target/linux/generic/pending-4.9/470-mtd-spi-nor-support-limiting-4K-sectors-support-base.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Sat, 4 Nov 2017 07:40:23 +0100
   3 Subject: [PATCH] mtd: spi-nor: support limiting 4K sectors support based on
   4  flash size
   5
   6 Some devices need 4K sectors to be able to deal with small flash chips.
   7 For instance, w25x05 is 64 KiB in size, and without 4K sectors, the
   8 entire chip is just one erase block.
   9 On bigger flash chip sizes, using 4K sectors can significantly slow down
  10 many operations, including using a writable filesystem. There are several
  11 platforms where it makes sense to use a single kernel on both kinds of
  12 devices.
  13
  14 To support this properly, allow configuring an upper flash chip size
  15 limit for 4K sectors support.
  16
  17 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  18 ---
  19
  20 --- a/drivers/mtd/spi-nor/Kconfig
  21 +++ b/drivers/mtd/spi-nor/Kconfig
  22 @@ -29,6 +29,17 @@ config MTD_SPI_NOR_USE_4K_SECTORS
  23           Please note that some tools/drivers/filesystems may not work with
  24           4096 B erase size (e.g. UBIFS requires 15 KiB as a minimum).
  25
  26 +config MTD_SPI_NOR_USE_4K_SECTORS_LIMIT
  27 +       int "Maximum flash chip size to use 4K sectors on (in KiB)"
  28 +       depends on MTD_SPI_NOR_USE_4K_SECTORS
  29 +       default "4096"
  30 +       help
  31 +         There are many flash chips that support 4K sectors, but are so large
  32 +         that using them significantly slows down writing large amounts of
  33 +         data or using a writable filesystem.
  34 +         Any flash chip larger than the size specified in this option will
  35 +         not use 4K sectors.
  36 +
  37  config SPI_ATMEL_QUADSPI
  38         tristate "Atmel Quad SPI Controller"
  39         depends on ARCH_AT91 || (ARM && COMPILE_TEST)
  40 --- a/drivers/mtd/spi-nor/spi-nor.c
  41 +++ b/drivers/mtd/spi-nor/spi-nor.c
  42 @@ -1642,10 +1642,12 @@ int spi_nor_scan(struct spi_nor *nor, co
  43
  44  #ifdef CONFIG_MTD_SPI_NOR_USE_4K_SECTORS
  45         /* prefer "small sector" erase if possible */
  46 -       if (info->flags & SECT_4K) {
  47 +       if ((info->flags & SECT_4K) && (mtd->size <=
  48 +           CONFIG_MTD_SPI_NOR_USE_4K_SECTORS_LIMIT * 1024)) {
  49                 nor->erase_opcode = SPINOR_OP_BE_4K;
  50                 mtd->erasesize = 4096;
  51 -       } else if (info->flags & SECT_4K_PMC) {
  52 +       } else if ((info->flags & SECT_4K_PMC) && (mtd->size <=
  53 +                  CONFIG_MTD_SPI_NOR_USE_4K_SECTORS_LIMIT * 1024)) {
  54                 nor->erase_opcode = SPINOR_OP_BE_4K_PMC;
  55                 mtd->erasesize = 4096;
  56         } else