[U-Boot] [PATCH] Exynos5: i2c: Fix read NACK handling and remove some redundancy

[Akshay Saraswat]

From: Gabe Black <gabeblack at google.com>

The exynos s3c24x0 i2c driver wouldn't do the right thing when a NACK was
received on a read because it didn't attempt a read before waiting for the
read to finish. Putting a call to ReadWriteByte in the NACK path fixed a
problem where getting a NACK reading from a device would jam up the bus and
prevent future accesses like probing from working.

Because other than the ReadWriteByte call the NACK and normal paths were
almost the same thing, and to avoid future instances of the NACK path not
working because it's not exercised normally, this change also consolidates
those two paths.

Signed-off-by: Gabe Black <gabeblack at google.com>
Signed-off-by: Akshay Saraswat <akshay.s at samsung.com>
---
 drivers/i2c/s3c24x0_i2c.c | 53 ++++++++++++++++-------------------------------
 1 file changed, 18 insertions(+), 35 deletions(-)

diff --git a/drivers/i2c/s3c24x0_i2c.c b/drivers/i2c/s3c24x0_i2c.c
index d2b4eb0..91298a7 100644
--- a/drivers/i2c/s3c24x0_i2c.c
+++ b/drivers/i2c/s3c24x0_i2c.c
@@ -366,21 +366,25 @@ static int i2c_transfer(struct s3c24x0_i2c *i2c,
 		break;
 
 	case I2C_READ:
-		if (result == I2C_OK) {
-			writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
-			writel(chip, &i2c->iicds);
-			/* send START */
-			writel(readl(&i2c->iicstat) | I2C_START_STOP,
-			       &i2c->iicstat);
-			ReadWriteByte(i2c);
-			result = WaitForXfer(i2c);
+	{
+		int was_ok = (result == I2C_OK);
+
+		writel(chip, &i2c->iicds);
+		/* resend START */
+		writel(I2C_MODE_MR | I2C_TXRX_ENA |
+					I2C_START_STOP, &i2c->iicstat);
+		ReadWriteByte(i2c);
+		result = WaitForXfer(i2c);
+
+		if (was_ok || IsACK(i2c)) {
 			i = 0;
 			while ((i < data_len) && (result == I2C_OK)) {
 				/* disable ACK for final READ */
-				if (i == data_len - 1)
-					writel(readl(&i2c->iiccon)
-							& ~I2CCON_ACKGEN,
-							&i2c->iiccon);
+				if (i == data_len - 1) {
+					writel(readl(&i2c->iiccon) &
+					      ~I2CCON_ACKGEN,
+					      &i2c->iiccon);
+				}
 				ReadWriteByte(i2c);
 				result = WaitForXfer(i2c);
 				data[i] = readl(&i2c->iicds);
@@ -388,35 +392,14 @@ static int i2c_transfer(struct s3c24x0_i2c *i2c,
 			}
 
 		} else {
-			writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
-			writel(chip, &i2c->iicds);
-			/* send START */
-			writel(readl(&i2c->iicstat) | I2C_START_STOP,
-			       &i2c->iicstat);
-			result = WaitForXfer(i2c);
-
-			if (IsACK(i2c)) {
-				i = 0;
-				while ((i < data_len) && (result == I2C_OK)) {
-					/* disable ACK for final READ */
-					if (i == data_len - 1)
-						writel(readl(&i2c->iiccon) &
-							~I2CCON_ACKGEN,
-							&i2c->iiccon);
-					ReadWriteByte(i2c);
-					result = WaitForXfer(i2c);
-					data[i] = readl(&i2c->iicds);
-					i++;
-				}
-			} else {
-				result = I2C_NACK;
-			}
+			result = I2C_NACK;
 		}
 
 		/* send STOP */
 		writel(I2C_MODE_MR | I2C_TXRX_ENA, &i2c->iicstat);
 		ReadWriteByte(i2c);
 		break;
+	}
 
 	default:
 		debug("i2c_transfer: bad call\n");
-- 
1.8.0