mpc83xx: Fix empty i2c reads/writes in fsl_i2c.c

Fix empty i2c reads/writes, i2c_write(0x50, 0x00, 0, NULL, 0)
which is used to se if an slave will ACK after receiving its address.

Correct i2c probing to use this method as the old method could upset
a slave as it wrote a data byte to it.

Add a small delay in i2c_init() to let the controller
shutdown any ongoing I2C activity.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>

diff --git a/drivers/fsl_i2c.c b/drivers/fsl_i2c.c
index c92909608a38099e4401f0ed88155c67e098c7c8..ebae5af154ee95bcadd738e8a78a57372f66d7c7 100644 (file)
--- a/drivers/fsl_i2c.c
+++ b/drivers/fsl_i2c.c
@@ -58,6 +58,7 @@ i2c_init(int speed, int slaveadd)
        dev = (struct fsl_i2c *) (CFG_IMMR + CFG_I2C_OFFSET);
 
        writeb(0, &dev->cr);                    /* stop I2C controller */
+       udelay(5);                              /* let it shutdown in peace */
        writeb(0x3F, &dev->fdr);                /* set bus speed */
        writeb(0x3F, &dev->dfsrr);              /* set default filter */
        writeb(slaveadd << 1, &dev->adr);       /* write slave address */
@@ -191,15 +192,17 @@ __i2c_read(u8 *data, int length)
 int
 i2c_read(u8 dev, uint addr, int alen, u8 *data, int length)
 {
-       int i = 0;
+       int i = -1; /* signal error */
        u8 *a = (u8*)&addr;
 
        if (i2c_wait4bus() >= 0
            && i2c_write_addr(dev, I2C_WRITE_BIT, 0) != 0
-           && __i2c_write(&a[4 - alen], alen) == alen
-           && i2c_write_addr(dev, I2C_READ_BIT, 1) != 0) {
+           && __i2c_write(&a[4 - alen], alen) == alen)
+               i = 0; /* No error so far */
+
+       if (length
+           && i2c_write_addr(dev, I2C_READ_BIT, 1) != 0)
                i = __i2c_read(data, length);
-       }
 
        writeb(I2C_CR_MEN, &i2c_dev[i2c_bus_num]->cr);
 
@@ -212,7 +215,7 @@ i2c_read(u8 dev, uint addr, int alen, u8 *data, int length)
 int
 i2c_write(u8 dev, uint addr, int alen, u8 *data, int length)
 {
-       int i = 0;
+       int i = -1; /* signal error */
        u8 *a = (u8*)&addr;
 
        if (i2c_wait4bus() >= 0
@@ -232,16 +235,14 @@ i2c_write(u8 dev, uint addr, int alen, u8 *data, int length)
 int
 i2c_probe(uchar chip)
 {
-       int tmp;
-
-       /*
-        * Try to read the first location of the chip.  The underlying
-        * driver doesn't appear to support sending just the chip address
-        * and looking for an <ACK> back.
+       /* For unknow reason the controller will ACK when
+        * probing for a slave with the same address, so skip
+        * it.
         */
-       udelay(10000);
+       if (chip == (readb(&i2c_dev[i2c_bus_num]->adr) >> 1))
+               return -1;
 
-       return i2c_read(chip, 0, 1, (uchar *)&tmp, 1);
+       return i2c_read(chip, 0, 0, NULL, 0);
 }
 
 uchar