mtd: nand: hack ONFI for non-power-of-2 dimensions

mtd: nand: hack ONFI for non-power-of-2 dimensions

Some bright specification writers decided to write this in the ONFI spec
(from ONFI 3.0, Section 3.1):

  "The number of blocks and number of pages per block is not required to
  be a power of two. In the case where one of these values is not a
  power of two, the corresponding address shall be rounded to an
  integral number of bits such that it addresses a range up to the
  subsequent power of two value. The host shall not access upper
  addresses in a range that is shown as not supported."

This breaks every assumption MTD makes about NAND block/chip-size
dimensions -- they *must* be a power of two!

And of course, an enterprising manufacturer has made use of this lovely
freedom. Exhibit A: Micron MT29F32G08CBADAWP

  "- Plane size: 2 planes x 1064 blocks per plane
   - Device size: 32Gb: 2128 blockss [sic]"

This quickly hits a BUG() in nand_base.c, since the extra dimensions
overflow so we think it's a second chip (on my single-chip setup):

    ONFI param page 0 valid
    ONFI flash detected
    NAND device: Manufacturer ID: 0x2c, Chip ID: 0x44 (Micron MT29F32G08CBADAWP), 4256MiB, page size: 8192, OOB size: 744
    ------------[ cut here ]------------
    kernel BUG at drivers/mtd/nand/nand_base.c:203!
    Internal error: Oops - BUG: 0 [#1] SMP ARM
    [... trim ...]
    [<c02cf3e4>] (nand_select_chip+0x18/0x2c) from [<c02d25c0>] (nand_do_read_ops+0x90/0x424)
    [<c02d25c0>] (nand_do_read_ops+0x90/0x424) from [<c02d2dd8>] (nand_read+0x54/0x78)
    [<c02d2dd8>] (nand_read+0x54/0x78) from [<c02ad2c8>] (mtd_read+0x84/0xbc)
    [<c02ad2c8>] (mtd_read+0x84/0xbc) from [<c02d4b28>] (scan_read.clone.4+0x4c/0x64)
    [<c02d4b28>] (scan_read.clone.4+0x4c/0x64) from [<c02d4c88>] (search_bbt+0x148/0x290)
    [<c02d4c88>] (search_bbt+0x148/0x290) from [<c02d4ea4>] (nand_scan_bbt+0xd4/0x5c0)
    [... trim ...]
    ---[ end trace 0c9363860d865ff2 ]---

So to fix this, just truncate these dimensions down to the greatest
power-of-2 dimension that is less than or equal to the specified
dimension.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Cc: <stable@vger.kernel.org>