diff --git a/drivers/i2c/rcar_i2c.c b/drivers/i2c/rcar_i2c.c
index a57f72a..d7b2720 100644
--- a/drivers/i2c/rcar_i2c.c
+++ b/drivers/i2c/rcar_i2c.c
@@ -18,35 +18,40 @@
 #include <asm/io.h>
 #include <wait_bit.h>
 
-#define RCAR_I2C_ICSCR			0x00
-#define RCAR_I2C_ICMCR			0x04
-#define RCAR_I2C_ICMCR_MDBS		BIT(7)
-#define RCAR_I2C_ICMCR_FSCL		BIT(6)
-#define RCAR_I2C_ICMCR_FSDA		BIT(5)
-#define RCAR_I2C_ICMCR_OBPC		BIT(4)
-#define RCAR_I2C_ICMCR_MIE		BIT(3)
+#define RCAR_I2C_ICSCR			0x00 /* slave ctrl */
+#define RCAR_I2C_ICMCR			0x04 /* master ctrl */
+#define RCAR_I2C_ICMCR_MDBS		BIT(7) /* non-fifo mode switch */
+#define RCAR_I2C_ICMCR_FSCL		BIT(6) /* override SCL pin */
+#define RCAR_I2C_ICMCR_FSDA		BIT(5) /* override SDA pin */
+#define RCAR_I2C_ICMCR_OBPC		BIT(4) /* override pins */
+#define RCAR_I2C_ICMCR_MIE		BIT(3) /* master if enable */
 #define RCAR_I2C_ICMCR_TSBE		BIT(2)
-#define RCAR_I2C_ICMCR_FSB		BIT(1)
-#define RCAR_I2C_ICMCR_ESG		BIT(0)
-#define RCAR_I2C_ICSSR			0x08
-#define RCAR_I2C_ICMSR			0x0c
+#define RCAR_I2C_ICMCR_FSB		BIT(1) /* force stop bit */
+#define RCAR_I2C_ICMCR_ESG		BIT(0) /* enable start bit gen */
+#define RCAR_I2C_ICSSR			0x08 /* slave status */
+#define RCAR_I2C_ICMSR			0x0c /* master status */
 #define RCAR_I2C_ICMSR_MASK		0x7f
-#define RCAR_I2C_ICMSR_MNR		BIT(6)
-#define RCAR_I2C_ICMSR_MAL		BIT(5)
-#define RCAR_I2C_ICMSR_MST		BIT(4)
+#define RCAR_I2C_ICMSR_MNR		BIT(6) /* Nack */
+#define RCAR_I2C_ICMSR_MAL		BIT(5) /* Arbitration lost */
+#define RCAR_I2C_ICMSR_MST		BIT(4) /* Stop */
 #define RCAR_I2C_ICMSR_MDE		BIT(3)
 #define RCAR_I2C_ICMSR_MDT		BIT(2)
 #define RCAR_I2C_ICMSR_MDR		BIT(1)
 #define RCAR_I2C_ICMSR_MAT		BIT(0)
-#define RCAR_I2C_ICSIER			0x10
-#define RCAR_I2C_ICMIER			0x14
-#define RCAR_I2C_ICCCR			0x18
+#define RCAR_I2C_ICSIER			0x10 /* slave irq enable */
+#define RCAR_I2C_ICMIER			0x14 /* master irq enable */
+#define RCAR_I2C_ICCCR			0x18 /* clock dividers */
 #define RCAR_I2C_ICCCR_SCGD_OFF		3
-#define RCAR_I2C_ICSAR			0x1c
-#define RCAR_I2C_ICMAR			0x20
-#define RCAR_I2C_ICRXD_ICTXD		0x24
+#define RCAR_I2C_ICSAR			0x1c /* slave address */
+#define RCAR_I2C_ICMAR			0x20 /* master address */
+#define RCAR_I2C_ICRXD_ICTXD		0x24 /* data port */
+/*
+ * First Bit Setup Cycle (Gen3).
+ * Defines 1st bit delay between SDA and SCL.
+ */
 #define RCAR_I2C_ICFBSCR		0x38
-#define RCAR_I2C_ICFBSCR_TCYC17		0x0f
+#define RCAR_I2C_ICFBSCR_TCYC17		0x0f /* 17*Tcyc */
+
 
 enum rcar_i2c_type {
 	RCAR_I2C_TYPE_GEN2,