[PATCH v3 0/4] rtc: Add StarFive JH7110 RTC support

[Owen O'Hehir <oo.hehir@gmail.com>]

The JH7110 has an RTC in its always-on domain that mainline does not
support. This series adds a binding, a driver, a MAINTAINERS entry and
the SoC DT node.

The driver is based on the StarFive vendor driver (rtc-starfive.c,
commit ebac2b5 in the StarFive 6.12 tree), reworked for mainline:
- hardware calibration and the default time set in probe are dropped
- wakeup uses the generic wake IRQ helpers instead of the irq_desc hack
- set_time waits for the counter to load the new time
- read_time re-reads if the time rolls over between TIME and DATE
- the offset rounds to the nearest step and follows the sysfs sign
  convention (positive = slower)
- the 32.768 kHz counter clock is described in the binding and enabled

Thanks to ziv.xu and Hal Feng at StarFive for the original driver.

Tested on a VisionFive 2 v1.3B with next-20261105 and v7.3.1: setting
and reading the time across the 2000-2099 range (out-of-range years
refused), leap day and century rollover, the alarm interrupt with
cancel, the offset, the rate over 60 s, and setting the system clock at
boot. Not tested: suspend wakeup, drift over hours, and keeping time
across a power-off, as the board has no RTC battery connector.

Known behaviour: the RTC loses about the length of a reboot across a
warm reboot; the counter appears to stop during reset. After the
StarFive vendor kernel the first boot found an invalid time. I would
appreciate an opinion on whether this is expected of the hardware or
something the driver should handle.

Changes in v3:
- dt-bindings: add Conor's Acked-by
- driver: add my copyright line; drop the extra space before the
  register bit field defines (as requested by E Shattow)
- dts: rename the node label from rtc to soc_rtc, leaving rtc free for
  a carrier board's RTC (as requested by E Shattow)

Changes in v2:
- dt-bindings: list myself as maintainer instead of the RTC subsystem
  maintainer (as requested by Conor)
- MAINTAINERS: new patch adding an entry for the driver & binding
- driver: drop the <linux/mod_devicetable.h> include (as requested by Uwe)

v1: https://lore.kernel.org/r/20261106175600.3877614-0-oo.hehir@gmail.com
v2: https://lore.kernel.org/r/20261108212826.15890-1-oo.hehir@gmail.com

Owen O'Hehir (3):
  dt-bindings: rtc: Add StarFive JH7110 RTC
  MAINTAINERS: Add entry for the StarFive JH7110 RTC driver
  riscv: dts: starfive: jh7110: Add the RTC node

ziv.xu (1):
  rtc: Add StarFive JH7110 RTC driver

 .../bindings/rtc/starfive,jh7110-rtc.yaml     |  85 +++++
 MAINTAINERS                                   |   7 +
 arch/riscv/boot/dts/starfive/jh7110.dtsi      |  14 +
 drivers/rtc/Kconfig                           |  11 +
 drivers/rtc/Makefile                          |   1 +
 drivers/rtc/rtc-jh7110.c                      | 324 ++++++++++++++++++
 6 files changed, 442 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/rtc/starfive,jh7110-rtc.yaml
 create mode 100644 drivers/rtc/rtc-jh7110.c


base-commit: ddfe51b0a0f5dc9e415cc2c8ad8db17532dd426b
-- 
2.43.0