Re: [PATCH v3 4/8] m25p80: Add the mx25l25635f SFPD table

[Cédric Le Goater]

On 10/10/22 12:51, Francisco Iglesias wrote:
> Hi  Cedric,
>
> On [2022 Oct 10] Mon 11:58:40, Michael Walle wrote:
> > Am 2022-10-10 08:23, schrieb Cédric Le Goater:
> > > On 10/7/22 16:44, Francisco Iglesias wrote:
> >
> > > > > --- a/hw/block/m25p80.c
> > > > > +++ b/hw/block/m25p80.c
> > > > > @@ -234,6 +234,8 @@ static const FlashPartInfo known_devices[] = {
> > > > >        { INFO("mx25l12855e", 0xc22618,      0,  64 << 10, 256, 0) },
> > > > >        { INFO6("mx25l25635e", 0xc22019,     0xc22019,  64 << 10,
> > > > > 512, 0),
> > > > >          .sfdp_read = m25p80_sfdp_mx25l25635e },
> > > > > +    { INFO6("mx25l25635f", 0xc22019,     0xc22019,  64 << 10,
> > > > > 512, 0),
>
> I think I missed the (ER_4K | ER_32K) flags above (in case we go for a v4 we
> can add it in).

sure.

> > > > I think I'm not seeing the extended id part in the datasheet I've
> > > > found so
> > > > might be that you can switch to just INFO and _ext_id 0 above
> > >
> > > This was added by commit 6bbe036f32dc ("m25p80: Return the JEDEC ID
> > > twice for
> > > mx25l25635e") to fix a real breakage on HW.
> >
> >  From my experience, the ID has a particular length, at least three bytes
> > and if you read past that length for some (all?) devices the id bytes just
> > get repeated. I.e. the counter in the device will just wrap to offset 0
> > again. If you want to emulate the hardware correctly, you would have to
> > take that into consideration.
>
> If we decide to go with Michael's proposal above you can use '0' on the
> 'extended_id' and enable 's->data_read_loop = true' when reading the ID.

This part :

            for (; i < SPI_NOR_MAX_ID_LEN; i++) {
                s->data[i] = 0;
            }

will fill the remaining JEDEC ID bytes with zeros which is not what we
want for the mx25l25635e chip.

Thanks,
C.

> Best regards,
> Francisco
>
> > But I don't think it's worth it, OTOH there seems to be some broken
> > software which rely on that (undefined?) behavior.
> >
> > -michael