[v2,4/6] spi: spi-mem: reject partial cycle transfers in 8D-8D-8D mode

In 8D-8D-8D mode two bytes are transferred per cycle. So an odd number
of bytes cannot be transferred because it would leave a residual half
cycle at the end. Consider such a transfer invalid and reject it.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Mark Brown <broonie@kernel.org>

---

Changes in v2:
- Add Mark's R-by (spell corrected).

 drivers/spi/spi-mem.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

On 5/31/21 9:17 PM, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> In 8D-8D-8D mode two bytes are transferred per cycle. So an odd number
> of bytes cannot be transferred because it would leave a residual half
> cycle at the end. Consider such a transfer invalid and reject it.
> 
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> Reviewed-by: Mark Brown <broonie@kernel.org>
> 
> ---
> 
> Changes in v2:
> - Add Mark's R-by (spell corrected).
> 
>  drivers/spi/spi-mem.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 1513553e4080..ab9eefbaa1d9 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -162,7 +162,17 @@ static bool spi_mem_check_buswidth(struct spi_mem *mem,
>  bool spi_mem_dtr_supports_op(struct spi_mem *mem,
>                              const struct spi_mem_op *op)
>  {
> -       if (op->cmd.nbytes != 2)
> +       if (op->cmd.buswidth == 8 && op->cmd.nbytes % 2)

!IS_ALIGNED(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)

dummy is sent on the same buswidth as data's indeed, but I would
s/op->dummy.buswidth/op->data.buswidth for code consistency reasons.

>                 return false;
> 
>         return spi_mem_check_buswidth(mem, op);
> --
> 2.30.0
>

On 23/12/21 11:43AM, Tudor.Ambarus@microchip.com wrote:
> On 5/31/21 9:17 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > In 8D-8D-8D mode two bytes are transferred per cycle. So an odd number
> > of bytes cannot be transferred because it would leave a residual half
> > cycle at the end. Consider such a transfer invalid and reject it.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> > Reviewed-by: Mark Brown <broonie@kernel.org>
> > 
> > ---
> > 
> > Changes in v2:
> > - Add Mark's R-by (spell corrected).
> > 
> >  drivers/spi/spi-mem.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> > index 1513553e4080..ab9eefbaa1d9 100644
> > --- a/drivers/spi/spi-mem.c
> > +++ b/drivers/spi/spi-mem.c
> > @@ -162,7 +162,17 @@ static bool spi_mem_check_buswidth(struct spi_mem *mem,
> >  bool spi_mem_dtr_supports_op(struct spi_mem *mem,
> >                              const struct spi_mem_op *op)
> >  {
> > -       if (op->cmd.nbytes != 2)
> > +       if (op->cmd.buswidth == 8 && op->cmd.nbytes % 2)
> 
> !IS_ALIGNED(op->cmd.nbytes, 2)?

Ok.

> 
> > +               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)
> 
> dummy is sent on the same buswidth as data's indeed, but I would
> s/op->dummy.buswidth/op->data.buswidth for code consistency reasons.

This looks like a typo. It should indeed be data.buswidth.

> 
> >                 return false;
> > 
> >         return spi_mem_check_buswidth(mem, op);
> > --
> > 2.30.0
> > 
>