atsam: update smarteeprom implementation

- Use define for SmartEEPROM buffer address
- Check buffer overflow
- Do not perform operation when timeout occurs

Signed-off-by: Alexandre d'Alton <alex@alexdalton.org>

tmk_core/common/arm_atsam/eeprom.c

@@ -24,22 +24,29 @@
 #endif
 
 __attribute__((aligned(4))) static uint8_t buffer[EEPROM_SIZE];
-volatile uint8_t *SmartEEPROM8 = (uint8_t *) 0x44000000;
+volatile uint8_t *SmartEEPROM8 = (uint8_t *) SEEPROM_ADDR;
 
 uint8_t eeprom_read_byte(const uint8_t *addr) {
     uintptr_t offset = (uintptr_t)addr;
+    if (offset >= EEPROM_SIZE)
+        return 0xff;
 
     if (NVMCTRL->SEESTAT.bit.PSZ == 0 || NVMCTRL->SEESTAT.bit.SBLK == 0)
         return buffer[offset];
 
     int timeout = 10000;
     while (NVMCTRL->SEESTAT.bit.BUSY && timeout-- > 0)
         ;
-    return SmartEEPROM8[offset];
+    if (!NVMCTRL->SEESTAT.bit.BUSY)
+        return SmartEEPROM8[offset];
+
+    return 0xff;
 }
 
 void eeprom_write_byte(uint8_t *addr, uint8_t value) {
     uintptr_t offset = (uintptr_t)addr;
+    if (offset >= EEPROM_SIZE)
+        return;
 
     if (NVMCTRL->SEESTAT.bit.PSZ == 0 || NVMCTRL->SEESTAT.bit.SBLK == 0) {
         buffer[offset] = value;
@@ -49,8 +56,8 @@ void eeprom_write_byte(uint8_t *addr, uint8_t value) {
     int timeout = 10000;
     while (NVMCTRL->SEESTAT.bit.BUSY && timeout-- > 0)
         ;
-
-    SmartEEPROM8[offset] = value;
+    if (!NVMCTRL->SEESTAT.bit.BUSY)
+        SmartEEPROM8[offset] = value;
 }
 
 uint16_t eeprom_read_word(const uint16_t *addr) {