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commit 0b657bdb4c330d632d16a7d7f4412764c2daadbb Author: Marco Casaroli <[email protected]> AuthorDate: Sat Oct 17 20:07:56 2026 +0200 Documentation/rp23xx: Describe the RTC alarm. The rp23xx RTC driver now registers the POWMAN always-on timer as /dev/rtc0, with alarm support. The chip page described only the system clock. Describe /dev/rtc0 and its alarm in the RTC section and in the peripheral table. Assisted-by: Claude Code:claude-opus-5-5 Signed-off-by: Marco Casaroli <[email protected]> --- Documentation/platforms/arm/rp23xx/index.rst | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/Documentation/platforms/arm/rp23xx/index.rst b/Documentation/platforms/arm/rp23xx/index.rst index 9d650248181..5b6c5b360d4 100644 --- a/Documentation/platforms/arm/rp23xx/index.rst +++ b/Documentation/platforms/arm/rp23xx/index.rst @@ -45,7 +45,7 @@ TRNG Working Hardware RNG at /dev/random and /dev/urandom Flash MTD Working Unused flash tail as an MTD device, answers BIOC_XIPBASE Timer Working /dev/timerN on TIMER0/TIMER1, 1 us resolution Tickless Working Optional, RP2350 TIMER via the alarm/oneshot -RTC Working POWMAN always-on timer, backs the system clock +RTC Working POWMAN always-on timer, system clock and /dev/rtc0 with alarm OTP Working Reads via /dev/efuse; programming is opt-in ============== ============ ===== @@ -258,6 +258,14 @@ library (`powman_timer_start_lposc()`, `powman_timer_set_ms()` and <https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/pico_aon_timer>`_ wrapper. +The always-on timer also has one alarm comparator. With ``RTC_DRIVER``, the +common board bring-up registers the timer as ``/dev/rtc0``. With +``RTC_ALARM`` too, ``/dev/rtc0`` supports ``RTC_SET_ALARM``, +``RTC_SET_RELATIVE``, ``RTC_RD_ALARM`` and ``RTC_CANCEL_ALARM``, for example +through ``apps/examples/alarm``. The comparator stays asserted while the +time is past the alarm time, so the interrupt handler disables the alarm +first. An alarm fires once. + Programming ============
