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

Ezequiel Garcia
2013-11-30T11:19:20Z

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