irq: Support sleeping when mcu is idle

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/pru/main.c

@@ -46,12 +46,24 @@ irq_restore(irqstatus_t flag)
 {
 }
 
+void
+irq_wait(void)
+{
+    asm("slp 1");
+}
+
 static void
 timer_set(uint32_t value)
 {
     CT_IEP.TMR_CMP0 = value;
 }
 
+uint32_t
+timer_get_next(void)
+{
+    return CT_IEP.TMR_CMP0;
+}
+
 uint32_t
 timer_read_time(void)
 {

src/pru/pru0.c

@@ -135,8 +135,7 @@ static void
 process_io(void)
 {
     for (;;) {
-        if (!(read_r31() & (1 << (WAKE_PRU0_IRQ + R31_IRQ_OFFSET))))
-            continue;
+        asm("slp 1");
         CT_INTC.SECR0 = (1 << KICK_PRU0_FROM_ARM_EVENT) | (1 << KICK_PRU0_EVENT);
         check_can_send();
         check_can_read();
@@ -327,6 +326,10 @@ main(void)
                              , CHAN_DESC, CHAN_PORT) != PRU_RPMSG_SUCCESS)
         ;
 
+    // Allow PRU0 and PRU1 to wake from sleep
+    PRU0_CTRL.WAKEUP_EN = 1 << (WAKE_PRU0_IRQ + R31_IRQ_OFFSET);
+    PRU1_CTRL.WAKEUP_EN = 1 << (WAKE_PRU1_IRQ + R31_IRQ_OFFSET);
+
     // Wait for PRU1 to be ready
     memset(SHARED_MEM, 0, sizeof(*SHARED_MEM));
     writel(&SHARED_MEM->signal, SIGNAL_PRU0_WAITING);