Documentation/mtd/intel-spi.txt

   1 Upgrading BIOS using intel-spi
   2 ------------------------------
   3
   4 Many Intel CPUs like Baytrail and Braswell include SPI serial flash host
   5 controller which is used to hold BIOS and other platform specific data.
   6 Since contents of the SPI serial flash is crucial for machine to function,
   7 it is typically protected by different hardware protection mechanisms to
   8 avoid accidental (or on purpose) overwrite of the content.
   9
  10 Not all manufacturers protect the SPI serial flash, mainly because it
  11 allows upgrading the BIOS image directly from an OS.
  12
  13 The intel-spi driver makes it possible to read and write the SPI serial
  14 flash, if certain protection bits are not set and locked. If it finds
  15 any of them set, the whole MTD device is made read-only to prevent
  16 partial overwrites. By default the driver exposes SPI serial flash
  17 contents as read-only but it can be changed from kernel command line,
  18 passing "intel-spi.writeable=1".
  19
  20 Please keep in mind that overwriting the BIOS image on SPI serial flash
  21 might render the machine unbootable and requires special equipment like
  22 Dediprog to revive. You have been warned!
  23
  24 Below are the steps how to upgrade MinnowBoard MAX BIOS directly from
  25 Linux.
  26
  27  1) Download and extract the latest Minnowboard MAX BIOS SPI image
  28     [1]. At the time writing this the latest image is v92.
  29
  30  2) Install mtd-utils package [2]. We need this in order to erase the SPI
  31     serial flash. Distros like Debian and Fedora have this prepackaged with
  32     name "mtd-utils".
  33
  34  3) Add "intel-spi.writeable=1" to the kernel command line and reboot
  35     the board (you can also reload the driver passing "writeable=1" as
  36     module parameter to modprobe).
  37
  38  4) Once the board is up and running again, find the right MTD partition
  39     (it is named as "BIOS"):
  40
  41     # cat /proc/mtd
  42     dev:    size   erasesize  name
  43     mtd0: 00800000 00001000 "BIOS"
  44
  45     So here it will be /dev/mtd0 but it may vary.
  46
  47  5) Make backup of the existing image first:
  48
  49     # dd if=/dev/mtd0ro of=bios.bak
  50     16384+0 records in
  51     16384+0 records out
  52     8388608 bytes (8.4 MB) copied, 10.0269 s, 837 kB/s
  53
  54  6) Verify the backup
  55
  56     # sha1sum /dev/mtd0ro bios.bak
  57     fdbb011920572ca6c991377c4b418a0502668b73  /dev/mtd0ro
  58     fdbb011920572ca6c991377c4b418a0502668b73  bios.bak
  59
  60     The SHA1 sums must match. Otherwise do not continue any further!
  61
  62  7) Erase the SPI serial flash. After this step, do not reboot the
  63     board! Otherwise it will not start anymore.
  64
  65     # flash_erase /dev/mtd0 0 0
  66     Erasing 4 Kibyte @ 7ff000 -- 100 % complete
  67
  68  8) Once completed without errors you can write the new BIOS image:
  69
  70     # dd if=MNW2MAX1.X64.0092.R01.1605221712.bin of=/dev/mtd0
  71
  72  9) Verify that the new content of the SPI serial flash matches the new
  73     BIOS image:
  74
  75     # sha1sum /dev/mtd0ro MNW2MAX1.X64.0092.R01.1605221712.bin
  76     9b4df9e4be2057fceec3a5529ec3d950836c87a2  /dev/mtd0ro
  77     9b4df9e4be2057fceec3a5529ec3d950836c87a2 MNW2MAX1.X64.0092.R01.1605221712.bin
  78
  79     The SHA1 sums should match.
  80
  81  10) Now you can reboot your board and observe the new BIOS starting up
  82      properly.
  83
  84 References
  85 ----------
  86
  87 [1] https://firmware.intel.com/sites/default/files/MinnowBoard.MAX_.X64.92.R01.zip
  88 [2] http://www.linux-mtd.infradead.org/