Re: spi-nor: maxronix MX25L12835F support

From: Heiko Thiery <heiko.thiery@gmail.com>
To: Vignesh Raghavendra <vigneshr@ti.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 08:10:03 +0100	[thread overview]
Message-ID: <CAEyMn7b+vHNiSRJTP2Qs3doK2n3xgCQm9YFBCYEn09GWLehQ0Q@mail.gmail.com> (raw)
In-Reply-To: <5ea9c0cb-3281-7bfd-e2b1-8217eff94c20@ti.com>

Hi Vignesh,

Am Do., 4. März 2021 um 08:02 Uhr schrieb Vignesh Raghavendra <vigneshr@ti.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.

So in that case removing the flags can only be done on chips/flashes
that are checked and reviewed for a valid functional SFDP detection.

-- 
Heiko

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