mtd: nand_wait: warn if the nand is busy on exit

This patch allow to detect buggy driver/hardware with
bad RnB (dev_ready) management or when timeout occurs in polling mode.

This works when dev_ready is set or not set.
There are 2 methods to wait for an erase/program command completion:

1. Wait until nand RnB pin goes high (that's what chip->dev_ready usually does)
2. Poll the device: send a status (0x70) command and read status byte in a loop
   until bit NAND_STATUS_READY is set

In all cases, you should send a status command after completion, to check if
the operation was successful. And if the operation completed, the status should
have bit NAND_STATUS_READY set.

Signed-off-by: Matthieu CASTET <matthieu.castet@parrot.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 1d5c951ebcb0..01505406ca7b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -865,6 +865,8 @@ static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
         led_trigger_event(nand_led_trigger, LED_OFF);
 
         status = (int)chip->read_byte(mtd);
+        /* This can happen if in case of timeout or buggy dev_ready */
+        WARN_ON(!(status & NAND_STATUS_READY));
         return status;
 }