On Wed, Nov 06, 2013 at 10:00:09PM +0000, Gupta, Pekon wrote:
> > From: Ezequiel Garcia
> [...]
>
> > But: on the other hand, I'd really like you to convince me as to
> > why is it so bad to require the DTB to have the proper GPMC bus width.
> >
> No its not at all bad, all I want is either of the one way (not mixture of both).
> - Either depend on DT completely (which is current case for all drivers)
> - OR depend on ONFI and nand_flash_id[] for bus-width detection.
>
>
> > Once again:
> > 1. the NAND devices aren't hot-pluggable
> > 2. the "user" (who is actually an engineer, not some regular dummy user)
> > knows perfectly well the width of the device.
> >
> > What's the problem with describing the hardware in the DT and saving us
> > lots of runtime re-configuration trouble?
>
> I agree with both your arguments above.
> So shouldn't we kill NAND_BUSWIDTH_AUTO ?
> And probably therefore NAND_BUSWIDTH_AUTO isn't that popular.
>
> Now what remains is ONFI probe, which should always happen in x8 mode.
> So for that below patch should be sufficient ..
>
Hm.. that might work. Maybe you should submit this as RFC/PATCH to catch
the attention of some more people. And we can keep discussing on this
new idea...
I should get an 8-bit module for the BBB, so this means I'll be able
to run 8-bit and 16-bit tests.
> ----------------------
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index ec1db1e..d1220fb 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2942,14 +2942,8 @@ 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 */
> + nand_set_defaults(chip, 0);
>
> chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
> for (i = 0; i < 3; i++) {
> @@ -2962,7 +2956,7 @@ 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 +2974,7 @@ 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 +3027,12 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
> }
>
> return 1;
> +
> +return_error:
> + /* revert original bus-width */
> + nand_set_defaults( chip->options & NAND_BUSWIDTH_16);
> + return 0;
> +
> }
>
> /*
> -------------------------
>
>
> with regards, pekon
--
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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