casaroli opened a new pull request, #19526:
URL: https://github.com/apache/nuttx/pull/19526
## Summary
The RP2350 has no dedicated RTC block (the RP2040's was removed). This adds
an
RTC driver built on the **POWMAN always-on timer** — a 64-bit millisecond
counter clocked from the low-power oscillator, so it keeps running across
warm
resets.
- New `arch/arm/src/rp23xx/rp23xx_rtc.c` implementing the simple
`up_rtc_initialize()` / `up_rtc_time()` / `up_rtc_settime()` interface that
backs the system clock (seconds resolution).
- New `CONFIG_RP23XX_RTC` (default n) which `select`s `CONFIG_RTC`, plus the
Make.defs / CMakeLists build wiring.
- `up_rtc_initialize()` sources the timer from the low-power oscillator at a
1 kHz tick and starts it, preserving the value if the timer is already
running. POWMAN writes carry the required `0x5afe` password (only the low
16
bits are data, hence the 64-bit time is written across four registers).
- Documents the RTC on the rp23xx platform page.
## Impact
Opt-in and off by default, so no impact on existing configurations. When
enabled it backs `CLOCK_REALTIME` with the always-on timer, so the system
time
is seeded from it at boot and `clock_settime()` persists to it.
## Testing
Tested on a Pimoroni Pico Plus 2 (RP2350), `raspberrypi-pico-2:nsh` +
`CONFIG_RP23XX_RTC`, flashed via a Raspberry Pi Debug Probe. Verbatim
console:
```
nsh> date
Thu, Jan 01 00:00:18 1970
nsh> date -s "Jul 24 22:00:00 2026"
nsh> date
Fri, Jul 24 22:00:00 2026
nsh> date
Fri, Jul 24 22:00:03 2026
```
- The initial `date` shows the timer already running from boot (~18 s uptime,
epoch 1970 while unset).
- `date -s` sets it, `date` reads it back, and a later `date` shows it has
advanced in real time — the counter is running and keeping time.
`tools/checkpatch.sh -c -g HEAD` is clean (including codespell).
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