linux-kernel - Re: [PATCH v2 6/8] mtd: spi-nor: core: Add helpers to read/write any register

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Message-ID: <f3dcb594fbf512faa33361b8bfc7b98f@walle.cc>
Date:   Tue, 22 Mar 2022 00:13:10 +0100
From:   Michael Walle <michael@...le.cc>
To:     Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc:     p.yadav@...com, miquel.raynal@...tlin.com, richard@....at,
        vigneshr@...com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, nicolas.ferre@...rochip.com,
        Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>
Subject: Re: [PATCH v2 6/8] mtd: spi-nor: core: Add helpers to read/write any
 register

Am 2022-02-28 12:17, 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>
> ---
>  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 281e3d25f74c..f1aa1e2ea7c9 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);
> +}
> +
>  /**
>   * spi_nor_write_enable() - Set write enable latch with Write Enable 
> command.
>   * @nor:	pointer to 'struct spi_nor'.
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index f952061d5c24..7c704475946d 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -554,6 +554,10 @@ ssize_t spi_nor_read_data(struct spi_nor *nor,
> loff_t from, size_t len,
>  			  u8 *buf);
>  ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
>  			   const u8 *buf);
> +int spi_nor_read_reg(struct spi_nor *nor, struct spi_mem_op *op,
> +		     enum spi_nor_protocol proto);
> +int spi_nor_write_reg(struct spi_nor *nor, struct spi_mem_op *op,
> +		      enum spi_nor_protocol proto);

These look rather odd. I'd expect to see an address and such for
such a "random register read/write". Looks like these functions
don't do much except calling spi_nor_spimem_setup_op() and
exec_op() and don't have anything to do with register access
(except maybe for the write enable). Can't we have a bit more
sophisticated interface in the core? Something that calls into
the flash driver to assemble the spi_mem_op automatically? Assuming
that this will be used more often to access registers in a flash.

-michael

>  int spi_nor_erase_sector(struct spi_nor *nor, u32 addr);
> 
>  int spi_nor_otp_read_secr(struct spi_nor *nor, loff_t addr, size_t
> len, u8 *buf);