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   1 From 7e4404113686868858a34210c28ae122e967aa64 Mon Sep 17 00:00:00 2001
   2 From: Mauri Sandberg <sandberg@mailfence.com>
   3 Date: Tue, 9 Mar 2021 19:48:59 +0200
   4 Subject: [PATCH] mtd: cfi_cmdset_0002: Disable buffered writes for AMD chip
   5  0x2201
   6
   7 Buffer writes do not work with AMD chip 0x2201. The chip in question
   8 is a AMD/Spansion/Cypress Semiconductor S29GL256N and datasheet [1]
   9 talks about writing buffers being possible. While waiting for a neater
  10 solution resort to writing word-sized chunks only.
  11
  12 Without the patch kernel logs will be flooded with entries like below:
  13
  14 jffs2_scan_eraseblock(): End of filesystem marker found at 0x0
  15 jffs2_build_filesystem(): unlocking the mtd device...
  16 done.
  17 jffs2_build_filesystem(): erasing all blocks after the end marker...
  18 MTD do_write_buffer_wait(): software timeout, address:0x01ec000a.
  19 jffs2: Write clean marker to block at 0x01920000 failed: -5
  20 MTD do_write_buffer_wait(): software timeout, address:0x01e2000a.
  21 jffs2: Write clean marker to block at 0x01880000 failed: -5
  22 MTD do_write_buffer_wait(): software timeout, address:0x01e0000a.
  23 jffs2: Write clean marker to block at 0x01860000 failed: -5
  24 MTD do_write_buffer_wait(): software timeout, address:0x01dc000a.
  25 jffs2: Write clean marker to block at 0x01820000 failed: -5
  26 MTD do_write_buffer_wait(): software timeout, address:0x01da000a.
  27 jffs2: Write clean marker to block at 0x01800000 failed: -5
  28 ...
  29
  30 Tested on a Buffalo wzr-hp-g300nh running kernel 5.10.16.
  31
  32 [1] https://www.cypress.com/file/219941/download
  33 or  https://datasheetspdf.com/pdf-file/565708/SPANSION/S29GL256N/1
  34
  35 Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
  36 Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
  37 Link: https://lore.kernel.org/r/20210309174859.362060-1-sandberg@mailfence.com
  38 ---
  39  drivers/mtd/chips/cfi_cmdset_0002.c | 4 ++++
  40  1 file changed, 4 insertions(+)
  41
  42 --- a/drivers/mtd/chips/cfi_cmdset_0002.c
  43 +++ b/drivers/mtd/chips/cfi_cmdset_0002.c
  44 @@ -276,6 +276,10 @@ static void fixup_use_write_buffers(stru
  45  {
  46         struct map_info *map = mtd->priv;
  47         struct cfi_private *cfi = map->fldrv_priv;
  48 +
  49 +       if (cfi->mfr == CFI_MFR_AMD && cfi->id == 0x2201)
  50 +               return;
  51 +
  52         if (cfi->cfiq->BufWriteTimeoutTyp) {
  53                 pr_debug("Using buffer write method\n");
  54                 mtd->_write = cfi_amdstd_write_buffers;