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machine: move errors.New calls to globals

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Calling errors.New in an error path causes a heap allocation at an
already unfortunate moment. It is more efficient to create these error
values in globals and return these constant globals. If these errors are
not used (because the related code was optimized out), the globals will
also be optimized out.
This commit is contained in:
Ayke van Laethem
2020-04-04 14:33:29 +02:00
committed by Ron Evans
parent 9f8715c143
commit b8f5627c9f
8 changed files with 70 additions and 55 deletions
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src/machine/machine_atsamd21.go
+11 -12
View File
@@ -10,7 +10,6 @@ package machine
import (
"device/arm"
"device/sam"
"errors"
"runtime/interrupt"
"unsafe"
)
@@ -549,13 +548,13 @@ func (i2c I2C) Tx(addr uint16, w, r []byte) error {
for !i2c.Bus.INTFLAG.HasBits(sam.SERCOM_I2CM_INTFLAG_MB) {
timeout--
if timeout == 0 {
return errors.New("I2C timeout on ready to write data")
return errI2CWriteTimeout
}
}
// ACK received (0: ACK, 1: NACK)
if i2c.Bus.STATUS.HasBits(sam.SERCOM_I2CM_STATUS_RXNACK) {
return errors.New("I2C write error: expected ACK not NACK")
return errI2CAckExpected
}
// write data
@@ -581,13 +580,13 @@ func (i2c I2C) Tx(addr uint16, w, r []byte) error {
// In that case, send a stop condition and return error.
if i2c.Bus.INTFLAG.HasBits(sam.SERCOM_I2CM_INTFLAG_MB) {
i2c.Bus.CTRLB.SetBits(wireCmdStop << sam.SERCOM_I2CM_CTRLB_CMD_Pos) // Stop condition
return errors.New("I2C read error: expected ACK not NACK")
return errI2CAckExpected
}
}
// ACK received (0: ACK, 1: NACK)
if i2c.Bus.STATUS.HasBits(sam.SERCOM_I2CM_STATUS_RXNACK) {
return errors.New("I2C read error: expected ACK not NACK")
return errI2CAckExpected
}
// read first byte
@@ -624,16 +623,16 @@ func (i2c I2C) WriteByte(data byte) error {
for !i2c.Bus.INTFLAG.HasBits(sam.SERCOM_I2CM_INTFLAG_MB) {
// check for bus error
if sam.SERCOM3_I2CM.STATUS.HasBits(sam.SERCOM_I2CM_STATUS_BUSERR) {
return errors.New("I2C bus error")
return errI2CBusError
}
timeout--
if timeout == 0 {
return errors.New("I2C timeout on write data")
return errI2CWriteTimeout
}
}
if i2c.Bus.STATUS.HasBits(sam.SERCOM_I2CM_STATUS_RXNACK) {
return errors.New("I2C write error: expected ACK not NACK")
return errI2CAckExpected
}
return nil
@@ -652,7 +651,7 @@ func (i2c I2C) sendAddress(address uint16, write bool) error {
!i2c.Bus.STATUS.HasBits(wireOwnerState<<sam.SERCOM_I2CM_STATUS_BUSSTATE_Pos) {
timeout--
if timeout == 0 {
return errors.New("I2C timeout on bus ready")
return errI2CBusReadyTimeout
}
}
i2c.Bus.ADDR.Set(uint32(data))
@@ -666,7 +665,7 @@ func (i2c I2C) signalStop() error {
for i2c.Bus.SYNCBUSY.HasBits(sam.SERCOM_I2CM_SYNCBUSY_SYSOP) {
timeout--
if timeout == 0 {
return errors.New("I2C timeout on signal stop")
return errI2CSignalStopTimeout
}
}
return nil
@@ -678,7 +677,7 @@ func (i2c I2C) signalRead() error {
for i2c.Bus.SYNCBUSY.HasBits(sam.SERCOM_I2CM_SYNCBUSY_SYSOP) {
timeout--
if timeout == 0 {
return errors.New("I2C timeout on signal read")
return errI2CSignalReadTimeout
}
}
return nil
@@ -1286,7 +1285,7 @@ func (usbcdc USBCDC) WriteByte(c byte) error {
for (getEPINTFLAG(usb_CDC_ENDPOINT_IN) & sam.USB_DEVICE_EPINTFLAG_TRCPT1) == 0 {
timeout--
if timeout == 0 {
return errors.New("USBCDC write byte timeout")
return errUSBCDCWriteByteTimeout
}
}
}