[U-Boot] [PATCH v2 1/4] mtd: nand: add NAND_BUSWIDTH_AUTO to autodetect bus width

[Scott Wood]

On Mon, 2013-09-30 at 23:52 +0530, Pekon Gupta wrote:
> From: Matthieu CASTET <matthieu.castet at parrot.com>
> 
> This patch is modified version from following linux patch
> http://lists.infradead.org/pipermail/linux-mtd/2012-November/044803.html
> So retaining the authorship to Matthieu CASTET <matthieu.castet at parrot.com>
> 
> *Modifications from original patch*
> (1) use CONFIG_SYS_NAND_ONFI_DETECTION instead of (chip->options & NAND_BUSWIDTH_AUTO)
> (2) allow re-assigning of callbacks in nand_set_defaults() depending on bus-width
> 
> *Original patch message*
> The driver call nand_scan_ident in 8 bit mode, then
> readid or onfi detection are done (and detect bus width).
> The driver should update its bus width before calling nand_scan_tail.
> 
> This work because readid and onfi are read work 8 byte mode.
> 
> Note that nand_scan_ident send command (NAND_CMD_RESET, NAND_CMD_READID, NAND_CMD_PARAM), address and read data
> The ONFI specificication is not very clear for x16 device if high byte of address should be driven to 0,
> but according to [1] it should be ok to not drive it during autodetection.
> 
> [1]
> 3.3.2. Target Initialization
> 
> [...]
> The Read ID and Read Parameter Page commands only use the lower 8-bits of the data bus.
> The host shall not issue commands that use a word data width on x16 devices until the host
> determines the device supports a 16-bit data bus width in the parameter page.
> 
> Signed-off-by: Pekon Gupta <pekon at ti.com>
> ---
>  drivers/mtd/nand/nand_base.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 9e05cef..4ef0edb 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2514,7 +2514,7 @@ static void nand_set_defaults(struct nand_chip *chip, int busw)
>  
>  	if (!chip->select_chip)
>  		chip->select_chip = nand_select_chip;
> -	if (!chip->read_byte)
> +	if ((!chip->read_byte) || (chip->read_byte == nand_read_byte))
>  		chip->read_byte = busw ? nand_read_byte16 : nand_read_byte;

Unnecessary parens (and doesn't match equivalent Linux code).

This change corresponds to Linux commit
68e8078072e802e77134664f11d2ffbfbd2f8fbe.

-Scott