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Message-Id: <20231123160721.64561-2-tudor.ambarus@linaro.org>
Date: Thu, 23 Nov 2023 18:07:20 +0200
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: pratyush@...nel.org, michael@...le.cc
Cc: linux-mtd@...ts.infradead.org, linux-doc@...r.kernel.org,
corbet@....net, linux-kernel@...r.kernel.org,
Tudor Ambarus <tudor.ambarus@...aro.org>
Subject: [PATCH 1/2] 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.
Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
---
Documentation/driver-api/mtd/spi-nor.rst | 189 +++++++++++++++++++++++
1 file changed, 189 insertions(+)
diff --git a/Documentation/driver-api/mtd/spi-nor.rst b/Documentation/driver-api/mtd/spi-nor.rst
index c22f8c0f7950..cc8e81e09544 100644
--- a/Documentation/driver-api/mtd/spi-nor.rst
+++ b/Documentation/driver-api/mtd/spi-nor.rst
@@ -63,3 +63,192 @@ 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/spi1.0/spi-nor/partname
+ sst26vf064b
+ root@1:~# cat /sys/bus/spi/devices/spi1.0/spi-nor/jedec_id
+ bf2643
+ root@1:~# cat /sys/bus/spi/devices/spi1.0/spi-nor/manufacturer
+ sst
+ root@1:~# hexdump -C /sys/bus/spi/devices/spi1.0/spi-nor/sfdp
+ 00000000 53 46 44 50 06 01 02 ff 00 06 01 10 30 00 00 ff |SFDP........0...|
+ 00000010 81 00 01 06 00 01 00 ff bf 00 01 18 00 02 00 01 |................|
+ 00000020 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
+ 00000030 fd 20 f1 ff ff ff ff 03 44 eb 08 6b 08 3b 80 bb |. ......D..k.;..|
+ 00000040 fe ff ff ff ff ff 00 ff ff ff 44 0b 0c 20 0d d8 |..........D.. ..|
+ 00000050 0f d8 10 d8 20 91 48 24 80 6f 1d 81 ed 0f 77 38 |.... .H$.o....w8|
+ 00000060 30 b0 30 b0 f7 ff ff ff 29 c2 5c ff f0 30 c0 80 |0.0.....).\..0..|
+ 00000070 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
+ *
+ 00000100 ff 00 04 ff f3 7f 00 00 f5 7f 00 00 f9 ff 7d 00 |..............}.|
+ 00000110 f5 7f 00 00 f3 7f 00 00 ff ff ff ff ff ff ff ff |................|
+ 00000120 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
+ *
+ 00000200 bf 26 43 ff b9 5f fd ff 30 f2 60 f3 32 ff 0a 12 |.&C.._..0.`.2...|
+ 00000210 23 46 ff 0f 19 32 0f 19 19 ff ff ff ff ff ff ff |#F...2..........|
+ 00000220 00 66 99 38 ff 05 01 35 06 04 02 32 b0 30 72 42 |.f.8...5...2.0rB|
+ 00000230 8d e8 98 88 a5 85 c0 9f af 5a ff ff 06 ec 06 0c |.........Z......|
+ 00000240 00 03 08 0b ff ff ff ff ff 07 ff ff 02 02 ff 06 |................|
+ 00000250 03 00 fd fd 04 07 00 fc 03 00 fe fe 02 02 07 0e |................|
+ 00000260
+ root@1:~# sha256sum /sys/bus/spi/devices/spi1.0/spi-nor/sfdp
+ 428f34d0461876f189ac97f93e68a05fa6428c6650b3b7baf736a921e5898ed1 /sys/bus/spi/devices/spi1.0/spi-nor/sfdp
+
+3/ Dump debugfs data::
+
+ root@1:~# cat /sys/kernel/debug/spi-nor/spi1.0/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/spi1.0/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.
+
+a/ Generate a 2 MB file::
+
+ 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
+
+b/ Verify erase::
+
+ root@1:~# mtd_debug write /dev/mtd1 0 2097152 spi_test
+ Copied 2097152 bytes from spi_test to address 0x00000000 in flash
+
+ root@1:~# mtd_debug erase /dev/mtd1 0 2097152
+ Erased 2097152 bytes from address 0x00000000 in flash
+
+ root@1:~# mtd_debug read /dev/mtd1 0 2097152 spi_read
+ Copied 2097152 bytes from address 0x00000000 in flash to spi_read
+
+ root@1:~# hexdump -C spi_read
+ 00000000 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
+ *
+ 00200000
+
+c/ Write, read back and compare::
+
+ root@1:~# mtd_debug write /dev/mtd1 0 2097152 spi_test
+ Copied 2097152 bytes from spi_test to address 0x00000000 in flash
+
+ root@1:~# mtd_debug read /dev/mtd1 0 2097152 spi_read
+ Copied 2097152 bytes from address 0x00000000 in flash to spi_read
+
+ root@1:~# sha1sum spi_*
+ 51eeddc316a4121cf96e76e526d94d638283ec22 spi_read
+ 51eeddc316a4121cf96e76e526d94d638283ec22 spi_test
+
+d/ Dump mtd_info data::
+
+ root@1:~# mtd_debug info /dev/mtd1
+ 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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