Re: [PATCH v13 09/15] mtd: spi-nor: core: enable octal DTR mode when possible

[Pratyush Yadav]

On 29/09/20 11:26AM, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
> Hi,
> 
> On 9/16/20 3:44 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Allow flashes to specify a hook to enable octal DTR mode. Use this hook
> > whenever possible to get optimal transfer speeds.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@xxxxxx>
> > ---
> >  drivers/mtd/spi-nor/core.c | 35 +++++++++++++++++++++++++++++++++++
> >  drivers/mtd/spi-nor/core.h |  2 ++
> >  2 files changed, 37 insertions(+)
> > 
> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> > index 87c568debf14..6ee93544d72f 100644
> > --- a/drivers/mtd/spi-nor/core.c
> > +++ b/drivers/mtd/spi-nor/core.c
> > @@ -3069,6 +3069,35 @@ static int spi_nor_init_params(struct spi_nor *nor)
> >         return 0;
> >  }
> > 
> > +/** spi_nor_octal_dtr_enable() - enable Octal DTR I/O if needed
> > + * @nor:                 pointer to a 'struct spi_nor'
> > + * @enable:              whether to enable or disable Octal DTR
> > + *
> > + * Return: 0 on success, -errno otherwise.
> > + */
> > +static int spi_nor_octal_dtr_enable(struct spi_nor *nor, bool enable)
> > +{
> > +       int ret;
> > +
> > +       if (!nor->params->octal_dtr_enable)
> > +               return 0;
> > +
> > +       if (!(nor->read_proto == SNOR_PROTO_8_8_8_DTR &&
> > +             nor->write_proto == SNOR_PROTO_8_8_8_DTR))
> > +               return 0;
> > +
> > +       ret = nor->params->octal_dtr_enable(nor, enable);
> > +       if (ret)
> > +               return ret;
> > +
> > +       if (enable)
> > +               nor->reg_proto = SNOR_PROTO_8_8_8_DTR;
> > +       else
> > +               nor->reg_proto = SNOR_PROTO_1_1_1;
> > +
> > +       return 0;
> > +}
> > +
> >  /**
> >   * spi_nor_quad_enable() - enable/disable Quad I/O if needed.
> >   * @nor:                pointer to a 'struct spi_nor'
> > @@ -3109,6 +3138,12 @@ static int spi_nor_init(struct spi_nor *nor)
> >  {
> >         int err;
> > 
> > +       err = spi_nor_octal_dtr_enable(nor, true);
> > +       if (err) {
> > +               dev_dbg(nor->dev, "octal mode not supported\n");
> > +               return err;
> > +       }
> > +
> >         err = spi_nor_quad_enable(nor, true);
> 
> Is it possible to enable octal dtr and quad at the same time?
> Maybe an 'if/else if' here depending on the values of nor->read_proto and
> nor->write_proto

No it is not. If you look inside spi_nor_octal_dtr_enable() and 
spi_nor_quad_enable(), they both are a no-op if the protocol does not 
match. spi_nor_quad_enable() was already doing it this way so I made 
spi_nor_octal_dtr_enable() follow suit. So this is effectively an 
if-else on the value of nor->read_proto. I don't think an explicit one 
is needed.

-- 
Regards,
Pratyush Yadav
Texas Instruments India