[PATCH 1/2] mtd: spi-nor: Fix RDCR controller capability core check

[Takahiro.Kuwano at infineon.com]

> Hello SPI NOR folks :-)
> 
> + Takahiro
> 
Hello!

> On 08/01/2026 at 13:14:29 +01, Miquel Raynal <miquel.raynal at bootlin.com> wrote:
> 
> > Commit 5008c3ec3f89 ("mtd: spi-nor: core: Check read CR support") adds a
> > controller check to make sure the core will not use CR reads on
> > controllers not supporting them. The approach is valid but the fix is
> > incorrect. Unfortunately, the author could not catch it, because the
> > expected behavior was met. The patch indeed drops the RDCR capability,
> > but it does it for all controllers!
> >
> > The issue comes from the use of spi_nor_spimem_check_op() which is an
> > internal helper dedicated to check page operations, ie. it is only used
> > for page reads and page programs (despite its generic name).
> >
> > This helper looks for the biggest number of address bytes that can be
> > used for a page operation and tries 4 then 3. It then calls the usual
> > spi-mem helpers to do the checks. These will always fail because there
> > is now an inconsistency: the address cycles are forced to 4 (then 3)
> > bytes, but the bus width during the address cycles rightfully remains 0:
> > impossible, the operation is invalid.
> >
> > The correct check in this case is to directly call spi_mem_supports_op()
> > which doesn't messes up with the operation content.
> >
> > Fixes: 5008c3ec3f89 ("mtd: spi-nor: core: Check read CR support")
> > Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
> 
> These two patches are fixes which need to get in, I'd like to pick them
> for the next fixes MTD PR that I am preparing, but I was expecting some
> kind of acknowledgement on it.
> 
> Cheng Ming already faced the same issue on his side an identical patch
> already.
> 
> Thanks,
> Miquèl
> 
> > ---
> >  drivers/mtd/spi-nor/core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> > index d3f8a78efd3b..1f2e312feec7 100644
> > --- a/drivers/mtd/spi-nor/core.c
> > +++ b/drivers/mtd/spi-nor/core.c
> > @@ -2466,7 +2466,7 @@ spi_nor_spimem_adjust_hwcaps(struct spi_nor *nor, u32 *hwcaps)
> >
> >               spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
> >
> > -             if (spi_nor_spimem_check_op(nor, &op))
> > +             if (!spi_mem_supports_op(nor->spimem, &op))
> >                       nor->flags |= SNOR_F_NO_READ_CR;
> >       }
> >  }

Acked-by: Takahiro Kuwano <takahiro.kuwano at infineon.com>