spi-intel.rst (3227B)
1============================== 2Upgrading BIOS using spi-intel 3============================== 4 5Many Intel CPUs like Baytrail and Braswell include SPI serial flash host 6controller 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 to 9avoid accidental (or on purpose) overwrite of the content. 10 11Not all manufacturers protect the SPI serial flash, mainly because it 12allows upgrading the BIOS image directly from an OS. 13 14The spi-intel driver makes it possible to read and write the SPI serial 15flash, if certain protection bits are not set and locked. If it finds 16any of them set, the whole MTD device is made read-only to prevent 17partial overwrites. By default the driver exposes SPI serial flash 18contents 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 flash 22might render the machine unbootable and requires special equipment like 23Dediprog to revive. You have been warned! 24 25Below are the steps how to upgrade MinnowBoard MAX BIOS directly from 26Linux. 27 28 1) Download and extract the latest Minnowboard MAX BIOS SPI image 29 [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 SPI 32 serial flash. Distros like Debian and Fedora have this prepackaged with 33 name "mtd-utils". 34 35 3) Add "spi_intel.writeable=1" to the kernel command line and reboot 36 the board (you can also reload the driver passing "writeable=1" as 37 module parameter to modprobe). 38 39 4) Once the board is up and running again, find the right MTD partition 40 (it is named as "BIOS"):: 41 42 # cat /proc/mtd 43 dev: size erasesize name 44 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.bak 51 16384+0 records in 52 16384+0 records out 53 8388608 bytes (8.4 MB) copied, 10.0269 s, 837 kB/s 54 55 6) Verify the backup:: 56 57 # sha1sum /dev/mtd0ro bios.bak 58 fdbb011920572ca6c991377c4b418a0502668b73 /dev/mtd0ro 59 fdbb011920572ca6c991377c4b418a0502668b73 bios.bak 60 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 the 64 board! Otherwise it will not start anymore:: 65 66 # flash_erase /dev/mtd0 0 0 67 Erasing 4 Kibyte @ 7ff000 -- 100 % complete 68 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/mtd0 72 73 9) Verify that the new content of the SPI serial flash matches the new 74 BIOS image:: 75 76 # sha1sum /dev/mtd0ro MNW2MAX1.X64.0092.R01.1605221712.bin 77 9b4df9e4be2057fceec3a5529ec3d950836c87a2 /dev/mtd0ro 78 9b4df9e4be2057fceec3a5529ec3d950836c87a2 MNW2MAX1.X64.0092.R01.1605221712.bin 79 80 The SHA1 sums should match. 81 82 10) Now you can reboot your board and observe the new BIOS starting up 83 properly. 84 85References 86---------- 87 88[1] https://firmware.intel.com/sites/default/files/MinnowBoard%2EMAX_%2EX64%2E92%2ER01%2Ezip 89 90[2] http://www.linux-mtd.infradead.org/