System Calls cleanup, multiple Processes and context switch

[cortex-from-scratch] / systick.c

diff --git a/systick.c b/systick.c
index ed062c0..f459512 100644 (file)
--- a/systick.c
+++ b/systick.c
@@ -1,8 +1,25 @@
+/* (CC-BY-NC-SA) ROBIN KRENS - ROBIN @ ROBINKRENS.NL
+ * 
+ * $LOG$
+ * 2019/8/14 - ROBIN KRENS     
+ * Initial version 
+ * 
+ * $DESCRIPTION$
+ * SysTick of Cortex M* MCUs. Have a look at the more complex RTC 
+ * in case more accurate timing is needed.
+ *
+ * 
+ * */
+
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
-#include <stm32.h>
-#include <mmap.h>
+
+#include <sys/robsys.h>
+#include <sys/mmap.h>
+
+#include <lib/regfunc.h>
+#include <lib/tinyprintf.h>
 
 struct interrupt_frame {
 
@@ -19,25 +36,58 @@ struct interrupt_frame {
 //__attribute__ ((interrupt))
 void * systick_handler(/* struct interrupt_frame * frame */) {
 
-//     uint32_t volatile status;
-       uart_puts("TICKING\n");
-//     for(;;);
+       printf("Ticking...\n");
+
 }
 
 
-void systick_init() {
+__attribute__ ((naked))
+               void * pendsv_handler_c(void) {
+//
+//     asm volatile ("push {r0-r11, lr}");
+//     asm volatile ("mrs %0, psp" : "=r" (oldpsp));
+//     asm volatile ("push {lr}");
+//
+//     //asm volatile ("push {lr}");
+//     
+//     //printf("FROM MSP %x", oldpsp);
+//     //PSP_array[curr_task] = oldpsp;
+//     //curr_task = next_task;
+//     //newpsp = PSP_array[next_task];        
+//
+//     asm volatile ("msr psp, %0" : : "r" (newpsp)); 
+//
+//     asm volatile("pop {lr}");
+//     //asm volatile ("pop {r0-r12}");
+//     asm volatile("bx lr"); // return
+}
 
-       /* Enable the counter and enable the interrupt
-        * associated with it */
-       *STK_CTRL = (volatile uint32_t) 0x00000003;
+uint32_t set_psp(uint32_t) __attribute__( ( naked ) );
+uint32_t set_psp(uint32_t stackie) {
+  
+       asm volatile ("msr psp, r0" "\n\t"
+                 "bx lr");
+}
 
-       /* The counter reload register here holds 
-        * 0x1000 -- that's 4096 clock cycles -- if 
-        * it is down to zero it is restores the value */
-       *STK_RELOAD = (volatile uint32_t) 0x00400000; 
+void systick_init() {
 
        /* Every time the counter counts down to zero
-        * a systick exception is asserted. Systick has
+        * a systick exception is invoked. Systick has
         * exception number 15. in the vector table  */
        ivt_set_gate(15, systick_handler, 0); 
+
+       /* Get calibration and set this to 1 sec
+        * !Most boards have a 1 ms or 10 ms 
+        * calibration value */
+       int calib = (*STK_CALIB << 0) * 200;
+
+       /* The counter reload registers counts down to zero
+        * and then it is restores the value */
+       rwrite(STK_RELOAD, calib);
+       
+       /* Enable the counter and enable the interrupt
+        * associated with it */
+       rsetbit(STK_CTRL, 0);
+       rsetbit(STK_CTRL, 1);
+
 }