On Thu, Sep 11, 2014 at 12:02:08PM -0300, Ezequiel Garcia wrote:
> This commit adds a new platform-data boolean property that enables use
> of a flash-based bad block table. This can also be enabled by setting
> the 'nand-on-flash-bbt' devicetree property.
>
> If the flash BBT is not enabled, the driver falls back to use OOB
> bad block markers only, as before. If the flash BBT is enabled the
> kernel will keep track of bad blocks using a BBT, in addition to
> the OOB markers.
>
> As explained by Brian Norris the reasons for using a BBT are:
>
> ""
> The primary reason would be that NAND datasheets specify it these days.
> A better argument is that nobody guarantees that you can write a
> bad block marker to a worn out block; you may just get program failures.
>
> This has been acknowledged by several developers over the last several
> years.
>
> Additionally, you get a boot-time performance improvement if you only
> have to read a few pages, instead of a page or two from every block on
> the flash.
> ""
>
> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>
Pushed this one to l2-mtd.git. Thanks!
But I do have one question below, and I have comments for patch 2.
> ---
> arch/arm/mach-omap2/gpmc.c | 2 ++
> drivers/mtd/nand/omap2.c | 6 +++++-
> include/linux/platform_data/mtd-nand-omap2.h | 1 +
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
> index 2f97228..b55a225 100644
> --- a/arch/arm/mach-omap2/gpmc.c
> +++ b/arch/arm/mach-omap2/gpmc.c
> @@ -1440,6 +1440,8 @@ static int gpmc_probe_nand_child(struct platform_device *pdev,
> break;
> }
>
> + gpmc_nand_data->flash_bbt = of_get_nand_on_flash_bbt(child);
> +
> val = of_get_nand_bus_width(child);
> if (val == 16)
> gpmc_nand_data->devsize = NAND_BUSWIDTH_16;
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index 5967b38..e1a9b31 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -1663,7 +1663,6 @@ static int omap_nand_probe(struct platform_device *pdev)
> mtd->owner = THIS_MODULE;
> nand_chip = &info->nand;
> nand_chip->ecc.priv = NULL;
> - nand_chip->options |= NAND_SKIP_BBTSCAN;
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> nand_chip->IO_ADDR_R = devm_ioremap_resource(&pdev->dev, res);
> @@ -1692,6 +1691,11 @@ static int omap_nand_probe(struct platform_device *pdev)
> nand_chip->chip_delay = 50;
> }
>
> + if (pdata->flash_bbt)
> + nand_chip->bbt_options |= NAND_BBT_USE_FLASH | NAND_BBT_NO_OOB;
> + else
> + nand_chip->options |= NAND_SKIP_BBTSCAN;
Can you remind me: why do you use SKIP_BBTSCAN? Doesn't that mean you're
skipping all boot-time scanning for bad blocks, and resorting to
on-demand scanning (chip->block_bad()) every time you need to check for
bad blocks?
> +
> /* scan NAND device connected to chip controller */
> nand_chip->options |= pdata->devsize & NAND_BUSWIDTH_16;
> if (nand_scan_ident(mtd, 1, NULL)) {
> diff --git a/include/linux/platform_data/mtd-nand-omap2.h b/include/linux/platform_data/mtd-nand-omap2.h
> index 16ec262..090bbab 100644
> --- a/include/linux/platform_data/mtd-nand-omap2.h
> +++ b/include/linux/platform_data/mtd-nand-omap2.h
> @@ -71,6 +71,7 @@ struct omap_nand_platform_data {
> struct mtd_partition *parts;
> int nr_parts;
> bool dev_ready;
> + bool flash_bbt;
> enum nand_io xfer_type;
> int devsize;
> enum omap_ecc ecc_opt;
Brian
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