Re: [PATCH v8 3/9] mtd: spi-nor: core: Allow specifying the byte order in Octal DTR mode

[Michael Walle <mwalle@kernel.org>]

> From: JaimeLiao <jaimeliao@mxic.com.tw>

Same remark as for patch 2/9.

> Macronix swaps bytes on a 16-bit boundary when configured in Octal DTR.
> The byte order of 16-bit words is swapped when read or written in 
> 8D-8D-8D
> mode compared to STR modes. Allow operations to specify the byte order 
> in
> DTR mode, so that controllers can swap the bytes back at run-time to
> address the flash's endianness requirements, if they are capable. If 
> the
> controllers are not capable of swapping the bytes, the protocol is
> downgrade via spi_nor_spimem_adjust_hwcaps(). When available, the 
> swapping
> of the bytes is always done regardless if it's a data or register 
> access,
> so that we comply with the JESD216 requirements: "Byte order of 16-bit
> words is swapped when read in 8D-8D-8D mode compared to 1-1-1".
> 
> Merge Tudor's patch and add modifications for suiting newer version
> of Linux kernel.
> 
> Suggested-by: Michael Walle <mwalle@kernel.org>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
> Signed-off-by: JaimeLiao <jaimeliao@mxic.com.tw>
> ---
>  drivers/mtd/spi-nor/core.c | 5 +++++
>  drivers/mtd/spi-nor/core.h | 1 +
>  2 files changed, 6 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 4129764fad8c..0076007e1cde 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -113,6 +113,11 @@ void spi_nor_spimem_setup_op(const struct spi_nor 
> *nor,
>  		op->cmd.opcode = (op->cmd.opcode << 8) | ext;
>  		op->cmd.nbytes = 2;
>  	}
> +
> +	/* SWAP16 is only applicable when Octal DTR mode */
> +	if (nor->read_proto == SNOR_PROTO_8_8_8_DTR)

Why is it read_proto now? For all the former patches, the local
proto variable was used.

> +		if (nor->flags & SNOR_F_SWAP16)

Please fold this into the former condition.
if (proto == SNOR_PROTO_8_8_8_DTR && nor->flags & SNOR_F_SWAP16)
    op->data.swap16 = true;

-michael

> +			op->data.swap16 = true;
>  }
> 
>  /**
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index d36c0e072954..3c5190ac0a79 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -140,6 +140,7 @@ enum spi_nor_option_flags {
>  	SNOR_F_RWW		= BIT(14),
>  	SNOR_F_ECC		= BIT(15),
>  	SNOR_F_NO_WP		= BIT(16),
> +	SNOR_F_SWAP16		= BIT(17),
>  };
> 
>  struct spi_nor_read_command {