spi-nor: maxronix MX25L12835F support

[Heiko Thiery]

Hi Vignesh,

Am Di., 2. März 2021 um 06:49 Uhr schrieb Vignesh Raghavendra <vigneshr at ti.com>:
>
>
>
> On 3/1/21 8:55 PM, Tudor.Ambarus at 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 at 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.

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?

-- 
Heiko