[PATCH v6 01/11] mtd: cfi_cmdset_0002: Use chip_good() to retry in do_write_oneword() - Linux-stable-mirror

26 May 2019

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.
Signed-off-by: Tokunori Ikegami ikegami.t@gmail.com
Signed-off-by: Felix Fietkau nbd@nbd.name
Co-Developed-by: Hauke Mehrtens hauke@hauke-m.de
Co-Developed-by: Koen Vandeputte koen.vandeputte@ncentric.com
Reported-by: Fabio Bettoni fbettoni@gmail.com
Cc: Chris Packham chris.packham@alliedtelesis.co.nz
Cc: Joakim Tjernlund Joakim.Tjernlund@infinera.com
Cc: linux-mtd@lists.infradead.org
Cc: stable@vger.kernel.org
---
Changes since v5:
- Rebased on top of Liu Jian's fixes in master.
- Change to follow Liu Jian's fixes in master for the write buffer.
- Change the email address of Tokunori Ikegami to ikegami.t@gmail.com.
Changes since v4:
- None.
Changes since v3:
- Update the commit message for the comments.
- Drop the addition of blanks lines around xip_enable().
- Delete unnecessary setting the ret variable to -EIO.
- Change the email address of Tokunori Ikegami to ikegami_to@yahoo.co.jp.
Changes since v2:
- Just update the commit message for the comment.
Changes since v1:
- Just update the commit message.
Background:
This is required for OpenWrt Project to result the flash write issue as
below patche.
https://git.openwrt.org/?p=openwrt/openwrt.git;a=commitdiff;h=ddc11c3932c7b7b7df7d5fbd48f207e77619eaa7
Also the original patch in OpenWRT is below.
https://github.com/openwrt/openwrt/blob/v18.06.0/target/linux/ar71xx/patches-4.9/403-mtd_fix_cfi_cmdset_0002_status_check.patch
The reason to use chip_good() is that just actually fix the issue.
And also in the past I had fixed the erase function also as same way by the
patch below.
  https://patchwork.ozlabs.org/patch/922656/
    Note: The reason for the patch for erase is same.
In my understanding the chip_ready() is just checked the value twice from
flash.
So I think that sometimes incorrect value is read twice and it is depended
on the flash device behavior but not sure..
So change to use chip_good() instead of chip_ready().
drivers/mtd/chips/cfi_cmdset_0002.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)
 mode change 100644 => 100755 drivers/mtd/chips/cfi_cmdset_0002.c

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
old mode 100644
new mode 100755
index c8fa5906bdf9..348b54820e4c
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -1628,29 +1628,35 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip,
    		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:
-- 
2.11.0


    