mtd: gpmi: change the BCH layout setting for large oob NAND

The code change updated the NAND driver BCH ECC layout algorithm to
support large oob size NAND chips(oob > 1024 bytes) and proposed a new
way to set ECC layout.

Current implementation requires each chunk size larger than oob size so
the bad block marker (BBM) can be guaranteed located in data chunk. The
ECC layout always using the unbalanced layout(Ecc for both meta and
Data0 chunk), but for the NAND chips with oob larger than 1k, the driver
cannot support because BCH doesn’t support GF 15 for 2K chunk.

The change keeps the data chunk no larger than 1k and adjust the ECC
strength or ECC layout to locate the BBM in data chunk. General idea for
large oob NAND chips is

1.Try all ECC strength from the minimum value required by NAND spec to
the maximum one that works, any ECC makes the BBM locate in data chunk
can be chosen.

2.If none of them works, using separate ECC for meta, which will add one
extra ecc with the same ECC strength as other data chunks. This extra
ECC can guarantee BBM located in data chunk, of course, we need to check
if oob can afford it.

Previous code has two methods for ECC layout setting, the
legacy_calc_ecc_layout and calc_ecc_layout_by_info, the difference
between these two methods is, legacy_calc_ecc_layout set the chunk size
larger chan oob size and then set the maximum ECC strength that oob can
afford. While the calc_ecc_layout_by_info set chunk size and ECC
strength according to NAND spec. It has been proved that the first
method cannot provide safe ECC strength for some modern NAND chips, so
in current code,

1. Driver read NAND parameters first and then chose the proper ECC
layout setting method.

2. If the oob is large or NAND required data chunk larger than oob size,
chose calc_ecc_for_large_oob, otherwise use calc_ecc_layout_by_info

3. legacy_calc_ecc_layout only used for some NAND chips does not contains
necessary information. So this is only a backup plan, it is NOT
recommended to use these NAND chips.

Signed-off-by: Han Xu <b45815@freescale.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>

1 files changed, 136 insertions, 69 deletions

diff --git a/drivers/mtd/nand/raw/mxs_nand.c b/drivers/mtd/nand/raw/mxs_nand.c
index fe8097c1460..8da59e39c01 100644
--- a/drivers/mtd/nand/raw/mxs_nand.c
+++ b/drivers/mtd/nand/raw/mxs_nand.c
@@ -112,53 +112,32 @@ static uint32_t mxs_nand_aux_status_offset(void)
 	return (MXS_NAND_METADATA_SIZE + 0x3) & ~0x3;
 }
 
-static inline int mxs_nand_calc_mark_offset(struct bch_geometry *geo,
-					    uint32_t page_data_size)
+static inline bool mxs_nand_bbm_in_data_chunk(struct bch_geometry *geo, struct mtd_info *mtd,
+		unsigned int *chunk_num)
 {
-	uint32_t chunk_data_size_in_bits = geo->ecc_chunk_size * 8;
-	uint32_t chunk_ecc_size_in_bits = geo->ecc_strength * geo->gf_len;
-	uint32_t chunk_total_size_in_bits;
-	uint32_t block_mark_chunk_number;
-	uint32_t block_mark_chunk_bit_offset;
-	uint32_t block_mark_bit_offset;
+	unsigned int i, j;
 
-	chunk_total_size_in_bits =
-			chunk_data_size_in_bits + chunk_ecc_size_in_bits;
-
-	/* Compute the bit offset of the block mark within the physical page. */
-	block_mark_bit_offset = page_data_size * 8;
-
-	/* Subtract the metadata bits. */
-	block_mark_bit_offset -= MXS_NAND_METADATA_SIZE * 8;
-
-	/*
-	 * Compute the chunk number (starting at zero) in which the block mark
-	 * appears.
-	 */
-	block_mark_chunk_number =
-			block_mark_bit_offset / chunk_total_size_in_bits;
-
-	/*
-	 * Compute the bit offset of the block mark within its chunk, and
-	 * validate it.
-	 */
-	block_mark_chunk_bit_offset = block_mark_bit_offset -
-			(block_mark_chunk_number * chunk_total_size_in_bits);
+	if (geo->ecc_chunk0_size != geo->ecc_chunkn_size) {
+		dev_err(this->dev, "The size of chunk0 must equal to chunkn\n");
+		return false;
+	}
 
-	if (block_mark_chunk_bit_offset > chunk_data_size_in_bits)
-		return -EINVAL;
+	i = (mtd->writesize * 8 - MXS_NAND_METADATA_SIZE * 8) /
+		(geo->gf_len * geo->ecc_strength +
+				geo->ecc_chunkn_size * 8);
 
-	/*
-	 * Now that we know the chunk number in which the block mark appears,
-	 * we can subtract all the ECC bits that appear before it.
-	 */
-	block_mark_bit_offset -=
-		block_mark_chunk_number * chunk_ecc_size_in_bits;
+	j = (mtd->writesize * 8 - MXS_NAND_METADATA_SIZE * 8) -
+		(geo->gf_len * geo->ecc_strength +
+				geo->ecc_chunkn_size * 8) * i;
 
-	geo->block_mark_byte_offset = block_mark_bit_offset >> 3;
-	geo->block_mark_bit_offset = block_mark_bit_offset & 0x7;
+	if (j < geo->ecc_chunkn_size * 8) {
+		*chunk_num = i + 1;
+		dev_dbg(this->dev, "Set ecc to %d and bbm in chunk %d\n",
+			geo->ecc_strength, *chunk_num);
+		return true;
+	}
 
-	return 0;
+	return false;
 }
 
 static inline int mxs_nand_calc_ecc_layout_by_info(struct bch_geometry *geo,
@@ -168,6 +147,7 @@ static inline int mxs_nand_calc_ecc_layout_by_info(struct bch_geometry *geo,
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
 	struct mxs_nand_info *nand_info = nand_get_controller_data(chip);
+	unsigned int block_mark_bit_offset;
 
 	switch (ecc_step) {
 	case SZ_512:
@@ -180,45 +160,51 @@ static inline int mxs_nand_calc_ecc_layout_by_info(struct bch_geometry *geo,
 		return -EINVAL;
 	}
 
-	geo->ecc_chunk_size = ecc_step;
+	geo->ecc_chunk0_size = ecc_step;
+	geo->ecc_chunkn_size = ecc_step;
 	geo->ecc_strength = round_up(ecc_strength, 2);
 
 	/* Keep the C >= O */
-	if (geo->ecc_chunk_size < mtd->oobsize)
+	if (geo->ecc_chunkn_size < mtd->oobsize)
 		return -EINVAL;
 
 	if (geo->ecc_strength > nand_info->max_ecc_strength_supported)
 		return -EINVAL;
 
-	geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunk_size;
+	geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunkn_size;
+
+	/* For bit swap. */
+	block_mark_bit_offset = mtd->writesize * 8 -
+		(geo->ecc_strength * geo->gf_len * (geo->ecc_chunk_count - 1)
+				+ MXS_NAND_METADATA_SIZE * 8);
+
+	geo->block_mark_byte_offset = block_mark_bit_offset / 8;
+	geo->block_mark_bit_offset  = block_mark_bit_offset % 8;
 
 	return 0;
 }
 
-static inline int mxs_nand_calc_ecc_layout(struct bch_geometry *geo,
+static inline int mxs_nand_legacy_calc_ecc_layout(struct bch_geometry *geo,
 					   struct mtd_info *mtd)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
 	struct mxs_nand_info *nand_info = nand_get_controller_data(chip);
+	unsigned int block_mark_bit_offset;
 
 	/* The default for the length of Galois Field. */
 	geo->gf_len = 13;
 
 	/* The default for chunk size. */
-	geo->ecc_chunk_size = 512;
+	geo->ecc_chunk0_size = 512;
+	geo->ecc_chunkn_size = 512;
 
-	if (geo->ecc_chunk_size < mtd->oobsize) {
+	if (geo->ecc_chunkn_size < mtd->oobsize) {
 		geo->gf_len = 14;
-		geo->ecc_chunk_size *= 2;
+		geo->ecc_chunk0_size *= 2;
+		geo->ecc_chunkn_size *= 2;
 	}
 
-	if (mtd->oobsize > geo->ecc_chunk_size) {
-		printf("Not support the NAND chips whose oob size is larger then %d bytes!\n",
-		       geo->ecc_chunk_size);
-		return -EINVAL;
-	}
-
-	geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunk_size;
+	geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunkn_size;
 
 	/*
 	 * Determine the ECC layout with the formula:
@@ -234,6 +220,84 @@ static inline int mxs_nand_calc_ecc_layout(struct bch_geometry *geo,
 	geo->ecc_strength = min(round_down(geo->ecc_strength, 2),
 				nand_info->max_ecc_strength_supported);
 
+	block_mark_bit_offset = mtd->writesize * 8 -
+		(geo->ecc_strength * geo->gf_len * (geo->ecc_chunk_count - 1)
+				+ MXS_NAND_METADATA_SIZE * 8);
+
+	geo->block_mark_byte_offset = block_mark_bit_offset / 8;
+	geo->block_mark_bit_offset  = block_mark_bit_offset % 8;
+
+	return 0;
+}
+
+static inline int mxs_nand_calc_ecc_for_large_oob(struct bch_geometry *geo,
+					   struct mtd_info *mtd)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct mxs_nand_info *nand_info = nand_get_controller_data(chip);
+	unsigned int block_mark_bit_offset;
+	unsigned int max_ecc;
+	unsigned int bbm_chunk;
+	unsigned int i;
+
+	/* sanity check for the minimum ecc nand required */
+	if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
+		return -EINVAL;
+	geo->ecc_strength = chip->ecc_strength_ds;
+
+	/* calculate the maximum ecc platform can support*/
+	geo->gf_len = 14;
+	geo->ecc_chunk0_size = 1024;
+	geo->ecc_chunkn_size = 1024;
+	geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunkn_size;
+	max_ecc = ((mtd->oobsize - MXS_NAND_METADATA_SIZE) * 8)
+			/ (geo->gf_len * geo->ecc_chunk_count);
+	max_ecc = min(round_down(max_ecc, 2),
+				nand_info->max_ecc_strength_supported);
+
+
+	/* search a supported ecc strength that makes bbm */
+	/* located in data chunk  */
+	geo->ecc_strength = chip->ecc_strength_ds;
+	while (!(geo->ecc_strength > max_ecc)) {
+		if (mxs_nand_bbm_in_data_chunk(geo, mtd, &bbm_chunk))
+			break;
+		geo->ecc_strength += 2;
+	}
+
+	/* if none of them works, keep using the minimum ecc */
+	/* nand required but changing ecc page layout  */
+	if (geo->ecc_strength > max_ecc) {
+		geo->ecc_strength = chip->ecc_strength_ds;
+		/* add extra ecc for meta data */
+		geo->ecc_chunk0_size = 0;
+		geo->ecc_chunk_count = (mtd->writesize / geo->ecc_chunkn_size) + 1;
+		geo->ecc_for_meta = 1;
+		/* check if oob can afford this extra ecc chunk */
+		if (mtd->oobsize * 8 < MXS_NAND_METADATA_SIZE * 8 +
+				geo->gf_len * geo->ecc_strength
+				* geo->ecc_chunk_count) {
+			printf("unsupported NAND chip with new layout\n");
+			return -EINVAL;
+		}
+
+		/* calculate in which chunk bbm located */
+		bbm_chunk = (mtd->writesize * 8 - MXS_NAND_METADATA_SIZE * 8 -
+			geo->gf_len * geo->ecc_strength) /
+			(geo->gf_len * geo->ecc_strength +
+					geo->ecc_chunkn_size * 8) + 1;
+	}
+
+	/* calculate the number of ecc chunk behind the bbm */
+	i = (mtd->writesize / geo->ecc_chunkn_size) - bbm_chunk + 1;
+
+	block_mark_bit_offset = mtd->writesize * 8 -
+		(geo->ecc_strength * geo->gf_len * (geo->ecc_chunk_count - i)
+				+ MXS_NAND_METADATA_SIZE * 8);
+
+	geo->block_mark_byte_offset = block_mark_bit_offset / 8;
+	geo->block_mark_bit_offset  = block_mark_bit_offset % 8;
+
 	return 0;
 }
 
@@ -983,18 +1047,23 @@ static int mxs_nand_set_geometry(struct mtd_info *mtd, struct bch_geometry *geo)
 	struct nand_chip *nand = mtd_to_nand(mtd);
 	struct mxs_nand_info *nand_info = nand_get_controller_data(nand);
 
-	if (chip->ecc.strength > 0 && chip->ecc.size > 0)
-		return mxs_nand_calc_ecc_layout_by_info(geo, mtd,
-				chip->ecc.strength, chip->ecc.size);
+	if (chip->ecc_strength_ds > nand_info->max_ecc_strength_supported) {
+		printf("unsupported NAND chip, minimum ecc required %d\n"
+			, chip->ecc_strength_ds);
+		return -EINVAL;
+	}
+
+	if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0) &&
+			(mtd->oobsize < 1024)) {
+		dev_warn(this->dev, "use legacy bch geometry\n");
+		return mxs_nand_legacy_calc_ecc_layout(geo, mtd);
+	}
 
-	if (nand_info->use_minimum_ecc ||
-		mxs_nand_calc_ecc_layout(geo, mtd)) {
-		if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
-			return -EINVAL;
+	if (mtd->oobsize > 1024 || chip->ecc_step_ds < mtd->oobsize)
+		return mxs_nand_calc_ecc_for_large_oob(geo, mtd);
 
-		return mxs_nand_calc_ecc_layout_by_info(geo, mtd,
+	return mxs_nand_calc_ecc_layout_by_info(geo, mtd,
 				chip->ecc_strength_ds, chip->ecc_step_ds);
-	}
 
 	return 0;
 }
@@ -1025,8 +1094,6 @@ int mxs_nand_setup_ecc(struct mtd_info *mtd)
 	if (ret)
 		return ret;
 
-	mxs_nand_calc_mark_offset(geo, mtd->writesize);
-
 	/* Configure BCH and set NFC geometry */
 	mxs_reset_block(&bch_regs->hw_bch_ctrl_reg);
 
@@ -1034,7 +1101,7 @@ int mxs_nand_setup_ecc(struct mtd_info *mtd)
 	tmp = (geo->ecc_chunk_count - 1) << BCH_FLASHLAYOUT0_NBLOCKS_OFFSET;
 	tmp |= MXS_NAND_METADATA_SIZE << BCH_FLASHLAYOUT0_META_SIZE_OFFSET;
 	tmp |= (geo->ecc_strength >> 1) << BCH_FLASHLAYOUT0_ECC0_OFFSET;
-	tmp |= geo->ecc_chunk_size >> MXS_NAND_CHUNK_DATA_CHUNK_SIZE_SHIFT;
+	tmp |= geo->ecc_chunk0_size >> MXS_NAND_CHUNK_DATA_CHUNK_SIZE_SHIFT;
 	tmp |= (geo->gf_len == 14 ? 1 : 0) <<
 		BCH_FLASHLAYOUT0_GF13_0_GF14_1_OFFSET;
 	writel(tmp, &bch_regs->hw_bch_flash0layout0);
@@ -1043,7 +1110,7 @@ int mxs_nand_setup_ecc(struct mtd_info *mtd)
 	tmp = (mtd->writesize + mtd->oobsize)
 		<< BCH_FLASHLAYOUT1_PAGE_SIZE_OFFSET;
 	tmp |= (geo->ecc_strength >> 1) << BCH_FLASHLAYOUT1_ECCN_OFFSET;
-	tmp |= geo->ecc_chunk_size >> MXS_NAND_CHUNK_DATA_CHUNK_SIZE_SHIFT;
+	tmp |= geo->ecc_chunkn_size >> MXS_NAND_CHUNK_DATA_CHUNK_SIZE_SHIFT;
 	tmp |= (geo->gf_len == 14 ? 1 : 0) <<
 		BCH_FLASHLAYOUT1_GF13_0_GF14_1_OFFSET;
 	writel(tmp, &bch_regs->hw_bch_flash0layout1);
@@ -1268,7 +1335,7 @@ int mxs_nand_init_ctrl(struct mxs_nand_info *nand_info)
 
 	nand->ecc.layout	= &fake_ecc_layout;
 	nand->ecc.mode		= NAND_ECC_HW;
-	nand->ecc.size		= nand_info->bch_geometry.ecc_chunk_size;
+	nand->ecc.size		= nand_info->bch_geometry.ecc_chunkn_size;
 	nand->ecc.strength	= nand_info->bch_geometry.ecc_strength;
 
 	/* second phase scan */