Re: spi-nor: maxronix MX25L12835F support

[Vignesh Raghavendra <vigneshr@ti.com>]

On 3/1/21 8:55 PM, Tudor.Ambarus@microchip.com wrote:
> On 3/1/21 4:42 PM, Michael Walle wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> Am 2021-03-01 15:09, schrieb Tudor.Ambarus@microchip.com:
>>> On 3/1/21 3:50 PM, Michael Walle wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know
>>>> the content is safe
>>>>
>>>> Am 2021-03-01 14:36, schrieb Pratyush Yadav:
>>>>> I think printing the correct flash name is somewhat important. Other
>>>>> than the handful of people who are reading this thread, few would
>>>>> know
>>>>> that SPI NOR calls mx25l12835f as mx25l12805d or vice versa. This can
>>>>> cause a lot of confusion among people trying to debug any issues.
>>>>
>>>> Unfortunately, this is kind of a mess. If multiple flash devices
>>>> share the same id, it seems to be first come first serve. The kernel
>>>> will print the name which was introduced first.
>>>>
>>>> This isn't the only flash which is affected. Have a look at
>>>>   drivers/mtd/spi-nor/winbond.c
>>>> There are all kind of flash names, some of them are not even existing
>>>> as this particular string, eg. take w25q64jwm, its actually "Winbond
>>>> W25Q64JW-IM or W25Q64JW-JM".
>>>>
>>>> So yes, it would be nice to have such a thing, but for now, I will
>>>> take the kernel output as a rough estimation what might really be
>>>> used on the board.
>>>>
>>>
>>> How about naming them something like "updated-flash-name ||
>>> first-name".
>>> Anyway, these are just workarounds. Manufacturers shouldn't use the
>>> same
>>> JEDEC ID for new flashes. They should at least add an extended ID.
>>
>> Mh, what about a list of names? I mean yes it is a workaround, but
>> there is actual hardware doing this, so IMHO linux has to deal with
>> it in some way. OTOH that list might be long and doesn't look good
>> in dmesg (or wherever that string might be used).
>>
>> It might come in handy to have a mechanism in place if someone
>> really cares about it though.
>>
> 
> A list of names with differentiation at run-time, where possible,
> sounds good. Otherwise we'll stick to a default name, whatever that
> will be. Do you care to scratch a patch for the list of names idea?
> 
> We'll still have a single flash entry, with a list of names, and we
> still need to either do the SFDP detection first, or to trigger the
> SFDP detection with an explicit flash info flag. I'll follow Pratyush's
> steps and evaluate the "detect SFDP first" idea.
> 

If we do go down the road of "detect SFDP first", we should add
SPI_NOR_SKIP_SFDP to flashes that currently don't claim DUAL/QUAD/OCTAL
capability currently in order to avoid any surprises due to wrong values
in the table.

Regards
Vignesh



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