mtd: nand: check status before reporting timeout

In commit b70af9bef4 ("mtd: nand: increase ready wait timeout and
report timeouts"), we increased the likelihood of scheduling during
nand_wait(). This makes us more likely to hit the time_before(...)
condition, since a lot of time may pass before we get scheduled again.

Now, the loop was already buggy, since we don't check if the NAND is
ready after exiting the loop; we simply print out a timeout warning. Fix
this by doing a final status check before printing a timeout message.

This isn't actually a critical bug, since the only effect is a false
warning print. But too many prints never hurt anyone, did they? :)

Side note: perhaps I'm not smart enough, but I'm not sure what the best
policy is for this kind of loop; do we busy loop (i.e., no
cond_resched()) to keep the lowest I/O latency (it's not great if the
resched is delaying Richard's system ~400ms)? Or do we allow
rescheduling, to play nice with the rest of the system (since some
operations can take quite a while)?

Reported-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Harvey Hunt <harvey.hunt@imgtec.com>

drivers/mtd/nand/nand_base.c

@@ -566,8 +566,8 @@ void nand_wait_ready(struct mtd_info *mtd)
 		cond_resched();
 	} while (time_before(jiffies, timeo));
 
-	pr_warn_ratelimited(
-		"timeout while waiting for chip to become ready\n");
+	if (!chip->dev_ready(mtd))
+		pr_warn_ratelimited("timeout while waiting for chip to become ready\n");
 out:
 	led_trigger_event(nand_led_trigger, LED_OFF);
 }