1Upgrading BIOS using intel-spi 2------------------------------ 3 4Many Intel CPUs like Baytrail and Braswell include SPI serial flash host 5controller which is used to hold BIOS and other platform specific data. 6Since contents of the SPI serial flash is crucial for machine to function, 7it is typically protected by different hardware protection mechanisms to 8avoid accidental (or on purpose) overwrite of the content. 9 10Not all manufacturers protect the SPI serial flash, mainly because it 11allows upgrading the BIOS image directly from an OS. 12 13The intel-spi driver makes it possible to read and write the SPI serial 14flash, if certain protection bits are not set and locked. If it finds 15any of them set, the whole MTD device is made read-only to prevent 16partial overwrites. By default the driver exposes SPI serial flash 17contents as read-only but it can be changed from kernel command line, 18passing "intel-spi.writeable=1". 19 20Please keep in mind that overwriting the BIOS image on SPI serial flash 21might render the machine unbootable and requires special equipment like 22Dediprog to revive. You have been warned! 23 24Below are the steps how to upgrade MinnowBoard MAX BIOS directly from 25Linux. 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 84References 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/ 89