Re: [RFH] SPI and SPI-NOR patch help

[Tom Rini <trini@konsulko.com>]

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On Thu, Feb 19, 2026 at 02:13:24PM +0200, Tudor Ambarus wrote:
> Hi,
> 
> + Pratush,
> + Vignesh,
> + Marek,
> 
> On 2/18/26 11:23 AM, Miquel Raynal wrote:
> > Hello Tom,
> > 
> > On 16/02/2026 at 09:31:10 -06, Tom Rini <trini@konsulko.com> wrote:
> > 
> >> On Mon, Feb 16, 2026 at 09:21:55AM +0100, Michael Walle wrote:
> >>> On Sat Feb 14, 2026 at 7:58 PM CET, Conor Dooley wrote:
> >>>> On Fri, Feb 13, 2026 at 10:46:07AM -0600, Tom Rini wrote:
> >>>>> Hey all,
> >>>>>
> >>>>> To be blunt, U-Boot needs help with reviewing and maintaining the SPI
> >>>>> and SPI-NOR subsystems. We haven't had someone with time to actively
> >>>>> work in this area for some time. I'm going through the outstanding
> >>>>> changes now, but it also seems a common problem is that with respect to
> >>>>> device IDs, most of the new ones also aren't in the upstream Linux
> >>>>> Kernel. Is there some better and generic solution we're missing so that
> >>>>> we don't have large and often growing device ID tables? I'd rather not
> >>>>> make that problem worse, so I've rejected two of those types of updates
> >>>>> today and I'm just setting aside a large number of others.
> >>>>
> >>>> Dunno if your timing was cursed on sending this, but Tudor submitted his
> >>>> resignation from spi-nor maintainership in the kernel about 10 mins
> >>>> after.
> >>>> I think Michael Walle might be responsible for what you're talking about
> >>>> here, with his 773bbe1044973 ("mtd: spi-nor: add generic flash driver"),
> >>>> but idk jack about spi-nor stuff.
> >>>
> >>> Yeah. Nowadays SPI-NOR flashes come with self describing tables,
> >>> which are already supported by u-boot, I think. The only change that
> >>> seems to be missing is the fallback to it if an id isn't found in
> >>> the flashdb. Only thing is, the SFDP doesn't describe all features,
> >>> most prominent example being locking. So if you need that, you'll
> >>> still need to have an entry per flash.
> >>>
> >>> In fact, in linux I'm planning to change to make it probe SFDP first
> >>> and then amend it with the flashdb information (if there is an
> >>> entry).
> >>
> >> Thanks for explaining. So in that U-Boot does have SFDP support, the
> >> first thing is platforms should likely be enabling that instead of just
> >> adding IDs, at least for basic support.
> 
> Right.
> 
> SFDP is behind a config, because of size constraints I assume. And then we
> also have a tiny duplicate version of the driver for stricter size
> constraints. Are these size constraints defined somewhere? We need to know
> them in order to choose a direction. 
> 
> Also, I'd argue that having the tiny version of the driver was ideal.
> Instead we should have tried to modularize SPI NOR, by SFDP, static
> initialization of flashes, manufacturer drivers.

Some platforms define their overall size constraints, and so we know for
sure a hard limit even in full U-Boot. More platforms do this for SPL,
but not all. So the general answer does end up being that we always care
about if there is a more size-considerate solution with minimal
trade-offs. Especially since we are also in a more minimal overall
space.

-- 
Tom

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