Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:8 as permitted sender) client-ip=2620:137:e000::3:8;
MIME-Version: 1.0
Date:   Thu, 23 Nov 2023 17:14:51 +0100
From:   Michael Walle <michael@walle.cc>
To:     Tudor Ambarus <tudor.ambarus@linaro.org>
Cc:     pratyush@kernel.org, linux-mtd@lists.infradead.org,
        linux-doc@vger.kernel.org, corbet@lwn.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] docs: mtd: spi-nor: add sections about flash
 additions and testing
In-Reply-To: <20231123160721.64561-2-tudor.ambarus@linaro.org>
References: <20231123160721.64561-1-tudor.ambarus@linaro.org>
 <20231123160721.64561-2-tudor.ambarus@linaro.org>
Message-ID: <7194991f6f307a84356e18543f27cf49@walle.cc>
Content-Type: text/plain; charset=US-ASCII;
 format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi Tudor,

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

Thanks for doing this :)

> Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.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

Please use "xxd -p" (and maybe mention that if xxd is not available,
"hexdump -Cv" could be used instead). With xxd one can just use "xxd 
-rp"
to generate a binary again.

Otherwise looks good. So with the above fixed:

Reviewed-by: Michael Walle <michael@walle.cc>

> +    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