[PATCH 2/2] mtd: add switch to support NAND flash on big endian bus

[Ricard Wanderlof]

On Wed, 13 Apr 2011, Hans-Christian Egtvedt wrote:

> This patch adds a new kconfig symbol to the MTD NAND system, MTD_NAND_BE_BUS.
> This symbol is used by the nand base to properly convert the data read from the
> bus into the format the CPU expects.
>
> The patch fixes 16-bit NAND flash support on big endian architectures (at least
> AVR32) with NAND flash hooked up to a big endian external bus.
>
> Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt at atmel.com>
> ---
> drivers/mtd/nand/Kconfig     |    8 ++++++++
> drivers/mtd/nand/nand_base.c |    8 ++++++++
> 2 files changed, 16 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
> index edec457..bb3a54a 100644
> --- a/drivers/mtd/nand/Kconfig
> +++ b/drivers/mtd/nand/Kconfig
> @@ -22,6 +22,14 @@ menuconfig MTD_NAND
>
> if MTD_NAND
>
> +config MTD_NAND_BE_BUS
> +	bool "NAND device on big endian bus"
> +	default n
> +	help
> +	  This option will assume data read from the bus is in big endian
> +	  format. This is vital when reading command values from the bus, as
> +	  only the lower 8 bit are in use then.
> +
> config MTD_NAND_VERIFY_WRITE
> 	bool "Verify NAND page writes"
> 	help
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index c54a4cb..bbb0c1d 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -180,7 +180,11 @@ static uint8_t nand_read_byte(struct mtd_info *mtd)
> static uint8_t nand_read_byte16(struct mtd_info *mtd)
> {
> 	struct nand_chip *chip = mtd->priv;
> +#if CONFIG_MTD_NAND_BE_BUS
> +	return (uint8_t) be16_to_cpu(readw(chip->IO_ADDR_R));
> +#else
> 	return (uint8_t) cpu_to_le16(readw(chip->IO_ADDR_R));
> +#endif }

Wouldn't one expect a certain symmetry here, i.e. if one function is
cpu_to_le16, the other one would be called cpu_to_be16 ? I guess in most 
cases cpu_to_le16 would be the same as le16_to_cpu, etc, but it still 
looks as if someone made a mistake.

/Ricard
-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30