[PATCH 3.16 21/72] mtd: cfi_cmdset_0002: Use chip_good() to retry in do_write_oneword()

[Ben Hutchings]

3.16.79-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Tokunori Ikegami <ikegami.t@xxxxxxxxx>

commit 37c673ade35c707d50583b5b25091ff8ebdeafd7 upstream.

As reported by the OpenWRT team, write requests sometimes fail on some
platforms.
Currently to check the state chip_ready() is used correctly as described by
the flash memory S29GL256P11TFI01 datasheet.
Also chip_good() is used to check if the write is succeeded and it was
implemented by the commit fb4a90bfcd6d8 ("[MTD] CFI-0002 - Improve error
checking").
But actually the write failure is caused on some platforms and also it can
be fixed by using chip_good() to check the state and retry instead.
Also it seems that it is caused after repeated about 1,000 times to retry
the write one word with the reset command.
By using chip_good() to check the state to be done it can be reduced the
retry with reset.
It is depended on the actual flash chip behavior so the root cause is
unknown.

Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
Cc: Joakim Tjernlund <Joakim.Tjernlund@xxxxxxxxxxxx>
Cc: linux-mtd@xxxxxxxxxxxxxxxxxxx
Reported-by: Fabio Bettoni <fbettoni@xxxxxxxxx>
Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
Signed-off-by: Hauke Mehrtens <hauke@xxxxxxxxxx>
Signed-off-by: Tokunori Ikegami <ikegami.t@xxxxxxxxx>
[vigneshr@xxxxxx: Fix a checkpatch warning]
Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
[bwh: Backported to 3.16:
 - chip_good() doesn't take a chip parameter
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -1295,29 +1295,36 @@ static int __xipram do_write_oneword(str
 			continue;
 		}
 
-		if (time_after(jiffies, timeo) && !chip_ready(map, adr)){
+		/*
+		 * We check "time_after" and "!chip_good" before checking
+		 * "chip_good" to avoid the failure due to scheduling.
+		 */
+		if (time_after(jiffies, timeo) &&
+		    !chip_good(map, adr, datum)) {
 			xip_enable(map, chip, adr);
 			printk(KERN_WARNING "MTD %s(): software timeout\n", __func__);
 			xip_disable(map, chip, adr);
+			ret = -EIO;
 			break;
 		}
 
-		if (chip_ready(map, adr))
+		if (chip_good(map, adr, datum))
 			break;
 
 		/* Latency issues. Drop the lock, wait a while and retry */
 		UDELAY(map, chip, adr, 1);
 	}
+
 	/* Did we succeed? */
-	if (!chip_good(map, adr, datum)) {
+	if (ret) {
 		/* reset on all failures. */
 		map_write( map, CMD(0xF0), chip->start );
 		/* FIXME - should have reset delay before continuing */
 
-		if (++retry_cnt <= MAX_RETRIES)
+		if (++retry_cnt <= MAX_RETRIES) {
+			ret = 0;
 			goto retry;
-
-		ret = -EIO;
+		}
 	}
 	xip_enable(map, chip, adr);
  op_done: