samd/modmachine: Get the bootloader magic address from the lib.

Instead of being hard-coded, and then it works for all MCUs.

That fits except for a Sparkfun SAMD51 Thing Plus (known) bug, which uses
192k - 4 as magic address.  Therefore, that address is set as well to avoid
a problem when this bug is fixed by Sparkfun.

ports/samd/boards/SPARKFUN_SAMD51_THING_PLUS/mpconfigboard.h

@@ -2,3 +2,9 @@
 #define MICROPY_HW_MCU_NAME         "SAMD51J20A"
 
 #define MICROPY_HW_XOSC32K          (1)
+
+// There seems to be an inconsistency in the SAMD51 Thing bootloader in that
+// the bootloader magic address is at the end of a 192k RAM area, instead of
+// 256k. Since the SAMD51x20A has 256k RAM, the loader symbol is at that address
+// and so there is a fix here using the previous definition.
+#define DBL_TAP_ADDR_ALT    ((volatile uint32_t *)(HSRAM_ADDR + HSRAM_SIZE - 0x10000 - 4))

ports/samd/modmachine.c

@@ -41,21 +41,26 @@
 #include "hpl_pm_base.h"
 
 #if MICROPY_PY_MACHINE
-
 #if defined(MCU_SAMD21)
-#define DBL_TAP_ADDR ((volatile uint32_t *)(0x20000000 + 32 * 1024 - 4))
+#define DBL_TAP_ADDR    ((volatile uint32_t *)(HMCRAMC0_ADDR + HMCRAMC0_SIZE - 4))
 #elif defined(MCU_SAMD51)
-#define DBL_TAP_ADDR ((volatile uint32_t *)(0x20000000 + 192 * 1024 - 4))
+#define DBL_TAP_ADDR    ((volatile uint32_t *)(HSRAM_ADDR + HSRAM_SIZE - 4))
 #endif
+// A board may define a DPL_TAP_ADDR_ALT, which will be set as well
+// Needed at the moment for Sparkfun SAMD51 Thing Plus
 #define DBL_TAP_MAGIC_LOADER 0xf01669ef
 #define DBL_TAP_MAGIC_RESET 0xf02669ef
 
 #define LIGHTSLEEP_CPU_FREQ 200000
 
 extern bool EIC_occured;
+extern uint32_t _dbl_tap_addr;
 
 STATIC mp_obj_t machine_reset(void) {
     *DBL_TAP_ADDR = DBL_TAP_MAGIC_RESET;
+    #ifdef DBL_TAP_ADDR_ALT
+    *DBL_TAP_ADDR_ALT = DBL_TAP_MAGIC_RESET;
+    #endif
     NVIC_SystemReset();
     return mp_const_none;
 }
@@ -63,6 +68,9 @@ MP_DEFINE_CONST_FUN_OBJ_0(machine_reset_obj, machine_reset);
 
 STATIC mp_obj_t machine_bootloader(void) {
     *DBL_TAP_ADDR = DBL_TAP_MAGIC_LOADER;
+    #ifdef DBL_TAP_ADDR_ALT
+    *DBL_TAP_ADDR_ALT = DBL_TAP_MAGIC_LOADER;
+    #endif
     NVIC_SystemReset();
     return mp_const_none;
 }