all: add HiFive1 rev B board with RISC-V architecture

This page has been a big help in adding support for this new chip:
https://wiki.osdev.org/HiFive-1_Bare_Bones

src/device/riscv/riscv.go

@@ -0,0 +1,10 @@
+package riscv
+
+// Run the given assembly code. The code will be marked as having side effects,
+// as it doesn't produce output and thus would normally be eliminated by the
+// optimizer.
+func Asm(asm string)
+
+// ReadRegister returns the contents of the specified register. The register
+// must be a processor register, reachable with the "mov" instruction.
+func ReadRegister(name string) uintptr

src/device/riscv/start.S

@@ -0,0 +1,13 @@
+.section .init
+.global _start
+.type _start,@function
+
+_start:
+    // Workaround for missing support of the la pseudo-instruction in Clang 8:
+    // https://reviews.llvm.org/D55325
+    lui sp,      %hi(_stack_top)
+    addi sp, sp, %lo(_stack_top)
+    // see https://gnu-mcu-eclipse.github.io/arch/riscv/programmer/#the-gp-global-pointer-register
+    lui gp,      %hi(__global_pointer$)
+    addi gp, gp, %lo(__global_pointer$)
+    call main

src/machine/board_fe310.go

@@ -0,0 +1,38 @@
+// +build hifive1b
+
+package machine
+
+const (
+	P00 Pin = 0
+	P01 Pin = 1
+	P02 Pin = 2
+	P03 Pin = 3
+	P04 Pin = 4
+	P05 Pin = 5
+	P06 Pin = 6
+	P07 Pin = 7
+	P08 Pin = 8
+	P09 Pin = 9
+	P10 Pin = 10
+	P11 Pin = 11
+	P12 Pin = 12
+	P13 Pin = 13
+	P14 Pin = 14
+	P15 Pin = 15
+	P16 Pin = 16
+	P17 Pin = 17
+	P18 Pin = 18
+	P19 Pin = 19
+	P20 Pin = 20
+	P21 Pin = 21
+	P22 Pin = 22
+	P23 Pin = 23
+	P24 Pin = 24
+	P25 Pin = 25
+	P26 Pin = 26
+	P27 Pin = 27
+	P28 Pin = 28
+	P29 Pin = 29
+	P30 Pin = 30
+	P31 Pin = 31
+)

src/machine/board_hifive1b.go

@@ -0,0 +1,19 @@
+// +build hifive1b
+
+package machine
+
+const (
+	LED       = LED1
+	LED1      = LED_RED
+	LED2      = LED_GREEN
+	LED3      = LED_BLUE
+	LED_RED   = P22
+	LED_GREEN = P19
+	LED_BLUE  = P21
+)
+
+const (
+	// TODO: figure out the pin numbers for these.
+	UART_TX_PIN = NoPin
+	UART_RX_PIN = NoPin
+)

src/machine/i2c.go

@@ -1,4 +1,4 @@
-// +build !stm32f4disco
+// +build !stm32f4disco,!hifive1b
 
 package machine
 

src/machine/machine_fe310.go

@@ -0,0 +1,54 @@
+// +build fe310
+
+package machine
+
+import (
+	"device/sifive"
+)
+
+type PinMode uint8
+
+const (
+	PinInput PinMode = iota
+	PinOutput
+)
+
+// Configure this pin with the given configuration.
+func (p Pin) Configure(config PinConfig) {
+	sifive.GPIO0.INPUT_EN.SetBits(1 << uint8(p))
+	if config.Mode == PinOutput {
+		sifive.GPIO0.OUTPUT_EN.SetBits(1 << uint8(p))
+	}
+}
+
+// Set the pin to high or low.
+func (p Pin) Set(high bool) {
+	if high {
+		sifive.GPIO0.PORT.SetBits(1 << uint8(p))
+	} else {
+		sifive.GPIO0.PORT.ClearBits(1 << uint8(p))
+	}
+}
+
+type UART struct {
+	Bus    *sifive.UART_Type
+	Buffer *RingBuffer
+}
+
+var (
+	UART0 = UART{Bus: sifive.UART0, Buffer: NewRingBuffer()}
+)
+
+func (uart UART) Configure(config UARTConfig) {
+	// Assuming a 16Mhz Crystal (which is Y1 on the HiFive1), the divisor for a
+	// 115200 baud rate is 138.
+	sifive.UART0.DIV.Set(138)
+	sifive.UART0.TXCTRL.Set(sifive.UART_TXCTRL_ENABLE)
+}
+
+func (uart UART) WriteByte(c byte) {
+	for sifive.UART0.TXDATA.Get()&sifive.UART_TXDATA_FULL != 0 {
+	}
+
+	sifive.UART0.TXDATA.Set(uint32(c))
+}

src/machine/machine_generic.go

@@ -1,4 +1,4 @@
-// +build !avr,!nrf,!sam,!stm32
+// +build !avr,!nrf,!sam,!sifive,!stm32
 
 package machine
 

src/machine/spi.go

@@ -1,4 +1,4 @@
-// +build !stm32f407,!avr
+// +build !stm32f407,!avr,!hifive1b
 
 package machine
 

src/machine/uart.go

@@ -1,4 +1,4 @@
-// +build avr nrf sam stm32
+// +build avr nrf sam sifive stm32
 
 package machine
 

src/os/file_other.go

@@ -1,4 +1,4 @@
-// +build avr cortexm wasm
+// +build avr cortexm tinygo.riscv wasm
 
 package os
 

src/os/file_unix.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!avr,!cortexm
+// +build darwin linux,!avr,!cortexm,!tinygo.riscv
 
 package os
 

src/runtime/arch_arm.go

@@ -1,4 +1,4 @@
-// +build arm,!avr,!cortexm
+// +build arm,!avr,!cortexm,!tinygo.riscv
 
 package runtime
 

src/runtime/arch_avr.go

@@ -2,26 +2,11 @@
 
 package runtime
 
-import (
-	"unsafe"
-)
-
-const GOARCH = "avr"
+const GOARCH = "arm" // avr pretends to be arm
 
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 8
 
-//go:extern _heap_start
-var heapStartSymbol unsafe.Pointer
-
-//go:extern _heap_end
-var heapEndSymbol unsafe.Pointer
-
-var (
-	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
-	heapEnd   = uintptr(unsafe.Pointer(&heapEndSymbol))
-)
-
 // Align on a word boundary.
 func align(ptr uintptr) uintptr {
 	// No alignment necessary on the AVR.

src/runtime/arch_cortexm.go

@@ -3,8 +3,6 @@
 package runtime
 
 import (
-	"unsafe"
-
 	"device/arm"
 )
 
@@ -13,29 +11,6 @@ const GOARCH = "arm"
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 32
 
-//go:extern _heap_start
-var heapStartSymbol unsafe.Pointer
-
-//go:extern _heap_end
-var heapEndSymbol unsafe.Pointer
-
-//go:extern _globals_start
-var globalsStartSymbol unsafe.Pointer
-
-//go:extern _globals_end
-var globalsEndSymbol unsafe.Pointer
-
-//go:extern _stack_top
-var stackTopSymbol unsafe.Pointer
-
-var (
-	heapStart    = uintptr(unsafe.Pointer(&heapStartSymbol))
-	heapEnd      = uintptr(unsafe.Pointer(&heapEndSymbol))
-	globalsStart = uintptr(unsafe.Pointer(&globalsStartSymbol))
-	globalsEnd   = uintptr(unsafe.Pointer(&globalsEndSymbol))
-	stackTop     = uintptr(unsafe.Pointer(&stackTopSymbol))
-)
-
 // Align on word boundary.
 func align(ptr uintptr) uintptr {
 	return (ptr + 3) &^ 3

src/runtime/arch_tinygoriscv.go

@@ -0,0 +1,19 @@
+// +build tinygo.riscv
+
+package runtime
+
+import "device/riscv"
+
+const GOARCH = "arm" // riscv pretends to be arm
+
+// The bitness of the CPU (e.g. 8, 32, 64).
+const TargetBits = 32
+
+// Align on word boundary.
+func align(ptr uintptr) uintptr {
+	return (ptr + 3) &^ 3
+}
+
+func getCurrentStackPointer() uintptr {
+	return riscv.ReadRegister("sp")
+}

src/runtime/baremetal.go

@@ -0,0 +1,30 @@
+// +build avr cortexm tinygo.riscv
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+//go:extern _heap_start
+var heapStartSymbol unsafe.Pointer
+
+//go:extern _heap_end
+var heapEndSymbol unsafe.Pointer
+
+//go:extern _globals_start
+var globalsStartSymbol unsafe.Pointer
+
+//go:extern _globals_end
+var globalsEndSymbol unsafe.Pointer
+
+//go:extern _stack_top
+var stackTopSymbol unsafe.Pointer
+
+var (
+	heapStart    = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd      = uintptr(unsafe.Pointer(&heapEndSymbol))
+	globalsStart = uintptr(unsafe.Pointer(&globalsStartSymbol))
+	globalsEnd   = uintptr(unsafe.Pointer(&globalsEndSymbol))
+	stackTop     = uintptr(unsafe.Pointer(&stackTopSymbol))
+)

src/runtime/gc_globals_conservative.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build cortexm
+// +build cortexm tinygo.riscv
 
 package runtime
 

src/runtime/gc_globals_precise.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build !cortexm
+// +build !cortexm,!tinygo.riscv
 
 package runtime
 

src/runtime/gc_stack_portable.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build !cortexm
+// +build !cortexm,!tinygo.riscv
 
 package runtime
 

src/runtime/gc_stack_raw.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build cortexm
+// +build cortexm tinygo.riscv
 
 package runtime
 

src/runtime/runtime_fe310.go

@@ -0,0 +1,115 @@
+// +build fe310
+
+// This file implements target-specific things for the FE310 chip as used in the
+// HiFive1.
+
+package runtime
+
+import (
+	"machine"
+	"unsafe"
+
+	"device/riscv"
+	"device/sifive"
+)
+
+type timeUnit int64
+
+const tickMicros = 32768 // RTC runs at 32.768kHz
+
+//go:extern _sbss
+var _sbss unsafe.Pointer
+
+//go:extern _ebss
+var _ebss unsafe.Pointer
+
+//go:extern _sdata
+var _sdata unsafe.Pointer
+
+//go:extern _sidata
+var _sidata unsafe.Pointer
+
+//go:extern _edata
+var _edata unsafe.Pointer
+
+//go:export main
+func main() {
+	preinit()
+	initAll()
+	callMain()
+	abort()
+}
+
+func init() {
+	pric_init()
+	machine.UART0.Configure(machine.UARTConfig{})
+}
+
+func pric_init() {
+	// Make sure the HFROSC is on
+	sifive.PRIC.HFROSCCFG.SetBits(sifive.PRIC_HFROSCCFG_ENABLE)
+
+	// Run off 16 MHz Crystal for accuracy.
+	sifive.PRIC.PLLCFG.SetBits(sifive.PRIC_PLLCFG_REFSEL | sifive.PRIC_PLLCFG_BYPASS)
+	sifive.PRIC.PLLCFG.SetBits(sifive.PRIC_PLLCFG_SEL)
+
+	// Turn off HFROSC to save power
+	sifive.PRIC.HFROSCCFG.ClearBits(sifive.PRIC_HFROSCCFG_ENABLE)
+
+	// Enable the RTC.
+	sifive.RTC.CONFIG.Set(sifive.RTC_CONFIG_ENALWAYS)
+}
+
+func preinit() {
+	// Initialize .bss: zero-initialized global variables.
+	ptr := uintptr(unsafe.Pointer(&_sbss))
+	for ptr != uintptr(unsafe.Pointer(&_ebss)) {
+		*(*uint32)(unsafe.Pointer(ptr)) = 0
+		ptr += 4
+	}
+
+	// Initialize .data: global variables initialized from flash.
+	src := uintptr(unsafe.Pointer(&_sidata))
+	dst := uintptr(unsafe.Pointer(&_sdata))
+	for dst != uintptr(unsafe.Pointer(&_edata)) {
+		*(*uint32)(unsafe.Pointer(dst)) = *(*uint32)(unsafe.Pointer(src))
+		dst += 4
+		src += 4
+	}
+}
+
+func putchar(c byte) {
+	machine.UART0.WriteByte(c)
+}
+
+func ticks() timeUnit {
+	// Combining the low bits and the high bits yields a time span of over 270
+	// years without counter rollover.
+	highBits := sifive.RTC.HI.Get()
+	for {
+		lowBits := sifive.RTC.LO.Get()
+		newHighBits := sifive.RTC.HI.Get()
+		if newHighBits == highBits {
+			// High bits stayed the same.
+			return timeUnit(lowBits) | (timeUnit(highBits) << 32)
+		}
+		// Retry, because there was a rollover in the low bits (happening every
+		// 1.5 days).
+		highBits = newHighBits
+	}
+}
+
+const asyncScheduler = false
+
+func sleepTicks(d timeUnit) {
+	target := ticks() + d
+	for ticks() < target {
+	}
+}
+
+func abort() {
+	// lock up forever
+	for {
+		riscv.Asm("wfi")
+	}
+}

src/runtime/runtime_tinygoriscv.go

@@ -0,0 +1,19 @@
+// +build tinygo.riscv
+
+package runtime
+
+import "unsafe"
+
+// Implement memset for LLVM.
+//go:export memset
+func libc_memset(ptr unsafe.Pointer, c byte, size uintptr) {
+	for i := uintptr(0); i < size; i++ {
+		*(*byte)(unsafe.Pointer(uintptr(ptr) + i)) = c
+	}
+}
+
+// Implement memmove for LLVM.
+//go:export memmove
+func libc_memmove(dst, src unsafe.Pointer, size uintptr) {
+	memmove(dst, src, size)
+}

src/runtime/runtime_unix.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!avr,!cortexm
+// +build darwin linux,!avr,!cortexm,!tinygo.riscv
 
 package runtime