1 files changed, 57 insertions, 0 deletions
diff --git a/src/stm32/dfu_reboot.c b/src/stm32/dfu_reboot.c
new file mode 100644
index 00000000..04952a48
--- /dev/null
+++ b/src/stm32/dfu_reboot.c
@@ -0,0 +1,57 @@
+// Reboot into stm32 ROM dfu bootloader
+//
+// Copyright (C) 2019-2022  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "internal.h" // NVIC_SystemReset
+#include "board/irq.h" // irq_disable
+
+// Many stm32 chips have a USB capable "DFU bootloader" in their ROM.
+// In order to invoke that bootloader it is necessary to reset the
+// chip and jump to a chip specific hardware address.
+//
+// To reset the chip, the dfu_reboot() code sets a flag in memory (at
+// an arbitrary position that is unlikely to be overwritten during a
+// chip reset), and resets the chip.  If dfu_reboot_check() sees that
+// flag on the next boot it will perform a code jump to the ROM
+// address.
+
+// Location of ram address to set internal flag
+#if CONFIG_MACH_STM32H7
+  #define USB_BOOT_FLAG_ADDR (0x24000000 + 0x8000) // Place flag in "AXI SRAM"
+#else
+  #define USB_BOOT_FLAG_ADDR (CONFIG_RAM_START + CONFIG_RAM_SIZE - 1024)
+#endif
+
+// Signature to set in memory to flag that a dfu reboot is requested
+#define USB_BOOT_FLAG 0x55534220424f4f54 // "USB BOOT"
+
+// Flag that bootloader is desired and reboot
+void
+dfu_reboot(void)
+{
+    if (!CONFIG_STM32_DFU_ROM_ADDRESS)
+        return;
+    irq_disable();
+    uint64_t *bflag = (void*)USB_BOOT_FLAG_ADDR;
+    *bflag = USB_BOOT_FLAG;
+#if CONFIG_MACH_STM32H7
+    SCB_CleanDCache_by_Addr((void*)bflag, sizeof(*bflag));
+#endif
+    NVIC_SystemReset();
+}
+
+// Check if rebooting into system DFU Bootloader
+void
+dfu_reboot_check(void)
+{
+    if (!CONFIG_STM32_DFU_ROM_ADDRESS)
+        return;
+    if (*(uint64_t*)USB_BOOT_FLAG_ADDR != USB_BOOT_FLAG)
+        return;
+    *(uint64_t*)USB_BOOT_FLAG_ADDR = 0;
+    uint32_t *sysbase = (uint32_t*)CONFIG_STM32_DFU_ROM_ADDRESS;
+    asm volatile("mov sp, %0\n bx %1"
+                 : : "r"(sysbase[0]), "r"(sysbase[1]));
+}