target/linux/generic/pending-5.15/402-mtd-spi-nor-write-support-for-minor-aligned-partitions.patch

   1 From acacdac272927ae1d96e0bca51eb82899671eaea Mon Sep 17 00:00:00 2001
   2 From: John Thomson <git@johnthomson.fastmail.com.au>
   3 Date: Fri, 25 Dec 2020 18:50:08 +1000
   4 Subject: [PATCH] mtd: spi-nor: write support for minor aligned partitions
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 Do not prevent writing to mtd partitions where a partition boundary sits
  10 on a minor erasesize boundary.
  11 This addresses a FIXME that has been present since the start of the
  12 linux git history:
  13 /* Doesn't start on a boundary of major erase size */
  14 /* FIXME: Let it be writable if it is on a boundary of
  15  * _minor_ erase size though */
  16
  17 Allow a uniform erase region spi-nor device to be configured
  18 to use the non-uniform erase regions code path for an erase with:
  19 CONFIG_MTD_SPI_NOR_USE_VARIABLE_ERASE=y
  20
  21 On supporting hardware (SECT_4K: majority of current SPI-NOR device)
  22 provide the facility for an erase to use the least number
  23 of SPI-NOR operations, as well as access to 4K erase without
  24 requiring CONFIG_MTD_SPI_NOR_USE_4K_SECTORS
  25
  26 Introduce erasesize_minor to the mtd struct,
  27 the smallest erasesize supported by the device
  28
  29 On existing devices, this is useful where write support is wanted
  30 for data on a 4K partition, such as some u-boot-env partitions,
  31 or RouterBoot soft_config, while still netting the performance
  32 benefits of using 64K sectors
  33
  34 Performance:
  35 time mtd erase firmware
  36 OpenWrt 5.10 ramips MT7621 w25q128jv 0xfc0000 partition length
  37
  38 Without this patch
  39 MTD_SPI_NOR_USE_4K_SECTORS=y    |n
  40 real    2m 11.66s               |0m 50.86s
  41 user    0m 0.00s                |0m 0.00s
  42 sys     1m 56.20s               |0m 50.80s
  43
  44 With this patch
  45 MTD_SPI_NOR_USE_VARIABLE_ERASE=n|y              |4K_SECTORS=y
  46 real    0m 51.68s               |0m 50.85s      |2m 12.89s
  47 user    0m 0.00s                |0m 0.00s       |0m 0.01s
  48 sys     0m 46.94s               |0m 50.38s      |2m 12.46s
  49
  50 Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>
  51 Signed-off-by: Thibaut VARÈNE <hacks+kernel@slashdirt.org>
  52
  53 ---
  54
  55 checkpatch does not like the printk(KERN_WARNING
  56 these should be changed separately beforehand?
  57
  58 Changes v1 -> v2:
  59 Added mtdcore sysfs for erasesize_minor
  60 Removed finding minor erasesize for variable erase regions device,
  61 as untested and no responses regarding it.
  62 Moved IF_ENABLED for SPINOR variable erase to guard setting
  63 erasesize_minor in spi-nor/core.c
  64 Removed setting erasesize to minor where partition boundaries require
  65 minor erase to be writable
  66 Simplified minor boundary check by relying on minor being a factor of
  67 major
  68
  69 Changes RFC -> v1:
  70 Fix uninitialized variable smatch warning
  71 Reported-by: kernel test robot <lkp@intel.com>
  72 Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
  73 ---
  74  drivers/mtd/mtdcore.c       | 10 ++++++++++
  75  drivers/mtd/mtdpart.c       | 35 +++++++++++++++++++++++++----------
  76  drivers/mtd/spi-nor/Kconfig | 10 ++++++++++
  77  drivers/mtd/spi-nor/core.c  | 11 +++++++++--
  78  include/linux/mtd/mtd.h     |  2 ++
  79  5 files changed, 56 insertions(+), 12 deletions(-)
  80
  81 --- a/drivers/mtd/mtdcore.c
  82 +++ b/drivers/mtd/mtdcore.c
  83 @@ -169,6 +169,15 @@ static ssize_t mtd_erasesize_show(struct
  84  }
  85  MTD_DEVICE_ATTR_RO(erasesize);
  86
  87 +static ssize_t mtd_erasesize_minor_show(struct device *dev,
  88 +               struct device_attribute *attr, char *buf)
  89 +{
  90 +       struct mtd_info *mtd = dev_get_drvdata(dev);
  91 +
  92 +       return sysfs_emit(buf, "%lu\n", (unsigned long)mtd->erasesize_minor);
  93 +}
  94 +MTD_DEVICE_ATTR_RO(erasesize_minor);
  95 +
  96  static ssize_t mtd_writesize_show(struct device *dev,
  97                 struct device_attribute *attr, char *buf)
  98  {
  99 @@ -314,6 +323,7 @@ static struct attribute *mtd_attrs[] = {
 100         &dev_attr_flags.attr,
 101         &dev_attr_size.attr,
 102         &dev_attr_erasesize.attr,
 103 +       &dev_attr_erasesize_minor.attr,
 104         &dev_attr_writesize.attr,
 105         &dev_attr_subpagesize.attr,
 106         &dev_attr_oobsize.attr,
 107 --- a/drivers/mtd/mtdpart.c
 108 +++ b/drivers/mtd/mtdpart.c
 109 @@ -41,6 +41,7 @@ static struct mtd_info *allocate_partiti
 110         struct mtd_info *master = mtd_get_master(parent);
 111         int wr_alignment = (parent->flags & MTD_NO_ERASE) ?
 112                            master->writesize : master->erasesize;
 113 +       int wr_alignment_minor = 0;
 114         u64 parent_size = mtd_is_partition(parent) ?
 115                           parent->part.size : parent->size;
 116         struct mtd_info *child;
 117 @@ -165,6 +166,7 @@ static struct mtd_info *allocate_partiti
 118         } else {
 119                 /* Single erase size */
 120                 child->erasesize = master->erasesize;
 121 +               child->erasesize_minor = master->erasesize_minor;
 122         }
 123
 124         /*
 125 @@ -172,26 +174,39 @@ static struct mtd_info *allocate_partiti
 126          * exposes several regions with different erasesize. Adjust
 127          * wr_alignment accordingly.
 128          */
 129 -       if (!(child->flags & MTD_NO_ERASE))
 130 +       if (!(child->flags & MTD_NO_ERASE)) {
 131                 wr_alignment = child->erasesize;
 132 +               wr_alignment_minor = child->erasesize_minor;
 133 +       }
 134
 135         tmp = mtd_get_master_ofs(child, 0);
 136         remainder = do_div(tmp, wr_alignment);
 137         if ((child->flags & MTD_WRITEABLE) && remainder) {
 138 -               /* Doesn't start on a boundary of major erase size */
 139 -               /* FIXME: Let it be writable if it is on a boundary of
 140 -                * _minor_ erase size though */
 141 -               child->flags &= ~MTD_WRITEABLE;
 142 -               printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase/write block boundary -- force read-only\n",
 143 -                       part->name);
 144 +               if (wr_alignment_minor) {
 145 +                       /* rely on minor being a factor of major erasesize */
 146 +                       tmp = remainder;
 147 +                       remainder = do_div(tmp, wr_alignment_minor);
 148 +               }
 149 +               if (remainder) {
 150 +                       child->flags &= ~MTD_WRITEABLE;
 151 +                       printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase/write block boundary -- force read-only\n",
 152 +                               part->name);
 153 +               }
 154         }
 155
 156         tmp = mtd_get_master_ofs(child, 0) + child->part.size;
 157         remainder = do_div(tmp, wr_alignment);
 158         if ((child->flags & MTD_WRITEABLE) && remainder) {
 159 -               child->flags &= ~MTD_WRITEABLE;
 160 -               printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase/write block -- force read-only\n",
 161 -                       part->name);
 162 +               if (wr_alignment_minor) {
 163 +                       tmp = remainder;
 164 +                       remainder = do_div(tmp, wr_alignment_minor);
 165 +               }
 166 +
 167 +               if (remainder) {
 168 +                       child->flags &= ~MTD_WRITEABLE;
 169 +                       printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase/write block -- force read-only\n",
 170 +                               part->name);
 171 +               }
 172         }
 173
 174         child->size = child->part.size;
 175 --- a/drivers/mtd/spi-nor/Kconfig
 176 +++ b/drivers/mtd/spi-nor/Kconfig
 177 @@ -10,6 +10,16 @@ menuconfig MTD_SPI_NOR
 178
 179  if MTD_SPI_NOR
 180
 181 +config MTD_SPI_NOR_USE_VARIABLE_ERASE
 182 +       bool "Disable uniform_erase to allow use of all hardware supported erasesizes"
 183 +       depends on !MTD_SPI_NOR_USE_4K_SECTORS
 184 +       default n
 185 +       help
 186 +         Allow mixed use of all hardware supported erasesizes,
 187 +         by forcing spi_nor to use the multiple eraseregions code path.
 188 +         For example: A 68K erase will use one 64K erase, and one 4K erase
 189 +         on supporting hardware.
 190 +
 191  config MTD_SPI_NOR_USE_4K_SECTORS
 192         bool "Use small 4096 B erase sectors"
 193         default y
 194 --- a/drivers/mtd/spi-nor/core.c
 195 +++ b/drivers/mtd/spi-nor/core.c
 196 @@ -1271,6 +1271,8 @@ static u8 spi_nor_convert_3to4_erase(u8
 197
 198  static bool spi_nor_has_uniform_erase(const struct spi_nor *nor)
 199  {
 200 +       if (IS_ENABLED(CONFIG_MTD_SPI_NOR_USE_VARIABLE_ERASE))
 201 +               return false;
 202         return !!nor->params->erase_map.uniform_erase_type;
 203  }
 204
 205 @@ -2391,6 +2393,7 @@ static int spi_nor_select_erase(struct s
 206  {
 207         struct spi_nor_erase_map *map = &nor->params->erase_map;
 208         const struct spi_nor_erase_type *erase = NULL;
 209 +       const struct spi_nor_erase_type *erase_minor = NULL;
 210         struct mtd_info *mtd = &nor->mtd;
 211         u32 wanted_size = nor->info->sector_size;
 212         int i;
 213 @@ -2423,8 +2426,9 @@ static int spi_nor_select_erase(struct s
 214          */
 215         for (i = SNOR_ERASE_TYPE_MAX - 1; i >= 0; i--) {
 216                 if (map->erase_type[i].size) {
 217 -                       erase = &map->erase_type[i];
 218 -                       break;
 219 +                       if (!erase)
 220 +                               erase = &map->erase_type[i];
 221 +                       erase_minor = &map->erase_type[i];
 222                 }
 223         }
 224
 225 @@ -2432,6 +2436,9 @@ static int spi_nor_select_erase(struct s
 226                 return -EINVAL;
 227
 228         mtd->erasesize = erase->size;
 229 +       if (IS_ENABLED(CONFIG_MTD_SPI_NOR_USE_VARIABLE_ERASE) &&
 230 +                       erase_minor && erase_minor->size < erase->size)
 231 +               mtd->erasesize_minor = erase_minor->size;
 232         return 0;
 233  }
 234
 235 --- a/include/linux/mtd/mtd.h
 236 +++ b/include/linux/mtd/mtd.h
 237 @@ -243,6 +243,8 @@ struct mtd_info {
 238          * information below if they desire
 239          */
 240         uint32_t erasesize;
 241 +       /* "Minor" (smallest) erase size supported by the whole device */
 242 +       uint32_t erasesize_minor;
 243         /* Minimal writable flash unit size. In case of NOR flash it is 1 (even
 244          * though individual bits can be cleared), in case of NAND flash it is
 245          * one NAND page (or half, or one-fourths of it), in case of ECC-ed NOR