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1==============================2Upgrading BIOS using spi-intel3==============================4 5Many Intel CPUs like Baytrail and Braswell include SPI serial flash host6controller which is used to hold BIOS and other platform specific data.7Since contents of the SPI serial flash is crucial for machine to function,8it is typically protected by different hardware protection mechanisms to9avoid accidental (or on purpose) overwrite of the content.10 11Not all manufacturers protect the SPI serial flash, mainly because it12allows upgrading the BIOS image directly from an OS.13 14The spi-intel driver makes it possible to read and write the SPI serial15flash, if certain protection bits are not set and locked. If it finds16any of them set, the whole MTD device is made read-only to prevent17partial overwrites. By default the driver exposes SPI serial flash18contents as read-only but it can be changed from kernel command line,19passing "spi_intel.writeable=1".20 21Please keep in mind that overwriting the BIOS image on SPI serial flash22might render the machine unbootable and requires special equipment like23Dediprog to revive. You have been warned!24 25Below are the steps how to upgrade MinnowBoard MAX BIOS directly from26Linux.27 28 1) Download and extract the latest Minnowboard MAX BIOS SPI image29 [1]. At the time writing this the latest image is v92.30 31 2) Install mtd-utils package [2]. We need this in order to erase the SPI32 serial flash. Distros like Debian and Fedora have this prepackaged with33 name "mtd-utils".34 35 3) Add "spi_intel.writeable=1" to the kernel command line and reboot36 the board (you can also reload the driver passing "writeable=1" as37 module parameter to modprobe).38 39 4) Once the board is up and running again, find the right MTD partition40 (it is named as "BIOS")::41 42 # cat /proc/mtd43 dev: size erasesize name44 mtd0: 00800000 00001000 "BIOS"45 46 So here it will be /dev/mtd0 but it may vary.47 48 5) Make backup of the existing image first::49 50 # dd if=/dev/mtd0ro of=bios.bak51 16384+0 records in52 16384+0 records out53 8388608 bytes (8.4 MB) copied, 10.0269 s, 837 kB/s54 55 6) Verify the backup::56 57 # sha1sum /dev/mtd0ro bios.bak58 fdbb011920572ca6c991377c4b418a0502668b73 /dev/mtd0ro59 fdbb011920572ca6c991377c4b418a0502668b73 bios.bak60 61 The SHA1 sums must match. Otherwise do not continue any further!62 63 7) Erase the SPI serial flash. After this step, do not reboot the64 board! Otherwise it will not start anymore::65 66 # flash_erase /dev/mtd0 0 067 Erasing 4 Kibyte @ 7ff000 -- 100 % complete68 69 8) Once completed without errors you can write the new BIOS image::70 71 # dd if=MNW2MAX1.X64.0092.R01.1605221712.bin of=/dev/mtd072 73 9) Verify that the new content of the SPI serial flash matches the new74 BIOS image::75 76 # sha1sum /dev/mtd0ro MNW2MAX1.X64.0092.R01.1605221712.bin77 9b4df9e4be2057fceec3a5529ec3d950836c87a2 /dev/mtd0ro78 9b4df9e4be2057fceec3a5529ec3d950836c87a2 MNW2MAX1.X64.0092.R01.1605221712.bin79 80 The SHA1 sums should match.81 82 10) Now you can reboot your board and observe the new BIOS starting up83 properly.84 85References86----------87 88[1] https://firmware.intel.com/sites/default/files/MinnowBoard%2EMAX_%2EX64%2E92%2ER01%2Ezip89 90[2] http://www.linux-mtd.infradead.org/91