Patch "mtd: cfi_cmdset_0002: Use chip_good() to retry in do_write_oneword()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

mtd: cfi_cmdset_0002: Use chip_good() to retry in do_write_oneword()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mtd-cfi_cmdset_0002-use-chip_good-to-retry-in-do_write_oneword.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From 37c673ade35c707d50583b5b25091ff8ebdeafd7 Mon Sep 17 00:00:00 2001
From: Tokunori Ikegami <[email protected]>
Date: Tue, 6 Aug 2019 04:03:18 +0900
Subject: mtd: cfi_cmdset_0002: Use chip_good() to retry in do_write_oneword()

From: Tokunori Ikegami <[email protected]>

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.

---
 drivers/mtd/chips/cfi_cmdset_0002.c |   18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

@@ -1626,29 +1626,35 @@ 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:

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mtd-cfi_cmdset_0002-use-chip_good-to-retry-in-do_write_oneword.patch

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/