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

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Date:   Fri, 18 May 2018 16:00:15 +0300
From:   Radu Pirea <radu.pirea@...rochip.com>
To:     Marek Vasut <marek.vasut@...il.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 01:03 PM, Marek Vasut wrote:
> 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 ?

I tested the memory with at25 driver and it works with no line changed 
in driver. :)

>