[PATCH v2 1/2] docs: mtd: spi-nor: add sections about flash additions and testing
Tudor Ambarus
tudor.ambarus at linaro.org
Fri Nov 24 10:49:01 PST 2023
Add sections about how to propose a new flash addition and about the
minimum testing requirements.
Signed-off-by: Tudor Ambarus <tudor.ambarus at linaro.org>
Reviewed-by: Michael Walle <michael at walle.cc>
Reviewed-by: Pratyush Yadav <pratyush at kernel.org>
---
Documentation/driver-api/mtd/spi-nor.rst | 187 +++++++++++++++++++++++
1 file changed, 187 insertions(+)
diff --git a/Documentation/driver-api/mtd/spi-nor.rst b/Documentation/driver-api/mtd/spi-nor.rst
index c22f8c0f7950..3b2e1a6a88bf 100644
--- a/Documentation/driver-api/mtd/spi-nor.rst
+++ b/Documentation/driver-api/mtd/spi-nor.rst
@@ -63,3 +63,190 @@ The main API is spi_nor_scan(). Before you call the hook, a driver should
initialize the necessary fields for spi_nor{}. Please see
drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to spi-fsl-qspi.c
when you want to write a new driver for a SPI NOR controller.
+
+How to propose a new flash addition
+-----------------------------------
+
+Most SPI NOR flashes comply with the JEDEC JESD216
+Serial Flash Discoverable Parameter (SFDP) standard. SFDP describes
+the functional and feature capabilities of serial flash devices in a
+standard set of internal read-only parameter tables.
+
+The SPI NOR driver queries the SFDP tables in order to determine the
+flash's parameters and settings. If the flash defines the SFDP tables
+it's likely that you won't need a flash entry at all, and instead
+rely on the generic flash driver which probes the flash solely based
+on its SFDP data. All one has to do is to specify the "jedec,spi-nor"
+compatible in the device tree.
+
+There are cases however where you need to define an explicit flash
+entry. This typically happens when the flash has settings or support
+that is not covered by the SFDP tables (e.g. Block Protection), or
+when the flash contains mangled SFDP data. If the later, one needs
+to implement the ``spi_nor_fixups`` hooks in order to amend the SFDP
+parameters with the correct values.
+
+Minimum testing requirements
+-----------------------------
+
+Do all the tests from below and paste them in the commit's comments
+section, after the ``---`` marker.
+
+1) Specify the controller that you used to test the flash and specify
+ the frequency at which the flash was operated, e.g.::
+
+ This flash is populated on the X board and was tested at Y
+ frequency using the Z (put compatible) SPI controller.
+
+2) Dump the sysfs entries and print the md5/sha1/sha256 SFDP checksum::
+
+ root at 1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/partname
+ sst26vf064b
+ root at 1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/jedec_id
+ bf2643
+ root at 1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/manufacturer
+ sst
+ root at 1:~# xxd -p /sys/bus/spi/devices/spi0.0/spi-nor/sfdp
+ 53464450060102ff00060110300000ff81000106000100ffbf0001180002
+ 0001fffffffffffffffffffffffffffffffffd20f1ffffffff0344eb086b
+ 083b80bbfeffffffffff00ffffff440b0c200dd80fd810d820914824806f
+ 1d81ed0f773830b030b0f7ffffff29c25cfff030c080ffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffff0004fff37f0000f57f0000f9ff
+ 7d00f57f0000f37f0000ffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+ ffffbf2643ffb95ffdff30f260f332ff0a122346ff0f19320f1919ffffff
+ ffffffff00669938ff05013506040232b03072428de89888a585c09faf5a
+ ffff06ec060c0003080bffffffffff07ffff0202ff060300fdfd040700fc
+ 0300fefe0202070e
+ root at 1:~# sha256sum /sys/bus/spi/devices/spi0.0/spi-nor/sfdp
+ 428f34d0461876f189ac97f93e68a05fa6428c6650b3b7baf736a921e5898ed1 /sys/bus/spi/devices/spi0.0/spi-nor/sfdp
+
+ Please dump the SFDP tables using ``xxd -p``. It enables us to do
+ the reverse operation and convert the hexdump to binary with
+ ``xxd -rp``. Dumping the SFDP data with ``hexdump -Cv`` is accepted,
+ but less desirable.
+
+3) Dump debugfs data::
+
+ root at 1:~# cat /sys/kernel/debug/spi-nor/spi0.0/capabilities
+ Supported read modes by the flash
+ 1S-1S-1S
+ opcode 0x03
+ mode cycles 0
+ dummy cycles 0
+ 1S-1S-1S (fast read)
+ opcode 0x0b
+ mode cycles 0
+ dummy cycles 8
+ 1S-1S-2S
+ opcode 0x3b
+ mode cycles 0
+ dummy cycles 8
+ 1S-2S-2S
+ opcode 0xbb
+ mode cycles 4
+ dummy cycles 0
+ 1S-1S-4S
+ opcode 0x6b
+ mode cycles 0
+ dummy cycles 8
+ 1S-4S-4S
+ opcode 0xeb
+ mode cycles 2
+ dummy cycles 4
+ 4S-4S-4S
+ opcode 0x0b
+ mode cycles 2
+ dummy cycles 4
+
+ Supported page program modes by the flash
+ 1S-1S-1S
+ opcode 0x02
+
+ root at 1:~# cat /sys/kernel/debug/spi-nor/spi0.0/params
+ name sst26vf064b
+ id bf 26 43 bf 26 43
+ size 8.00 MiB
+ write size 1
+ page size 256
+ address nbytes 3
+ flags HAS_LOCK | HAS_16BIT_SR | SOFT_RESET | SWP_IS_VOLATILE
+
+ opcodes
+ read 0xeb
+ dummy cycles 6
+ erase 0x20
+ program 0x02
+ 8D extension none
+
+ protocols
+ read 1S-4S-4S
+ write 1S-1S-1S
+ register 1S-1S-1S
+
+ erase commands
+ 20 (4.00 KiB) [0]
+ d8 (8.00 KiB) [1]
+ d8 (32.0 KiB) [2]
+ d8 (64.0 KiB) [3]
+ c7 (8.00 MiB)
+
+ sector map
+ region (in hex) | erase mask | flags
+ ------------------+------------+----------
+ 00000000-00007fff | [01 ] |
+ 00008000-0000ffff | [0 2 ] |
+ 00010000-007effff | [0 3] |
+ 007f0000-007f7fff | [0 2 ] |
+ 007f8000-007fffff | [01 ] |
+
+4) Use `mtd-utils <https://git.infradead.org/mtd-utils.git>`__
+ and verify that erase, read and page program operations work fine::
+
+ root at 1:~# dd if=/dev/urandom of=./spi_test bs=1M count=2
+ 2+0 records in
+ 2+0 records out
+ 2097152 bytes (2.1 MB, 2.0 MiB) copied, 0.848566 s, 2.5 MB/s
+
+ 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:~# hexdump spi_read
+ 0000000 ffff ffff ffff ffff ffff ffff ffff ffff
+ *
+ 0200000
+
+ root at 1:~# sha256sum spi_read
+ 4bda3a28f4ffe603c0ec1258c0034d65a1a0d35ab7bd523a834608adabf03cc5 spi_read
+
+ 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:~# mtd_debug info /dev/mtd0
+ mtd.type = MTD_NORFLASH
+ mtd.flags = MTD_CAP_NORFLASH
+ mtd.size = 8388608 (8M)
+ mtd.erasesize = 4096 (4K)
+ mtd.writesize = 1
+ mtd.oobsize = 0
+ regions = 0
--
2.34.1
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