cpu/stm32: add rtc_mem

cpu/stm32/Makefile.features

@@ -17,6 +17,8 @@ ifneq (,$(filter $(CPU_FAM),f0 f1 f3 g0 g4 l0 l1 l4 l5 wb wl))
   FEATURES_PROVIDED += periph_flashpage_pagewise
 endif
 
+FEATURES_PROVIDED += periph_rtc_mem
+
 # The f2, f4 and f7 do not support the pagewise api
 ifneq (,$(filter $(CPU_FAM),f2 f4 f7))
   FEATURES_PROVIDED += periph_flashpage

cpu/stm32/periph/rtc_all.c

@@ -209,7 +209,7 @@ static int bcd2val(uint32_t val, int shift, uint32_t mask)
     return (((tmp >> 4) * 10) + (tmp & 0x0f));
 }
 
-static inline void rtc_unlock(void)
+extern inline void rtc_unlock(void)
 {
     /* enable backup clock domain */
     stmclk_dbp_unlock();
@@ -221,7 +221,7 @@ static inline void rtc_unlock(void)
     while (!(RTC_REG_ISR & RTC_ISR_INITF)) {}
 }
 
-static inline void rtc_lock(void)
+extern inline void rtc_lock(void)
 {
     /* exit RTC init mode */
     RTC_REG_ISR &= ~RTC_ISR_INIT;

cpu/stm32/periph/rtc_mem.c

@@ -0,0 +1,158 @@
+/*
+ * Copyright (C) 2021 Inria
+ *
+ * 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.
+ */
+
+/**
+ * @ingroup     cpu_stm32
+ * @{
+ * @file
+ * @brief       Low-level RTC backup memory implementation
+ *
+ * @author      Kaspar Schleiser <[email protected]>
+ * @author      Francisco Molina <[email protected]>
+ * @}
+ */
+
+#include <string.h>
+
+#include "cpu.h"
+#include "periph/rtc_mem.h"
+
+#if defined(RTC_BKP31R)
+#define RTC_MEM_SIZE    32
+#elif defined(RTC_BKP30R)
+#define RTC_MEM_SIZE    31
+#elif defined(RTC_BKP29R)
+#define RTC_MEM_SIZE    30
+#elif defined(RTC_BKP28R)
+#define RTC_MEM_SIZE    29
+#elif defined(RTC_BKP27R)
+#define RTC_MEM_SIZE    28
+#elif defined(RTC_BKP26R)
+#define RTC_MEM_SIZE    27
+#elif defined(RTC_BKP25R)
+#define RTC_MEM_SIZE    26
+#elif defined(RTC_BKP24R)
+#define RTC_MEM_SIZE    25
+#elif defined(RTC_BKP23R)
+#define RTC_MEM_SIZE    24
+#elif defined(RTC_BKP22R)
+#define RTC_MEM_SIZE    23
+#elif defined(RTC_BKP21R)
+#define RTC_MEM_SIZE    22
+#elif defined(RTC_BKP20R)
+#define RTC_MEM_SIZE    21
+#elif defined(RTC_BKP19R)
+#define RTC_MEM_SIZE    20
+#elif defined(RTC_BKP18R)
+#define RTC_MEM_SIZE    19
+#elif defined(RTC_BKP17R)
+#define RTC_MEM_SIZE    18
+#elif defined(RTC_BKP16R)
+#define RTC_MEM_SIZE    17
+#elif defined(RTC_BKP15R)
+#define RTC_MEM_SIZE    16
+#elif defined(RTC_BKP14R)
+#define RTC_MEM_SIZE    15
+#elif defined(RTC_BKP13R)
+#define RTC_MEM_SIZE    14
+#elif defined(RTC_BKP12R)
+#define RTC_MEM_SIZE    13
+#elif defined(RTC_BKP11R)
+#define RTC_MEM_SIZE    12
+#elif defined(RTC_BKP10R)
+#define RTC_MEM_SIZE    11
+#elif defined(RTC_BKP9R)
+#define RTC_MEM_SIZE    10
+#elif defined(RTC_BKP8R)
+#define RTC_MEM_SIZE    9
+#elif defined(RTC_BKP7R)
+#define RTC_MEM_SIZE    8
+#elif defined(RTC_BKP6R)
+#define RTC_MEM_SIZE    8
+#elif defined(RTC_BKP5R)
+#define RTC_MEM_SIZE    6
+#elif defined(RTC_BKP4R)
+#define RTC_MEM_SIZE    5
+#elif defined(RTC_BKP3R)
+#define RTC_MEM_SIZE    4
+#elif defined(RTC_BKP2R)
+#define RTC_MEM_SIZE    3
+#elif defined(RTC_BKP1R)
+#define RTC_MEM_SIZE    2
+#elif defined(RTC_BKP0R)
+#define RTC_MEM_SIZE    1
+#endif
+
+extern void rtc_lock(void);
+extern void rtc_enable(void);
+extern void rtc_unlock(void);
+
+size_t rtc_mem_size(void)
+{
+    return RTC_MEM_SIZE * 4;
+}
+
+void rtc_mem_write(unsigned offset, const void *data, size_t len)
+{
+    if (offset + len > rtc_mem_size()) {
+        return;
+    }
+
+    volatile uint32_t *rtcregs = &RTC->BKP0R;
+    rtcregs += offset / 4;
+    offset %= 4;
+
+    rtc_unlock();
+
+    if (offset) {
+        unsigned to_copy = (len >= 4 - offset) ? 4 - offset : len;
+        uint32_t tmp = *rtcregs;
+        memcpy(((uint8_t*)&tmp) + offset, data, to_copy);
+        *rtcregs++ = tmp;
+        len -= to_copy;
+        data += to_copy;
+    }
+
+    while (len) {
+        unsigned to_copy = (len >= 4) ? 4 : len;
+        uint32_t tmp = *rtcregs;
+        memcpy(((uint8_t*)&tmp), data, to_copy);
+        *rtcregs++ = tmp;
+        len -= to_copy;
+        data += to_copy;
+    }
+
+    rtc_lock();
+}
+
+void rtc_mem_read(unsigned offset, void *data, size_t len)
+{
+    if (offset + len > rtc_mem_size()) {
+        return;
+    }
+
+    volatile uint32_t *rtcregs = &RTC->BKP0R;
+    rtcregs += offset / 4;
+    offset %= 4;
+
+    if (offset) {
+        unsigned to_copy = (len >= 4 - offset) ? 4 - offset : len;
+        uint32_t tmp = *rtcregs++;
+        memcpy(data, ((uint8_t*)&tmp) + offset, to_copy);
+        len -= to_copy;
+        data += to_copy;
+    }
+
+    while (len) {
+        unsigned to_copy = (len >= 4) ? 4 : len;
+        uint32_t tmp = *rtcregs++;
+        memcpy(data, ((uint8_t*)&tmp), to_copy);
+        len -= to_copy;
+        data += to_copy;
+    }
+}