Re: [RFC] Special handling for NAND_CMD_PAGEPROG and NAND_CMD_READ0

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Wed, 9 Nov 2016 18:57:04 +0100
Marc Gonzalez <marc_gonzalez@sigmadesigns.com> wrote:

> Sample code to generate some discussion around having the framework
> send I/O commands (for read_page and write_page) when it is dealing
> with "high-level" NFCs that send the commands themselves.
> ---
>  drivers/mtd/nand/nand_base.c  | 6 ++++--
>  drivers/mtd/nand/tango_nand.c | 7 ++++++-
>  include/linux/mtd/nand.h      | 6 ++++++
>  3 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 50cdf37cb8e4..b4149101342c 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -1970,7 +1970,8 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
>  						 __func__, buf);
>  
>  read_retry:
> -			chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
> +			if (!(chip->options & NAND_FOO))
> +				chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
>  

You'll have to patch the standard implementations provided by the core
(nand_read/write_page_xx()) to send these READ0/SEQIN/PAGEPROG commands
when the NAND_FOO flag is set.

>  			/*
>  			 * Now read the page into the buffer.  Absent an error,
> @@ -2681,7 +2682,8 @@ static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
>  
>  	if (!cached || !NAND_HAS_CACHEPROG(chip)) {
>  
> -		chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
> +		if (!(chip->options & NAND_FOO))
> +			chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

If you ask the core to not send NAND_CMD_PAGEPROG, it should also not
send the SEQIN command. 

>  		status = chip->waitfunc(mtd, chip);
>  		/*
>  		 * See if operation failed and additional status checks are
> diff --git a/drivers/mtd/nand/tango_nand.c b/drivers/mtd/nand/tango_nand.c
> index 74e39a92771c..d3679fdf2020 100644
> --- a/drivers/mtd/nand/tango_nand.c
> +++ b/drivers/mtd/nand/tango_nand.c
> @@ -401,13 +401,17 @@ static int raw_write(struct nand_chip *chip, const u8 *buf, const u8 *oob)
>  static int tango_read_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
>  		uint8_t *buf, int oob_required, int page)
>  {
> +	chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
>  	return raw_read(chip, buf, chip->oob_poi);
>  }
>  
>  static int tango_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
>  		const uint8_t *buf, int oob_required, int page)
>  {
> -	return raw_write(chip, buf, chip->oob_poi);
> +	/* what about NAND_CMD_SEQIN ? */

You should send SEQIN as well, and patch the core to not send it when
NAND_FOO is set.

> +	raw_write(chip, buf, chip->oob_poi);
> +	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
> +	return 0;
>  }
>  
>  static int tango_read_oob(struct mtd_info *mtd, struct nand_chip *chip, int page)
> @@ -527,6 +531,7 @@ static int chip_init(struct device *dev, struct device_node *np)
>  	chip->setup_data_interface = tango_set_timings;
>  	chip->options = NAND_USE_BOUNCE_BUFFER
>  		| NAND_NO_SUBPAGE_WRITE
> +		| NAND_FOO
>  		| NAND_WAIT_TCCS;
>  	chip->controller = &nfc->hw;
>  	tchip->base = nfc->pbus_base + (cs * 256);
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> index 06d0c9d740f7..fd8968f3ccca 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -220,6 +220,12 @@ enum nand_ecc_algo {
>   */
>  #define NAND_WAIT_TCCS		0x00200000
>  
> +/*
> + * Controller sends NAND_CMD_PAGEPROG (write_page) and NAND_CMD_READ0 (read_page)
> + * therefore the framework should not send these commands.
> + */
> +#define NAND_FOO		0x00400000
> +

Nice name :-).

>  /* Options set by nand scan */
>  /* Nand scan has allocated controller struct */
>  #define NAND_CONTROLLER_ALLOC	0x80000000