[U-Boot] [PATCH 11/24] mxc_i2c: don't disable controller after every transaction

Troy Kisky
2012-06-22T04:12:06Z

This helps in a multiple bus master environment which
is why I also added a wait for bus idle.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
---
drivers/i2c/mxc_i2c.c | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/drivers/i2c/mxc_i2c.c b/drivers/i2c/mxc_i2c.c
index 2ef7b92..e433312 100644
--- a/drivers/i2c/mxc_i2c.c
+++ b/drivers/i2c/mxc_i2c.c
@@ -190,22 +190,16 @@ static int tx_byte(struct mxc_i2c_regs *i2c_regs, u8 byte)
}

/*
- * Stop the controller
+ * Stop I2C transaction
*/
void i2c_imx_stop(void)
{
struct mxc_i2c_regs *i2c_regs = (struct mxc_i2c_regs *)I2C_BASE;
- unsigned int temp = 0;
+ unsigned int temp = readb(&i2c_regs->i2cr);

- /* Stop I2C transaction */
- temp = readb(&i2c_regs->i2cr);
temp &= ~(I2CR_MSTA | I2CR_MTX);
writeb(temp, &i2c_regs->i2cr);
-
wait_for_sr_state(i2c_regs, ST_BUS_IDLE);
-
- /* Disable I2C controller */
- writeb(0, &i2c_regs->i2cr);
}

/*
@@ -219,11 +213,15 @@ static int i2c_init_transfer(struct mxc_i2c_regs *i2c_regs,
int ret;

/* Enable I2C controller */
+ if (!(readb(&i2c_regs->i2cr) & I2CR_IEN)) {
+ writeb(I2CR_IEN, &i2c_regs->i2cr);
+ /* Wait for controller to be stable */
+ udelay(50);
+ }
writeb(0, &i2c_regs->i2sr);
- writeb(I2CR_IEN, &i2c_regs->i2cr);
-
- /* Wait for controller to be stable */
- udelay(50);
+ ret = wait_for_sr_state(i2c_regs, ST_BUS_IDLE);
+ if (ret < 0)
+ goto exit;

/* Start I2C transaction */
temp = readb(&i2c_regs->i2cr);
@@ -250,6 +248,8 @@ static int i2c_init_transfer(struct mxc_i2c_regs *i2c_regs,
return 0;
exit:
i2c_imx_stop();
+ /* Disable I2C controller */
+ writeb(0, &i2c_regs->i2cr);
return ret;
}

@@ -294,10 +294,7 @@ int i2c_read(uchar chip, uint addr, int alen, uchar *buf, int len)
* controller from generating another clock cycle
*/
if (i == (len - 1)) {
- temp = readb(&i2c_regs->i2cr);
- temp &= ~(I2CR_MSTA | I2CR_MTX);
- writeb(temp, &i2c_regs->i2cr);
- wait_for_sr_state(i2c_regs, ST_BUS_IDLE);
+ i2c_imx_stop(i2c_regs);
} else if (i == (len - 2)) {
temp = readb(&i2c_regs->i2cr);
temp |= I2CR_TX_NO_AK;
--
1.7.9.5