linux-kernel - Re: [PATCH v10 08/17] mtd: spi-nor: core: use dummy cycle and address width info from SFDP

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Date:   Mon, 20 Jul 2020 21:54:56 +0530
From:   Pratyush Yadav <me@...avpratyush.com>
To:     Tudor.Ambarus@...rochip.com
Cc:     p.yadav@...com, miquel.raynal@...tlin.com, richard@....at,
        vigneshr@...com, broonie@...nel.org, Nicolas.Ferre@...rochip.com,
        alexandre.belloni@...tlin.com, Ludovic.Desroches@...rochip.com,
        matthias.bgg@...il.com, michal.simek@...inx.com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, boris.brezillon@...labora.com,
        nsekhar@...com
Subject: Re: [PATCH v10 08/17] mtd: spi-nor: core: use dummy cycle and
 address width info from SFDP

Hi Tudor,

On 08/07/20 04:03PM, Tudor.Ambarus@...rochip.com wrote:
> On 6/23/20 9:30 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > The xSPI Profile 1.0 table specifies how many dummy cycles and address
> > bytes are needed for the Read Status Register command in octal DTR mode.
> > Use that information to send the correct Read SR command.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@...com>
> > ---
> >  drivers/mtd/spi-nor/core.c | 25 +++++++++++++++++++++++--
> >  1 file changed, 23 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> > index 7d24e63fcca8..f2748f1d9957 100644
> > --- a/drivers/mtd/spi-nor/core.c
> > +++ b/drivers/mtd/spi-nor/core.c
> > @@ -357,6 +357,8 @@ int spi_nor_write_disable(struct spi_nor *nor)
> >  static int spi_nor_read_sr(struct spi_nor *nor, u8 *sr)
> >  {
> >         int ret;
> > +       u8 addr_bytes = nor->params->rdsr_addr_nbytes;
> > +       u8 dummy = nor->params->rdsr_dummy;
> 
> no need to introduce local variables for a single dereference

Ok.
 
> > 
> >         if (nor->spimem) {
> >                 struct spi_mem_op op =
> > @@ -365,10 +367,21 @@ static int spi_nor_read_sr(struct spi_nor *nor, u8 *sr)
> >                                    SPI_MEM_OP_NO_DUMMY,
> >                                    SPI_MEM_OP_DATA_IN(1, sr, 1));
> > 
> > +               if (spi_nor_protocol_is_dtr(nor->reg_proto)) {
> > +                       op.addr.nbytes = addr_bytes;
> > +                       op.addr.val = 0;
> 
> isn't addr already initialized to 0?

Yes, it is. But I figured it won't hurt to be explicit about what we 
intend the address to be.

> > +                       op.dummy.nbytes = dummy;
> > +               }
> > +
> > +               spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
> > +
> >                 ret = spi_mem_exec_op(nor->spimem, &op);
> >         } else {
> > -               ret = nor->controller_ops->read_reg(nor, SPINOR_OP_RDSR,
> > -                                                   sr, 1);
> > +               if (spi_nor_protocol_is_dtr(nor->reg_proto))
> > +                       ret = -ENOTSUPP;
> > +               else
> > +                       ret = nor->controller_ops->read_reg(nor, SPINOR_OP_RDSR,
> > +                                                           sr, 1);
> >         }
> 
> doesn't this belong to a previous patch?

It does. Will fix.
 
> > 
> >         if (ret)
> > @@ -388,6 +401,8 @@ static int spi_nor_read_sr(struct spi_nor *nor, u8 *sr)
> >  static int spi_nor_read_fsr(struct spi_nor *nor, u8 *fsr)
> >  {
> >         int ret;
> > +       u8 addr_bytes = nor->params->rdsr_addr_nbytes;
> > +       u8 dummy = nor->params->rdsr_dummy;
> > 
> >         if (nor->spimem) {
> >                 struct spi_mem_op op =
> > @@ -396,6 +411,12 @@ static int spi_nor_read_fsr(struct spi_nor *nor, u8 *fsr)
> >                                    SPI_MEM_OP_NO_DUMMY,
> >                                    SPI_MEM_OP_DATA_IN(1, fsr, 1));
> > 
> > +               if (spi_nor_protocol_is_dtr(nor->reg_proto)) {
> > +                       op.addr.nbytes = addr_bytes;
> > +                       op.addr.val = 0;
> > +                       op.dummy.nbytes = dummy;
> > +               }
> > +
> >                 spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
> > 
> >                 ret = spi_mem_exec_op(nor->spimem, &op);

-- 
Regards,
Pratyush Yadav