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mtd: spi-nor: Add steps for testing locking with CMP

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Extend the test coverage by giving guidelines to verify the CMP bit acts
according to our expectations.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
This commit is contained in:
Miquel Raynal
2026-05-26 16:56:46 +02:00
committed by Pratyush Yadav
parent e3fb31d884
commit f5d81415a7
1 changed files with 37 additions and 0 deletions
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37
Documentation/driver-api/mtd/spi-nor.rst
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@@ -336,3 +336,40 @@ section, after the ``---`` marker.
------------------+----------+---------
00000000-0000ffff | locked | 1
00010000-03ffffff | unlocked | 1023
If the flash features a Complement (CMP) bit, we can protect with
more granularity above half of the capacity. Let's lock all but one
block, then unlock one more block::
root@1:~# all_but_one=$((($size / $bs) - ($ss / $bs)))
root@1:~# flash_lock -u /dev/mtd0
root@1:~# flash_lock -l /dev/mtd0 $ss $all_but_one # all but the first
root@1:~# show_sectors
software locked sectors
region (in hex) | status | #sectors
------------------+----------+---------
00000000-0000ffff | unlocked | 1
00010000-03ffffff | locked | 1023
root@1:~# flash_lock -u /dev/mtd0 $ss $(($ss / $bs)) # all but the two first
root@1:~# show_sectors
software locked sectors
region (in hex) | status | #sectors
------------------+----------+---------
00000000-0001ffff | unlocked | 2
00020000-03ffffff | locked | 1022
root@1:~# flash_lock -u /dev/mtd0
root@1:~# flash_lock -l /dev/mtd0 0 $all_but_one # same from the other side
root@1:~# show_sectors
software locked sectors
region (in hex) | status | #sectors
------------------+----------+---------
00000000-03feffff | locked | 1023
03ff0000-03ffffff | unlocked | 1
root@1:~# flash_lock -u /dev/mtd0 $(($size - (2 * $ss))) $(($ss / $bs)) # all but two
root@1:~# show_sectors
software locked sectors
region (in hex) | status | #sectors
------------------+----------+---------
00000000-03fdffff | locked | 1022
03fe0000-03ffffff | unlocked | 2