Re: [PATCH v7 06/14] spi: spi-mem: Kill the spi_mem_dtr_supports_op() helper

Pratyush Yadav
2021-12-21T10:12:01Z

On 21/12/21 10:58AM, Miquel Raynal wrote:
> Hi Pratyush,
>
> p.yadav@ti.com wrote on Tue, 21 Dec 2021 00:28:42 +0530:
>
> > On 17/12/21 05:16PM, Miquel Raynal wrote:
> > > Now that spi_mem_default_supports_op() has access to the static
> > > controller capabilities (related to memory operations), and now that
> > > these capabilities have been filled by the impacted controllers, there
> > > is no need for a specific helper checking only DTR operations, so let's
> > > just kill spi_mem_dtr_supports_op() and simply use
> > > spi_mem_default_supports_op() instead.
> > >
> > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > ---
> > > drivers/spi/spi-cadence-quadspi.c | 5 +----
> > > drivers/spi/spi-mem.c | 10 ----------
> > > drivers/spi/spi-mxic.c | 10 +---------
> > > include/linux/spi/spi-mem.h | 11 -----------
> > > 4 files changed, 2 insertions(+), 34 deletions(-)
> > >
> > > diff --git a/drivers/spi/spi-mxic.c b/drivers/spi/spi-mxic.c
> > > index e137b1ec85d4..67d05ee8d6a0 100644
> > > --- a/drivers/spi/spi-mxic.c
> > > +++ b/drivers/spi/spi-mxic.c
> > > @@ -335,8 +335,6 @@ static int mxic_spi_data_xfer(struct mxic_spi *mxic, const void *txbuf,
> > > static bool mxic_spi_mem_supports_op(struct spi_mem *mem,
> > > const struct spi_mem_op *op)
> > > {
> > > - bool all_false;
> > > -
> > > if (op->data.buswidth > 8 || op->addr.buswidth > 8 ||
> > > op->dummy.buswidth > 8 || op->cmd.buswidth > 8)
> > > return false;
> > > @@ -348,13 +346,7 @@ static bool mxic_spi_mem_supports_op(struct spi_mem *mem,
> > > if (op->addr.nbytes > 7)
> > > return false;
> > >
> > > - all_false = !op->cmd.dtr && !op->addr.dtr && !op->dummy.dtr &&
> > > - !op->data.dtr;
> > > -
> > > - if (all_false)
> > > - return spi_mem_default_supports_op(mem, op);
> > > - else
> > > - return spi_mem_dtr_supports_op(mem, op);
> > > + return spi_mem_default_supports_op(mem, op);
> >
> > Does this controller support mixed DTR modes? If it doesn't then it
> > should reject mixed DTR ops before calling
> > spi_mem_default_supports_op(). Anyway, the current driver doesn't check
> > for it either so this change does not make anything worse at the very
> > least.
>
> The Cadence SPI driver does something like:
>
> all_true = cmd.dtr && addr.dtr ...;
> all_false = !cmd.dtr && !addr.dtr ...;
> if (!all_true || !all_false)
> return false;
>
> This basically rules out any mixed DTR operation.
>
> I believe Macronix code is inspired from this function, but they
> intentionally dropped the all_true check, making the situation boolean:
> either there is at least one DTR op, or there is none. So I believe
> this was done on purpose and this controller supports mixed DTR ops.

I see that your other patches in this series touch this driver so you
should have the datasheet right? Can you look and see for sure if it
does? I am fine with the patch as it is but if we can make the check
stricter it would be nice.

>
> > Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
>
> Thanks,
> Miquèl

--
Regards,
Pratyush Yadav
Texas Instruments Inc.