[PATCH v3] mtd/nand: don't use {read,write}_buf for 8-bit transfers

[Ezequiel Garcia]

On Fri, Nov 29, 2013 at 10:04:28PM -0800, Brian Norris wrote:
> Hi Ezequiel,
> 
> On Fri, Nov 29, 2013 at 09:20:19AM -0300, Ezequiel Garcia wrote:
> > On Tue, Nov 26, 2013 at 11:35:12PM -0800, Brian Norris wrote:
> > > + Pekon, Ezequiel
> > > 
> > > Can one of you see how this patch works with your BeagleBones w/ x16
> > > NAND?
> 
> I see that you are pushing to straighten out the auto-buswidth part of
> nand_base, and I think there may be good reasons to do so. But I think
> that part of your problem can be resolved by a patch like Uwe's, where
> rather than forcing the entire driver to be configured for x8 just to
> use ONFI, we can fix the ONFI operations to use the lower 8 bits.
> 
> IOW, I expect that a patch like Uwe's can shed some better light on the
> auto-buswidh situation. (This is why I CC'd you and Pekon.)
> 
> Unfortunately, I realized that Uwe's patch doesn't go far enough, I
> don't think. It looks like it needs something like the following diff
> (only compile-tested).
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index bd39f7b67906..1ab264457d94 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2933,7 +2933,7 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
>  					int *busw)
>  {
>  	struct nand_onfi_params *p = &chip->onfi_params;
> -	int i;
> +	int i, j;
>  	int val;
>  
>  	/* Try ONFI for unknown chip or LP */
> @@ -2942,18 +2942,10 @@ 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;
> -	}
> -
>  	chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
>  	for (i = 0; i < 3; i++) {
> -		chip->read_buf(mtd, (uint8_t *)p, sizeof(*p));
> +		for (j = 0; j < sizeof(*p); j++)
> +			*(uint8_t *)p = chip->read_byte(mtd);
>  		if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
>  				le16_to_cpu(p->crc)) {
>  			break;
> 
> What do you think? (And more importantly, how does this test out for
> you?)
> 

Let me try this out and let you know.
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com