share DMA enabling logic among drivers

Author: soypat

rp2-pio/piolib/dma.go

@@ -40,6 +40,28 @@ func (arb *dmaArbiter) Channel(channel uint8) dmaChannel {
 	}
 }
 
+func (dma *dmaChannel) helperIsEnabled() bool {
+	return dma.IsValid()
+}
+
+func (dma *dmaChannel) helperEnableDMA(enabled bool) error {
+	dmaAlreadyEnabled := dma.helperIsEnabled()
+	if !enabled || dmaAlreadyEnabled {
+		if !enabled && dmaAlreadyEnabled {
+			dma.Unclaim()
+			*dma = dmaChannel{} // Invalidate DMA channel.
+		}
+		return nil
+	}
+	channel, ok := _DMA.ClaimChannel()
+	if !ok {
+		return errDMAUnavail
+	}
+	channel.dl = dma.dl // save deadliner from existing DMA channel, maybe set by user in future.
+	*dma = channel
+	return nil
+}
+
 type dmaChannel struct {
 	hw  *dmaChannelHW
 	arb *dmaArbiter

rp2-pio/piolib/parallel8.go

@@ -80,29 +80,17 @@ func (pl *Parallel8Tx) Write(data []uint8) error {
 }
 
 func (pl *Parallel8Tx) IsDMAEnabled() bool {
-	return pl.dma.IsValid()
+	return pl.dma.helperIsEnabled()
 }
 
 func (pl *Parallel8Tx) EnableDMA(enabled bool) error {
 	if !pl.sm.IsValid() {
 		return errors.New("PIO Statemachine needs initializing") //Not initialized
 	}
-	dmaAlreadyEnabled := pl.IsDMAEnabled()
-	if !enabled || dmaAlreadyEnabled {
-		if !enabled && dmaAlreadyEnabled {
-			pl.dma.Unclaim()
-			pl.dma = dmaChannel{} // Invalidate DMA channel.
-		}
-		return nil
-	}
-
-	channel, ok := _DMA.ClaimChannel()
-	if !ok {
-		return errDMAUnavail
+	err := pl.dma.helperEnableDMA(enabled)
+	if !enabled || err != nil {
+		return err
 	}
-
-	channel.dl = pl.dma.dl // Copy deadline.
-	pl.dma = channel
 	cc := pl.dma.CurrentConfig()
 	cc.setBSwap(false)
 	cc.setTransferDataSize(dmaTxSize8)

rp2-pio/piolib/spi3w.go

@@ -266,21 +266,7 @@ func (spi *SPI3w) prepTx(readbits, writebits uint32) {
 // DMA code below.
 
 func (spi *SPI3w) EnableDMA(enabled bool) error {
-	dmaAlreadyEnabled := spi.IsDMAEnabled()
-	if !enabled || dmaAlreadyEnabled {
-		if !enabled && dmaAlreadyEnabled {
-			spi.dma.Unclaim()
-			spi.dma = dmaChannel{} // Invalidate DMA channel.
-		}
-		return nil
-	}
-	channel, ok := _DMA.ClaimChannel()
-	if !ok {
-		return errDMAUnavail
-	}
-	channel.dl = spi.dma.dl // Copy deadline.
-	spi.dma = channel
-	return nil
+	return spi.dma.helperEnableDMA(enabled)
 }
 
 func (spi *SPI3w) readDMA(r []uint32) error {
@@ -302,7 +288,7 @@ func (spi *SPI3w) writeDMA(w []uint32) error {
 }
 
 func (spi *SPI3w) IsDMAEnabled() bool {
-	return spi.dma.IsValid()
+	return spi.dma.helperIsEnabled()
 }
 
 func pinPadCtrl(pin machine.Pin) *volatile.Register32 {

rp2-pio/piolib/ws2812b.go

@@ -17,6 +17,8 @@ type WS2812B struct {
 }
 
 func NewWS2812B(sm pio.StateMachine, pin machine.Pin) (*WS2812B, error) {
+	// See ws2812b.pio for more information on how the timings are calculated.
+	// WS2812B Datasheet:
 	// https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf
 	const (
 		baseline      = 1250.
@@ -78,7 +80,7 @@ func (ws *WS2812B) PutColor(c color.Color) {
 }
 
 // WriteRaw writes raw GRB values to a strip of WS2812B LEDs. Each uint32 is a WS2812B color
-// which can be created with 3 uint8 color values::
+// which can be created with 3 uint8 color values:
 //
 //	color := uint32(g)<<24 | uint32(r)<<16 | uint32(b)<<8
 func (ws *WS2812B) WriteRaw(rawGRB []uint32) error {
@@ -101,25 +103,6 @@ func (ws *WS2812B) WriteRaw(rawGRB []uint32) error {
 	return nil
 }
 
-// EnableDMA enables DMA for vectorized writes.
-func (ws *WS2812B) EnableDMA(enabled bool) error {
-	dmaAlreadyEnabled := ws.IsDMAEnabled()
-	if !enabled || dmaAlreadyEnabled {
-		if !enabled && dmaAlreadyEnabled {
-			ws.dma.Unclaim()
-			ws.dma = dmaChannel{} // Invalidate DMA channel.
-		}
-		return nil
-	}
-	channel, ok := _DMA.ClaimChannel()
-	if !ok {
-		return errDMAUnavail
-	}
-	channel.dl = ws.dma.dl // Copy deadline.
-	ws.dma = channel
-	return nil
-}
-
 func (ws *WS2812B) writeDMA(w []uint32) error {
 	dreq := dmaPIO_TxDREQ(ws.sm)
 	err := ws.dma.Push32(&ws.sm.TxReg().Reg, w, dreq)
@@ -129,7 +112,12 @@ func (ws *WS2812B) writeDMA(w []uint32) error {
 	return nil
 }
 
+// EnableDMA enables DMA for vectorized writes.
+func (ws *WS2812B) EnableDMA(enabled bool) error {
+	return ws.dma.helperEnableDMA(enabled)
+}
+
 // IsDMAEnabled returns true if DMA is enabled.
 func (ws *WS2812B) IsDMAEnabled() bool {
-	return ws.dma.IsValid()
+	return ws.dma.helperIsEnabled()
 }