From: Masahiro Yamada yamada.masahiro@socionext.com
[ Upstream commit 0d55c668b218a1db68b5044bce4de74e1bd0f0c8 ]
NAND devices need additional data area (OOB) for error correction, but it is also used for Bad Block Marker (BBM). In many cases, the first byte in OOB is used for BBM, but the location actually depends on chip vendors. The NAND controller should preserve the precious BBM to keep track of bad blocks.
In Denali IP, the SPARE_AREA_SKIP_BYTES register is used to specify the number of bytes to skip from the start of OOB. The ECC engine will automatically skip the specified number of bytes when it gets access to OOB area.
The same value for SPARE_AREA_SKIP_BYTES should be used between firmware and the operating system if you intend to use the NAND device across the control hand-off.
In fact, the current denali.c code expects firmware to have already set the SPARE_AREA_SKIP_BYTES register, then reads the value out.
If no firmware (or bootloader) has initialized the controller, the register value is zero, which is the default after power-on-reset. In other words, the Linux driver cannot initialize the controller by itself.
Some possible solutions are:
[1] Add a DT property to specify the skipped bytes in OOB [2] Associate the preferred value with compatible [3] Hard-code the default value in the driver
My first attempt was [1], but in the review process, [3] was suggested as a counter-implementation. (https://lore.kernel.org/patchwork/patch/983055/)
The default value 8 was chosen to match to the boot ROM of the UniPhier platform. The preferred value may vary by platform. If so, please trade up to a different solution.
Signed-off-by: Masahiro Yamada yamada.masahiro@socionext.com Reviewed-by: Boris Brezillon boris.brezillon@bootlin.com Signed-off-by: Miquel Raynal miquel.raynal@bootlin.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/mtd/nand/raw/denali.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/mtd/nand/raw/denali.c b/drivers/mtd/nand/raw/denali.c index c502075e5721..ff955f085351 100644 --- a/drivers/mtd/nand/raw/denali.c +++ b/drivers/mtd/nand/raw/denali.c @@ -28,6 +28,7 @@ MODULE_LICENSE("GPL");
#define DENALI_NAND_NAME "denali-nand" +#define DENALI_DEFAULT_OOB_SKIP_BYTES 8
/* for Indexed Addressing */ #define DENALI_INDEXED_CTRL 0x00 @@ -1106,12 +1107,17 @@ static void denali_hw_init(struct denali_nand_info *denali) denali->revision = swab16(ioread32(denali->reg + REVISION));
/* - * tell driver how many bit controller will skip before - * writing ECC code in OOB, this register may be already - * set by firmware. So we read this value out. - * if this value is 0, just let it be. + * Set how many bytes should be skipped before writing data in OOB. + * If a non-zero value has already been set (by firmware or something), + * just use it. Otherwise, set the driver default. */ denali->oob_skip_bytes = ioread32(denali->reg + SPARE_AREA_SKIP_BYTES); + if (!denali->oob_skip_bytes) { + denali->oob_skip_bytes = DENALI_DEFAULT_OOB_SKIP_BYTES; + iowrite32(denali->oob_skip_bytes, + denali->reg + SPARE_AREA_SKIP_BYTES); + } + denali_detect_max_banks(denali); iowrite32(0x0F, denali->reg + RB_PIN_ENABLED); iowrite32(CHIP_EN_DONT_CARE__FLAG, denali->reg + CHIP_ENABLE_DONT_CARE);