systick: provide access to a global count of systick cycles

System tick is now maintening a global count of cycles at main clock
frequency, independantly of the systick timer interrupt frequency.

The number of cycles can be obtained using systick_get_tick_cycles().

diff --git a/core/systick.c b/core/systick.c
index 266250d..18fdc1e 100644 (file)
--- a/core/systick.c
+++ b/core/systick.c
@@ -34,8 +34,11 @@
 static volatile uint32_t sleep_count = 0;
 static volatile uint32_t tick_ms = 0;
 static volatile uint32_t systick_running = 0;
+static volatile uint32_t tick_reload = 0;
 
 /* Wraps every 50 days or so with a 1ms tick */
+static volatile uint32_t global_wrapping_system_ticks_cycles;
+/* The systick cycles run at get_main_clock(), and would wrap more often! */
 static volatile uint32_t global_wrapping_system_ticks = 0;
 
 
@@ -51,6 +54,7 @@ void SysTick_Handler(void)
 {
        int i = 0;
        global_wrapping_system_ticks++;
+       global_wrapping_system_ticks_cycles += tick_reload;
        if (sleep_count != 0) {
                sleep_count--;
        }
@@ -139,6 +143,12 @@ uint32_t systick_get_tick_count(void)
        return global_wrapping_system_ticks;
 }
 
+uint32_t systick_get_tick_cycles(void)
+{
+       struct lpc_system_tick* systick = LPC_SYSTICK;
+       return global_wrapping_system_ticks_cycles - systick->value;
+}
+
 /***************************************************************************** */
 /* Power up the system tick timer.
  * ms is the interval between system tick timer interrupts. If set to 0, the default
@@ -160,8 +170,10 @@ void systick_timer_on(uint32_t ms)
        reload = reload >> 1; /* Divide by 2 */
        systick->reload_val = (reload & 0xffffff);
        tick_ms = ms;
+       tick_reload = systick->reload_val;
 
        /* Start counting from the reload value, writting anything would do ... */
+       global_wrapping_system_ticks_cycles = tick_reload;
        systick->value = reload;
 
        /* And enable counter interrupt */
@@ -179,6 +191,7 @@ void systick_timer_off(void)
        systick->control = 0;
        systick->reload_val = 0;
        tick_ms = 0;
+       tick_reload = 0;
        systick_running = 0;
 }
 

diff --git a/include/core/system.h b/include/core/system.h
index 8686bd6..e1f5a7b 100644 (file)
--- a/include/core/system.h
+++ b/include/core/system.h
@@ -129,6 +129,8 @@ uint32_t systick_get_timer_val(void);
 
 /* Get the system tick */
 uint32_t systick_get_tick_count(void);
+/* Get the systick cycles since start */
+uint32_t systick_get_tick_cycles(void);
 
 /* Power up the system tick timer.
  * ms is the interval between system tick timer interrupts. If set to 0, the default