[PATCH v2 3/6] mtd: rawnand: sunxi: do not count BBM bytes twice

Richard Genoud
2026-03-05T10:02:16Z

BBM is part of USER_DATA section, so we should remove it twice

This was working ok because we are on the safe size, advertising that
there was 2 bytes less available than in reality.

But we can't change old platforms, since it may lead to a different ECC
strength, so, introduce a legacy flag for old platforms, and switch the
new platforms to the correct count.

Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
---
drivers/mtd/nand/raw/sunxi_nand.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
index 8af449e548d4..d126dc18ef27 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -275,6 +275,8 @@ static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
* @has_ecc_block_512: If the ECC can handle 512B or only 1024B chuncks
* @has_ecc_clk: If the controller needs an ECC clock.
* @has_mbus_clk: If the controller needs a mbus clock.
+ * @legacy_max_strength:If the maximize strength function was off by 2 bytes
+ * NB: this should not be used in new controllers
* @reg_io_data: I/O data register
* @reg_ecc_err_cnt: ECC error counter register
* @reg_user_data: User data register
@@ -304,6 +306,7 @@ struct sunxi_nfc_caps {
bool has_ecc_block_512;
bool has_ecc_clk;
bool has_mbus_clk;
+ bool legacy_max_strength;
unsigned int reg_io_data;
unsigned int reg_ecc_err_cnt;
unsigned int reg_user_data;
@@ -1805,10 +1808,22 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct nand_chip *nand,
ecc->size = 1024;
nsectors = mtd->writesize / ecc->size;

- /* Reserve 2 bytes for the BBM */
- bytes = (mtd->oobsize - 2) / nsectors;
+ /*
+ * The 2 BBM bytes should not be removed from the grand total,
+ * because they are part of the USER_DATA_SZ.
+ * But we can't modify that for older platform since it may
+ * result in a stronger ECC at the end, and break the
+ * compatibility.
+ */
+ if (nfc->caps->legacy_max_strength)
+ bytes = (mtd->oobsize - 2) / nsectors;
+ else
+ bytes = mtd->oobsize / nsectors;

- /* 4 non-ECC bytes are added before each ECC bytes section */
+ /*
+ * USER_DATA_SZ non-ECC bytes are added before each ECC bytes
+ * section, they contain the 2 BBM bytes
+ */
bytes -= USER_DATA_SZ;

/* and bytes has to be even. */
@@ -2373,6 +2388,7 @@ static const u8 sunxi_user_data_len_h6[] = {

static const struct sunxi_nfc_caps sunxi_nfc_a10_caps = {
.has_ecc_block_512 = true,
+ .legacy_max_strength = true,
.reg_io_data = NFC_REG_A10_IO_DATA,
.reg_ecc_err_cnt = NFC_REG_A10_ECC_ERR_CNT,
.reg_user_data = NFC_REG_A10_USER_DATA,
@@ -2394,6 +2410,7 @@ static const struct sunxi_nfc_caps sunxi_nfc_a10_caps = {
static const struct sunxi_nfc_caps sunxi_nfc_a23_caps = {
.has_mdma = true,
.has_ecc_block_512 = true,
+ .legacy_max_strength = true,
.reg_io_data = NFC_REG_A23_IO_DATA,
.reg_ecc_err_cnt = NFC_REG_A10_ECC_ERR_CNT,
.reg_user_data = NFC_REG_A10_USER_DATA,