linux-kernel - Re: [PATCH 1/2] docs: mtd: spi-nor: add sections about flash additions and testing

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Date:   Fri, 24 Nov 2023 15:57:04 +0000
From:   Tudor Ambarus <tudor.ambarus@...aro.org>
To:     Pratyush Yadav <pratyush@...nel.org>
Cc:     michael@...le.cc, linux-mtd@...ts.infradead.org,
        linux-doc@...r.kernel.org, corbet@....net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] docs: mtd: spi-nor: add sections about flash
 additions and testing



On 11/24/23 14:36, Pratyush Yadav wrote:
> Hi,
> 
> 
> On Thu, Nov 23 2023, Tudor Ambarus wrote:
> 
>> 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.
> [...]
>> +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
> 
> Perhaps mention that the 2 MiB region should already be erased.
> Otherwise some flashes might refuse the writes (like the ones with ECC

right, then maybe we could do a

/erase
/read
/dump and see 0xff
/sha1sum to have the 0xff checksum
/write
/read what was written
/sha1sum on the read to make it's different that the 0xff checksum and
that the write worked

> -- Cypress S28 family comes to mind). Experienced engineers should know
> this already but it might trip up some beginners.
> 
> Looks good otherwise. Thanks for working on this.
> 
> Reviewed-by: Pratyush Yadav <pratyush@...nel.org>
> 
>> +
>> +    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
>> +
> [...]
>