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 Signed-off-by: Hauke Mehrtens hauke@hauke-m.de 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 v7: Rebased on top of polling status register support in master.

Changes since v6: - Change the tag of Hauke Mehrtens to Signed-off-by as confirmed with him. - Removed the tag of Koen Vandeputte as confirmed with him. - Address the ./scripts/checkpatch.pl issues. - Fix to remain the file type as 100644.

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 | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c index f4da7bd552e9..19787a14350b 100644 --- a/drivers/mtd/chips/cfi_cmdset_0002.c +++ b/drivers/mtd/chips/cfi_cmdset_0002.c @@ -1717,31 +1717,36 @@ static int __xipram do_write_oneword(struct map_info *map, struct flchip *chip, continue; }

- if (time_after(jiffies, timeo) && - !chip_ready(map, chip, 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, chip, 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, chip, adr)) + if (chip_good(map, chip, 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, chip, adr, datum)) { + if (ret) { /* reset on all failures. */ cfi_check_err_status(map, chip, adr); 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: