Commit 43309f3b authored by Richard Zhao's avatar Richard Zhao Committed by Ben Dooks
Browse files

i2c: imx: check busy bit when START/STOP 



The controller can't do anything else before it actually generates START/STOP.
So we check busy bit to make sure START/STOP is successfully finished.

If we don't check busy bit, START/STOP may fail on some fast CPUs.

Signed-off-by: default avatarRichard Zhao <linuxzsc@gmail.com>
Signed-off-by: default avatarBen Dooks <ben-linux@fluff.org>
parent 1836d959

drivers/i2c/busses/i2c-imx.c

+44 −18
Original line number Diff line number Diff line
@@ -120,19 +120,25 @@ struct imx_i2c_struct { 
	wait_queue_head_t	queue;

	unsigned long		i2csr;

	unsigned int 		disable_delay;

	int			stopped;

};



/** Functions for IMX I2C adapter driver ***************************************

*******************************************************************************/



static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx)

static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy)

{

	unsigned long orig_jiffies = jiffies;

	unsigned int temp;



	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);



	/* wait for bus not busy */

	while (readb(i2c_imx->base + IMX_I2C_I2SR) & I2SR_IBB) {

	while (1) {

		temp = readb(i2c_imx->base + IMX_I2C_I2SR);

		if (for_busy && (temp & I2SR_IBB))

			break;

		if (!for_busy && !(temp & I2SR_IBB))

			break;

		if (signal_pending(current)) {

			dev_dbg(&i2c_imx->adapter.dev,

				"<%s> I2C Interrupted\n", __func__);
@@ -179,39 +185,55 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx) 
	return 0;

}



static void i2c_imx_start(struct imx_i2c_struct *i2c_imx)

static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)

{

	unsigned int temp = 0;

	int result;



	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);



	/* Enable I2C controller */

	writeb(0, i2c_imx->base + IMX_I2C_I2SR);

	writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR);



	/* Wait controller to be stable */

	udelay(50);



	/* Start I2C transaction */

	temp = readb(i2c_imx->base + IMX_I2C_I2CR);

	temp |= I2CR_MSTA;

	writeb(temp, i2c_imx->base + IMX_I2C_I2CR);

	result = i2c_imx_bus_busy(i2c_imx, 1);

	if (result)

		return result;

	i2c_imx->stopped = 0;



	temp |= I2CR_IIEN | I2CR_MTX | I2CR_TXAK;

	writeb(temp, i2c_imx->base + IMX_I2C_I2CR);

	return result;

}



static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)

{

	unsigned int temp = 0;



	if (!i2c_imx->stopped) {

		/* Stop I2C transaction */

		dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);

		temp = readb(i2c_imx->base + IMX_I2C_I2CR);

	temp &= ~I2CR_MSTA;

		temp &= ~(I2CR_MSTA | I2CR_MTX);

		writeb(temp, i2c_imx->base + IMX_I2C_I2CR);

	/* setup chip registers to defaults */

	writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR);

	writeb(0, i2c_imx->base + IMX_I2C_I2SR);

		i2c_imx->stopped = 1;

	}

	/*

	 * This delay caused by an i.MXL hardware bug.

	 * If no (or too short) delay, no "STOP" bit will be generated.

	 */

	udelay(i2c_imx->disable_delay);



	if (!i2c_imx->stopped)

		i2c_imx_bus_busy(i2c_imx, 0);



	/* Disable I2C controller */

	writeb(0, i2c_imx->base + IMX_I2C_I2CR);

}
@@ -341,11 +363,15 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs) 
		if (result)

			return result;

		if (i == (msgs->len - 1)) {

			/* It must generate STOP before read I2DR to prevent

			   controller from generating another clock cycle */

			dev_dbg(&i2c_imx->adapter.dev,

				"<%s> clear MSTA\n", __func__);

			temp = readb(i2c_imx->base + IMX_I2C_I2CR);

			temp &= ~I2CR_MSTA;

			temp &= ~(I2CR_MSTA | I2CR_MTX);

			writeb(temp, i2c_imx->base + IMX_I2C_I2CR);

			i2c_imx_bus_busy(i2c_imx, 0);

			i2c_imx->stopped = 1;

		} else if (i == (msgs->len - 2)) {

			dev_dbg(&i2c_imx->adapter.dev,

				"<%s> set TXAK\n", __func__);
@@ -370,14 +396,11 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter, 


	dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);



	/* Check if i2c bus is not busy */

	result = i2c_imx_bus_busy(i2c_imx);

	/* Start I2C transfer */

	result = i2c_imx_start(i2c_imx);

	if (result)

		goto fail0;



	/* Start I2C transfer */

	i2c_imx_start(i2c_imx);



	/* read/write data */

	for (i = 0; i < num; i++) {

		if (i) {
@@ -386,6 +409,9 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter, 
			temp = readb(i2c_imx->base + IMX_I2C_I2CR);

			temp |= I2CR_RSTA;

			writeb(temp, i2c_imx->base + IMX_I2C_I2CR);

			result =  i2c_imx_bus_busy(i2c_imx, 1);

			if (result)

				goto fail0;

		}

		dev_dbg(&i2c_imx->adapter.dev,

			"<%s> transfer message: %d\n", __func__, i);

CRA Git | Maintained and supported by SUSTech CRA and CCSE