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Subject[PATCH] mtd: nand: Prevent possible kernel lockup in nand_command()
Date
If a NAND device is not really present or pin muxes are not correctly
configured we can lock up the kernel waiting infinitely for NAND_STATUS
to be ready.

This can be easily reproduced on TI's DRA7-evm board by booting it
without NAND support in u-boot and disabling NAND pin muxes in the kernel.

Add timeout when waiting for NAND_CMD_RESET completion. As per ONFi v4.0
tRST can be upto 250ms for EZ-NAND and 5ms for raw NAND.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
---
drivers/mtd/nand/nand_base.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index df7eb4f..d1e6695 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -566,6 +566,25 @@ void nand_wait_ready(struct mtd_info *mtd)
EXPORT_SYMBOL_GPL(nand_wait_ready);

/**
+ * nand_wait_status_ready - [GENERIC] Wait for the ready status after commands.
+ * @mtd: MTD device structure
+ * @timeo: Timeout in ms
+ *
+ * Wait for status ready (i.e. command done) or timeout.
+ */
+static void nand_wait_status_ready(struct mtd_info *mtd, unsigned long timeo)
+{
+ register struct nand_chip *chip = mtd->priv;
+
+ timeo = jiffies + msecs_to_jiffies(timeo);
+ do {
+ if ((chip->read_byte(mtd) & NAND_STATUS_READY))
+ break;
+ touch_softlockup_watchdog();
+ } while (time_before(jiffies, timeo));
+};
+
+/**
* nand_command - [DEFAULT] Send command to NAND device
* @mtd: MTD device structure
* @command: the command to be sent
@@ -643,8 +662,8 @@ 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))
- ;
+ /* EZ-NAND can take upto 250ms as per ONFi v4.0 */
+ nand_wait_status_ready(mtd, 250);
return;

/* This applies to read commands */
@@ -740,8 +759,8 @@ 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))
- ;
+ /* EZ-NAND can take upto 250ms as per ONFi v4.0 */
+ nand_wait_status_ready(mtd, 250);
return;

case NAND_CMD_RNDOUT:
--
2.1.0


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