machine/stm32, nrf: flash API (#3472)

machine/stm32, nrf: implement machine.Flash

Implements the machine.Flash interface using the same definition as the tinyfs BlockDevice.

This implementation covers the stm32f4, stm32l4, stm32wlx, nrf51, nrf52, and nrf528xx processors.

src/machine/machine_nrf.go

@@ -3,7 +3,9 @@
 package machine
 
 import (
+	"bytes"
 	"device/nrf"
+	"encoding/binary"
 	"runtime/interrupt"
 	"unsafe"
 )
@@ -382,3 +384,109 @@ func ReadTemperature() int32 {
 	nrf.TEMP.EVENTS_DATARDY.Set(0)
 	return temp
 }
+
+const memoryStart = 0x0
+
+// compile-time check for ensuring we fulfill BlockDevice interface
+var _ BlockDevice = flashBlockDevice{}
+
+var Flash flashBlockDevice
+
+type flashBlockDevice struct {
+}
+
+// ReadAt reads the given number of bytes from the block device.
+func (f flashBlockDevice) ReadAt(p []byte, off int64) (n int, err error) {
+	if FlashDataStart()+uintptr(off)+uintptr(len(p)) > FlashDataEnd() {
+		return 0, errFlashCannotReadPastEOF
+	}
+
+	data := unsafe.Slice((*byte)(unsafe.Pointer(FlashDataStart()+uintptr(off))), len(p))
+	copy(p, data)
+
+	return len(p), nil
+}
+
+// WriteAt writes the given number of bytes to the block device.
+// Only double-word (64 bits) length data can be programmed. See rm0461 page 78.
+// If the length of p is not long enough it will be padded with 0xFF bytes.
+// This method assumes that the destination is already erased.
+func (f flashBlockDevice) WriteAt(p []byte, off int64) (n int, err error) {
+	if FlashDataStart()+uintptr(off)+uintptr(len(p)) > FlashDataEnd() {
+		return 0, errFlashCannotWritePastEOF
+	}
+
+	address := FlashDataStart() + uintptr(off)
+	padded := f.pad(p)
+
+	waitWhileFlashBusy()
+
+	nrf.NVMC.SetCONFIG_WEN(nrf.NVMC_CONFIG_WEN_Wen)
+	defer nrf.NVMC.SetCONFIG_WEN(nrf.NVMC_CONFIG_WEN_Ren)
+
+	for j := 0; j < len(padded); j += int(f.WriteBlockSize()) {
+		// write word
+		*(*uint32)(unsafe.Pointer(address)) = binary.LittleEndian.Uint32(padded[j : j+int(f.WriteBlockSize())])
+		address += uintptr(f.WriteBlockSize())
+		waitWhileFlashBusy()
+	}
+
+	return len(padded), nil
+}
+
+// Size returns the number of bytes in this block device.
+func (f flashBlockDevice) Size() int64 {
+	return int64(FlashDataEnd() - FlashDataStart())
+}
+
+const writeBlockSize = 4
+
+// WriteBlockSize returns the block size in which data can be written to
+// memory. It can be used by a client to optimize writes, non-aligned writes
+// should always work correctly.
+func (f flashBlockDevice) WriteBlockSize() int64 {
+	return writeBlockSize
+}
+
+// EraseBlockSize returns the smallest erasable area on this particular chip
+// in bytes. This is used for the block size in EraseBlocks.
+// It must be a power of two, and may be as small as 1. A typical size is 4096.
+func (f flashBlockDevice) EraseBlockSize() int64 {
+	return eraseBlockSize()
+}
+
+// EraseBlocks erases the given number of blocks. An implementation may
+// transparently coalesce ranges of blocks into larger bundles if the chip
+// supports this. The start and len parameters are in block numbers, use
+// EraseBlockSize to map addresses to blocks.
+func (f flashBlockDevice) EraseBlocks(start, len int64) error {
+	address := FlashDataStart() + uintptr(start*f.EraseBlockSize())
+	waitWhileFlashBusy()
+
+	nrf.NVMC.SetCONFIG_WEN(nrf.NVMC_CONFIG_WEN_Een)
+	defer nrf.NVMC.SetCONFIG_WEN(nrf.NVMC_CONFIG_WEN_Ren)
+
+	for i := start; i < start+len; i++ {
+		nrf.NVMC.ERASEPAGE.Set(uint32(address))
+		waitWhileFlashBusy()
+		address += uintptr(f.EraseBlockSize())
+	}
+
+	return nil
+}
+
+// pad data if needed so it is long enough for correct byte alignment on writes.
+func (f flashBlockDevice) pad(p []byte) []byte {
+	paddingNeeded := f.WriteBlockSize() - (int64(len(p)) % f.WriteBlockSize())
+	if paddingNeeded == 0 {
+		return p
+	}
+
+	padding := bytes.Repeat([]byte{0xff}, int(paddingNeeded))
+	return append(p, padding...)
+}
+
+func waitWhileFlashBusy() {
+	for nrf.NVMC.GetREADY() != nrf.NVMC_READY_READY_Ready {
+	}
+}