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i2c-imx: fix clear IFF race condition 

During i2c read the original pattern was:

1. write i2c slave address
2. wait for transmit complete + clear IIF
3. wait for receive acknowledge
4. wait for IIF interrupt

Due to the clear of the I2SR register, the IIF flag was cleared, too. So
in step 4 the Interrupt wasn't detected. To fix this problem, we move
the clean of IIF before the writing of the slave address. So that it
looks this way:

0. clear IIF
1. write i2c slave address
2. wait for transmit complete
3. wait for receive acknowledge
4. wait for IIF interrupt

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Marc Kleine-Budde 2009-12-09 15:12:09 +01:00
parent ed85e6d361
commit 6d34576586
1 changed files with 3 additions and 2 deletions
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5
drivers/i2c/i2c-imx.c
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@ -177,8 +177,6 @@ static int i2c_imx_trx_complete(struct i2c_adapter *adapter)
dev_err(adapter->dev, "<%s> TXR timeout\n", __func__);
return -EIO;
}
writeb(0x0, base + IMX_I2C_I2SR);
}
return 0;
@ -360,6 +358,9 @@ static int i2c_imx_read(struct i2c_adapter *adapter, struct i2c_msg *msgs)
"<%s> write slave address: addr=0x%02x\n",
__func__, (msgs->addr << 1) | 0x01);
/* clear IIF */
writeb(0x0, base + IMX_I2C_I2SR);
/* write slave address */
writeb((msgs->addr << 1) | 0x01, base + IMX_I2C_I2DR);