fixed: system halt if the flash chip was not found

u-boot-tree/drivers/mtd/nand/zynq_nand.c

@@ -279,6 +279,7 @@ static int zynq_nand_init_nand_flash(int option)
 	status = zynq_nand_waitfor_ecc_completion();
 	if (status < 0) {
 		printf("%s: Timeout\n", __func__);
+		udelay(100);
 		return status;
 	}
 
@@ -776,6 +777,9 @@ static void zynq_nand_cmd_function(struct mtd_info *mtd, unsigned int command,
 	unsigned long end_cmd_valid = 0;
 	unsigned long i;
 	
+	/* Wait max 10 time units */
+	int timeout = 10;
+
 	//printf(" zynq_nand(): Command=0x%02x Column=0x%02x PageAddr=0x%08x\n",command,column,page_addr);
 
 	xnand = (struct zynq_nand_info *)chip->priv;
@@ -896,8 +900,14 @@ static void zynq_nand_cmd_function(struct mtd_info *mtd, unsigned int command,
 	    (command == NAND_CMD_RESET) ||
 	    (command == NAND_CMD_PARAM) ||
 	    (command == NAND_CMD_GET_FEATURES)) {
-		while (!chip->dev_ready(mtd))
-				;
+		while (!chip->dev_ready(mtd)){
+			if (timeout==0) {
+				printf("ERROR: nand flash command timeout\n");
+				break;
+			}
+			timeout--;
+			udelay(10);
+		}
 		return;
 	}
 }