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i2c: imx: check busy bit when START/STOP

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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: Richard Zhao <linuxzsc@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
This commit is contained in:
Richard Zhao 2009-10-17 17:46:22 +08:00 committed by Ben Dooks
parent 1836d95928
commit 43309f3b52
1 changed files with 44 additions and 18 deletions
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62
drivers/i2c/busses/i2c-imx.c
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@ -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;
/* Stop I2C transaction */
dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
temp = readb(i2c_imx->base + IMX_I2C_I2CR);
temp &= ~I2CR_MSTA;
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);
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 | I2CR_MTX);
writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
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);