a04db67ea9
See the following bug: https://bugs.llvm.org/show_bug.cgi?id=42881 I think this is a bug in LLVM, but the code in question wasn't the best code anyway. By fixing this, about 16 bytes of code are saved on ARM chips (and much more on AVR).
115 строки
2,3 КиБ
Go
115 строки
2,3 КиБ
Go
// +build fe310
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// This file implements target-specific things for the FE310 chip as used in the
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// HiFive1.
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package runtime
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import (
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"machine"
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"unsafe"
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"device/riscv"
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"device/sifive"
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)
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type timeUnit int64
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const tickMicros = 32768 // RTC runs at 32.768kHz
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//go:extern _sbss
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var _sbss unsafe.Pointer
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//go:extern _ebss
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var _ebss unsafe.Pointer
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//go:extern _sdata
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var _sdata unsafe.Pointer
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//go:extern _sidata
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var _sidata unsafe.Pointer
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//go:extern _edata
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var _edata unsafe.Pointer
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//go:export main
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func main() {
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preinit()
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initAll()
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callMain()
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abort()
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}
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func init() {
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pric_init()
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machine.UART0.Configure(machine.UARTConfig{})
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}
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func pric_init() {
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// Make sure the HFROSC is on
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sifive.PRIC.HFROSCCFG.SetBits(sifive.PRIC_HFROSCCFG_ENABLE)
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// Run off 16 MHz Crystal for accuracy.
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sifive.PRIC.PLLCFG.SetBits(sifive.PRIC_PLLCFG_REFSEL | sifive.PRIC_PLLCFG_BYPASS)
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sifive.PRIC.PLLCFG.SetBits(sifive.PRIC_PLLCFG_SEL)
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// Turn off HFROSC to save power
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sifive.PRIC.HFROSCCFG.ClearBits(sifive.PRIC_HFROSCCFG_ENABLE)
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// Enable the RTC.
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sifive.RTC.CONFIG.Set(sifive.RTC_CONFIG_ENALWAYS)
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}
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func preinit() {
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// Initialize .bss: zero-initialized global variables.
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ptr := unsafe.Pointer(&_sbss)
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for ptr != unsafe.Pointer(&_ebss) {
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*(*uint32)(ptr) = 0
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ptr = unsafe.Pointer(uintptr(ptr) + 4)
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}
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// Initialize .data: global variables initialized from flash.
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src := unsafe.Pointer(&_sidata)
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dst := unsafe.Pointer(&_sdata)
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for dst != unsafe.Pointer(&_edata) {
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*(*uint32)(dst) = *(*uint32)(src)
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dst = unsafe.Pointer(uintptr(dst) + 4)
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src = unsafe.Pointer(uintptr(src) + 4)
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}
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}
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func putchar(c byte) {
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machine.UART0.WriteByte(c)
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}
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func ticks() timeUnit {
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// Combining the low bits and the high bits yields a time span of over 270
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// years without counter rollover.
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highBits := sifive.RTC.HI.Get()
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for {
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lowBits := sifive.RTC.LO.Get()
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newHighBits := sifive.RTC.HI.Get()
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if newHighBits == highBits {
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// High bits stayed the same.
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return timeUnit(lowBits) | (timeUnit(highBits) << 32)
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}
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// Retry, because there was a rollover in the low bits (happening every
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// 1.5 days).
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highBits = newHighBits
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}
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}
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const asyncScheduler = false
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func sleepTicks(d timeUnit) {
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target := ticks() + d
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for ticks() < target {
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}
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}
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func abort() {
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// lock up forever
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for {
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riscv.Asm("wfi")
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}
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}
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