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

[Michael Walle]

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

-michael