Add new system for startup.

Now instead of init() and main() being responsible for all
initialization, individual modules can link in their own
initialization routines.

There are 7 levels for these initializiation routines.

So far these are how the levels are defined

level 0 - Here the world is dark. Nothing is initialized.
          This level is responsible for initializing the
          system clock.

level 1 - The system clock has been configured, but nothing else. Not
          even global variables. This level is responsible for loading
          the data sections from flash and clearing the .bss section.

level 2 - USART2 is enabled and set to be the main kernel logging
          vehicle. From this point on klogf(...) can be used.

level 3 - The NVIC is reset to point to the flash. From this point
          on interrupts can be received. I expect this is where
          most core initialization routines will take place

levels 4 to 7 - User initializiation levels.

main - main() is called after all 8 initialization levels have executed,
       so in a sense main() is like a 9th initialization level, except
       that there is can be only one main() routine whereas there can be
       multiple initalization routines per level.

3 files changed, 20 insertions, 53 deletions

diff --git a/02-usart/src/arch/stm32l4xxx/peripherals/clock.c b/02-usart/src/arch/stm32l4xxx/peripherals/clock.c
index 1029d39..9051572 100644
--- a/02-usart/src/arch/stm32l4xxx/peripherals/clock.c
+++ b/02-usart/src/arch/stm32l4xxx/peripherals/clock.c
@@ -5,10 +5,13 @@
 #include "arch/stm32l4xxx/peripherals/clock.h"
 #include "arch/stm32l4xxx/peripherals/flash.h"
 
+#include "kern/init.h"
+
 #include <stdint.h>
 
 #define TIMEOUT 10000
 
+
 int pll_off()
 {
   uint32_t c;
@@ -66,8 +69,16 @@ int configure_pll(
   return 0;
 }
 
+static _no_init uint8_t clock_mHz;
+uint8_t get_clock_mhz()
+{
+  return clock_mHz;
+}
+
 int set_system_clock_MHz(uint8_t mhz)
 {
+  clock_mHz = mhz;
+
   /* Set the source of the system colck to MSI temporarily. */
   set_system_clock_src(SYSTEM_CLOCK_SRC_MSI);
 
diff --git a/02-usart/src/arch/stm32l4xxx/peripherals/init.c b/02-usart/src/arch/stm32l4xxx/peripherals/init.c
deleted file mode 100644
index 47bfaa5..0000000
--- a/02-usart/src/arch/stm32l4xxx/peripherals/init.c
+++ /dev/null
@@ -1,49 +0,0 @@
-#include "arch.h"
-#include "arch/stm32l4xxx/peripherals/system.h"
-
-/* Forward-declare the main function. This is implemented in main.c. */
-void main();
-
-/* These are defined in the linker script. */
-
-#ifdef ARCH_STM32L4
-extern uint32_t INIT_DATA_VALUES;
-extern uint32_t DATA_SEGMENT_START;
-extern uint32_t DATA_SEGMENT_STOP;
-extern uint32_t BSS_START;
-extern uint32_t BSS_END;
-
-/*
- * Runs before main. Initializes the data and bss segments by loading them
- * into memory.
- */
-_Noreturn void on_reset()
-{
-  uint32_t* src;
-  uint32_t* dest;
-
-  src = &INIT_DATA_VALUES;
-  dest = &DATA_SEGMENT_START;
-
-  /* Copy the values from flash into the data segment. */
-  while (dest != &DATA_SEGMENT_STOP) {
-    *(dest++) = *(src++);
-  }
-
-  /* Everything in the BSS segment is set to zero. */
-  dest = &BSS_START;
-  while (dest != &BSS_END) {
-    *(dest++) = 0;
-  }
-
-  /* Set the vector offset table to be at the start
-   * of FLASH memory. */
-  SCB.vto_r = 0x08000000;
-
-  /* Jump to main. */
-  main();
-
-  for(;;);
-}
-
-#endif /* ARCH_STM32L4 */
diff --git a/02-usart/src/arch/stm32l4xxx/peripherals/usart.c b/02-usart/src/arch/stm32l4xxx/peripherals/usart.c
index d37eee2..7309b48 100644
--- a/02-usart/src/arch/stm32l4xxx/peripherals/usart.c
+++ b/02-usart/src/arch/stm32l4xxx/peripherals/usart.c
@@ -97,9 +97,8 @@ void usart_enable_dma(__IO usart_t* usart, usart_enable_t enabled)
   };
 }
 
-void usart_printf(__IO usart_t* usart, const char* fmt, ...)
+void usart_vprintf(__IO usart_t* usart, const char* fmt, va_list l)
 {
-  va_list l;
   union {
     void* ptr;
     char* str;
@@ -107,8 +106,6 @@ void usart_printf(__IO usart_t* usart, const char* fmt, ...)
   } b;
   char buf[128];
 
-  va_start(l, fmt);
-
   while (*fmt != 0) {
     if (*fmt == '%') {
       switch (*(++fmt)) {
@@ -145,3 +142,11 @@ void usart_printf(__IO usart_t* usart, const char* fmt, ...)
 end:
   va_end(l);
 }
+
+void usart_printf(__IO usart_t* usart, const char* fmt, ...)
+{
+  va_list l;
+  va_start(l, fmt);
+
+  usart_vprintf(usart, fmt, l);
+}