linux-kernel - Re: [PATCH v3 6/9] mtd: spi-nor: core: Add helpers to read/write any register

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Message-ID: <20220419123245.zu4hypebz77ckygn@ti.com>
Date:   Tue, 19 Apr 2022 18:02:45 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     <Tudor.Ambarus@...rochip.com>
CC:     <michael@...le.cc>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Nicolas.Ferre@...rochip.com>,
        <Takahiro.Kuwano@...ineon.com>
Subject: Re: [PATCH v3 6/9] mtd: spi-nor: core: Add helpers to read/write any
 register

On 19/04/22 12:08PM, Tudor.Ambarus@...rochip.com wrote:
> On 4/19/22 14:46, Michael Walle wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Am 2022-04-19 13:19, schrieb Michael Walle:
> >> Am 2022-04-11 11:10, schrieb Tudor Ambarus:
> >>> There are manufacturers that use registers indexed by address. Some of
> >>> them support "read/write any register" opcodes. Provide core methods
> >>> that
> >>> can be used by all manufacturers. SPI NOR controller ops are
> >>> intentionally
> >>> not supported as we intend to move all the SPI NOR controller drivers
> >>> under the SPI subsystem.
> >>>
> >>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
> >>> Tested-by: Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>
> >>> Reviewed-by: Pratyush Yadav <p.yadav@...com>
> >>
> >> I still don't like it because the function doesn't do
> >> anything what the function name might suggest. The read
> >> just executes an op, the write executes an op with a
> >> write enable before. All the behavior is determined by the
> >> 'op' argument.
> >>
> >> Anyway,
> >> Reviewed-by: Michael Walle <michael@...le.cc>
> >>
> >>> ---
> >>> v3: no changes
> >>>
> >>>  drivers/mtd/spi-nor/core.c | 41
> >>> ++++++++++++++++++++++++++++++++++++++
> >>>  drivers/mtd/spi-nor/core.h |  4 ++++
> >>>  2 files changed, 45 insertions(+)
> >>>
> >>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> >>> index 6165dc7bfd17..42794328d3b6 100644
> >>> --- a/drivers/mtd/spi-nor/core.c
> >>> +++ b/drivers/mtd/spi-nor/core.c
> >>> @@ -307,6 +307,47 @@ ssize_t spi_nor_write_data(struct spi_nor *nor,
> >>> loff_t to, size_t len,
> >>>      return nor->controller_ops->write(nor, to, len, buf);
> >>>  }
> >>>
> >>> +/**
> >>> + * spi_nor_read_reg() - read register to flash memory
> >>> + * @nor:        pointer to 'struct spi_nor'.
> >>> + * @op:             SPI memory operation. op->data.buf must be DMA-able.
> >>> + * @proto:  SPI protocol to use for the register operation.
> >>> + *
> >>> + * Return: zero on success, -errno otherwise
> >>> + */
> >>> +int spi_nor_read_reg(struct spi_nor *nor, struct spi_mem_op *op,
> >>> +                 enum spi_nor_protocol proto)
> >>> +{
> >>> +    if (!nor->spimem)
> >>> +            return -EOPNOTSUPP;
> >>> +
> >>> +    spi_nor_spimem_setup_op(nor, op, proto);
> >>> +    return spi_nor_spimem_exec_op(nor, op);
> >>> +}
> >>> +
> >>> +/**
> >>> + * spi_nor_write_reg() - write register to flash memory
> >>> + * @nor:        pointer to 'struct spi_nor'
> >>> + * @op:             SPI memory operation. op->data.buf must be DMA-able.
> >>> + * @proto:  SPI protocol to use for the register operation.
> >>> + *
> >>> + * Return: zero on success, -errno otherwise
> >>> + */
> >>> +int spi_nor_write_reg(struct spi_nor *nor, struct spi_mem_op *op,
> >>> +                  enum spi_nor_protocol proto)
> >>> +{
> >>> +    int ret;
> >>> +
> >>> +    if (!nor->spimem)
> >>> +            return -EOPNOTSUPP;
> >>> +
> >>> +    ret = spi_nor_write_enable(nor);
> >>> +    if (ret)
> >>> +            return ret;
> >>> +    spi_nor_spimem_setup_op(nor, op, proto);
> >>> +    return spi_nor_spimem_exec_op(nor, op);
> > 
> > After seeing your next two patches. Shouldn't the
> > spi_nor_wait_until_ready() call be here too?
> > 
> 
> I thought of this too, but seems that for a reason that I don't
> remember, we don't call for spi_nor_wait_until_ready after we
> write the octal DTR bit. Pratyush, do you remember why?

We are not sure the protocol changed correctly so we can't rely on 
spi_nor_wait_until_ready(). We read the ID instead to be sure.

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.