drivers/periph: define rtc_mem and implement it for sam0_common

cpu/sam0_common/periph/rtc_rtt.c

@@ -25,6 +25,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 #include "periph/rtc.h"
 #include "periph/rtt.h"
 #include "periph_conf.h"
@@ -215,10 +216,70 @@ static void _rtt_clock_setup(void)
 #endif /* MODULE_PERIPH_RTT */
 #endif /* !CPU_COMMON_SAMD21 - Clock Setup */
 
+#ifdef MODULE_PERIPH_RTC_MEM
+/* first two GP registers are shared with COMP[0] / ALARM[0] */
+#ifdef RTC_MODE2_CTRLB_GP2EN
+#define RTC_GPR_START       (2)
+#else
+#define RTC_GPR_START       (0)
+#endif
+
+#define RTC_GPR_NUM_AVAIL   (RTC_GPR_NUM - RTC_GPR_START)
+#define RTC_MEM_SIZE        (RTC_GPR_NUM_AVAIL * sizeof(uint32_t))
+
+size_t rtc_mem_size(void)
+{
+    return RTC_MEM_SIZE;
+}
+
+static void _read_gp(uint32_t *dst)
+{
+    for (unsigned i = RTC_GPR_START; i < RTC_GPR_NUM; ++i) {
+        dst[i - RTC_GPR_START] = RTC->MODE0.GP[i].reg;
+    }
+}
+
+static void _write_gp(const uint32_t *src)
+{
+    for (unsigned i = RTC_GPR_START; i < RTC_GPR_NUM; ++i) {
+        _wait_syncbusy();
+        RTC->MODE0.GP[i].reg = src[i - RTC_GPR_START];
+    }
+}
+
+void rtc_mem_read(unsigned offset, void *data, size_t len)
+{
+    uint32_t tmp[RTC_GPR_NUM_AVAIL];
+
+    if (offset + len > RTC_MEM_SIZE) {
+        assert(0);
+        return;
+    }
+
+    _read_gp(tmp);
+    memcpy(data, ((uint8_t *)tmp) + offset, len);
+}
+
+void rtc_mem_write(unsigned offset, void *data, size_t len)
+{
+    uint32_t tmp[RTC_GPR_NUM_AVAIL];
+
+    if (offset + len > RTC_MEM_SIZE) {
+        assert(0);
+        return;
+    }
+
+    _read_gp(tmp);
+    memcpy(((uint8_t *)tmp) + offset, data, len);
+    _write_gp(tmp);
+}
+#endif /* MODULE_PERIPH_RTC_MEM */
+
 #ifdef MODULE_PERIPH_RTC
 static void _rtc_init(void)
 {
 #ifdef REG_RTC_MODE2_CTRLA
+    /* skip reset if already in RTC mode */
     if (RTC->MODE2.CTRLA.bit.MODE == RTC_MODE2_CTRLA_MODE_CLOCK_Val) {
         return;
     }
@@ -229,6 +290,11 @@ static void _rtc_init(void)
     RTC->MODE2.CTRLA.reg = RTC_MODE2_CTRLA_PRESCALER_DIV1024   /* CLK_RTC_CNT = 1KHz / 1024 -> 1Hz */
                          | RTC_MODE2_CTRLA_CLOCKSYNC           /* Clock Read Synchronization Enable */
                          | RTC_MODE2_CTRLA_MODE_CLOCK;
+#ifdef RTC_MODE2_CTRLB_GP2EN
+    /* RTC driver does not use COMP[1] or ALARM[1] */
+    /* Use second set of Compare registers as general purpose register */
+    RTC->MODE2.CTRLB.reg = RTC_MODE2_CTRLB_GP2EN;
+#endif
 #else
     if (RTC->MODE2.CTRL.bit.MODE == RTC_MODE2_CTRL_MODE_CLOCK_Val) {
         return;
@@ -268,10 +334,26 @@ void rtc_init(void)
 #ifdef MODULE_PERIPH_RTT
 void rtt_init(void)
 {
+
     _rtt_clock_setup();
     _poweron();
+
+#ifdef MODULE_PERIPH_RTC_MEM
+    uint32_t backup[RTC_GPR_NUM_AVAIL];
+    _read_gp(backup);
+#endif
+
     _rtt_reset();
 
+#ifdef MODULE_PERIPH_RTC_MEM
+#ifdef RTC_MODE2_CTRLB_GP2EN
+    /* RTC driver does not use COMP[1] or ALARM[1] */
+    /* Use second set of Compare registers as general purpose register */
+    RTC->MODE2.CTRLB.reg = RTC_MODE2_CTRLB_GP2EN;
+#endif
+    _write_gp(backup);
+#endif /* MODULE_PERIPH_RTC_MEM */
+
     /* set 32bit counting mode & enable the RTC */
 #ifdef REG_RTC_MODE0_CTRLA
     RTC->MODE0.CTRLA.reg = RTC_MODE0_CTRLA_MODE(0)

cpu/samd5x/Kconfig

@@ -15,6 +15,7 @@ config CPU_COMMON_SAMD5X
     select HAS_PERIPH_DMA
     select HAS_PERIPH_GPIO_TAMPER_WAKE
     select HAS_PERIPH_HWRNG
+    select HAS_PERIPH_RTC_MEM
     select HAS_PERIPH_SPI_ON_QSPI
 
 config CPU_FAM_SAMD51

cpu/samd5x/Makefile.features

@@ -4,6 +4,7 @@ FEATURES_PROVIDED += periph_hwrng
 FEATURES_PROVIDED += backup_ram
 FEATURES_PROVIDED += cortexm_mpu
 FEATURES_PROVIDED += periph_gpio_tamper_wake
+FEATURES_PROVIDED += periph_rtc_mem
 FEATURES_PROVIDED += periph_spi_on_qspi
 
 include $(RIOTCPU)/sam0_common/Makefile.features

cpu/saml21/Kconfig

@@ -13,6 +13,7 @@ config CPU_COMMON_SAML21
     select HAS_CPU_SAML21
     select HAS_PERIPH_DMA
     select HAS_PERIPH_GPIO_FAST_READ
+    select HAS_PERIPH_RTC_MEM
 
 config CPU_FAM_SAML21
     bool

cpu/saml21/Makefile.features

@@ -10,6 +10,7 @@ FEATURES_PROVIDED += periph_gpio_fast_read
 # It can still be used in normal and standby mode, but code that relies on it
 # being availiable during deep sleep / backup mode will not be portable here.
 FEATURES_PROVIDED += backup_ram
+FEATURES_PROVIDED += periph_rtc_mem
 
 ifeq (,$(filter $(CPU_MODELS_WITHOUT_HWRNG),$(CPU_MODEL)))
   FEATURES_PROVIDED += periph_hwrng

drivers/include/periph/rtc_mem.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2021 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @defgroup    drivers_periph_rtc_mem Low-Power RTC Memory
+ * @ingroup     drivers_periph_rtc
+ * @brief       Low-level RTC Memory peripheral driver
+ *
+ * This API provides an interface to access low-power memory present on some RTCs.
+ * This memory is retained even when the rest of the system is powered off.
+ *
+ * @{
+ * @file
+ * @brief       Low-level RTC memory peripheral driver interface definitions
+ *
+ * @author      Benjamin Valentin <[email protected]>
+ */
+
+#ifndef PERIPH_RTC_MEM_H
+#define PERIPH_RTC_MEM_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Get the amount of RTC memory.
+ *
+ * @return  The usable amount of RTC memory in bytes
+ */
+size_t rtc_mem_size(void);
+
+/**
+ * @brief Read from RTC memory
+ *
+ * @note  Reading beyond @ref rtc_mem_size are illegal and trigger an
+ *        assertion / be discarded.
+ *
+ * @param[in]  offset   Offset to the start of RTC memory in bytes
+ * @param[out] data     Destination buffer
+ * @param[in]  len      Amount of bytes to read
+ */
+void rtc_mem_read(unsigned offset, void *data, size_t len);
+
+/**
+ * @brief Write to RTC memory
+ *
+ * @note  Writing beyond @ref rtc_mem_size are illegal and trigger an
+ *        assertion / be discarded.
+ *
+ * @param[in] offset    Offset to the start of RTC memory in bytes
+ * @param[in] data      Source buffer
+ * @param[in] len       Amount of bytes to write
+ */
+void rtc_mem_write(unsigned offset, const void *data, size_t len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_RTC_MEM_H */
+/** @} */

kconfigs/Kconfig.features

@@ -257,6 +257,11 @@ config HAS_PERIPH_RTC
     help
         Indicates that an RTC peripheral is present.
 
+config HAS_PERIPH_RTC_MEM
+    bool
+    help
+        Indicates that the RTC peripheral provides storage memory for deep sleep.
+
 config HAS_PERIPH_RTC_MS
     bool
     help

tests/periph_rtc/Makefile

@@ -2,6 +2,7 @@ include ../Makefile.tests_common
 
 FEATURES_REQUIRED += periph_rtc
 FEATURES_OPTIONAL += periph_rtc_ms
+FEATURES_OPTIONAL += periph_rtc_mem
 
 DISABLE_MODULE += periph_init_rtc
 

tests/periph_rtc/main.c

@@ -23,10 +23,12 @@
 
 #include <stdio.h>
 #include <time.h>
+#include <string.h>
 
 #include "mutex.h"
 #include "periph_conf.h"
 #include "periph/rtc.h"
+#include "periph/rtc_mem.h"
 #include "xtimer.h"
 
 #define PERIOD              (2U)
@@ -69,6 +71,58 @@ static void cb(void *arg)
     mutex_unlock(arg);
 }
 
+#ifdef MODULE_PERIPH_RTC_MEM
+static const uint8_t riot_msg_offset = 1;
+static const char riot_msg[] = "RIOT";
+static void _set_rtc_mem(void)
+{
+    /* first fill the whole memory */
+    uint8_t size = rtc_mem_size();
+    while (size--) {
+        rtc_mem_write(size, &size, sizeof(size));
+    }
+
+    /* write test data */
+    rtc_mem_write(riot_msg_offset, riot_msg, sizeof(riot_msg) - 1);
+}
+
+static void _get_rtc_mem(void)
+{
+    char buf[4];
+    rtc_mem_read(riot_msg_offset, buf, sizeof(buf));
+
+    if (memcmp(buf, riot_msg, sizeof(buf))) {
+        puts("RTC mem content does not match");
+        for (unsigned i = 0; i < sizeof(buf); ++i) {
+            printf("%02x - %02x\n", riot_msg[i], buf[i]);
+        }
+        return;
+    }
+
+    uint8_t size = rtc_mem_size();
+    while (size--) {
+        uint8_t data;
+
+        if (size >= riot_msg_offset &&
+            size < riot_msg_offset + sizeof(riot_msg)) {
+            continue;
+        }
+
+        rtc_mem_read(size, &data, 1);
+        if (data != size) {
+            puts("RTC mem content does not match");
+            printf("%02x: %02x\n", size, data);
+        }
+    }
+
+
+    puts("RTC mem OK");
+}
+#else
+static inline void _set_rtc_mem(void) {}
+static inline void _get_rtc_mem(void) {}
+#endif
+
 int main(void)
 {
     struct tm time = {
@@ -88,6 +142,9 @@ int main(void)
 
     rtc_init();
 
+    _set_rtc_mem();
+    _get_rtc_mem();
+
     /* set RTC */
     print_time("  Setting clock to ", &time);
     rtc_set_time(&time);
@@ -149,17 +206,17 @@ int main(void)
     puts("");
 
     /* loop over a few alarm cycles */
-    while (1) {
+    do {
         mutex_lock(&rtc_mtx);
         puts("Alarm!");
 
-        if (++cnt < REPEAT) {
-            struct tm time;
-            rtc_get_alarm(&time);
-            inc_secs(&time, PERIOD);
-            rtc_set_alarm(&time, cb, &rtc_mtx);
-        }
-    }
+        struct tm time;
+        rtc_get_alarm(&time);
+        inc_secs(&time, PERIOD);
+        rtc_set_alarm(&time, cb, &rtc_mtx);
+    } while (++cnt < REPEAT);
+
+    _get_rtc_mem();
 
     return 0;
 }

tests/periph_rtt/Makefile

@@ -3,6 +3,7 @@ include ../Makefile.tests_common
 
 FEATURES_REQUIRED = periph_rtt
 FEATURES_OPTIONAL += periph_rtt_set_counter
+FEATURES_OPTIONAL += periph_rtc_mem
 
 DISABLE_MODULE += periph_init_rtt