Import of the watch repository from Pebble

src/fw/startup/startup_stm32.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! Initial firmware startup, contains the vector table that the bootloader loads.
+//! Based on "https://github.com/pfalcon/cortex-uni-startup/blob/master/startup.c"
+//! by Paul Sokolovsky (public domain)
+
+#include <stdint.h>
+#include <string.h>
+#include <stdbool.h>
+#include "mcu/cache.h"
+#include "util/attributes.h"
+
+//! These symbols are defined in the linker script for use in initializing
+//! the data sections. uint8_t since we do arithmetic with section lengths.
+//! These are arrays to avoid the need for an & when dealing with linker symbols.
+extern uint8_t __data_load_start[];
+extern uint8_t __data_start[];
+extern uint8_t __data_end[];
+extern uint8_t __bss_start[];
+extern uint8_t __bss_end[];
+extern uint8_t _estack[];
+
+#if MICRO_FAMILY_STM32F7
+extern uint8_t __dtcm_bss_start[];
+extern uint8_t __dtcm_bss_end[];
+#endif
+
+//! Firmware main function, ResetHandler calls this
+extern int main(void);
+
+//! STM32 system initialization function, defined in the standard peripheral library
+extern void SystemInit(void);
+
+//! This function is what gets called when the processor first
+//! starts execution following a reset event. The data and bss
+//! sections are initialized, then we call the firmware's main
+//! function
+NORETURN Reset_Handler(void) {
+  // Copy data section from flash to RAM
+  memcpy(__data_start, __data_load_start, __data_end - __data_start);
+
+  // Clear the bss section, assumes .bss goes directly after .data
+  memset(__bss_start, 0, __bss_end - __bss_start);
+
+#if MICRO_FAMILY_STM32F7
+  // Clear the DTCM bss section
+  memset(__dtcm_bss_start, 0, __dtcm_bss_end - __dtcm_bss_start);
+#endif
+
+  SystemInit();
+
+  icache_enable();
+  dcache_enable();
+
+  main();
+
+  // Main shouldn't return
+  while (true) {}
+}