Skip to content

Commit bb1f9e3

Browse files
ambarusambarus
committed
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: Michael Walle <michael@walle.cc> Reviewed-by: Pratyush Yadav <pratyush@kernel.org> Link: https://lore.kernel.org/r/20231124184902.1194235-2-tudor.ambarus@linaro.org Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
1 parent 4137f32 commit bb1f9e3

File tree

1 file changed

+202
-0
lines changed

1 file changed

+202
-0
lines changed

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

Lines changed: 202 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -63,3 +63,205 @@ The main API is spi_nor_scan(). Before you call the hook, a driver should
6363
initialize the necessary fields for spi_nor{}. Please see
6464
drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to spi-fsl-qspi.c
6565
when you want to write a new driver for a SPI NOR controller.
66+
67+
How to propose a new flash addition
68+
-----------------------------------
69+
70+
Most SPI NOR flashes comply with the JEDEC JESD216
71+
Serial Flash Discoverable Parameter (SFDP) standard. SFDP describes
72+
the functional and feature capabilities of serial flash devices in a
73+
standard set of internal read-only parameter tables.
74+
75+
The SPI NOR driver queries the SFDP tables in order to determine the
76+
flash's parameters and settings. If the flash defines the SFDP tables
77+
it's likely that you won't need a flash entry at all, and instead
78+
rely on the generic flash driver which probes the flash solely based
79+
on its SFDP data. All one has to do is to specify the "jedec,spi-nor"
80+
compatible in the device tree.
81+
82+
There are cases however where you need to define an explicit flash
83+
entry. This typically happens when the flash has settings or support
84+
that is not covered by the SFDP tables (e.g. Block Protection), or
85+
when the flash contains mangled SFDP data. If the later, one needs
86+
to implement the ``spi_nor_fixups`` hooks in order to amend the SFDP
87+
parameters with the correct values.
88+
89+
Minimum testing requirements
90+
-----------------------------
91+
92+
Do all the tests from below and paste them in the commit's comments
93+
section, after the ``---`` marker.
94+
95+
1) Specify the controller that you used to test the flash and specify
96+
the frequency at which the flash was operated, e.g.::
97+
98+
This flash is populated on the X board and was tested at Y
99+
frequency using the Z (put compatible) SPI controller.
100+
101+
2) Dump the sysfs entries and print the md5/sha1/sha256 SFDP checksum::
102+
103+
root@1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/partname
104+
sst26vf064b
105+
root@1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/jedec_id
106+
bf2643
107+
root@1:~# cat /sys/bus/spi/devices/spi0.0/spi-nor/manufacturer
108+
sst
109+
root@1:~# xxd -p /sys/bus/spi/devices/spi0.0/spi-nor/sfdp
110+
53464450060102ff00060110300000ff81000106000100ffbf0001180002
111+
0001fffffffffffffffffffffffffffffffffd20f1ffffffff0344eb086b
112+
083b80bbfeffffffffff00ffffff440b0c200dd80fd810d820914824806f
113+
1d81ed0f773830b030b0f7ffffff29c25cfff030c080ffffffffffffffff
114+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
115+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
116+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
117+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
118+
ffffffffffffffffffffffffffffffffff0004fff37f0000f57f0000f9ff
119+
7d00f57f0000f37f0000ffffffffffffffffffffffffffffffffffffffff
120+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
121+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
122+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
123+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
124+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
125+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
126+
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
127+
ffffbf2643ffb95ffdff30f260f332ff0a122346ff0f19320f1919ffffff
128+
ffffffff00669938ff05013506040232b03072428de89888a585c09faf5a
129+
ffff06ec060c0003080bffffffffff07ffff0202ff060300fdfd040700fc
130+
0300fefe0202070e
131+
root@1:~# sha256sum /sys/bus/spi/devices/spi0.0/spi-nor/sfdp
132+
428f34d0461876f189ac97f93e68a05fa6428c6650b3b7baf736a921e5898ed1 /sys/bus/spi/devices/spi0.0/spi-nor/sfdp
133+
134+
Please dump the SFDP tables using ``xxd -p``. It enables us to do
135+
the reverse operation and convert the hexdump to binary with
136+
``xxd -rp``. Dumping the SFDP data with ``hexdump -Cv`` is accepted,
137+
but less desirable.
138+
139+
3) Dump debugfs data::
140+
141+
root@1:~# cat /sys/kernel/debug/spi-nor/spi0.0/capabilities
142+
Supported read modes by the flash
143+
1S-1S-1S
144+
opcode 0x03
145+
mode cycles 0
146+
dummy cycles 0
147+
1S-1S-1S (fast read)
148+
opcode 0x0b
149+
mode cycles 0
150+
dummy cycles 8
151+
1S-1S-2S
152+
opcode 0x3b
153+
mode cycles 0
154+
dummy cycles 8
155+
1S-2S-2S
156+
opcode 0xbb
157+
mode cycles 4
158+
dummy cycles 0
159+
1S-1S-4S
160+
opcode 0x6b
161+
mode cycles 0
162+
dummy cycles 8
163+
1S-4S-4S
164+
opcode 0xeb
165+
mode cycles 2
166+
dummy cycles 4
167+
4S-4S-4S
168+
opcode 0x0b
169+
mode cycles 2
170+
dummy cycles 4
171+
172+
Supported page program modes by the flash
173+
1S-1S-1S
174+
opcode 0x02
175+
176+
root@1:~# cat /sys/kernel/debug/spi-nor/spi0.0/params
177+
name sst26vf064b
178+
id bf 26 43 bf 26 43
179+
size 8.00 MiB
180+
write size 1
181+
page size 256
182+
address nbytes 3
183+
flags HAS_LOCK | HAS_16BIT_SR | SOFT_RESET | SWP_IS_VOLATILE
184+
185+
opcodes
186+
read 0xeb
187+
dummy cycles 6
188+
erase 0x20
189+
program 0x02
190+
8D extension none
191+
192+
protocols
193+
read 1S-4S-4S
194+
write 1S-1S-1S
195+
register 1S-1S-1S
196+
197+
erase commands
198+
20 (4.00 KiB) [0]
199+
d8 (8.00 KiB) [1]
200+
d8 (32.0 KiB) [2]
201+
d8 (64.0 KiB) [3]
202+
c7 (8.00 MiB)
203+
204+
sector map
205+
region (in hex) | erase mask | flags
206+
------------------+------------+----------
207+
00000000-00007fff | [01 ] |
208+
00008000-0000ffff | [0 2 ] |
209+
00010000-007effff | [0 3] |
210+
007f0000-007f7fff | [0 2 ] |
211+
007f8000-007fffff | [01 ] |
212+
213+
4) Use `mtd-utils <https://git.infradead.org/mtd-utils.git>`__
214+
and verify that erase, read and page program operations work fine::
215+
216+
root@1:~# dd if=/dev/urandom of=./spi_test bs=1M count=2
217+
2+0 records in
218+
2+0 records out
219+
2097152 bytes (2.1 MB, 2.0 MiB) copied, 0.848566 s, 2.5 MB/s
220+
221+
root@1:~# mtd_debug erase /dev/mtd0 0 2097152
222+
Erased 2097152 bytes from address 0x00000000 in flash
223+
224+
root@1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read
225+
Copied 2097152 bytes from address 0x00000000 in flash to spi_read
226+
227+
root@1:~# hexdump spi_read
228+
0000000 ffff ffff ffff ffff ffff ffff ffff ffff
229+
*
230+
0200000
231+
232+
root@1:~# sha256sum spi_read
233+
4bda3a28f4ffe603c0ec1258c0034d65a1a0d35ab7bd523a834608adabf03cc5 spi_read
234+
235+
root@1:~# mtd_debug write /dev/mtd0 0 2097152 spi_test
236+
Copied 2097152 bytes from spi_test to address 0x00000000 in flash
237+
238+
root@1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read
239+
Copied 2097152 bytes from address 0x00000000 in flash to spi_read
240+
241+
root@1:~# sha256sum spi*
242+
c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8 spi_read
243+
c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8 spi_test
244+
245+
If the flash comes erased by default and the previous erase was ignored,
246+
we won't catch it, thus test the erase again::
247+
248+
root@1:~# mtd_debug erase /dev/mtd0 0 2097152
249+
Erased 2097152 bytes from address 0x00000000 in flash
250+
251+
root@1:~# mtd_debug read /dev/mtd0 0 2097152 spi_read
252+
Copied 2097152 bytes from address 0x00000000 in flash to spi_read
253+
254+
root@1:~# sha256sum spi*
255+
4bda3a28f4ffe603c0ec1258c0034d65a1a0d35ab7bd523a834608adabf03cc5 spi_read
256+
c444216a6ba2a4a66cccd60a0dd062bce4b865dd52b200ef5e21838c4b899ac8 spi_test
257+
258+
Dump some other relevant data::
259+
260+
root@1:~# mtd_debug info /dev/mtd0
261+
mtd.type = MTD_NORFLASH
262+
mtd.flags = MTD_CAP_NORFLASH
263+
mtd.size = 8388608 (8M)
264+
mtd.erasesize = 4096 (4K)
265+
mtd.writesize = 1
266+
mtd.oobsize = 0
267+
regions = 0

0 commit comments

Comments
 (0)