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arch/arm/rp23xx: Add RTC using the POWMAN always-on timer.
The RP2350 has no dedicated RTC block (the RP2040 one was removed). Use the POWMAN always-on timer instead: a 64-bit millisecond counter clocked from the low-power oscillator, so it keeps running across warm resets. Enabling CONFIG_RP23XX_RTC selects CONFIG_RTC and builds the driver, which implements the simple up_rtc_initialize()/up_rtc_time()/up_rtc_settime() interface backing the system clock (seconds resolution). up_rtc_initialize() sources the timer from the low-power oscillator at a 1 kHz tick and starts it, preserving the value when the timer is already running. POWMAN register writes carry the required 0x5afe password. Document the RTC on the rp23xx platform page: an "RTC" section explaining how the POWMAN always-on timer is used (LPOSC clocking, the 0x5afe password and the four 16-bit time registers, stopping the counter to reload it), with reference links to the RP2350 datasheet Power chapter and the pico-sdk hardware_powman / pico_aon_timer implementation the driver mirrors. The same references are noted in the driver header. Assisted-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
This commit is contained in:
Marco Casaroli
Xiang Xiao
parent
216edd74db
commit
f0e4f61add
5 changed files with 288 additions and 0 deletions
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@ -45,6 +45,7 @@ TRNG Working Hardware RNG at /dev/random and /dev/urandom
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Flash MTD Working Unused flash tail as an MTD device, answers BIOC_XIPBASE
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Timer Working /dev/timerN on TIMER0/TIMER1, 1 us resolution
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Tickless Working Optional, RP2350 TIMER via the alarm/oneshot
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RTC Working POWMAN always-on timer, backs the system clock
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============== ============ =====
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Installation
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@ -218,6 +219,44 @@ The block chosen here is claimed exclusively by the scheduler and is removed
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from the `/dev/timer` driver's choices (see the Timer section), so the tickless
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clock and a `/dev/timer` device can run at the same time on different blocks.
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RTC
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===
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The RP2350 has no dedicated RTC block -- the one on the RP2040 was removed --
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so NuttX drives the real-time clock from the POWMAN *always-on timer*
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instead. This is a 64-bit millisecond counter that can be clocked from the
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low-power oscillator (LPOSC, nominally 32.768 kHz), so it keeps counting
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across warm resets and through the low-power states managed by POWMAN.
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Enable it with `RP23XX_RTC` (which selects `RTC`). The driver
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(`rp23xx_rtc.c`) implements the lightweight `up_rtc_initialize()`,
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`up_rtc_time()` and `up_rtc_settime()` interface that backs the NuttX system
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clock at one-second resolution. `up_rtc_initialize()` sources the timer from
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the low-power oscillator at a 1 kHz tick and starts it, but preserves the
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current value if the bootrom (or a previous boot) already left it running, so
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the wall-clock time survives a warm reset.
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Two POWMAN details the driver has to honour:
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* Every POWMAN register write must carry the `0x5afe` password in its top 16
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bits or it is silently ignored, so only the low 16 bits of each register
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hold data. The 64-bit time is therefore written and read through four
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16-bit registers, and bit operations use the atomic `SET`/`CLR` register
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aliases.
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* The counter must be stopped (`TIMER.RUN` cleared) while a new value is
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loaded and then restarted, otherwise the write is not latched cleanly.
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The implementation follows the POWMAN "Always-on Timer" description in the
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Power chapter of the `RP2350 datasheet
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<https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf>`_ and the
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reference `pico-sdk hardware_powman
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<https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/hardware_powman>`_
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library (`powman_timer_start_lposc()`, `powman_timer_set_ms()` and
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`powman_timer_get_ms()`), which the pico-sdk in turn exposes through its
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`pico_aon_timer
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<https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/pico_aon_timer>`_
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wrapper.
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Programming
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============
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@ -109,4 +109,8 @@ if(CONFIG_RP23XX_PSRAM)
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list(APPEND SRCS rp23xx_psram.c rp23xx_heaps.c)
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endif()
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if(CONFIG_RP23XX_RTC)
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list(APPEND SRCS rp23xx_rtc.c)
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endif()
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target_sources(arch PRIVATE ${SRCS})
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@ -868,6 +868,16 @@ config RP23XX_RNG
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/dev/random (and /dev/urandom when CONFIG_DEV_URANDOM selects the
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architecture source) via the TRNG entropy register (EHR).
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config RP23XX_RTC
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bool "Enable RTC (POWMAN always-on timer)"
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default n
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select RTC
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---help---
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Use the RP2350 POWMAN always-on timer as the real-time clock backing
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the system clock. The RP2350 has no dedicated RTC block; the POWMAN
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timer is a 64-bit millisecond counter clocked from the low-power
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oscillator, so it keeps running across warm resets.
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config RP23XX_ADC
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bool "Enable ADC Support"
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default n
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@ -113,3 +113,7 @@ ifeq ($(CONFIG_RP23XX_PSRAM),y)
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CHIP_CSRCS += rp23xx_psram.c
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CHIP_CSRCS += rp23xx_heaps.c
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endif
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ifeq ($(CONFIG_RP23XX_RTC),y)
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CHIP_CSRCS += rp23xx_rtc.c
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endif
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231
arch/arm/src/rp23xx/rp23xx_rtc.c
Normal file
231
arch/arm/src/rp23xx/rp23xx_rtc.c
Normal file
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@ -0,0 +1,231 @@
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/****************************************************************************
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* arch/arm/src/rp23xx/rp23xx_rtc.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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*
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* The RP2350 has no dedicated RTC block (the RP2040 one was removed). This
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* driver uses the POWMAN always-on timer instead: a 64-bit millisecond
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* counter, clocked from the low-power oscillator so it keeps running across
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* warm resets. It backs the NuttX system clock through the simple up_rtc_*
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* interface (seconds resolution).
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*
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* Reference: the POWMAN "Always-on Timer" in the Power chapter of the RP2350
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* datasheet (https://datasheets.raspberrypi.com/rp2350/rp2350-datasheet.pdf)
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* and the pico-sdk hardware_powman library
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* (https://github.com/raspberrypi/pico-sdk, src/rp2_common/hardware_powman),
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* whose powman_timer_start_lposc()/set_ms()/get_ms() this mirrors.
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*
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <time.h>
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#include <errno.h>
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#include <nuttx/arch.h>
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#include <nuttx/irq.h>
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#include "arm_internal.h"
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#include "hardware/rp23xx_powman.h"
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#ifdef CONFIG_RTC
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Every POWMAN write must carry this password in the top 16 bits, otherwise
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* it is ignored (and flagged in BADPASSWD). Only the low 16 bits are data,
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* which is why the 64-bit time is split across four registers.
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*/
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#define POWMAN_PASSWORD 0x5afe0000
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/* Atomic set/clear aliases of a bus register (RP2350 memory map). */
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#define POWMAN_SET_ALIAS 0x2000
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#define POWMAN_CLR_ALIAS 0x3000
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/* Nominal low-power oscillator frequency. */
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#define LPOSC_FREQ_HZ 32768
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/****************************************************************************
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* Public Data
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****************************************************************************/
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/* Variable determines the state of the RTC module; set once the counter is
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* running so the rest of the system knows the RTC is available.
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*/
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volatile bool g_rtc_enabled = false;
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static inline void powman_write(uint32_t reg, uint32_t value)
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{
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putreg32(POWMAN_PASSWORD | (value & 0xffff), reg);
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}
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static inline void powman_setbits(uint32_t reg, uint32_t bits)
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{
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putreg32(POWMAN_PASSWORD | bits, reg + POWMAN_SET_ALIAS);
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}
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static inline void powman_clrbits(uint32_t reg, uint32_t bits)
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{
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putreg32(POWMAN_PASSWORD | bits, reg + POWMAN_CLR_ALIAS);
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}
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/* Read the 64-bit millisecond counter, guarding against a carry from the low
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* word to the high word between the two reads.
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*/
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static uint64_t powman_get_ms(void)
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{
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uint32_t hi = getreg32(RP23XX_POWMAN_READ_TIME_UPPER);
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uint32_t lo;
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for (; ; )
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{
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uint32_t next;
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lo = getreg32(RP23XX_POWMAN_READ_TIME_LOWER);
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next = getreg32(RP23XX_POWMAN_READ_TIME_UPPER);
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if (hi == next)
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{
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break;
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}
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hi = next;
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}
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return ((uint64_t)hi << 32) | lo;
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}
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/* The counter must be stopped while its value is (re)loaded. */
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static void powman_set_ms(uint64_t ms)
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{
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bool running =
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(getreg32(RP23XX_POWMAN_TIMER) & RP23XX_POWMAN_TIMER_RUN) != 0;
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if (running)
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{
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powman_clrbits(RP23XX_POWMAN_TIMER, RP23XX_POWMAN_TIMER_RUN);
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}
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powman_write(RP23XX_POWMAN_SET_TIME_15TO0, (uint32_t)(ms));
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powman_write(RP23XX_POWMAN_SET_TIME_31TO16, (uint32_t)(ms >> 16));
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powman_write(RP23XX_POWMAN_SET_TIME_47TO32, (uint32_t)(ms >> 32));
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powman_write(RP23XX_POWMAN_SET_TIME_63TO48, (uint32_t)(ms >> 48));
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if (running)
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{
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powman_setbits(RP23XX_POWMAN_TIMER, RP23XX_POWMAN_TIMER_RUN);
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}
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: up_rtc_initialize
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*
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* Description:
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* Initialize the POWMAN always-on timer. If it is not already running
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* (e.g. left running by the bootrom), source it from the low-power
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* oscillator at a 1 kHz tick and start it. Preserves the current value
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* when it is already running.
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*
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****************************************************************************/
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int up_rtc_initialize(void)
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{
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if ((getreg32(RP23XX_POWMAN_TIMER) & RP23XX_POWMAN_TIMER_RUN) == 0)
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{
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uint32_t khz_int = LPOSC_FREQ_HZ / 1000;
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uint32_t khz_frac = (LPOSC_FREQ_HZ % 1000) * 65536 / 1000;
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int timeout = 1000000;
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powman_write(RP23XX_POWMAN_LPOSC_FREQ_KHZ_INT, khz_int);
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powman_write(RP23XX_POWMAN_LPOSC_FREQ_KHZ_FRAC, khz_frac);
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powman_setbits(RP23XX_POWMAN_TIMER, RP23XX_POWMAN_TIMER_USE_LPOSC);
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powman_setbits(RP23XX_POWMAN_TIMER, RP23XX_POWMAN_TIMER_RUN);
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/* Wait for the timer to accept the low-power oscillator source, but do
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* not spin forever if it never does.
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*/
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while ((getreg32(RP23XX_POWMAN_TIMER) &
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RP23XX_POWMAN_TIMER_USING_LPOSC) == 0 && --timeout > 0)
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{
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}
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}
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g_rtc_enabled = true;
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return OK;
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}
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/****************************************************************************
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* Name: up_rtc_time
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*
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* Description:
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* Get the current time in seconds.
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*
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****************************************************************************/
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time_t up_rtc_time(void)
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{
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return (time_t)(powman_get_ms() / 1000);
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}
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/****************************************************************************
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* Name: up_rtc_settime
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*
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* Description:
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* Set the RTC to the provided time value.
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*
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****************************************************************************/
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int up_rtc_settime(FAR const struct timespec *tp)
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{
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irqstate_t flags;
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uint64_t ms;
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ms = (uint64_t)tp->tv_sec * 1000 + tp->tv_nsec / 1000000;
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flags = enter_critical_section();
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powman_set_ms(ms);
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leave_critical_section(flags);
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return OK;
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}
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#endif /* CONFIG_RTC */
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