atsamd21: remove special handling for SPI-24mhz

src/machine/machine_atsamd21.go

@@ -8,7 +8,6 @@
 package machine
 
 import (
-	"device"
 	"device/arm"
 	"device/sam"
 	"errors"
@@ -1301,27 +1300,6 @@ var (
 // 		spi.Tx(nil, rx)
 //
 func (spi SPI) Tx(w, r []byte) error {
-	if spi.Bus.BAUD.Get() == 0x00 {
-		// When the SPI Freq is 24MHz, special processing is performed to improve the speed.
-
-		switch {
-		case w == nil:
-			// read only, so write zero and read a result.
-			spi.rx(r)
-		case r == nil:
-			// write only
-			spi.tx24mhz(w)
-
-		default:
-			// write/read
-			if len(w) != len(r) {
-				return ErrTxInvalidSliceSize
-			}
-
-			spi.txrx24mhz(w, r)
-		}
-
-	} else {
 	switch {
 	case w == nil:
 		// read only, so write zero and read a result.
@@ -1338,7 +1316,6 @@ func (spi SPI) Tx(w, r []byte) error {
 
 		spi.txrx(w, r)
 	}
-	}
 
 	return nil
 }
@@ -1390,48 +1367,6 @@ func (spi SPI) txrx(tx, rx []byte) {
 	rx[len(rx)-1] = byte(spi.Bus.DATA.Get())
 }
 
-// tx24mhz is a special tx/rx function for CPU Clock 48 Mhz and SPI Freq 24 Mhz
-func (spi SPI) tx24mhz(tx []byte) {
-	spi.Bus.DATA.Set(uint32(tx[0]))
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-
-	for i := 1; i < len(tx); i++ {
-		spi.Bus.DATA.Set(uint32(tx[i]))
-		device.Asm("nop")
-		device.Asm("nop")
-		spi.Bus.DATA.Get()
-	}
-	for !spi.Bus.INTFLAG.HasBits(sam.SERCOM_SPI_INTFLAG_RXC) {
-	}
-	spi.Bus.DATA.Get()
-}
-
-// txrx24mhz is a special tx/rx function for CPU Clock 48 Mhz and SPI Freq 24 Mhz
-func (spi SPI) txrx24mhz(tx, rx []byte) {
-	spi.Bus.DATA.Set(uint32(tx[0]))
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-	device.Asm("nop")
-
-	for i := 1; i < len(rx); i++ {
-		spi.Bus.DATA.Set(uint32(tx[i]))
-		device.Asm("nop")
-		device.Asm("nop")
-		rx[i-1] = byte(spi.Bus.DATA.Get())
-	}
-	for !spi.Bus.INTFLAG.HasBits(sam.SERCOM_SPI_INTFLAG_RXC) {
-	}
-	rx[len(rx)-1] = byte(spi.Bus.DATA.Get())
-}
-
 // TCC is one timer/counter peripheral, which consists of a counter and multiple
 // output channels (that can be connected to actual pins). You can set the
 // frequency using SetPeriod, but only for all the channels in this TCC