i2c: rcar: improve bus busy detection

I2C doesn't define a timeout for bus busy, so an arbitrary value like
LOOP_TIMEOUT is not a good idea. Let's use the timeout value in struct
adapter which is meant for such cases and is user-configurable (via
IOCTL). To reduce the load, wait 10us instead of 1us which is good
enough for the slow frequencies used by I2C. Finally, use the
poll_timeout helper instead of open coding it.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-rcar.c

@@ -19,6 +19,7 @@
 #include <linux/err.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/i2c.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -221,18 +222,18 @@ static void rcar_i2c_init(struct rcar_i2c_priv *priv)
 
 static int rcar_i2c_bus_barrier(struct rcar_i2c_priv *priv)
 {
-	int i;
-
-	for (i = 0; i < LOOP_TIMEOUT; i++) {
-		/* make sure that bus is not busy */
-		if (!(rcar_i2c_read(priv, ICMCR) & FSDA))
-			return 0;
-		udelay(1);
-	}
+	int ret;
+	u32 val;
 
+	ret = readl_poll_timeout(priv->io + ICMCR, val, !(val & FSDA), 10,
+				 priv->adap.timeout);
+	if (ret) {
 		/* Waiting did not help, try to recover */
 		priv->recovery_icmcr = MDBS | OBPC | FSDA | FSCL;
-	return i2c_recover_bus(&priv->adap);
+		ret = i2c_recover_bus(&priv->adap);
+	}
+
+	return ret;
 }
 
 static int rcar_i2c_clock_calculate(struct rcar_i2c_priv *priv)