M487: Get around h/w limit with WDT reset from PD

Use WKT to get around this h/w limit

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M480/device/startup_M480.c

@@ -392,10 +392,7 @@ void Reset_Handler_1(void)
 {
     /* Disable register write-protection function */
     SYS_UnlockReg();
-    
-    /* Disable Power-on Reset function */
-    SYS_DISABLE_POR();
-    
+
     /**
      * NOTE 1: Some register accesses require unlock.
      * NOTE 2: Because EBI (external SRAM) init is done in SystemInit(), SystemInit() must be called at the very start.

targets/TARGET_NUVOTON/TARGET_M480/mbed_overrides.c

@@ -1,5 +1,7 @@
-/* mbed Microcontroller Library
- * Copyright (c) 2015-2016 Nuvoton
+/*
+ * Copyright (c) 2015-2016, Nuvoton Technology Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -57,7 +59,7 @@ void mbed_sdk_init(void)
 
     /* Set PCLK0/PCLK1 to HCLK/2 */
     CLK->PCLKDIV = (CLK_PCLKDIV_PCLK0DIV2 | CLK_PCLKDIV_PCLK1DIV2); // PCLK divider set 2
-    
+
 #if DEVICE_ANALOGIN
     /* Vref connect to internal */
     SYS->VREFCTL = (SYS->VREFCTL & ~SYS_VREFCTL_VREFCTL_Msk) | SYS_VREFCTL_VREF_3_0V;
@@ -69,4 +71,23 @@ void mbed_sdk_init(void)
 
     /* Lock protected registers */
     SYS_LockReg();
+
+    /* Get around h/w limit with WDT reset from PD */
+    if (SYS_IS_WDT_RST()) {
+        /* Re-unlock protected clock setting */
+        SYS_UnlockReg();
+
+        /* Set up DPD power down mode */
+        CLK->PMUSTS |= CLK_PMUSTS_CLRWK_Msk;
+        CLK->PMUSTS |= CLK_PMUSTS_TMRWK_Msk;
+        CLK_SetPowerDownMode(CLK_PMUCTL_PDMSEL_DPD);
+
+        CLK_SET_WKTMR_INTERVAL(CLK_PMUCTL_WKTMRIS_256);
+        CLK_ENABLE_WKTMR();
+
+        CLK_PowerDown();
+
+        /* Lock protected registers */
+        SYS_LockReg();
+    }
 }

targets/TARGET_NUVOTON/TARGET_M480/reset_reason.c

@@ -1,5 +1,7 @@
-/* mbed Microcontroller Library
- * Copyright (c) 2017-2018 Nuvoton
+/*
+ * Copyright (c) 2017-2018, Nuvoton Technology Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,6 +39,12 @@ reset_reason_t hal_reset_reason_get(void)
     reset_reason_t reset_reason_cast;
     uint32_t reset_reason_count = 0;
 
+    /* Get around h/w limit with WDT reset from PD */
+    if (CLK->PMUSTS & CLK_PMUSTS_TMRWK_Msk) {
+        /* Per test, these reset reason flags will set with WKT reset. Clear them for this resolution. */
+        SYS_CLEAR_RST_SOURCE(SYS_RSTSTS_PINRF_Msk | SYS_RSTSTS_PORF_Msk);
+    }
+
     if (SYS_IS_POR_RST()) {
         reset_reason_cast = RESET_REASON_POWER_ON;
         reset_reason_count ++;
@@ -47,7 +55,8 @@ reset_reason_t hal_reset_reason_get(void)
         reset_reason_count ++;
     }
 
-    if (SYS_IS_WDT_RST()) {
+    /* Get around h/w limit with WDT reset from PD */
+    if (SYS_IS_WDT_RST() || (CLK->PMUSTS & CLK_PMUSTS_TMRWK_Msk)) {
         reset_reason_cast = RESET_REASON_WATCHDOG;
         reset_reason_count ++;
     }
@@ -101,6 +110,15 @@ uint32_t hal_reset_reason_get_raw(void)
 void hal_reset_reason_clear(void)
 {
     SYS_CLEAR_RST_SOURCE(SYS->RSTSTS);
+
+    /* Re-unlock protected clock setting */
+    SYS_UnlockReg();
+
+    /* Get around h/w limit with WDT reset from PD */
+    CLK->PMUSTS |= (CLK_PMUSTS_CLRWK_Msk | CLK_PMUSTS_TMRWK_Msk);
+
+    /* Lock protected registers */
+    SYS_LockReg();
 }
 
 #endif