DMA driven PWM implementation (#193)

Implements PWM via two DMA controlBlock that sets and resets a GPIO.

Author: simokawa

host/bcm283x/dma.go

@@ -417,7 +417,7 @@ type controlBlock struct {
 //
 // dreq can be dmaFire, dmaPwm, dmaPcmTx, etc. waits is additional wait state
 // between clocks.
-func (c *controlBlock) initBlock(srcAddr, dstAddr, l uint32, srcIO, dstIO bool, dreq dmaTransferInfo, waits int) error {
+func (c *controlBlock) initBlock(srcAddr, dstAddr, l uint32, srcIO, dstIO, srcInc, dstInc bool, dreq dmaTransferInfo, waits int) error {
 	if srcIO && dstIO {
 		return errors.New("only one of src and dst can be I/O")
 	}
@@ -444,27 +444,32 @@ func (c *controlBlock) initBlock(srcAddr, dstAddr, l uint32, srcIO, dstIO bool,
 	if srcAddr == 0 {
 		t |= dmaSrcIgnore
 		c.srcAddr = 0
-	} else if srcIO {
-		// Memory mapped register
-		c.srcAddr = physToBus(srcAddr)
-		// BUG: EXPERIMENTING.
-		//t |= dmaSrcInc
-		//c.srcAddr = physToUncachedPhys(srcAddr)
 	} else {
-		// Normal memory
-		t |= dmaSrcInc
-		c.srcAddr = physToUncachedPhys(srcAddr)
+		if srcIO {
+			// Memory mapped register
+			c.srcAddr = physToBus(srcAddr)
+		} else {
+			// Normal memory
+			c.srcAddr = physToUncachedPhys(srcAddr)
+		}
+		if srcInc {
+			t |= dmaSrcInc
+		}
 	}
 	if dstAddr == 0 {
 		t |= dmaDstIgnore
 		c.dstAddr = 0
-	} else if dstIO {
-		// Memory mapped register
-		c.dstAddr = physToBus(dstAddr)
 	} else {
-		// Normal memory
-		t |= dmaDstInc
-		c.dstAddr = physToUncachedPhys(dstAddr)
+		if dstIO {
+			// Memory mapped register
+			c.dstAddr = physToBus(dstAddr)
+		} else {
+			// Normal memory
+			c.dstAddr = physToUncachedPhys(dstAddr)
+		}
+		if dstInc {
+			t |= dmaDstInc
+		}
 	}
 	if dreq != dmaFire {
 		// dmaSrcDReq |
@@ -508,15 +513,12 @@ func (d *dmaChannel) isAvailable() bool {
 //
 // It doesn't clear the local controlBlock cached values.
 func (d *dmaChannel) reset() {
-	// Make sure nothing is happening.
 	d.cs = dmaReset
 	// Clear bits if needed.
-	d.cs = dmaEnd | dmaInterrupt
-	// Clear values and error bits.
+	// TODO(simokawa): Test if it works as expected.
+	d.cs = dmaInterrupt
 	d.cbAddr = 0
 	d.nextCB = 0
-	d.debug = dmaReadError | dmaFIFOError | dmaReadLastNotSetError
-	d.cs = 0
 }
 
 // startIO initializes the DMA channel to start a transmission.
@@ -642,6 +644,53 @@ func runIO(pCB pmem.Mem, liteOk bool) error {
 	return ch.wait()
 }
 
+func allocateCB(size int) ([]controlBlock, *videocore.Mem, error) {
+	buf, err := videocore.Alloc((size + 0xFFF) &^ 0xFFF)
+	if err != nil {
+		return nil, nil, err
+	}
+	var cb []controlBlock
+	if err := buf.AsPOD(&cb); err != nil {
+		buf.Close()
+		return nil, nil, err
+	}
+	return cb, buf, nil
+}
+
+func startPWMbyDMA(p *Pin, rng, data uint32) (*dmaChannel, *videocore.Mem, error) {
+	cb, buf, err := allocateCB(4096)
+	if err != nil {
+		return nil, nil, err
+	}
+	u := buf.Uint32()
+	cbBytes := uint32(32)
+	offsetBytes := cbBytes * 2
+	u[offsetBytes/4] = uint32(1) << uint(p.number&31)
+	physBuf := uint32(buf.PhysAddr())
+	physBit := physBuf + offsetBytes
+	dest := [2]uint32{
+		gpioBaseAddr + 0x28 + 4*uint32(p.number/32), // clear
+		gpioBaseAddr + 0x1C + 4*uint32(p.number/32), // set
+	}
+	waits := 0
+	// High
+	cb[0].initBlock(physBit, dest[1], data*4, false, true, false, false, dmaPWM, waits)
+	cb[0].nextCB = physBuf + cbBytes
+	// Low
+	cb[1].initBlock(physBit, dest[0], (rng-data)*4, false, true, false, false, dmaPWM, waits)
+	cb[1].nextCB = physBuf // Loop back to cb[0]
+
+	// OK with lite channels.
+	_, ch := pickChannel()
+	if ch == nil {
+		buf.Close()
+		return nil, nil, errors.New("bcm283x-dma: no channel available")
+	}
+	ch.startIO(physBuf)
+
+	return ch, buf, nil
+}
+
 // physToUncachedPhys returns the uncached physical memory address backing a
 // physical memory address.
 //
@@ -696,16 +745,16 @@ func smokeTest() error {
 			// process startup, which may cause undesirable glitches.
 
 			// Initializes the PWM clock right away to 1MHz.
-			_, waits, err := setPWMClockSource(1000000)
+			_, waits, err := setPWMClockSource(1000000, 10)
 			if err != nil {
 				return err
 			}
-			if err := cb.initBlock(uint32(pSrc), uint32(pDst)+holeSize, size-2*holeSize, false, false, dmaPWM, waits); err != nil {
+			if err := cb.initBlock(uint32(pSrc), uint32(pDst)+holeSize, size-2*holeSize, false, false, true, true, dmaPWM, waits); err != nil {
 				return err
 			}
 		} else {
 			// Use maximum performance.
-			if err := cb.initBlock(uint32(pSrc), uint32(pDst)+holeSize, size-2*holeSize, false, false, dmaFire, 0); err != nil {
+			if err := cb.initBlock(uint32(pSrc), uint32(pDst)+holeSize, size-2*holeSize, false, false, true, true, dmaFire, 0); err != nil {
 				return err
 			}
 		}
@@ -763,6 +812,17 @@ func (d *driverDMA) Close() error {
 	return nil
 }
 
+func resetDMA(ch int) error {
+	if ch < len(dmaMemory.channels) {
+		dmaMemory.channels[ch].reset()
+	} else if ch == 15 {
+		dmaChannel15.reset()
+	} else {
+		return fmt.Errorf("Invalid dma channel %d.", ch)
+	}
+	return nil
+}
+
 func init() {
 	if isArm {
 		periph.MustRegister(&driverDMA{})

host/bcm283x/dma_test.go

@@ -51,45 +51,45 @@ func TestDmaStride_String(t *testing.T) {
 
 func TestControlBlock(t *testing.T) {
 	c := controlBlock{}
-	if c.initBlock(0, 0, 0, true, true, dmaFire, 0) == nil {
+	if c.initBlock(0, 0, 0, true, true, false, false, dmaFire, 0) == nil {
 		t.Fatal("can't set both")
 	}
-	if c.initBlock(0, 0, 0, false, false, dmaFire, 0) == nil {
+	if c.initBlock(0, 0, 0, false, false, true, true, dmaFire, 0) == nil {
 		t.Fatal("need at least one addr")
 	}
-	if c.initBlock(0, 1, 0, true, false, dmaFire, 0) == nil {
+	if c.initBlock(0, 1, 0, true, false, false, true, dmaFire, 0) == nil {
 		t.Fatal("srcIO requires srcAddr")
 	}
-	if c.initBlock(1, 0, 0, false, true, dmaFire, 0) == nil {
+	if c.initBlock(1, 0, 0, false, true, true, false, dmaFire, 0) == nil {
 		t.Fatal("dstIO requires dstAddr")
 	}
-	if c.initBlock(1, 1, 0, false, false, dmaSrcIgnore, 0) == nil {
+	if c.initBlock(1, 1, 0, false, false, true, true, dmaSrcIgnore, 0) == nil {
 		t.Fatal("must not specify anything other than clock source")
 	}
-	if c.initBlock(1, 1, 0, false, false, dmaFire, 100) == nil {
+	if c.initBlock(1, 1, 0, false, false, true, true, dmaFire, 100) == nil {
 		t.Fatal("dstIO requires dstAddr")
 	}
-	if c.initBlock(1, 1, 0, false, false, dmaFire, 1) == nil {
+	if c.initBlock(1, 1, 0, false, false, true, true, dmaFire, 1) == nil {
 		t.Fatal("dmaFire can't use waits")
 	}
 
-	if err := c.initBlock(1, 0, 0, false, false, dmaFire, 0); err != nil {
+	if err := c.initBlock(1, 0, 0, false, false, true, true, dmaFire, 0); err != nil {
 		t.Fatal(err)
 	}
-	if err := c.initBlock(0, 1, 0, false, false, dmaFire, 0); err != nil {
+	if err := c.initBlock(0, 1, 0, false, false, true, true, dmaFire, 0); err != nil {
 		t.Fatal(err)
 	}
-	if err := c.initBlock(1, 0, 0, true, false, dmaFire, 0); err != nil {
+	if err := c.initBlock(1, 0, 0, true, false, false, true, dmaFire, 0); err != nil {
 		t.Fatal(err)
 	}
-	if err := c.initBlock(0, 1, 0, false, true, dmaPCMTX, 0); err != nil {
+	if err := c.initBlock(0, 1, 0, false, true, true, false, dmaPCMTX, 0); err != nil {
 		t.Fatal(err)
 	}
 }
 
 func TestControlBlockGo_String(t *testing.T) {
 	c := controlBlock{}
-	if err := c.initBlock(0, 1, 0, false, true, dmaPCMTX, 0); err != nil {
+	if err := c.initBlock(0, 1, 0, false, true, false, false, dmaPCMTX, 0); err != nil {
 		t.Fatal(err)
 	}
 	expected := "{\n  transferInfo: NoWideBursts|SrcIgnore|DstDReq|WaitResp|PCMTX,\n  srcAddr:      0x0,\n  dstAddr:      0x7e000001,\n  txLen:        0,\n  stride:       0x0,\n  nextCB:       0x0,\n}"
@@ -125,7 +125,7 @@ func TestDmaChannel_GoString(t *testing.T) {
 	d := dmaChannel{}
 	d.reset()
 	d.startIO(0)
-	expected := "{\n  cs:           WaitForOutstandingWrites|Active|pp8|p8,\n  cbAddr:       0x0,\n  transferInfo: Fire,\n  srcAddr:      0x0,\n  dstAddr:      0x0,\n  txLen:        0,\n  stride:       0x0,\n  nextCB:       0x0,\n  debug:        ReadError|FIFOError|ReadLastNotSetError,\n  reserved:     {...},\n}"
+	expected := "{\n  cs:           WaitForOutstandingWrites|Active|pp8|p8,\n  cbAddr:       0x0,\n  transferInfo: Fire,\n  srcAddr:      0x0,\n  dstAddr:      0x0,\n  txLen:        0,\n  stride:       0x0,\n  nextCB:       0x0,\n  debug:        0,\n  reserved:     {...},\n}"
 	if s := d.GoString(); s != expected {
 		t.Fatalf("%q", s)
 	}

host/bcm283x/pwm.go

@@ -220,7 +220,7 @@ func (p *pwmMap) reset() {
 // It may select an higher frequency than the one requested.
 //
 // Other potentially good clock sources are PCM, SPI and UART.
-func setPWMClockSource(hz uint64) (uint64, int, error) {
+func setPWMClockSource(hz uint64, div uint32) (uint64, int, error) {
 	if pwmMemory == nil {
 		return 0, 0, errors.New("subsystem PWM not initialized")
 	}
@@ -229,22 +229,19 @@ func setPWMClockSource(hz uint64) (uint64, int, error) {
 	}
 	actual, divs, err := clockMemory.pwm.set(hz, dmaWaitcyclesMax+1)
 	if err == nil {
-		pwmMemory.ctl = 0
-		Nanospin(10 * time.Microsecond)
-		pwmMemory.status = pwmStatusMask
-		Nanospin(10 * time.Microsecond)
 		// It acts as a clock multiplier, since this amount of data is sent per
 		// clock tick.
-		pwmMemory.rng1 = 10 // 32?
+		pwmMemory.rng1 = uint32(divs) * div
 		Nanospin(10 * time.Microsecond)
 		// Periph data (?)
 
 		// Use low priority.
 		pwmMemory.dmaCfg = pwmDMAEnable | pwmDMACfg(15<<pwmPanicShift|15)
 		Nanospin(10 * time.Microsecond)
-		pwmMemory.ctl = pwmClearFIFO
+		pwmMemory.ctl |= pwmClearFIFO
 		Nanospin(10 * time.Microsecond)
-		pwmMemory.ctl = pwm1UseFIFO | pwm1Enable
+		old := pwmMemory.ctl
+		pwmMemory.ctl = (old & ^pwmControl(0xff)) | pwm1UseFIFO | pwm1Enable
 	}
 	// Convert divisor into wait cycles.
 	return actual, divs - 1, err

host/bcm283x/pwm_test.go

@@ -9,14 +9,14 @@ import "testing"
 func TestPWMMap(t *testing.T) {
 	p := pwmMap{}
 	p.reset()
-	if _, _, err := setPWMClockSource(10); err == nil {
+	if _, _, err := setPWMClockSource(10, 10); err == nil {
 		t.Fatal("pwmMemory is nil")
 	}
 	defer func() {
 		pwmMemory = nil
 	}()
 	pwmMemory = &p
-	if _, _, err := setPWMClockSource(10); err == nil {
+	if _, _, err := setPWMClockSource(10, 10); err == nil {
 		t.Fatal("clockMemory is nil")
 	}
 }