[PATCH v10 04/27] spi: spi-mem: add spi_mem_dtr_supports_op()

[Jagan Teki]

On Sun, Jun 27, 2021 at 2:05 PM Pratyush Yadav <p.yadav at ti.com> wrote:
>
> On 26/06/21 02:44PM, Jagan Teki wrote:
> > On Sat, Jun 26, 2021 at 12:47 AM Pratyush Yadav <p.yadav at ti.com> wrote:
> > >
> > > spi_mem_default_supports_op() rejects DTR ops by default to ensure that
> > > the controller drivers that haven't been updated with DTR support
> > > continue to reject them. It also makes sure that controllers that don't
> > > support DTR mode at all (which is most of them at the moment) also
> > > reject them.
> > >
> > > This means that controller drivers that want to support DTR mode can't
> > > use spi_mem_default_supports_op(). Driver authors have to roll their own
> > > supports_op() function and mimic the buswidth checks. Or even worse,
> > > driver authors might skip it completely or get it wrong.
> > >
> > > Add spi_mem_dtr_supports_op(). It provides a basic sanity check for DTR
> > > ops and performs the buswidth requirement check. Move the logic for
> > > checking buswidth in spi_mem_default_supports_op() to a separate
> > > function so the logic is not repeated twice.
> > >
> > > Signed-off-by: Pratyush Yadav <p.yadav at ti.com>
> > > ---
> > >  drivers/spi/spi-mem.c | 32 +++++++++++++++++++++++++++++---
> > >  include/spi-mem.h     |  2 ++
> > >  2 files changed, 31 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> > > index 541cd0e5a7..9c1ede1b61 100644
> > > --- a/drivers/spi/spi-mem.c
> > > +++ b/drivers/spi/spi-mem.c
> > > @@ -145,8 +145,8 @@ static int spi_check_buswidth_req(struct spi_slave *slave, u8 buswidth, bool tx)
> > >         return -ENOTSUPP;
> > >  }
> > >
> > > -bool spi_mem_default_supports_op(struct spi_slave *slave,
> > > -                                const struct spi_mem_op *op)
> > > +static bool spi_mem_check_buswidth(struct spi_slave *slave,
> > > +                                  const struct spi_mem_op *op)
> > >  {
> > >         if (spi_check_buswidth_req(slave, op->cmd.buswidth, true))
> > >                 return false;
> > > @@ -164,13 +164,39 @@ bool spi_mem_default_supports_op(struct spi_slave *slave,
> > >                                    op->data.dir == SPI_MEM_DATA_OUT))
> > >                 return false;
> > >
> > > +       return true;
> > > +}
> > > +
> > > +bool spi_mem_dtr_supports_op(struct spi_slave *slave,
> > > +                            const struct spi_mem_op *op)
> > > +{
> > > +       if (op->cmd.buswidth == 8 && op->cmd.nbytes % 2)
> > > +               return false;
> > > +
> > > +       if (op->addr.nbytes && op->addr.buswidth == 8 && op->addr.nbytes % 2)
> > > +               return false;
> > > +
> > > +       if (op->dummy.nbytes && op->dummy.buswidth == 8 && op->dummy.nbytes % 2)
> > > +               return false;
> > > +
> > > +       if (op->data.dir != SPI_MEM_NO_DATA &&
> > > +           op->dummy.buswidth == 8 && op->data.nbytes % 2)
> > > +               return false;
> > > +
> > > +       return spi_mem_check_buswidth(slave, op);
> > > +}
> > > +EXPORT_SYMBOL_GPL(spi_mem_dtr_supports_op);
> >
> > Does this export_symbol is used in U-Boot?
>
> It is being used in drivers ported from Linux. I see it being used in
> spi-mem.c, mtdcore.c, x530_cert_parser.c, nand/core.c, etc. It is
> defined to an empty macro in include/linux/compat.h.

Ok, thanks for the details. Somehow we need to refactor the code, I
believe it would require lot of testing but possible.

Jagan.