Since commit ff94bc40af34 (mtd, ubi, ubifs: resync with Linux-3.14), chip->scan_bbt() is called at the end of nand_scan_tail(). It means the first read access happens immediately after the generic NAND initialization process.

It causes a problem to some SoCs of UniPhier platform because some of their register values need to be fixed up after the general initialization procedure has been finished. Otherwise, read asccess fails. Such a fix-up is SoC-specific enough to be written in a board file rather than in driver code.

One of possible and clean enough ways to work around this issue is postpone the BBT scanning until necessary fix-up is done in board_late_init() or somewhere else.

CONFIG_MTD_NAND_SKIP_BBTSCAN, if enabled, allows to skip the BBT scanning at the end of nand_scan_tail().

Signed-off-by: Masahiro Yamada yamada.m@jp.panasonic.com Cc: Scott Wood scottwood@freescale.com ---

If this patch is accepted, I will turn on this config option for my boards.

drivers/mtd/nand/Kconfig | 13 +++++++++++++ drivers/mtd/nand/nand.c | 4 ++++ 2 files changed, 17 insertions(+)

diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig index 75c2c06..e9d133d 100644 --- a/drivers/mtd/nand/Kconfig +++ b/drivers/mtd/nand/Kconfig @@ -2,6 +2,19 @@ menu "NAND Device Support"

if !SPL_BUILD

+MTD_NAND_SKIP_BBTSCAN + bool "Skip BBT scanning" + help + The current implementation of nand_scan_tail() calls scan_bbt handler + at the end of itself to build a bad block table. It means the first + read access happens in the initizalization procedure. It causes a + problem on some SoCs that need some extra SoC-specific settings + before starting read/write access. + + If this option is enabled, bad block scanning is skipped during the + nand device initialization. You are resposible to build a bad block + table lator. + config NAND_DENALI bool "Support Denali NAND controller" help diff --git a/drivers/mtd/nand/nand.c b/drivers/mtd/nand/nand.c index 4cf4c1c..a249647 100644 --- a/drivers/mtd/nand/nand.c +++ b/drivers/mtd/nand/nand.c @@ -88,6 +88,10 @@ static void nand_init_chip(int i) mtd->priv = nand; nand->IO_ADDR_R = nand->IO_ADDR_W = (void __iomem *)base_addr;

+#ifdef CONFIG_MTD_NAND_SKIP_BBTSCAN + nand->options |= NAND_SKIP_BBTSCAN; +#endif + if (board_nand_init(nand)) return;