linux-kernel - Re: [PATCH v2 4/6] spi: spi-mem: reject partial cycle transfers in 8D-8D-8D mode

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Date:   Thu, 23 Dec 2021 17:17:27 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     <Tudor.Ambarus@...rochip.com>
CC:     <michael@...le.cc>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <broonie@...nel.org>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>
Subject: Re: [PATCH v2 4/6] spi: spi-mem: reject partial cycle transfers in
 8D-8D-8D mode

On 23/12/21 11:43AM, Tudor.Ambarus@...rochip.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@...com>
> > Reviewed-by: Mark Brown <broonie@...nel.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
> > 
> 

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.