I2C: Fix twl4030 timeouts on omap3430

For some reason doing a twl4030 write-read cycle can hang the I2C bus
on omap3430. And doing the write and read separately in twl4030_i2c_read()
seems to fix the problem.

Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/drivers/i2c/chips/twl4030-core.c b/drivers/i2c/chips/twl4030-core.c
index c979241f377702fb19accef6a018e15b5459d0d4..86e0d5c266e96bc216ecef159056b89e99c94d0e 100644 (file)
--- a/drivers/i2c/chips/twl4030-core.c
+++ b/drivers/i2c/chips/twl4030-core.c
@@ -327,6 +327,7 @@ int twl4030_i2c_read(u8 mod_no, u8 * value, u8 reg, u8 num_bytes)
                return -EPERM;
        }
        mutex_lock(&twl->xfer_lock);
+
        /* [MSG1] fill the register address data */
        msg = &twl->xfer_msg[0];
        msg->addr = twl->address;
@@ -334,18 +335,31 @@ int twl4030_i2c_read(u8 mod_no, u8 * value, u8 reg, u8 num_bytes)
        msg->flags = 0; /* Read the register value */
        val = twl4030_map[mod_no].base + reg;
        msg->buf = &val;
+
+       /*
+        * REVISIT: If we combine I2C write-read transfer, twl4030 can hang.
+        * The only difference is that I2C clocks are now cut inbetween write
+        * and read transfers.
+        */
+       ret = i2c_transfer(twl->client.adapter, twl->xfer_msg, 1);
+       if (ret < 0)
+               goto out;
+
        /* [MSG2] fill the data rx buffer */
        msg = &twl->xfer_msg[1];
        msg->addr = twl->address;
        msg->flags = I2C_M_RD;  /* Read the register value */
        msg->len = num_bytes;   /* only n bytes */
        msg->buf = value;
-       ret = i2c_transfer(twl->client.adapter, twl->xfer_msg, 2);
+       ret = i2c_transfer(twl->client.adapter, twl->xfer_msg, 1);
+
+out:
        mutex_unlock(&twl->xfer_lock);
 
        /* i2cTransfer returns num messages.translate it pls.. */
        if (ret >= 0)
                ret = 0;
+
        return ret;
 }