From 785818fa8385fe55dab253e42a4c6728fca61333 Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Sat, 29 Apr 2017 11:06:43 +0200 Subject: [PATCH] mtd: nand: add core support for on-die ECC A number of NAND flashes have a capability called "on-die ECC" where the NAND chip itself is capable of detecting and correcting errors. Linux already has support for using the ECC implementation of the NAND controller, or a software based ECC implementation, but not for using the ECC implementation of the NAND controller. However, such an implementation is sometimes useful in situations where the NAND controller provides ECC algorithms that are not strong enough for the NAND chip used on the system. A typical case is a NAND chip that requires a 4-bit ECC, while the NAND controller only provides a 1-bit ECC algorithm. This commit introduces the support for the NAND_ECC_ON_DIE ECC mode: - Parsing of the "on-die" value for the "nand-ecc-mode" Device Tree property - Handling NAND_ECC_ON_DIE case in nand_scan_tail(). The idea is that the vendor specific code for the NAND chip must implement ->read_page() and ->write_page(). It may optionally provide its own ->read_page_raw() and ->write_page_raw() as well. For OOB operation, we assume the standard operations are good enough, but they can be overridden by the vendor specific code if needed. Signed-off-by: Thomas Petazzoni Reviewed-by: Richard Weinberger Signed-off-by: Boris Brezillon --- drivers/mtd/nand/nand_base.c | 13 +++++++++++++ include/linux/mtd/nand.h | 1 + 2 files changed, 14 insertions(+) diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index d474378ed810..f49aecd3f1de 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -4177,6 +4177,7 @@ static const char * const nand_ecc_modes[] = { [NAND_ECC_HW] = "hw", [NAND_ECC_HW_SYNDROME] = "hw_syndrome", [NAND_ECC_HW_OOB_FIRST] = "hw_oob_first", + [NAND_ECC_ON_DIE] = "on-die", }; static int of_get_nand_ecc_mode(struct device_node *np) @@ -4717,6 +4718,18 @@ int nand_scan_tail(struct mtd_info *mtd) } break; + case NAND_ECC_ON_DIE: + if (!ecc->read_page || !ecc->write_page) { + WARN(1, "No ECC functions supplied; on-die ECC not possible\n"); + ret = -EINVAL; + goto err_free; + } + if (!ecc->read_oob) + ecc->read_oob = nand_read_oob_std; + if (!ecc->write_oob) + ecc->write_oob = nand_write_oob_std; + break; + case NAND_ECC_NONE: pr_warn("NAND_ECC_NONE selected by board driver. This is not recommended!\n"); ecc->read_page = nand_read_page_raw; diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h index 8f67b1581683..603522097ec9 100644 --- a/include/linux/mtd/nand.h +++ b/include/linux/mtd/nand.h @@ -116,6 +116,7 @@ typedef enum { NAND_ECC_HW, NAND_ECC_HW_SYNDROME, NAND_ECC_HW_OOB_FIRST, + NAND_ECC_ON_DIE, } nand_ecc_modes_t; enum nand_ecc_algo { -- 2.20.1