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nand: omap2: Add support for flash-based bad block table

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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@vanguardiasur.com.ar>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
This commit is contained in:
Ezequiel García 2014-09-11 12:02:08 -03:00 committed by Brian Norris
parent 2d405ec5fd
commit fef775caa7
3 changed files with 8 additions and 1 deletions
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2
arch/arm/mach-omap2/gpmc.c
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@ -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;

6
drivers/mtd/nand/omap2.c
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@ -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;
/* scan NAND device connected to chip controller */
nand_chip->options |= pdata->devsize & NAND_BUSWIDTH_16;
if (nand_scan_ident(mtd, 1, NULL)) {

1
include/linux/platform_data/mtd-nand-omap2.h
View File

@ -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;