1 files changed, 45 insertions, 15 deletions

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 2440b7411978..3c94c4a81a55 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -270,14 +270,30 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
 
 	/* Rounds down to not include partial word at the end of buf */
 	words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD;
-	if (words_to_transfer > tx_fifo_avail)
-		words_to_transfer = tx_fifo_avail;
 
-	i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
-
-	buf += words_to_transfer * BYTES_PER_FIFO_WORD;
-	buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
-	tx_fifo_avail -= words_to_transfer;
+	/* It's very common to have < 4 bytes, so optimize that case. */
+	if (words_to_transfer) {
+		if (words_to_transfer > tx_fifo_avail)
+			words_to_transfer = tx_fifo_avail;
+
+		/*
+		 * Update state before writing to FIFO.  If this casues us
+		 * to finish writing all bytes (AKA buf_remaining goes to 0) we
+		 * have a potential for an interrupt (PACKET_XFER_COMPLETE is
+		 * not maskable).  We need to make sure that the isr sees
+		 * buf_remaining as 0 and doesn't call us back re-entrantly.
+		 */
+		buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
+		tx_fifo_avail -= words_to_transfer;
+		i2c_dev->msg_buf_remaining = buf_remaining;
+		i2c_dev->msg_buf = buf +
+			words_to_transfer * BYTES_PER_FIFO_WORD;
+		barrier();
+
+		i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
+
+		buf += words_to_transfer * BYTES_PER_FIFO_WORD;
+	}
 
 	/*
 	 * If there is a partial word at the end of buf, handle it manually to
@@ -287,14 +303,15 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
 	if (tx_fifo_avail > 0 && buf_remaining > 0) {
 		BUG_ON(buf_remaining > 3);
 		memcpy(&val, buf, buf_remaining);
+
+		/* Again update before writing to FIFO to make sure isr sees. */
+		i2c_dev->msg_buf_remaining = 0;
+		i2c_dev->msg_buf = NULL;
+		barrier();
+
 		i2c_writel(i2c_dev, val, I2C_TX_FIFO);
-		buf_remaining = 0;
-		tx_fifo_avail--;
 	}
 
-	BUG_ON(tx_fifo_avail > 0 && buf_remaining > 0);
-	i2c_dev->msg_buf_remaining = buf_remaining;
-	i2c_dev->msg_buf = buf;
 	return 0;
 }
 
@@ -411,9 +428,10 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 			tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
 	}
 
-	if ((status & I2C_INT_PACKET_XFER_COMPLETE) &&
-			!i2c_dev->msg_buf_remaining)
+	if (status & I2C_INT_PACKET_XFER_COMPLETE) {
+		BUG_ON(i2c_dev->msg_buf_remaining);
 		complete(&i2c_dev->msg_complete);
+	}
 
 	i2c_writel(i2c_dev, status, I2C_INT_STATUS);
 	if (i2c_dev->is_dvc)
@@ -531,7 +549,7 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 
 static u32 tegra_i2c_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C;
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 }
 
 static const struct i2c_algorithm tegra_i2c_algo = {
@@ -719,6 +737,17 @@ static int tegra_i2c_resume(struct platform_device *pdev)
 }
 #endif
 
+#if defined(CONFIG_OF)
+/* Match table for of_platform binding */
+static const struct of_device_id tegra_i2c_of_match[] __devinitconst = {
+	{ .compatible = "nvidia,tegra20-i2c", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, tegra_i2c_of_match);
+#else
+#define tegra_i2c_of_match NULL
+#endif
+
 static struct platform_driver tegra_i2c_driver = {
 	.probe   = tegra_i2c_probe,
 	.remove  = tegra_i2c_remove,
@@ -729,6 +758,7 @@ static struct platform_driver tegra_i2c_driver = {
 	.driver  = {
 		.name  = "tegra-i2c",
 		.owner = THIS_MODULE,
+		.of_match_table = tegra_i2c_of_match,
 	},
 };