Re: spi-nor: maxronix MX25L12835F support

From: Vignesh Raghavendra <vigneshr@ti.com>
To: Heiko Thiery <heiko.thiery@gmail.com>
Cc: <Tudor.Ambarus@microchip.com>, Michael Walle <michael@walle.cc>,
	<p.yadav@ti.com>, <ycllin@mxic.com.tw>, <zhengxunli@mxic.com.tw>,
	<juliensu@mxic.com.tw>, <linux-mtd@lists.infradead.org>
Subject: Re: spi-nor: maxronix MX25L12835F support
Date: Thu, 4 Mar 2021 12:32:08 +0530	[thread overview]
Message-ID: <5ea9c0cb-3281-7bfd-e2b1-8217eff94c20@ti.com> (raw)
In-Reply-To: <CAEyMn7Z0mYTrtd6TwKJqL6He9g-6o0yYJ2H78oG8gZy9mxXETw@mail.gmail.com>

On 3/3/21 7:14 PM, Heiko Thiery wrote:
> Hi Vignesh,
> 
[...]
>>>>>
>>>>> 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.
> 
> Does this mean that all entries that have DUAL/QUAD/OCTAL defined can
> have them removed And the correct values will be detected/set by SFDP?
> 

No, not all Dual/Quad/Octal SPI flashes have SFDP tables populated.
Removing DUAL/QUAD/OCTAL capabilities for a flash that does not have
SFDP tables populated (or has wrong values) will cause regression as
code may fallback to legacy SPI mode.

Regards
Vignesh

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