i2c: mpc: Wait for STOP to hit the bus

mpc_i2c_stop() only initiates STOP but does not wait for it to
hit the I2C bus. This is a problem when using I2C devices which
uses fairly long clock stretching just before STOP if you also
have an i2c-mux which may switch to another bus before STOP has
been processed.
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>

drivers/i2c/busses/i2c-mpc.c

@@ -576,7 +576,23 @@ static int mpc_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 			    mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, i);
 		}
 	}
-	mpc_i2c_stop(i2c);
+	mpc_i2c_stop(i2c); /* Initiate STOP */
+	orig_jiffies = jiffies;
+	/* Wait until STOP is seen, allow up to 1 s */
+	while (readb(i2c->base + MPC_I2C_SR) & CSR_MBB) {
+		if (time_after(jiffies, orig_jiffies + HZ)) {
+			u8 status = readb(i2c->base + MPC_I2C_SR);
+
+			dev_dbg(i2c->dev, "timeout\n");
+			if ((status & (CSR_MCF | CSR_MBB | CSR_RXAK)) != 0) {
+				writeb(status & ~CSR_MAL,
+				       i2c->base + MPC_I2C_SR);
+				mpc_i2c_fixup(i2c);
+			}
+			return -EIO;
+		}
+		cond_resched();
+	}
 	return (ret < 0) ? ret : num;
 }