[PATCH v2 19/27] mtd: spi-nor: Add steps for testing locking support

[Miquel Raynal]

As recently raised on the mailing list, it may be useful to propose a
list of steps to go through in order to proove the devices have been
described correctly, especially since all the block protection
information is not stored in any kind of table and is instead filled
manually by developpers.

Use the debugfs output to ease the comparison between expectations and
reality.

Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 Documentation/driver-api/mtd/spi-nor.rst | 128 +++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)

diff --git a/Documentation/driver-api/mtd/spi-nor.rst b/Documentation/driver-api/mtd/spi-nor.rst
index 148fa4288760..4755eb75fe5e 100644
--- a/Documentation/driver-api/mtd/spi-nor.rst
+++ b/Documentation/driver-api/mtd/spi-nor.rst
@@ -203,3 +203,131 @@ section, after the ``---`` marker.
     mtd.writesize = 1
     mtd.oobsize = 0
     regions = 0
+
+5) If your flash supports locking, please go through the following test
+   procedure to make sure it correctly behaves. The below example
+   expects the typical situation where eraseblocks and lock sectors have
+   the same size. In case you enabled MTD_SPI_NOR_USE_4K_SECTORS, you
+   must adapt `bs` accordingly.
+
+   Warning: These tests may hard lock your device! Make sure:
+   - The device is not hard locked already (#WP strapped to low and
+     SR_SRWD bit set)
+   - If you have a WPn pin, you may want to set `no-wp` in your DT for
+     the time of the test, to only make use of software protection.
+     Otherwise, clearing the locking state depends on the WPn
+     signal and if it is tied to low, the flash will be permanently
+     locked.
+
+   Test full chip locking and make sure expectations, the MEMISLOCKED
+   ioctl output, the debugfs output and experimental results are all
+   aligned::
+
+    root at 1:~# alias show_sectors='grep -A4 "locked sectors" /sys/kernel/debug/spi-nor/spi0.0/params'
+    root at 1:~# flash_lock -u /dev/mtd0
+    root at 1:~# flash_lock -i /dev/mtd0
+    Device: /dev/mtd0
+    Start: 0
+    Len: 0x4000000
+    Lock status: unlocked
+    Return code: 0
+    root at 1:~# mtd_debug erase /dev/mtd0 0 2097152
+    Erased 2097152 bytes from address 0x00000000 in flash
+    root at 1:~# mtd_debug write /dev/mtd0 0 2097152 spi_test
+    Copied 2097152 bytes from spi_test to address 0x00000000 in flash
+    root at 1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read
+    Copied 2097152 bytes from address 0x00000000 in flash to spi_read
+    root at 1:~# sha256sum spi*
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_read
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_test
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-03ffffff | unlocked | 1024
+
+    root at 1:~# flash_lock -l /dev/mtd0
+    root at 1:~# flash_lock -i /dev/mtd0
+    Device: /dev/mtd0
+    Start: 0
+    Len: 0x4000000
+    Lock status: locked
+    Return code: 1
+    root at 1:~# mtd_debug erase /dev/mtd0 0 2097152
+    Erased 2097152 bytes from address 0x00000000 in flash
+    root at 1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read
+    Copied 2097152 bytes from address 0x00000000 in flash to spi_read
+    root at 1:~# sha256sum spi*
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_read
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_test
+    root at 1:~# dd if=/dev/urandom of=./spi_test2 bs=1M count=2
+    2+0 records in
+    2+0 records out
+    root at 1:~# mtd_debug write /dev/mtd0 0 2097152 spi_test2
+    Copied 2097152 bytes from spi_test to address 0x00000000 in flash
+    root at 1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read2
+    Copied 2097152 bytes from address 0x00000000 in flash to spi_read
+    root at 1:~# sha256sum spi*
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_read
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_read2
+    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_test
+    bea9334df51c620440f86751cba0799214a016329f1736f9456d40cf40efdc88  spi_test2
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-03ffffff |   locked | 1024
+
+   Once we trust the debugfs output we can use it to test various
+   situations. Check top locking/unlocking (end of the device)::
+
+    root at 1:~# bs=$(cat /sys/class/mtd/mtd0/erasesize)
+    root at 1:~# size=$(cat /sys/class/mtd/mtd0/size)
+
+    root at 1:~# flash_lock -u /dev/mtd0
+    root at 1:~# flash_lock -l /dev/mtd0 $(($size - (2 * $bs))) 2 # last two
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-03fdffff | unlocked | 1022
+     03fe0000-03ffffff |   locked | 2
+    root at 1:~# flash_lock -u /dev/mtd0 $(($size - (2 * $bs))) 1 # last one
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-03feffff | unlocked | 1023
+     03ff0000-03ffffff |   locked | 1
+
+   If the flash features 4 block protection bits (BP), we can protect
+   more than 4MB (typically 128 64kiB-blocks or more), with a finer
+   grain than locking the entire device::
+
+    root at 1:~# flash_lock -u /dev/mtd0
+    root at 1:~# flash_lock -l /dev/mtd0 $(($size - (2**7 * $bs))) $((2**7))
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-037fffff | unlocked | 896
+     03800000-03ffffff |   locked | 128
+
+   If the flash features a Top/Bottom (TB) bit, we can protect the
+   beginning of the flash::
+
+    root at 1:~# flash_lock -u /dev/mtd0
+    root at 1:~# flash_lock -l /dev/mtd0 0 2 # first two
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-0001ffff |   locked | 2
+     00020000-03ffffff | unlocked | 1022
+    root at 1:~# flash_lock -u /dev/mtd0 $bs 1 # first one
+    root at 1:~# show_sectors
+    software locked sectors
+     region (in hex)   | status   | #blocks
+     ------------------+----------+--------
+     00000000-0000ffff |   locked | 1
+     00010000-03ffffff | unlocked | 1023

-- 
2.51.1