riscv: define CSR constants and use them where possible

src/device/riscv/csr.go

@@ -275,3 +275,61 @@ const (
 	DPC      CSR = 0x7B1 // Debug PC.
 	DSCRATCH CSR = 0x7B2 // Debug scratch register.
 )
+
+// Bitfields for the CSR registers above.
+const (
+	// MSTATUS (common bits between RV32 and RV64)
+	MSTATUS_SIE  = 1 << 1
+	MSTATUS_MIE  = 1 << 3
+	MSTATUS_SPIE = 1 << 5
+	MSTATUS_UBE  = 1 << 6
+	MSTATUS_MPIE = 1 << 7
+	MSTATUS_SPP  = 1 << 8
+	MSTATUS_MPRV = 1 << 17
+	MSTATUS_SUM  = 1 << 18
+	MSTATUS_MXR  = 1 << 19
+	MSTATUS_TVM  = 1 << 20
+	MSTATUS_TW   = 1 << 21
+	MSTATUS_TSR  = 1 << 22
+
+	MIE_SSIE = 1 << 1
+	MIE_MSIE = 1 << 3
+	MIE_STIE = 1 << 5
+	MIE_MTIE = 1 << 7
+	MIE_SEIE = 1 << 9
+	MIE_MEIE = 1 << 11
+
+	MIP_SSIP = 1 << 1
+	MIP_MSIP = 1 << 3
+	MIP_STIP = 1 << 5
+	MIP_MTIP = 1 << 7
+	MIP_SEIP = 1 << 9
+	MIP_MEIP = 1 << 11
+)
+
+// Interrupt constants
+const (
+	// MCAUSE values with the topmost bit (interrupt bit) set.
+	SupervisorSoftwareInterrupt = 1
+	MachineSoftwareInterrupt    = 3
+	SupervisorTimerInterrupt    = 5
+	MachineTimerInterrupt       = 7
+	SupervisorExternalInterrupt = 9
+	MachineExternalInterrupt    = 11
+
+	// MCAUSE values with the topmost bit (interrupt bit) clear.
+	InstructionAddressMisaligned = 0
+	InstructionAccessFault       = 1
+	IllegalInstruction           = 2
+	Breakpoint                   = 3
+	LoadAddressMisaligned        = 4
+	LoadAccessFault              = 5
+	StoreOrAMOAddressMisaligned  = 6
+	StoreOrAMOAccessFault        = 7
+	EnvironmentCallFromUMode     = 8
+	EnvironmentCallFromSMode     = 9
+	EnvironmentCallFromMMode     = 11
+	InstructionPageFault         = 12
+	LoadPageFault                = 13
+	StoreOrAMOPageFault          = 15
+)

src/runtime/interrupt/interrupt_esp32c3.go

@@ -189,13 +189,13 @@ func handleInterrupt() {
 		}
 
 		// enable CPU interrupts
-		riscv.MSTATUS.SetBits(1 << 3)
+		riscv.MSTATUS.SetBits(riscv.MSTATUS_MIE)
 
 		// Call registered interrupt handler(s)
 		callHandler(int(interruptNumber))
 
 		// disable CPU interrupts
-		riscv.MSTATUS.ClearBits(1 << 3)
+		riscv.MSTATUS.ClearBits(riscv.MSTATUS_MIE)
 
 		// restore interrupt threshold to enable interrupt again
 		reg.Set(thresholdSave)
@@ -207,7 +207,7 @@ func handleInterrupt() {
 
 		// do not enable CPU interrupts now
 		// the 'MRET' in src/device/riscv/handleinterrupt.S will copies the state of MPIE back into MIE, and subsequently clears MPIE.
-		// riscv.MSTATUS.SetBits(0x8)
+		// riscv.MSTATUS.SetBits(riscv.MSTATUS_MIE)
 	} else {
 		// Topmost bit is clear, so it is an exception of some sort.
 		// We could implement support for unsupported instructions here (such as
@@ -221,13 +221,13 @@ func handleException(mcause uintptr) {
 	println("*** Exception:   code:", uint32(mcause&0x1f))
 	println("*** Exception: mcause:", mcause)
 	switch uint32(mcause & 0x1f) {
-	case 1:
+	case riscv.InstructionAccessFault:
 		println("***    virtual address:", riscv.MTVAL.Get())
-	case 2:
+	case riscv.IllegalInstruction:
 		println("***            opcode:", riscv.MTVAL.Get())
-	case 5:
+	case riscv.LoadAccessFault:
 		println("***      read address:", riscv.MTVAL.Get())
-	case 7:
+	case riscv.StoreOrAMOAccessFault:
 		println("***     write address:", riscv.MTVAL.Get())
 	}
 	for {

src/runtime/runtime_fe310.go

@@ -38,10 +38,10 @@ func main() {
 
 	// Reset the MIE register and enable external interrupts.
 	// It must be reset here because it not zeroed at startup.
-	riscv.MIE.Set(1 << 11) // bit 11 is for machine external interrupts
+	riscv.MIE.Set(riscv.MIE_MEIE)
 
 	// Enable global interrupts now that they've been set up.
-	riscv.MSTATUS.SetBits(1 << 3) // MIE
+	riscv.MSTATUS.SetBits(riscv.MSTATUS_MIE) // MIE: machine external interrupts
 
 	preinit()
 	initPeripherals()
@@ -59,13 +59,13 @@ func handleInterrupt() {
 	if cause&(1<<31) != 0 {
 		// Topmost bit is set, which means that it is an interrupt.
 		switch code {
-		case 7: // Machine timer interrupt
+		case riscv.MachineTimerInterrupt:
 			// Signal timeout.
 			timerWakeup.Set(1)
 			// Disable the timer, to avoid triggering the interrupt right after
 			// this interrupt returns.
-			riscv.MIE.ClearBits(1 << 7) // MTIE bit
+			riscv.MIE.ClearBits(riscv.MIE_MTIE)
-		case 11: // Machine external interrupt
+		case riscv.MachineExternalInterrupt:
 			// Claim this interrupt.
 			id := sifive.PLIC.CLAIM.Get()
 			// Call the interrupt handler, if any is registered for this ID.
@@ -143,7 +143,7 @@ func sleepTicks(d timeUnit) {
 	target := uint64(ticks() + d)
 	sifive.CLINT.MTIMECMPH.Set(uint32(target >> 32))
 	sifive.CLINT.MTIMECMP.Set(uint32(target))
-	riscv.MIE.SetBits(1 << 7) // MTIE
+	riscv.MIE.SetBits(riscv.MIE_MTIE)
 	for {
 		if timerWakeup.Get() != 0 {
 			timerWakeup.Set(0)

src/runtime/runtime_k210.go

@@ -44,10 +44,10 @@ func main() {
 
 	// Reset the MIE register and enable external interrupts.
 	// It must be reset here because it not zeroed at startup.
-	riscv.MIE.Set(1 << 11) // bit 11 is for machine external interrupts
+	riscv.MIE.Set(riscv.MIE_MEIE) // MEIE is for machine external interrupts
 
 	// Enable global interrupts now that they've been set up.
-	riscv.MSTATUS.SetBits(1 << 3) // MIE
+	riscv.MSTATUS.SetBits(riscv.MSTATUS_MIE)
 
 	preinit()
 	initPeripherals()
@@ -77,13 +77,13 @@ func handleInterrupt() {
 	if cause&(1<<63) != 0 {
 		// Topmost bit is set, which means that it is an interrupt.
 		switch code {
-		case 7: // Machine timer interrupt
+		case riscv.MachineTimerInterrupt:
 			// Signal timeout.
 			timerWakeup.Set(1)
 			// Disable the timer, to avoid triggering the interrupt right after
 			// this interrupt returns.
-			riscv.MIE.ClearBits(1 << 7) // MTIE bit
+			riscv.MIE.ClearBits(riscv.MIE_MTIE)
-		case 11: // Machine external interrupt
+		case riscv.MachineExternalInterrupt:
 			hartId := riscv.MHARTID.Get()
 
 			// Claim this interrupt.
@@ -149,7 +149,7 @@ func ticks() timeUnit {
 func sleepTicks(d timeUnit) {
 	target := uint64(ticks() + d)
 	kendryte.CLINT.MTIMECMP[0].Set(target)
-	riscv.MIE.SetBits(1 << 7) // MTIE
+	riscv.MIE.SetBits(riscv.MIE_MTIE)
 	for {
 		if timerWakeup.Get() != 0 {
 			timerWakeup.Set(0)