1 files changed, 250 insertions, 0 deletions
diff --git a/software/global_interrupts/global_interrupts.c b/software/global_interrupts/global_interrupts.c
new file mode 100644
index 0000000..4d3a554
--- /dev/null
+++ b/software/global_interrupts/global_interrupts.c
@@ -0,0 +1,250 @@
+// See LICENSE for license details.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "platform.h"
+#include <string.h>
+#include "plic/plic_driver.h"
+#include "encoding.h"
+#include <unistd.h>
+
+#ifndef _SIFIVE_COREPLEXIP_ARTY_H
+#error 'global_interrupts' demo only supported for Coreplex IP Eval Kits
+#endif
+
+// Global Instance data for the PLIC
+// for use by the PLIC Driver.
+plic_instance_t g_plic;
+
+// Flag for state
+int g_switch1Wins;
+
+// Debounce counter (PWM can't go slow enough)
+int g_debounce;
+
+void debounce();
+
+// Structures for registering different interrupt handlers
+// for different parts of the application.
+typedef void (*interrupt_function_ptr_t) (void);
+
+// See bsp/env/<BOARD>/init.c for how this
+// interrupt vector is used.
+interrupt_function_ptr_t localISR[32]; 
+
+interrupt_function_ptr_t g_ext_interrupt_handlers[PLIC_NUM_INTERRUPTS];
+
+void set_timer() {
+  
+  volatile uint64_t * mtime       = (uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIME);
+  volatile uint64_t * mtimecmp    = (uint64_t*) (CLINT_CTRL_ADDR + CLINT_MTIMECMP);
+  uint64_t now = *mtime;
+  uint64_t then = now + 10*RTC_FREQ;
+  *mtimecmp = then;
+
+}
+
+/*Entry Point for Machine Timer Interrupt Handler*/
+void mti_isr(){
+ 
+  if (g_switch1Wins) {
+    printf("#### Giving Switch 1 Priority for 10 seconds ####\n");
+    // All other things being equal, lower IDs have
+    // higher priority. We have already set
+    // Switch 1 to priority 2
+    // in the setup, so by giving these equal priority Switch 1 will win.
+    PLIC_set_priority(&g_plic, INT_EXT_DEVICE_SW_2, 2);
+  } else {
+    printf("**** Giving Switch 2 Priority for 10 seconds ****\n");
+    // By setting Switch 2 a higher integer priority, it will win over switch 1.
+    PLIC_set_priority(&g_plic, INT_EXT_DEVICE_SW_2, 3);
+  }    
+  g_switch1Wins ^= 0x1;
+
+  set_timer();
+
+}
+
+/*Entry Point for PLIC Interrupt Handler*/
+void mei_isr(){
+  plic_source int_num  = PLIC_claim_interrupt(&g_plic);
+  if ((int_num >=1 ) && (int_num < PLIC_NUM_INTERRUPTS)) {
+    g_ext_interrupt_handlers[int_num]();
+  }
+  else {
+    exit(1 + (uintptr_t) int_num);
+  }
+  PLIC_complete_interrupt(&g_plic, int_num);
+}
+
+const char * instructions_msg = " \
+\n\
+                SIFIVE, INC.\n\
+E31/E51 Coreplex IP Eval Kit 'global_interrupts' demo.\n\
+\n\
+Switches  1 and 2 are enabled as External Global Interrupts \n\
+(they don't go through the PLIC). You an observe priorities.\n\
+Priorities invert every few seconds, which is driven by the \n\
+PWM0 global interrupt.                                      \n\
+\n";
+
+void print_instructions() {
+
+  write (STDOUT_FILENO, instructions_msg, strlen(instructions_msg));
+
+}
+
+void invalid_global_isr() {
+  printf("Unexpected global interrupt!\n");
+}
+
+void invalid_local_isr() {
+  printf ("Unexpected local interrupt!\n");
+}
+
+void switch_1_handler() {
+
+  printf("Switch 1 is on! Even if Switch 2 is on, Switch 1 must have higher priority right now.\n");
+  
+  // Set Green LED
+  GPIO_REG(GPIO_OUTPUT_VAL)  |=  (0x1 << GREEN_LED_OFFSET) ;
+  GPIO_REG(GPIO_OUTPUT_VAL)  &=  ~((0x1<< RED_LED_OFFSET));
+
+  debounce();
+  
+}
+
+void switch_2_handler() {
+  printf("Switch 2 is on! Even if Switch 1 is on, Switch 2 must have higher priority right now.\n");
+
+  // Set RED LED
+  GPIO_REG(GPIO_OUTPUT_VAL)  &=  ~(0x1 << GREEN_LED_OFFSET) ;
+  GPIO_REG(GPIO_OUTPUT_VAL)  |=   (0x1<< RED_LED_OFFSET);
+
+  debounce();
+}
+
+// We use PWM 0 as a 
+// timer interrupt for debouncing.
+
+void pwm_0_handler() {
+
+
+  if (g_debounce == 0) {
+    printf("    Done debouncing.\n");
+    
+    //Lower the threshold s.t. the switches can hit.
+    PLIC_set_threshold(&g_plic, 1);
+    
+    // Clear the PWM interrupt
+    PWM0_REG(PWM_CFG) = 0;
+    
+  } else {
+    // Keep waiting
+    g_debounce --;
+    // This clears out the interrupt and re-arms the timer.
+    PWM0_REG(PWM_CFG) = ((PWM_CFG_ONESHOT) | (PWM_CFG_ZEROCMP)| 0x7 | (PWM_CFG_STICKY));
+    
+  }
+
+}
+
+void debounce(int local_interrupt_num) {
+
+  printf("    Starting a debounce.\n");
+
+  g_debounce = 600;
+  
+  // This clears out the interrupt and re-arms the timer.
+  PWM0_REG(PWM_CFG) = ((PWM_CFG_ONESHOT) | (PWM_CFG_ZEROCMP)| 0x7 | (PWM_CFG_STICKY));
+  
+  // Set the threshold high enough that the
+  // switches won't cause the interrupt to fire,
+  // only the PWM or timer interrupts.
+  PLIC_set_threshold(&g_plic, 4);
+
+}
+
+int main(int argc, char **argv)
+{
+
+  for (int gisr = 0; gisr < PLIC_NUM_INTERRUPTS; gisr++){
+    g_ext_interrupt_handlers[PLIC_NUM_INTERRUPTS] = invalid_global_isr;
+  }
+  g_ext_interrupt_handlers[PWM0_INT_BASE + 0] = pwm_0_handler;
+  g_ext_interrupt_handlers[INT_EXT_DEVICE_SW_1] = switch_1_handler;
+  g_ext_interrupt_handlers[INT_EXT_DEVICE_SW_2] = switch_2_handler;
+  
+  for (int lisr = 0; lisr < 32; lisr++){
+    localISR[lisr] = invalid_local_isr;
+  }
+  
+  localISR[IRQ_M_TIMER] = mti_isr;
+  localISR[IRQ_M_EXT]   = mei_isr;
+
+  print_instructions();
+  
+  // Set up RGB LEDs for a visual.
+  
+  GPIO_REG(GPIO_OUTPUT_EN)   |=  ((0x1<< RED_LED_OFFSET)| (0x1<< GREEN_LED_OFFSET));
+  GPIO_REG(GPIO_OUTPUT_VAL)  |=  (0x1 << GREEN_LED_OFFSET) ;
+  GPIO_REG(GPIO_OUTPUT_VAL)  &=  ~(0x1<< RED_LED_OFFSET);
+				   
+  /**************************************************************************
+   * Set up the PLIC
+   *
+   *************************************************************************/
+  PLIC_init(&g_plic,
+	    PLIC_CTRL_ADDR,
+	    PLIC_NUM_INTERRUPTS,
+	    PLIC_NUM_PRIORITIES);
+
+  /**************************************************************************
+   * Give Switch 1 and Switch 2 Equal priority of 2.
+   *
+   *************************************************************************/
+
+  PLIC_enable_interrupt (&g_plic, PWM0_INT_BASE + 0);
+  PLIC_enable_interrupt (&g_plic, INT_EXT_DEVICE_SW_1);
+  PLIC_enable_interrupt (&g_plic, INT_EXT_DEVICE_SW_2);
+
+  // PWM always beats the switches, because we use it
+  // as a debouncer, and we lower the threshold
+  // to do so.
+
+  PWM0_REG(PWM_CFG) = 0;
+
+  // Make sure people aren't blinded by LEDs connected here.
+  PWM0_REG(PWM_CMP0)  = 0xFE;
+  PWM0_REG(PWM_CMP1)  = 0xFF;
+  PWM0_REG(PWM_CMP2)  = 0xFF;
+  PWM0_REG(PWM_CMP3)  = 0xFF;
+  PLIC_set_priority(&g_plic, PWM0_INT_BASE + 0   , 5);
+
+  // Start the switches out at the same priority. Switch1
+  // would win.
+  PLIC_set_priority(&g_plic, INT_EXT_DEVICE_SW_1, 2);
+  PLIC_set_priority(&g_plic, INT_EXT_DEVICE_SW_2, 2);
+
+  // Set up machine timer interrupt. Every few seconds it
+  // will invert the switch priorities.
+  set_timer();
+
+  // Enable timer interrupts.
+  set_csr(mie, MIP_MTIP);
+
+  // Enable Global (PLIC) interrupts.
+  set_csr(mie, MIP_MEIP);
+
+  g_switch1Wins = 1;
+  
+  // Enable all interrupts
+  set_csr(mstatus, MSTATUS_MIE);
+  
+  while(1){
+    asm volatile ("wfi");
+  }
+  
+  return 0;
+
+}