NAND: Add timeout for reset command

Without the timeout present an infinite loop can occur if the
NAND device is broken or not present.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index bfa7874..d33fee2 100644 (file)
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -75,6 +75,17 @@
 #include <jffs2/jffs2.h>
 #endif
 
+/*
+ * CONFIG_SYS_NAND_RESET_CNT is used as a timeout mechanism when resetting
+ * a flash.  NAND flash is initialized prior to interrupts so standard timers
+ * can't be used.  CONFIG_SYS_NAND_RESET_CNT should be set to a value
+ * which is greater than (max NAND reset time / NAND status read time).
+ * A conservative default of 200000 (500 us / 25 ns) is used as a default.
+ */
+#ifndef CONFIG_SYS_NAND_RESET_CNT
+#define CONFIG_SYS_NAND_RESET_CNT 200000
+#endif
+
 /* Define default oob placement schemes for large and small page devices */
 static struct nand_ecclayout nand_oob_8 = {
        .eccbytes = 3,
@@ -524,6 +535,7 @@ static void nand_command(struct mtd_info *mtd, unsigned int command,
 {
        register struct nand_chip *chip = mtd->priv;
        int ctrl = NAND_CTRL_CLE | NAND_CTRL_CHANGE;
+       uint32_t rst_sts_cnt = CONFIG_SYS_NAND_RESET_CNT;
 
        /*
         * Write out the command to the device.
@@ -590,7 +602,8 @@ static void nand_command(struct mtd_info *mtd, unsigned int command,
                               NAND_CTRL_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd,
                               NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);
-               while (!(chip->read_byte(mtd) & NAND_STATUS_READY)) ;
+               while (!(chip->read_byte(mtd) & NAND_STATUS_READY) &&
+                       (rst_sts_cnt--));
                return;
 
                /* This applies to read commands */
@@ -626,6 +639,7 @@ static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
                            int column, int page_addr)
 {
        register struct nand_chip *chip = mtd->priv;
+       uint32_t rst_sts_cnt = CONFIG_SYS_NAND_RESET_CNT;
 
        /* Emulate NAND_CMD_READOOB */
        if (command == NAND_CMD_READOOB) {
@@ -696,7 +710,8 @@ static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
                               NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
                chip->cmd_ctrl(mtd, NAND_CMD_NONE,
                               NAND_NCE | NAND_CTRL_CHANGE);
-               while (!(chip->read_byte(mtd) & NAND_STATUS_READY)) ;
+               while (!(chip->read_byte(mtd) & NAND_STATUS_READY) &&
+                       (rst_sts_cnt--));
                return;
 
        case NAND_CMD_RNDOUT: