Question about SPI-NOR micron-st.c driver and OSPI devices.

[Mike Williamson]

Hi Pratyush,

On Tue, Jan 24, 2023 at 7:46 AM Pratyush Yadav <ptyadav at amazon.de> wrote:
>
> Hi Mike,
>
> On Mon, Jan 16 2023, Mike Williamson wrote:
>
> > Hello,
> >
> > I am looking at the drivers/mtd/spi-not/micron-st.c file.
> >
> > I was wondering why the mt35xu512aba_fixups, and in general the patch below,
> > were not also applied to the mt35xu02g device entry?  Best I can tell, the
> > datasheets for the two parts (same family, different densities) look nearly
> > identical and the
> >
> > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2333941.html
> >
> > I ask because we are having some troubles with the mt35xu02g and I am
> > wondering if we need these fixups to run reliably in octal mode.
>
> When I wrote the patches for Octal DTR support on MT35 flash family, I
> only had the mt35xu512aba flash on me. And it was a new feature so I did
> not want to add it to a flash I could not test, and risk breaking it. I
> figured if someone really wanted Octal DTR support on the 02G part, they
> can populate the fixups and test it themselves.
>
> So this is what I suggest you do as well. Add the fixups, test it out,
> and if it works, upstream the patch.

I have tested using the fixups on the 02G part successfully, but we are
working out of a 5.10 branch TI is providing for a new SOC.  I'm not sure
when I will be able to test against mainline/next as I don't know the state
of the SOC drivers (for TI's AM62x).  I know they are working to get them
in, but I don't think they are there yet.

Knowing the motivation for leaving the fixups out is helpful. I have a bit of
confidence that the patch is likely the right fix for Octal DTR support.

> ... While you are at it, perhaps also
> convert it to use the PARSE_SFDP flag. See db391efe765c ("mtd: spi-nor:
> spansion: Remove NO_SFDP_FLAGS from s28hs512t info") or a30f53d8bc0f
> ("mtd: spi-nor: issi: is25wp256: Init flash based on SFDP") for example.
>

I will have a look.

Thanks,
Mike