Message-ID: <ba99ef52-0c98-45a9-91e0-4fd205649e00@linaro.org>
Date: Thu, 20 Mar 2025 08:08:50 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Richard Weinberger <richard@....at>, Vignesh Raghavendra
 <vigneshr@...com>, Santhosh Kumar K <s-k6@...com>,
 Pratyush Yadav <pratyush@...nel.org>, Michael Walle <michael@...le.cc>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 Steam Lin <stlin2@...bond.com>, linux-mtd@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/21] mtd: spinand: Use more specific naming for the
 reset op

Hi, Miquel,

On 3/19/25 5:32 PM, Miquel Raynal wrote:

>>>>> -#define SPINAND_RESET_OP						\
>>>>> +#define SPINAND_RESET_1S_0_0_OP						\
>>>> Hi, Miquel,
>>>>
>>>> Have you seen any reset op with address or data? If not, I'm not really
>>>> sure whether we shall change the name for these basic operations.
>>>>
>>>> Changing them to 1S-0-0 may also indicate that there are resets with
>>>> address or data fields, which I find confusing.
>>>>
>>>> I think the change is good for reads and writes. I'll check further in
>>>> the series and let you know.
>>>
>>> I want to rename this macro for two reasons:
>>> - We might see in the near future the addition of 8D-0-0 ops (I plan on
>>>   working on it).
>>> - I would like some kind of harmony among these macros.
>>>
>>> Now, whether is should be named like I proposed or just
>>> SPINAND_RESET_OP_1S, I have no strong preference and I can change that
>>> in an upcoming version.
>>>
>>> Which one would you prefer?
>>
>> I don't know. Which one is backed up by a standard?
> 
> Well, as far as I know, none of the SPI NAND devices follow a very
> specific standard. Most vendors in practice follow similar conventions,
> but they all deviate a bit from it.
> 
>> JESD216F defines
>> "(An-Bn-Cn): Command mode nomenclature used to indicate the number of
>> active pins used for the instruction (A), address (B), and data (C), and
>> the data rate used for each. Data rates(n) can be single (S) and dual (D)."
>>
>> Also, "(x-y-z) nomenclature is equivalent to(AS-BS-CS) unless otherwise
>> noted."
>>
>> What's an "active pin"?
>>
>> Then if I look at JESD251-1.01 and JESD251C, (An-Bn-Cn) is referred to
>> as "protocol mode". Write Enable, which is just an instruction command
>> with no address or data, is seen as a required command in both 4D-4D-4D
>> and 8D-8D-8D protocol modes, and it's defined as a "1.A" transaction
>> format command. And the transaction format is:
>> '''
>> The following transaction formats are used in Profile 1.0 mode 8D-8D-8D:
>> Format 1.A: Command and Command Extension
>> Format 1.B: Command, Command Extension, 4-byte Address, ‘n’ Latency
>> Cycles, and Read Data
>> Format 1.C: Command, Command Extension, and 4-byte Address
>> Format 1.D: Command, Command Extension, 4-byte Address, and Write Data
>> '''
>>
>> So according to these standards maybe we shall refer to it as:
>> WREN-8D-8D-8D-1A? This seems less intuitive than 8D-0-0, but I think it
>> all depends on what's an "active pin". I think it describes the protocol
>> mode, and not what's actually sent on the line. As we saw, WREN is
>> considered an 8D-8D-8D command, and not an 8D-0-0 command.
>>
>> For dual mode, which is not covered by xSPI, I guess we can use the
>> single spi transaction formats 0.{A,B,C,...}.
>>
>> How do you feel about a OP-An-Bn-Cn-transaction-format,
>> 	where A, B, C is {1, 2, 4, 8}
>> 	n is {S, D}
>> 	transaction format is {0,1,2,3}{A,B,C,...}
>>
>> Care must be taken care of at the transaction format, as I see there are
>> a few, depending on the xSPI profile and protocol mode.
> 
> I must admit I really dislike the transaction format abbreviation because

I'm not in love with the "transaction format" either.

> it is specific to a spec we do not follow and is not explicit. I have a
> strong preference towards keeping just "An-Bn-Cn", like I did in this

Okay.

> series. If people are in doubt, they can check what is in the op, it is
> self explanatory. I chose this in the first place because it is more
> explicit than just "An" which may feel like a cropped
> acronym. Furthermore, most octal capable datasheets I've looked at seem
> to use the "An-Bn-Cn" format, even for single opcodes.

So for RESET, WREN, WRDI and other opcodes that don't require address
and data, are those datasheets referring to these opcodes as 1-1-1 commands?
Can you point me to one of these datasheets, please?

In SPI NOR, WREN is just WREN, regardless of the number of lines it is
sent on, 1, 4, or 8. How would you model it here, 1-0-0, 4-0-0, 8-0-0
using the same opcode?

> 
> So unless there are strong arguments against, I'd prefer to keep the
> current formatting. TBH, it is not set in stone and can still evolve
> later if that's needed.

I find the naming scheme An-Bn-Cn good, I'm arguing that it's not needed
everywhere, opcode only commands are better off with it, I think.

Cheers,
ta

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