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Documentation / mtd / intel-spi.txt


Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

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/
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