Unverified Commit bb1f9e39 authored by Tudor Ambarus's avatar Tudor Ambarus
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docs: mtd: spi-nor: add sections about flash additions and testing 



Add sections about how to propose a new flash addition and about the
minimum testing requirements.

Reviewed-by: default avatarMichael Walle <michael@walle.cc>
Reviewed-by: default avatarPratyush Yadav <pratyush@kernel.org>
Link: https://lore.kernel.org/r/20231124184902.1194235-2-tudor.ambarus@linaro.org


Signed-off-by: default avatarTudor Ambarus <tudor.ambarus@linaro.org>
parent 4137f324

Documentation/driver-api/mtd/spi-nor.rst

+202 −0
Original line number Diff line number Diff line
@@ -63,3 +63,205 @@ 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@1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/partname

    sst26vf064b

    root@1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/jedec_id

    bf2643

    root@1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/manufacturer

    sst

    root@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@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@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@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@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@1:~# mtd_debug erase /dev/mtd0 0 2097152

    Erased 2097152 bytes from address 0x00000000 in flash



    root@1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read

    Copied 2097152 bytes from address 0x00000000 in flash to spi_read



    root@1:~# hexdump spi_read

    0000000 ffff ffff ffff ffff ffff ffff ffff ffff

    *

    0200000



    root@1:~# sha256sum spi_read

    4bda3a28f4ffe603c0ec1258c0034d65a1a0d35ab7bd523a834608adabf03cc5  spi_read



    root@1:~# mtd_debug write /dev/mtd0 0 2097152 spi_test

    Copied 2097152 bytes from spi_test to address 0x00000000 in flash



    root@1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read

    Copied 2097152 bytes from address 0x00000000 in flash to spi_read



    root@1:~# sha256sum spi*

    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_read

    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_test



   If the flash comes erased by default and the previous erase was ignored,

   we won't catch it, thus test the erase again::



    root@1:~# mtd_debug erase /dev/mtd0 0 2097152

    Erased 2097152 bytes from address 0x00000000 in flash



    root@1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read

    Copied 2097152 bytes from address 0x00000000 in flash to spi_read



    root@1:~# sha256sum spi*

    4bda3a28f4ffe603c0ec1258c0034d65a1a0d35ab7bd523a834608adabf03cc5  spi_read

    c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8  spi_test



   Dump some other relevant data::



    root@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