target/linux/generic/backport-5.15/423-v6.1-0001-mtd-track-maximum-number-of-bitflips-for-each-read-r.patch

   1 From e237285113963bd1dd2e925770aa8b3aa8a1894c Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Micha=C5=82=20K=C4=99pie=C5=84?= <kernel@kempniu.pl>
   3 Date: Wed, 29 Jun 2022 14:57:34 +0200
   4 Subject: [PATCH 1/4] mtd: track maximum number of bitflips for each read
   5  request
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 mtd_read_oob() callers are currently oblivious to the details of ECC
  11 errors detected during the read operation - they only learn (through the
  12 return value) whether any corrected bitflips or uncorrectable errors
  13 occurred.  More detailed ECC information can be useful to user-space
  14 applications for making better-informed choices about moving data
  15 around.
  16
  17 Extend struct mtd_oob_ops with a pointer to a newly-introduced struct
  18 mtd_req_stats and set its 'max_bitflips' field to the maximum number of
  19 bitflips found in a single ECC step during the read operation performed
  20 by mtd_read_oob().  This is a prerequisite for ultimately passing that
  21 value back to user space.
  22
  23 Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
  24 Signed-off-by: Michał Kępień <kernel@kempniu.pl>
  25 Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
  26 Link: https://lore.kernel.org/linux-mtd/20220629125737.14418-2-kernel@kempniu.pl
  27 ---
  28  drivers/mtd/mtdcore.c   | 5 +++++
  29  include/linux/mtd/mtd.h | 5 +++++
  30  2 files changed, 10 insertions(+)
  31
  32 --- a/drivers/mtd/mtdcore.c
  33 +++ b/drivers/mtd/mtdcore.c
  34 @@ -1669,6 +1669,9 @@ int mtd_read_oob(struct mtd_info *mtd, l
  35         if (!master->_read_oob && (!master->_read || ops->oobbuf))
  36                 return -EOPNOTSUPP;
  37
  38 +       if (ops->stats)
  39 +               memset(ops->stats, 0, sizeof(*ops->stats));
  40 +
  41         if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
  42                 ret_code = mtd_io_emulated_slc(mtd, from, true, ops);
  43         else
  44 @@ -1686,6 +1689,8 @@ int mtd_read_oob(struct mtd_info *mtd, l
  45                 return ret_code;
  46         if (mtd->ecc_strength == 0)
  47                 return 0;       /* device lacks ecc */
  48 +       if (ops->stats)
  49 +               ops->stats->max_bitflips = ret_code;
  50         return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
  51  }
  52  EXPORT_SYMBOL_GPL(mtd_read_oob);
  53 --- a/include/linux/mtd/mtd.h
  54 +++ b/include/linux/mtd/mtd.h
  55 @@ -40,6 +40,10 @@ struct mtd_erase_region_info {
  56         unsigned long *lockmap;         /* If keeping bitmap of locks */
  57  };
  58
  59 +struct mtd_req_stats {
  60 +       unsigned int max_bitflips;
  61 +};
  62 +
  63  /**
  64   * struct mtd_oob_ops - oob operation operands
  65   * @mode:      operation mode
  66 @@ -70,6 +74,7 @@ struct mtd_oob_ops {
  67         uint32_t        ooboffs;
  68         uint8_t         *datbuf;
  69         uint8_t         *oobbuf;
  70 +       struct mtd_req_stats *stats;
  71  };
  72
  73  #define MTD_MAX_OOBFREE_ENTRIES_LARGE  32