Openwrt/target/linux/generic/backport-5.10/408-v5.13-mtd-cfi_cmdset_0002-Disable-buffered-writes-for-AMD.patch

From 7e4404113686868858a34210c28ae122e967aa64 Mon Sep 17 00:00:00 2001
From: Mauri Sandberg <sandberg@mailfence.com>
Date: Tue, 9 Mar 2021 19:48:59 +0200
Subject: [PATCH] mtd: cfi_cmdset_0002: Disable buffered writes for AMD chip
 0x2201

Buffer writes do not work with AMD chip 0x2201. The chip in question
is a AMD/Spansion/Cypress Semiconductor S29GL256N and datasheet [1]
talks about writing buffers being possible. While waiting for a neater
solution resort to writing word-sized chunks only.

Without the patch kernel logs will be flooded with entries like below:

jffs2_scan_eraseblock(): End of filesystem marker found at 0x0
jffs2_build_filesystem(): unlocking the mtd device...
done.
jffs2_build_filesystem(): erasing all blocks after the end marker...
MTD do_write_buffer_wait(): software timeout, address:0x01ec000a.
jffs2: Write clean marker to block at 0x01920000 failed: -5
MTD do_write_buffer_wait(): software timeout, address:0x01e2000a.
jffs2: Write clean marker to block at 0x01880000 failed: -5
MTD do_write_buffer_wait(): software timeout, address:0x01e0000a.
jffs2: Write clean marker to block at 0x01860000 failed: -5
MTD do_write_buffer_wait(): software timeout, address:0x01dc000a.
jffs2: Write clean marker to block at 0x01820000 failed: -5
MTD do_write_buffer_wait(): software timeout, address:0x01da000a.
jffs2: Write clean marker to block at 0x01800000 failed: -5
...

Tested on a Buffalo wzr-hp-g300nh running kernel 5.10.16.

[1] https://www.cypress.com/file/219941/download
or  https://datasheetspdf.com/pdf-file/565708/SPANSION/S29GL256N/1

Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20210309174859.362060-1-sandberg@mailfence.com
---
 drivers/mtd/chips/cfi_cmdset_0002.c | 4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -272,6 +272,10 @@ static void fixup_use_write_buffers(stru
 {
 	struct map_info *map = mtd->priv;
 	struct cfi_private *cfi = map->fldrv_priv;
+
+	if (cfi->mfr == CFI_MFR_AMD && cfi->id == 0x2201)
+		return;
+
 	if (cfi->cfiq->BufWriteTimeoutTyp) {
 		pr_debug("Using buffer write method\n");
 		mtd->_write = cfi_amdstd_write_buffers;