Re: [PATCH] mtd: nand: auto-detection of NAND bus-width from ONFI param or nand_id[]

[Huang Shijie <b32955@freescale.com>]

于 2013年11月25日 20:32, Pekon Gupta 写道:
> This patch is alternative implementation for following commit which introduced
> NAND_BUSWIDTH_AUTO for detection of bus-width during device probe
>     commit 64b37b2a63eb2f80b65c7185f0013f8ffc637ae3
>     Author:     Matthieu CASTET<matthieu.castet@parrot.com>
>     AuthorDate: 2012-11-06
>
> As NAND device is identified only during nand_scan_ident(), so this patch
> assumes that NAND driver may un-initialized or partially congigured while
> calling nand_scan_ident(). Hence, this patch does following:
>
> (1) Temporarily configures 'bus-width=x8' mode before reading ONFI parameters,
>   (as required by ONFI spec Refer[*]), and then reverts to original bus-width.
>   This allows nand_flash_detect_onfi() to read ONFI paramers page even if
>   bus-width was un-initialized or incorrectly configured.
>
> (2) reconfigures driver with correct bus-width determined by:
>   - either by reading ONFI param OR
>   - as found in nand_flash_id[] table
>   So, any driver-specific callback overrides should be done post nand_scan_ident.
>
> This patch removes any dependency on either 'DT binding' or 'platform data' to
> for determining NAND device bus-width.
>
> [*] Reference: ONFI spec version 3.1 (section 3.5.3. 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@ti.com>
> ---
>   drivers/mtd/nand/nand_base.c | 43 ++++++++++++++++++-------------------------
>   include/linux/mtd/nand.h     |  7 -------
>   2 files changed, 18 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index bd39f7b..3d581a4 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2942,14 +2942,9 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
>   		chip->read_byte(mtd) != 'F' || chip->read_byte(mtd) != 'I')
>   		return 0;
>
> -	/*
> -	 * ONFI must be probed in 8-bit mode or with NAND_BUSWIDTH_AUTO, not
> -	 * with NAND_BUSWIDTH_16
> -	 */
> -	if (chip->options&  NAND_BUSWIDTH_16) {
> -		pr_err("ONFI cannot be probed in 16-bit mode; aborting\n");
> -		return 0;
> -	}
> +	/* ONFI must be probed in 8-bit mode only, so switch to x8 mode */
> +	if (chip->options&  NAND_BUSWIDTH_16)
> +		nand_set_defaults(chip, 0);
>
>   	chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
>   	for (i = 0; i<  3; i++) {
> @@ -2962,7 +2957,7 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
>
>   	if (i == 3) {
>   		pr_err("Could not find valid ONFI parameter page; aborting\n");
> -		return 0;
> +		goto return_error;
>   	}
>
>   	/* Check version */
> @@ -2980,7 +2975,7 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
>
>   	if (!chip->onfi_version) {
>   		pr_info("%s: unsupported ONFI version: %d\n", __func__, val);
> -		return 0;
> +		goto return_error;
>   	}
>
>   	sanitize_string(p->manufacturer, sizeof(p->manufacturer));
> @@ -3033,6 +3028,12 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
>   	}
If it is 16bit bus, could we reconfigure the bus width in here?
it's better to limit the influence only in the ONFI code.

thanks
Huang Shijie


>
>   	return 1;