mbv: small refactor interrupts

mbv/hal/intc.cc

@@ -1,7 +1,9 @@
 #include "intc.h"
 
+// this interrupt controller is tied to the pol0 design
 #include "pol0.h"
 
+namespace intc {
 namespace {
 
 struct IntC {
@@ -22,7 +24,7 @@ struct IntC {
 IntC* intc = reinterpret_cast<IntC*>(INTC_BASE);
 Isr isrs[NIRQ] = {};
 
-}
+}  // namespace
 
 bool SetIrqEnabled(uint8_t irqn, bool enabled) {
     uint32_t mask = 1 << irqn;
@@ -60,3 +62,5 @@ void InterruptHandler() {
         }
     }
 }
+
+}  // namespace intc

mbv/hal/intc.h

@@ -2,6 +2,8 @@
 
 #include <cstdint>
 
+namespace intc {
+
 using Isr = void(*)(void);
 
 /// Returns: true if the IRQ was previously enabled
@@ -14,3 +16,5 @@ void EnableInterrupts();
 
 // Feed this to the CPU's interrupt handler
 void InterruptHandler();
+
+}  // namespace intc

mbv/hal/interrupts.cc

@@ -1,5 +1,6 @@
 #include <cstdint>
 
+#include "bios.h"
 #include "interrupts.h"
 
 namespace {
@@ -26,27 +27,40 @@ void TrapHandler() {
 
         mip &= ~(kMieExternalInterruptMask);
         asm volatile("csrw mip, %0" :: "r"(mip));
+    } else {
+        BiosWozmon();
     }
 }
 
-}
+}  // namespace
 
 void SetExternalInterruptHandler(Isr handler) {
     external_handler = handler;
 }
 
 void EnableExternalInterrupts() {
-    uint32_t mstatus;
     uint32_t mie;
     Isr trap = TrapHandler;
 
-    asm volatile("csrr %0, mstatus" : "=r"(mstatus));
     asm volatile("csrr %0, mie" : "=r"(mie));
-
     asm volatile("csrw mtvec, %0" :: "r"(trap));
-
     mie |= kMieExternalInterruptMask;
     asm volatile("csrw mie, %0" :: "r"(mie));
-    mstatus |= kMstatusMieMask;
-    asm volatile("csrw mstatus, %0" :: "r"(mstatus));
+}
+
+bool EnableInterrupts(bool on) {
+    uint32_t mstatus;
+    bool was_on;
+    asm volatile("csrr %0, mstatus" : "=r"(mstatus));
+
+    was_on = (mstatus & kMstatusMieMask) > 0;
+
+    if (on) {
+        mstatus |= kMstatusMieMask;
+    } else {
+        mstatus &= ~kMstatusMieMask;
+    }
+
+    asm volatile("csrw mstatus, %0" :: "r"(mstatus));
+    return was_on;
 }

mbv/hal/interrupts.h

@@ -4,3 +4,6 @@ using Isr = void(*)();
 
 void SetExternalInterruptHandler(Isr handler);
 void EnableExternalInterrupts();
+
+/** Returns true if interrupts were enabled, false otherwise */
+bool EnableInterrupts(bool on);