From 2893e795fcbe0b36313a409d7d994880a3602689 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
Date: Thu, 3 May 2018 19:43:30 +0200
Subject: [PATCH] atmel-samd/samd21: Use XOSC32K on boards with a crystal

Use XOSC32K on boards that have BOARD_HAS_CRYSTAL defined and set to 1.
---
 .../boards/feather_m0_express/mpconfigboard.h   |  2 ++
 .../boards/metro_m0_express/mpconfigboard.h     |  2 ++
 ports/atmel-samd/clocks.h                       |  9 +++++++++
 ports/atmel-samd/samd21_clocks.c                | 17 +++++++++++++++--
 4 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h b/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h
index 56e9c8bb71..c85f553ba9 100644
--- a/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/feather_m0_express/mpconfigboard.h
@@ -46,3 +46,5 @@
                                GD25Q16C
 
 #include "external_flash/external_flash.h"
+
+#define BOARD_HAS_CRYSTAL 1
diff --git a/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h b/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h
index a433e99495..e635acd593 100644
--- a/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h
+++ b/ports/atmel-samd/boards/metro_m0_express/mpconfigboard.h
@@ -47,3 +47,5 @@
                                GD25Q16C
 
 #include "external_flash/external_flash.h"
+
+#define BOARD_HAS_CRYSTAL 1
diff --git a/ports/atmel-samd/clocks.h b/ports/atmel-samd/clocks.h
index e78e6173d9..6a61e49c7f 100644
--- a/ports/atmel-samd/clocks.h
+++ b/ports/atmel-samd/clocks.h
@@ -31,6 +31,7 @@
 #include <stdint.h>
 
 #include "include/sam.h"
+#include "mpconfigboard.h" // for BOARD_HAS_CRYSTAL
 
 #ifdef SAMD51
 #define CLOCK_48MHZ GCLK_GENCTRL_SRC_DFLL_Val
@@ -53,6 +54,14 @@ void disconnect_gclk_from_peripheral(uint8_t gclk, uint8_t peripheral);
 void enable_clock_generator(uint8_t gclk, uint32_t source, uint16_t divisor);
 void disable_clock_generator(uint8_t gclk);
 
+static inline bool board_has_crystal(void) {
+#ifdef BOARD_HAS_CRYSTAL
+    return BOARD_HAS_CRYSTAL == 1;
+#else
+    return false;
+#endif
+}
+
 void clock_init(void);
 
 #endif  // MICROPY_INCLUDED_ATMEL_SAMD_CLOCKS_H
diff --git a/ports/atmel-samd/samd21_clocks.c b/ports/atmel-samd/samd21_clocks.c
index b695a7fe8a..4fc039a588 100644
--- a/ports/atmel-samd/samd21_clocks.c
+++ b/ports/atmel-samd/samd21_clocks.c
@@ -94,6 +94,13 @@ static void init_clock_source_osc32k(void) {
     while (!SYSCTRL->PCLKSR.bit.OSC32KRDY) {}
 }
 
+static void init_clock_source_xosc32k(void) {
+    SYSCTRL->XOSC32K.reg = SYSCTRL_XOSC32K_EN32K |
+                           SYSCTRL_XOSC32K_XTALEN |
+                           SYSCTRL_XOSC32K_ENABLE;
+    while (!SYSCTRL->PCLKSR.bit.XOSC32KRDY) {}
+}
+
 static void init_clock_source_dfll48m(void) {
     SYSCTRL->DFLLCTRL.reg = SYSCTRL_DFLLCTRL_ENABLE;
     while (!SYSCTRL->PCLKSR.bit.DFLLRDY) {}
@@ -116,9 +123,15 @@ static void init_clock_source_dfll48m(void) {
 void clock_init(void)
 {
     init_clock_source_osc8m();
-    init_clock_source_osc32k();
+    if (board_has_crystal())
+        init_clock_source_xosc32k();
+    else
+        init_clock_source_osc32k();
     enable_clock_generator(0, GCLK_GENCTRL_SRC_DFLL48M_Val, 1);
     enable_clock_generator(1, GCLK_GENCTRL_SRC_DFLL48M_Val, 150);
     init_clock_source_dfll48m();
-    enable_clock_generator(2, GCLK_GENCTRL_SRC_OSC32K_Val, 32);
+    if (board_has_crystal())
+        enable_clock_generator(2, GCLK_GENCTRL_SRC_XOSC32K_Val, 32);
+    else
+        enable_clock_generator(2, GCLK_GENCTRL_SRC_OSC32K_Val, 32);
 }