xxxxxxxx/ Johan Hovold (5): dt-bindings: rtc: qcom-pm8xxx: add uefi-variable offset rtc: pm8xxx: add support for uefi offset rtc: pm8xxx: mitigate flash wear arm64: dts: qcom: sc8280xp-x13s: switch to uefi rtc offset arm64: dts: qcom: x1e80100: enable rtc Jonathan Marek (2): dt-bindings: rtc: qcom-pm8xxx: document qcom,no-alarm flag rtc: pm8xxx: implement qcom,no-alarm flag for non-HLOS owned alarm .../bindings/rtc/qcom-pm8xxx-rtc.yaml | 11 + .../qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 11 +- arch/arm64/boot/dts/qcom/x1e80100-pmics.dtsi | 4 +- drivers/rtc/rtc-pm8xxx.c | 194 +++++++++++++++--- include/linux/rtc.h | 1 + 5 files changed, 185 insertions(+), 36 deletions(-) -- 2.45.2
