From 0948cd19b27b0f66e12145dbf1c911f50c31d039 Mon Sep 17 00:00:00 2001
From: Davey Struijk <mail@daveystruijk.com>
Date: Fri, 25 Oct 2019 14:32:36 +0200
Subject: [PATCH] Allow writing option bytes to STM32F4 devices

---
 include/stlink.h  |  1 +
 src/common.c      | 88 ++++++++++++++++++++++++++++++++++++++++++++++-
 src/tools/flash.c |  6 +++-
 3 files changed, 93 insertions(+), 2 deletions(-)

diff --git a/include/stlink.h b/include/stlink.h
index 0715166..5defe4e 100644
--- a/include/stlink.h
+++ b/include/stlink.h
@@ -223,6 +223,7 @@ typedef struct flash_loader {
     int stlink_fread(stlink_t* sl, const char* path, bool is_ihex, stm32_addr_t addr, size_t size);
     int stlink_load_device_params(stlink_t *sl);
     int stlink_read_option_bytes_f2(stlink_t *sl, uint32_t* option_byte);
+    int stlink_read_option_bytes_f4(stlink_t *sl, uint32_t* option_byte);
 
 #include "stlink/sg.h"
 #include "stlink/usb.h"
diff --git a/src/common.c b/src/common.c
index bfcbe71..99bd7a8 100644
--- a/src/common.c
+++ b/src/common.c
@@ -187,6 +187,7 @@
 #define FLASH_F4_SR (FLASH_F4_REGS_ADDR + 0x0c)
 #define FLASH_F4_CR (FLASH_F4_REGS_ADDR + 0x10)
 #define FLASH_F4_OPT_CR (FLASH_F4_REGS_ADDR + 0x14)
+#define FLASH_F4_OPT_LOCK_BIT (1u << 0)
 #define FLASH_F4_CR_STRT 16
 #define FLASH_F4_CR_LOCK 31
 #define FLASH_F4_CR_SER 1
@@ -2711,6 +2712,56 @@ static int stlink_write_option_bytes_f2(stlink_t *sl, uint32_t option_byte) {
 	return 0;
 }
 
+/**
+ * Write option bytes
+ * @param sl
+ * @param option_byte value to write
+ * @return 0 on success, -ve on failure.
+ */
+static int stlink_write_option_bytes_f4(stlink_t *sl, uint32_t option_byte) {
+    uint32_t val;
+
+    stlink_read_debug32(sl, FLASH_F4_OPT_CR, &val);
+    if (val & FLASH_F4_OPT_LOCK_BIT) {
+        WLOG("Unlocking option flash\n");
+        //Unlock the FLASH_OPT_CR register (FLASH Programming manual page 15)
+        //https://www.st.com/resource/en/programming_manual/cd00233952.pdf
+        stlink_write_debug32(sl, FLASH_F4_OPT_KEYR, 0x08192A3B);
+        stlink_write_debug32(sl, FLASH_F4_OPT_KEYR, 0x4C5D6E7F);
+
+        stlink_read_debug32(sl, FLASH_F4_OPT_CR, &val);
+        if (val & FLASH_F4_OPT_LOCK_BIT) {
+            ELOG("Option flash unlock failed! System reset required to be able to unlock it again!\n");
+            return -1;
+        }
+    }
+
+    stlink_read_debug32(sl, FLASH_F4_OPT_CR, &val);
+    WLOG("option bytes CR = %x\n",val);
+
+    stlink_write_debug32(sl, FLASH_F4_OPT_CR, option_byte & 0x0FFFFFFC);
+
+    stlink_write_debug32(sl, FLASH_F4_OPT_CR, (option_byte & 0x0FFFFFFC)|0x00000002);
+
+
+    stlink_read_debug32(sl, FLASH_F4_SR, &val);
+    WLOG("wait BSY flag to be 0\n");
+
+    while(val & 0x00010000){
+        stlink_read_debug32(sl, FLASH_F4_SR, &val);
+    }
+    WLOG("BSY flag is 0\n");
+
+    stlink_read_debug32(sl, FLASH_F4_OPT_CR, &val);
+    WLOG("option bytes CR = %x\n",val);
+    WLOG("Option flash re-lock\n");
+    stlink_write_debug32(sl, FLASH_F4_OPT_CR, val | 0x00000001);
+
+    DLOG("STM32 F4 option bytes are written\n");
+
+	return 0;
+}
+
 /**
  * Read option bytes
  * @param sl
@@ -2744,6 +2795,39 @@ int stlink_read_option_bytes_f2(stlink_t *sl, uint32_t* option_byte) {
 	return 0;
 }
 
+/**
+ * Read option bytes
+ * @param sl
+ * @param option_byte value to write
+ * @return 0 on success, -ve on failure.
+ */
+int stlink_read_option_bytes_f4(stlink_t *sl, uint32_t* option_byte) {
+    uint32_t val;
+
+    stlink_read_debug32(sl, FLASH_F4_OPT_CR, &val);
+    if (val & FLASH_F4_OPT_LOCK_BIT) {
+        WLOG("Unlocking option flash\n");
+        //Unlock the FLASH_OPT_CR register (FLASH Programming manual page 15)
+        //https://www.st.com/resource/en/programming_manual/cd00233952.pdf
+        stlink_write_debug32(sl, FLASH_F4_OPT_KEYR, 0x08192A3B);
+        stlink_write_debug32(sl, FLASH_F4_OPT_KEYR, 0x4C5D6E7F);
+
+        stlink_read_debug32(sl, FLASH_F4_OPT_CR, &val);
+        if (val & FLASH_F4_OPT_LOCK_BIT) {
+            ELOG("Option flash unlock failed! System reset required to be able to unlock it again!\n");
+            return -1;
+        }
+    }
+
+    stlink_read_debug32(sl, FLASH_F4_OPT_CR, option_byte);
+    WLOG("option bytes CR = %x\n",option_byte);
+
+    WLOG("Option flash re-lock\n");
+    stlink_write_debug32(sl, FLASH_F4_OPT_CR, val | 0x00000001);
+
+	return 0;
+}
+
 /**
  * Write option bytes
  * @param sl
@@ -2803,10 +2887,12 @@ int stlink_fwrite_option_bytes_32bit(stlink_t *sl, uint32_t val) {
 
     if(sl->chip_id == STLINK_CHIPID_STM32_F2){
         return stlink_write_option_bytes_f2(sl, val);
+    }else if(sl->chip_id == STLINK_CHIPID_STM32_F446){
+        return stlink_write_option_bytes_f4(sl, val);
     }
     else
     {
-        ELOG("Option bytes writing is currently only supported for the STM32F2, STM32G0 and STM32L0\n");
+        ELOG("Option bytes writing is currently only supported for the STM32F2, STM32F4, STM32G0 and STM32L0\n");
         return -1;
     }
 }
diff --git a/src/tools/flash.c b/src/tools/flash.c
index 33e1c8d..f5fd1a3 100644
--- a/src/tools/flash.c
+++ b/src/tools/flash.c
@@ -214,8 +214,12 @@ int main(int ac, char** av)
                 uint32_t option_byte = 0;
                 err = stlink_read_option_bytes_f2(sl,&option_byte);
                 printf("%x\n",option_byte);
+            }else if(sl->chip_id == STLINK_CHIPID_STM32_F446){
+                uint32_t option_byte = 0;
+                err = stlink_read_option_bytes_f4(sl,&option_byte);
+                printf("%x\n",option_byte);
             }else{
-                printf("This format is available for STM32F2 Only\n");
+                printf("This format is available for STM32F2 and STM32F4 Only\n");
             }
         }else{
             if ((o.addr >= sl->flash_base) && (o.size == 0) &&