i2c, omap24xx: add i2c deblock sequenz

If a bus busy is detected when intializing the driver,
toggle 9 times the scl pin. Therefore enable the test mode
of the controller, in which the scl, sda pins can be
controlled manually.

Tested on the siemens boards pxm2, rut and dxr2.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Hannes Petermaier <oe5hpm@oevsv.at>
Cc: Lubomir Popov <lpopov@mm-sol.com>
Cc: Steve Sakoman <steve@sakoman.com>
Cc: Sandeep Paulraj <s-paulraj@ti.com>
Cc: Vincent Stehlé <v-stehle@ti.com>
Cc: Samuel Egli <samuel.egli@siemens.com>

drivers/i2c/omap24xx_i2c.c

@@ -153,11 +153,60 @@ static uint omap24_i2c_setspeed(struct i2c_adapter *adap, uint speed)
 
 	return 0;
 }
+
+static void omap24_i2c_deblock(struct i2c_adapter *adap)
+{
+	struct i2c *i2c_base = omap24_get_base(adap);
+	int i;
+	u16 systest;
+	u16 orgsystest;
+
+	/* set test mode ST_EN = 1 */
+	orgsystest = readw(&i2c_base->systest);
+	systest = orgsystest;
+	/* enable testmode */
+	systest |= I2C_SYSTEST_ST_EN;
+	writew(systest, &i2c_base->systest);
+	systest &= ~I2C_SYSTEST_TMODE_MASK;
+	systest |= 3 << I2C_SYSTEST_TMODE_SHIFT;
+	writew(systest, &i2c_base->systest);
+
+	/* set SCL, SDA  = 1 */
+	systest |= I2C_SYSTEST_SCL_O | I2C_SYSTEST_SDA_O;
+	writew(systest, &i2c_base->systest);
+	udelay(10);
+
+	/* toggle scl 9 clocks */
+	for (i = 0; i < 9; i++) {
+		/* SCL = 0 */
+		systest &= ~I2C_SYSTEST_SCL_O;
+		writew(systest, &i2c_base->systest);
+		udelay(10);
+		/* SCL = 1 */
+		systest |= I2C_SYSTEST_SCL_O;
+		writew(systest, &i2c_base->systest);
+		udelay(10);
+	}
+
+	/* send stop */
+	systest &= ~I2C_SYSTEST_SDA_O;
+	writew(systest, &i2c_base->systest);
+	udelay(10);
+	systest |= I2C_SYSTEST_SCL_O | I2C_SYSTEST_SDA_O;
+	writew(systest, &i2c_base->systest);
+	udelay(10);
+
+	/* restore original mode */
+	writew(orgsystest, &i2c_base->systest);
+}
+
 static void omap24_i2c_init(struct i2c_adapter *adap, int speed, int slaveadd)
 {
 	struct i2c *i2c_base = omap24_get_base(adap);
 	int timeout = I2C_TIMEOUT;
+	int deblock = 1;
 
+retry:
 	if (readw(&i2c_base->con) & I2C_CON_EN) {
 		writew(0, &i2c_base->con);
 		udelay(50000);
@@ -194,6 +243,14 @@ static void omap24_i2c_init(struct i2c_adapter *adap, int speed, int slaveadd)
 	udelay(1000);
 	flush_fifo(adap);
 	writew(0xFFFF, &i2c_base->stat);
+
+	/* Handle possible failed I2C state */
+	if (wait_for_bb(adap))
+		if (deblock == 1) {
+			omap24_i2c_deblock(adap);
+			deblock = 0;
+			goto retry;
+		}
 }
 
 static void flush_fifo(struct i2c_adapter *adap)