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

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>

diff --git a/Documentation/driver-api/mtd/spi-nor.rst b/Documentation/driver-api/mtd/spi-nor.rst
index f817a9193731d96ace05d41eed899001114a7bd6..747a326fb6c0d564f071d1adac0a9679ae0bea57 100644 (file)
--- a/Documentation/driver-api/mtd/spi-nor.rst
+++ b/Documentation/driver-api/mtd/spi-nor.rst
@@ -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