i2c-omap: OMAP3: Fix I2C lockup during timeout/error cases

Current OMAP3 I2C driver code does not follow the correct sequence for soft
reset. Due to this, lock up issues are reported during timeout/error cases.

This patch fixes above issue by disabling I2C controller as per OMAP3430 TRM
for soft reset. As per TRM, I2C controller needs to be disabled as a first
step during soft reset.

Here is correct soft reset sequence:
a. Ensure that the module is disabled
(clear the I2Ci.I2C_CON[15] I2C_EN bit to 0).
b. Set the I2Ci.I2C_SYSC[1] SRST bit to 1.
c. Enable the module by setting I2Ci.I2C_CON[15] I2C_EN bit to 1.
d. Check the I2Ci.I2C_SYSS[0] RDONE bit until it is set to 1 to
indicate the software reset is complete.

Tested on Zoom2, Zoom3, 3430SDP and 3630SDP

Signed-off-by: Manjunatha GK <manjugk@ti.com>
Signed-off-by: George, Harith<harith@ti.com>
Acked-by: Varadarajan, Charu Latha<charu@ti.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

drivers/i2c/busses/i2c-omap.c

@@ -286,6 +286,11 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
 	unsigned long internal_clk = 0;
 
 	if (dev->rev >= OMAP_I2C_REV_2) {
+		/* Disable I2C controller before soft reset */
+		omap_i2c_write_reg(dev, OMAP_I2C_CON_REG,
+			omap_i2c_read_reg(dev, OMAP_I2C_CON_REG) &
+				~(OMAP_I2C_CON_EN));
+
 		omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG, SYSC_SOFTRESET_MASK);
 		/* For some reason we need to set the EN bit before the
 		 * reset done bit gets set. */