linux-kernel - Re: [PATCH] mtd: spi-nor: add support for Microchip 25LC256

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Date:   Fri, 18 May 2018 12:03:31 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Radu Pirea <radu.pirea@...rochip.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        Zhiqiang.Hou@....com, pp@...ix.com, richard@....at,
        computersforpeace@...il.com, dwmw2@...radead.org
Subject: Re: [PATCH] mtd: spi-nor: add support for Microchip 25LC256

On 05/18/2018 11:50 AM, Radu Pirea wrote:
> 
> 
> On 05/16/2018 04:47 PM, Marek Vasut wrote:
>> On 05/16/2018 12:05 PM, Radu Pirea wrote:
>>> On Wed, 2018-05-16 at 00:17 +0200, Marek Vasut wrote:
>>>> On 05/15/2018 06:22 PM, Radu Pirea wrote:
>>>>> On Fri, 2018-05-04 at 20:40 +0200, Boris Brezillon wrote:
>>>>>> On Fri, 4 May 2018 18:54:04 +0300
>>>>>> Radu Pirea <radu.pirea@...rochip.com> wrote:
>>>>>>
>>>>>>> Added geometry description for Microchip 25LC256 memory.
>>>>>>
>>>>>> Same as for the dataflash stuff you posted a few weeks ago: I
>>>>>> don't
>>>>>> think this device belongs in the SPI NOR framework.
>>>>>
>>>>> Hi Boris,
>>>>>
>>>>> 25lc256 memory is similar with mr25h256, the only difference is the
>>>>> page size(64 vs 256). Because mr25h256 is already in SPI NOR
>>>>> framework
>>>>> I added here 25lc256.
>>>>
>>>> I think I must be reading the wrong datasheet, but can you show me
>>>> how
>>>> does it support things like READID opcode ?
>>>>
>>> Hi Marek,
>>>
>>> I read the datasheet for 25lc256 and for mr25h256 and none of them
>>> supports READID. Is this required for a chip to be included in spi-nor
>>> framework? I just followed the mr25h256 as an example.
>>
>> So I thought until you pointed out the MR25 devices.
>>
>> Does the 25LC device need erase or not ? I think the MR25s didn't, but I
>> might be wrong.
> 
> You are right. MR25s does not need erase and the same thing is true for
> 25LC.

Oh. And the command set is (except for readid) comparable to SPI NOR ?

>> Maybe the framework could support the 25LC afterall.
>>
> Yes, this was my impression too.

I am still thinking that the AT25 driver might be a better fit for such
devices. Can you take a look ?

-- 
Best regards,
Marek Vasut