fsl: verify writes to the MAC address EEPROM

Update the code which writes to the on-board EEPROM so that it can detect if
the write failed because the EEPROM is write-protected.  Most of the 8xxx-class
Freescale reference boards use an AT24C02 EEPROM to store MAC addresses and
similar information.  With this patch, if the EEPROM is protected, the
"mac save" command will display an error message indicating that the write
has not succeeded.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

board/freescale/common/sys_eeprom.c

@@ -204,7 +204,7 @@ static void update_crc(void)
  */
 static int prog_eeprom(void)
 {
-	int ret = 0; /* shut up gcc */
+	int ret = 0;
 	int i;
 	void *p;
 #ifdef CONFIG_SYS_EEPROM_BUS_NUM
@@ -225,6 +225,11 @@ static int prog_eeprom(void)
 	i2c_set_bus_num(CONFIG_SYS_EEPROM_BUS_NUM);
 #endif
 
+	/*
+	 * The AT24C02 datasheet says that data can only be written in page
+	 * mode, which means 8 bytes at a time, and it takes up to 5ms to
+	 * complete a given write.
+	 */
 	for (i = 0, p = &e; i < sizeof(e); i += 8, p += 8) {
 		ret = i2c_write(CONFIG_SYS_I2C_EEPROM_ADDR, i, CONFIG_SYS_I2C_EEPROM_ADDR_LEN,
 			p, min((sizeof(e) - i), 8));
@@ -233,12 +238,23 @@ static int prog_eeprom(void)
 		udelay(5000);	/* 5ms write cycle timing */
 	}
 
+	if (!ret) {
+		/* Verify the write by reading back the EEPROM and comparing */
+		struct eeprom e2;
+
+		ret = i2c_read(CONFIG_SYS_I2C_EEPROM_ADDR, 0,
+			CONFIG_SYS_I2C_EEPROM_ADDR_LEN, (void *)&e2, sizeof(e2));
+		if (!ret && memcmp(&e, &e2, sizeof(e)))
+			ret = -1;
+	}
+
 #ifdef CONFIG_SYS_EEPROM_BUS_NUM
 	i2c_set_bus_num(bus);
 #endif
 
 	if (ret) {
 		printf("Programming failed.\n");
+		has_been_read = 0;
 		return -1;
 	}