address remaining review comments

Author: ardnew

src/machine/board_teensy40.go

@@ -352,35 +352,41 @@ var (
 	I2C1  = &_I2C1
 	_I2C1 = I2C{
 		Bus: nxp.LPI2C1,
-		muxSDA: muxSelect{ // D18 (PA17 [AD_B1_01])
+		sda: I2C1_SDA_PIN, // D18 (PA17 [AD_B1_01])
+		scl: I2C1_SCL_PIN, // D19 (PA16 [AD_B1_00])
+		muxSDA: muxSelect{
 			mux: nxp.IOMUXC_LPI2C1_SDA_SELECT_INPUT_DAISY_GPIO_AD_B1_01_ALT3,
 			sel: &nxp.IOMUXC.LPI2C1_SDA_SELECT_INPUT,
 		},
-		muxSCL: muxSelect{ // D19 (PA16 [AD_B1_00])
+		muxSCL: muxSelect{
 			mux: nxp.IOMUXC_LPI2C1_SCL_SELECT_INPUT_DAISY_GPIO_AD_B1_00_ALT3,
 			sel: &nxp.IOMUXC.LPI2C1_SCL_SELECT_INPUT,
 		},
 	}
 	I2C2  = &_I2C2
 	_I2C2 = I2C{
 		Bus: nxp.LPI2C3,
-		muxSDA: muxSelect{ // D17 (PA22 [AD_B1_06])
+		sda: I2C2_SDA_PIN, // D17 (PA22 [AD_B1_06])
+		scl: I2C2_SCL_PIN, // D16 (PA23 [AD_B1_07])
+		muxSDA: muxSelect{
 			mux: nxp.IOMUXC_LPI2C3_SDA_SELECT_INPUT_DAISY_GPIO_AD_B1_06_ALT1,
 			sel: &nxp.IOMUXC.LPI2C3_SDA_SELECT_INPUT,
 		},
-		muxSCL: muxSelect{ // D16 (PA23 [AD_B1_07])
+		muxSCL: muxSelect{
 			mux: nxp.IOMUXC_LPI2C3_SCL_SELECT_INPUT_DAISY_GPIO_AD_B1_07_ALT1,
 			sel: &nxp.IOMUXC.LPI2C3_SCL_SELECT_INPUT,
 		},
 	}
 	I2C3  = &_I2C3
 	_I2C3 = I2C{
 		Bus: nxp.LPI2C4,
-		muxSDA: muxSelect{ // D25 (PA13 [AD_B0_13])
+		sda: I2C3_SDA_PIN, // D25 (PA13 [AD_B0_13])
+		scl: I2C3_SCL_PIN, // D24 (PA12 [AD_B0_12])
+		muxSDA: muxSelect{
 			mux: nxp.IOMUXC_LPI2C4_SDA_SELECT_INPUT_DAISY_GPIO_AD_B0_13_ALT0,
 			sel: &nxp.IOMUXC.LPI2C4_SDA_SELECT_INPUT,
 		},
-		muxSCL: muxSelect{ // D24 (PA12 [AD_B0_12])
+		muxSCL: muxSelect{
 			mux: nxp.IOMUXC_LPI2C4_SCL_SELECT_INPUT_DAISY_GPIO_AD_B0_12_ALT0,
 			sel: &nxp.IOMUXC.LPI2C4_SCL_SELECT_INPUT,
 		},

src/machine/machine_mimxrt1062_i2c.go

@@ -1,3 +1,4 @@
+//go:build mimxrt1062
 // +build mimxrt1062
 
 package machine
@@ -37,17 +38,15 @@ type I2CConfig struct {
 	SCL       Pin
 }
 
-func (c I2CConfig) getPins() (sda, scl Pin) {
-	if 0 == c.SDA && 0 == c.SCL {
-		// default pins if none specified
-		return I2C_SDA_PIN, I2C_SCL_PIN
-	}
-	return c.SDA, c.SCL
-}
-
 type I2C struct {
 	Bus *nxp.LPI2C_Type
 
+	// these pins are initialized by each global I2C variable declared in the
+	// board_teensy4x.go file according to the board manufacturer's default pin
+	// mapping. they can be overridden with the I2CConfig argument given to
+	// (*I2C) Configure(I2CConfig).
+	sda, scl Pin
+
 	// these hold the input selector ("daisy chain") values that select which pins
 	// are connected to the LPI2C device, and should be defined where the I2C
 	// instance is declared (e.g., in the board definition). see the godoc
@@ -150,11 +149,20 @@ const (
 	stateWaitForCompletion stateFlag = 0x5
 )
 
+func (i2c *I2C) setPins(c I2CConfig) (sda, scl Pin) {
+	// if both given pins are defined, or either receiver pin is undefined.
+	if 0 != c.SDA && 0 != c.SCL || 0 == i2c.sda || 0 == i2c.scl {
+		// override the receiver's pins.
+		i2c.sda, i2c.scl = c.SDA, c.SCL
+	}
+	// return the selected pins.
+	return i2c.sda, i2c.scl
+}
+
 // Configure is intended to setup an I2C interface for transmit/receive.
 func (i2c *I2C) Configure(config I2CConfig) {
-
 	// init pins
-	sda, scl := config.getPins()
+	sda, scl := i2c.setPins(config)
 
 	// configure the mux and pad control registers
 	sda.Configure(PinConfig{Mode: PinModeI2CSDA})
@@ -174,7 +182,6 @@ func (i2c *I2C) Configure(config I2CConfig) {
 }
 
 func (i2c I2C) Tx(addr uint16, w, r []byte) error {
-
 	// perform transmit transfer
 	if nil != w {
 		// generate start condition on bus
@@ -281,6 +288,10 @@ func (i2c *I2C) reset(freq uint32) {
 
 	// clear reset, and enable the interface
 	i2c.Bus.MCR.Set(nxp.LPI2C_MCR_MEN)
+
+	// wait for the I2C bus to idle
+	for i2c.Bus.MSR.Get()&nxp.LPI2C_MSR_BBF != 0 {
+	}
 }
 
 func (i2c *I2C) setFrequency(freq uint32) {

src/runtime/runtime_mimxrt1062_clock.go

@@ -166,6 +166,7 @@ func initClocks() {
 	nxp.ClockIpLpi2c1.Enable(false) // disable LPI2C
 	nxp.ClockIpLpi2c2.Enable(false) //
 	nxp.ClockIpLpi2c3.Enable(false) //
+	nxp.ClockIpLpi2c4.Enable(false) //
 	nxp.DivIpLpi2c.Div(0)           // divide LPI2C_CLK_PODF (DIV1)
 	nxp.MuxIpLpi2c.Mux(1)           // LPI2C select OSC
 
@@ -266,7 +267,6 @@ func initClocks() {
 }
 
 func enableTimerClocks() {
-
 	nxp.ClockIpGpt1.Enable(true)  // enable GPT/PIT
 	nxp.ClockIpGpt1S.Enable(true) //
 	nxp.ClockIpGpt2.Enable(true)  //
@@ -275,7 +275,6 @@ func enableTimerClocks() {
 }
 
 func enablePinClocks() {
-
 	nxp.ClockIpIomuxcGpr.Enable(true) // enable IOMUXC
 	nxp.ClockIpIomuxc.Enable(true)    //
 
@@ -286,7 +285,6 @@ func enablePinClocks() {
 }
 
 func enablePeripheralClocks() {
-
 	nxp.ClockIpAdc1.Enable(true) // enable ADC
 	nxp.ClockIpAdc2.Enable(true) //
 
@@ -309,6 +307,7 @@ func enablePeripheralClocks() {
 	nxp.ClockIpLpi2c1.Enable(true) // enable LPI2C
 	nxp.ClockIpLpi2c2.Enable(true) //
 	nxp.ClockIpLpi2c3.Enable(true) //
+	nxp.ClockIpLpi2c4.Enable(true) //
 
 	nxp.ClockIpCan1.Enable(true)  // enable CAN
 	nxp.ClockIpCan2.Enable(true)  //