[RFC 0/2] mtd: Support slc-mode for Toshiba TC58TEG5DCLTA00

[RFC 0/2] mtd: Support slc-mode for Toshiba TC58TEG5DCLTA00

[Chris Morgan]

From: Chris Morgan <macromorgan@hotmail.com>

Add support for slc-mode implemented in Linux for the Toshiba
TC58TEG5DCLTA00 NAND flash found on the NTC CHIP. This requires the
addition of a paired-pages scheme, a new parameter for MTD partitions
of slc-mode, and setting the correct paired-pages scheme for the
TC58TEG5DCLTA00 flash chip. I will likely need some help making sure
this is consistent with the quality expected of upstream, as well as
solving some remaining issues (such as ubifs partitions not working
with slc-mode set).

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>

Chris Morgan (2):
  mtd: Add partial support for Linux slc-mode for MLC NAND
  mtd: Add pairing info for Toshiba TC58TEG5DCLTA00 NAND

 drivers/mtd/mtdcore.c            | 320 ++++++++++++++++++++++++++++---
 drivers/mtd/mtdpart.c            |   7 +
 drivers/mtd/nand/raw/nand_base.c |  59 ++++++
 include/linux/mtd/mtd.h          | 126 ++++++++++++
 include/linux/mtd/partitions.h   |   2 +
 include/mtd/mtd-abi.h            |   1 +
 6 files changed, 491 insertions(+), 24 deletions(-)

-- 
2.30.2

[RFC 1/2] mtd: Add partial support for Linux slc-mode for MLC NAND

[Chris Morgan]

From: Chris Morgan <macromorgan@hotmail.com>

Add support for setting the slc-mode parameter for a given MLC NAND
device. This allows a given device to write only to the first set
of paried pages to help reduce data corruption and increase reliability
of the NAND.

I haven't tested these patches extensively yet, but thus far I have
been able to boot a FIT image written directly to an MTD partition
from within Linux via U-boot where the slc-mode parameter is set. I
am not able to attach a ubifs partition generated in Linux with the
slc-mode set.

As I am unfamiliar with NAND and have limited experience with the MTD
subsystems, please let me know what else I can do to improve the driver
(and possibly get it where ubifs can work).

Thank you.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
---
 drivers/mtd/mtdcore.c            | 320 ++++++++++++++++++++++++++++---
 drivers/mtd/mtdpart.c            |   7 +
 drivers/mtd/nand/raw/nand_base.c |  50 +++++
 include/linux/mtd/mtd.h          | 126 ++++++++++++
 include/linux/mtd/partitions.h   |   2 +
 include/mtd/mtd-abi.h            |   1 +
 6 files changed, 482 insertions(+), 24 deletions(-)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 0d1f94c6cb..884c95228a 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -397,6 +397,114 @@ static struct device_type mtd_devtype = {
 };
 #endif
 
+/**
+ * mtd_wunit_to_pairing_info - get pairing information of a wunit
+ * @mtd: pointer to new MTD device info structure
+ * @wunit: write unit we are interested in
+ * @info: returned pairing information
+ *
+ * Retrieve pairing information associated to the wunit.
+ * This is mainly useful when dealing with MLC/TLC NANDs where pages can be
+ * paired together, and where programming a page may influence the page it is
+ * paired with.
+ * The notion of page is replaced by the term wunit (write-unit) to stay
+ * consistent with the ->writesize field.
+ *
+ * The @wunit argument can be extracted from an absolute offset using
+ * mtd_offset_to_wunit(). @info is filled with the pairing information attached
+ * to @wunit.
+ *
+ * From the pairing info the MTD user can find all the wunits paired with
+ * @wunit using the following loop:
+ *
+ * for (i = 0; i < mtd_pairing_groups(mtd); i++) {
+ *	info.pair = i;
+ *	mtd_pairing_info_to_wunit(mtd, &info);
+ *	...
+ * }
+ */
+int mtd_wunit_to_pairing_info(struct mtd_info *mtd, int wunit,
+			      struct mtd_pairing_info *info)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+	int npairs = mtd_wunit_per_eb(master) / mtd_pairing_groups(master);
+
+	if (wunit < 0 || wunit >= npairs)
+		return -EINVAL;
+
+	if (master->pairing && master->pairing->get_info)
+		return master->pairing->get_info(master, wunit, info);
+
+	info->group = 0;
+	info->pair = wunit;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mtd_wunit_to_pairing_info);
+
+/**
+ * mtd_pairing_info_to_wunit - get wunit from pairing information
+ * @mtd: pointer to new MTD device info structure
+ * @info: pairing information struct
+ *
+ * Returns a positive number representing the wunit associated to the info
+ * struct, or a negative error code.
+ *
+ * This is the reverse of mtd_wunit_to_pairing_info(), and can help one to
+ * iterate over all wunits of a given pair (see mtd_wunit_to_pairing_info()
+ * doc).
+ *
+ * It can also be used to only program the first page of each pair (i.e.
+ * page attached to group 0), which allows one to use an MLC NAND in
+ * software-emulated SLC mode:
+ *
+ * info.group = 0;
+ * npairs = mtd_wunit_per_eb(mtd) / mtd_pairing_groups(mtd);
+ * for (info.pair = 0; info.pair < npairs; info.pair++) {
+ *	wunit = mtd_pairing_info_to_wunit(mtd, &info);
+ *	mtd_write(mtd, mtd_wunit_to_offset(mtd, blkoffs, wunit),
+ *		  mtd->writesize, &retlen, buf + (i * mtd->writesize));
+ * }
+ */
+int mtd_pairing_info_to_wunit(struct mtd_info *mtd,
+			      const struct mtd_pairing_info *info)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+	int ngroups = mtd_pairing_groups(master);
+	int npairs = mtd_wunit_per_eb(master) / ngroups;
+
+	if (!info || info->pair < 0 || info->pair >= npairs ||
+	    info->group < 0 || info->group >= ngroups)
+		return -EINVAL;
+
+	if (master->pairing && master->pairing->get_wunit)
+		return mtd->pairing->get_wunit(master, info);
+
+	return info->pair;
+}
+EXPORT_SYMBOL_GPL(mtd_pairing_info_to_wunit);
+
+/**
+ * mtd_pairing_groups - get the number of pairing groups
+ * @mtd: pointer to new MTD device info structure
+ *
+ * Returns the number of pairing groups.
+ *
+ * This number is usually equal to the number of bits exposed by a single
+ * cell, and can be used in conjunction with mtd_pairing_info_to_wunit()
+ * to iterate over all pages of a given pair.
+ */
+int mtd_pairing_groups(struct mtd_info *mtd)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->pairing || !master->pairing->ngroups)
+		return 1;
+
+	return master->pairing->ngroups;
+}
+EXPORT_SYMBOL_GPL(mtd_pairing_groups);
+
 /**
  *	add_mtd_device - register an MTD device
  *	@mtd: pointer to new MTD device info structure
@@ -412,6 +520,7 @@ int add_mtd_device(struct mtd_info *mtd)
 #ifndef __UBOOT__
 	struct mtd_notifier *not;
 #endif
+	struct mtd_info *master = mtd_get_master(mtd);
 	int i, error;
 
 #ifndef __UBOOT__
@@ -431,6 +540,20 @@ int add_mtd_device(struct mtd_info *mtd)
 #endif
 
 	BUG_ON(mtd->writesize == 0);
+
+	/*
+	 * MTD_SLC_ON_MLC_EMULATION can only be set on partitions, when the
+	 * master is an MLC NAND and has a proper pairing scheme defined.
+	 * We also reject masters that implement ->_writev() for now, because
+	 * NAND controller drivers don't implement this hook, and adding the
+	 * SLC -> MLC address/length conversion to this path is useless if we
+	 * don't have a user.
+	 */
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION &&
+	    (!mtd_is_partition(mtd) || master->type != MTD_MLCNANDFLASH ||
+	     !master->pairing))
+		return -EINVAL;
+
 	mutex_lock(&mtd_table_mutex);
 
 	i = idr_alloc(&mtd_idr, mtd, 0, 0, GFP_KERNEL);
@@ -446,6 +569,14 @@ int add_mtd_device(struct mtd_info *mtd)
 	if (mtd->bitflip_threshold == 0)
 		mtd->bitflip_threshold = mtd->ecc_strength;
 
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
+		int ngroups = mtd_pairing_groups(master);
+
+		mtd->erasesize /= ngroups;
+		mtd->size = (u64)mtd_div_by_eb(mtd->size, master) *
+			    mtd->erasesize;
+	}
+
 	if (is_power_of_2(mtd->erasesize))
 		mtd->erasesize_shift = ffs(mtd->erasesize) - 1;
 	else
@@ -880,17 +1011,29 @@ EXPORT_SYMBOL_GPL(__put_mtd_device);
  */
 int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
 {
+	struct mtd_info *master = mtd_get_master(mtd);
+	struct erase_info adjinstr;
 	if (instr->addr > mtd->size || instr->len > mtd->size - instr->addr)
 		return -EINVAL;
 	if (!(mtd->flags & MTD_WRITEABLE))
 		return -EROFS;
 	instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;
+	adjinstr = *instr;
+
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
+		adjinstr.addr = (loff_t)mtd_div_by_eb(instr->addr, mtd) *
+				master->erasesize;
+		adjinstr.len = ((u64)mtd_div_by_eb(instr->addr + instr->len, mtd) *
+				master->erasesize) -
+			       adjinstr.addr;
+	}
+
 	if (!instr->len) {
-		instr->state = MTD_ERASE_DONE;
-		mtd_erase_callback(instr);
+		adjinstr.state = MTD_ERASE_DONE;
+		mtd_erase_callback(&adjinstr);
 		return 0;
 	}
-	return mtd->_erase(mtd, instr);
+	return master->_erase(master, &adjinstr);
 }
 EXPORT_SYMBOL_GPL(mtd_erase);
 
@@ -1066,6 +1209,101 @@ static int mtd_check_oob_ops(struct mtd_info *mtd, loff_t offs,
 	return 0;
 }
 
+static int mtd_read_oob_std(struct mtd_info *mtd, loff_t from,
+			    struct mtd_oob_ops *ops)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
+
+	from = mtd_get_master_ofs(mtd, from);
+	if (master->_read_oob)
+		ret = master->_read_oob(master, from, ops);
+	else
+		ret = master->_read(master, from, ops->len, &ops->retlen,
+				 ops->datbuf);
+
+	return ret;
+}
+
+static int mtd_write_oob_std(struct mtd_info *mtd, loff_t to,
+			     struct mtd_oob_ops *ops)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
+
+	to = mtd_get_master_ofs(mtd, to);
+	if (master->_write_oob)
+		ret = master->_write_oob(master, to, ops);
+	else
+		ret = master->_write(master, to, ops->len, &ops->retlen,
+				  ops->datbuf);
+
+	return ret;
+}
+
+static int mtd_io_emulated_slc(struct mtd_info *mtd, loff_t start, bool read,
+			       struct mtd_oob_ops *ops)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+	int ngroups = mtd_pairing_groups(master);
+	int npairs = mtd_wunit_per_eb(master) / ngroups;
+	struct mtd_oob_ops adjops = *ops;
+	unsigned int wunit, oobavail;
+	struct mtd_pairing_info info;
+	int max_bitflips = 0;
+	u32 ebofs, pageofs;
+	loff_t base, pos;
+
+	ebofs = mtd_mod_by_eb(start, mtd);
+	base = (loff_t)mtd_div_by_eb(start, mtd) * master->erasesize;
+	info.group = 0;
+	info.pair = mtd_div_by_ws(ebofs, mtd);
+	pageofs = mtd_mod_by_ws(ebofs, mtd);
+	oobavail = mtd_oobavail(mtd, ops);
+
+	while (ops->retlen < ops->len || ops->oobretlen < ops->ooblen) {
+		int ret;
+
+		if (info.pair >= npairs) {
+			info.pair = 0;
+			base += master->erasesize;
+		}
+
+		wunit = mtd_pairing_info_to_wunit(master, &info);
+		pos = mtd_wunit_to_offset(mtd, base, wunit);
+
+		adjops.len = ops->len - ops->retlen;
+		if (adjops.len > mtd->writesize - pageofs)
+			adjops.len = mtd->writesize - pageofs;
+
+		adjops.ooblen = ops->ooblen - ops->oobretlen;
+		if (adjops.ooblen > oobavail - adjops.ooboffs)
+			adjops.ooblen = oobavail - adjops.ooboffs;
+
+		if (read) {
+			ret = mtd_read_oob_std(mtd, pos + pageofs, &adjops);
+			if (ret > 0)
+				max_bitflips = max(max_bitflips, ret);
+		} else {
+			ret = mtd_write_oob_std(mtd, pos + pageofs, &adjops);
+		}
+
+		if (ret < 0)
+			return ret;
+
+		max_bitflips = max(max_bitflips, ret);
+		ops->retlen += adjops.retlen;
+		ops->oobretlen += adjops.oobretlen;
+		adjops.datbuf += adjops.retlen;
+		adjops.oobbuf += adjops.oobretlen;
+		adjops.ooboffs = 0;
+		pageofs = 0;
+		info.pair++;
+	}
+
+	return max_bitflips;
+}
+
 int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 {
 	int ret_code;
@@ -1079,11 +1317,10 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 	if (!mtd->_read_oob && (!mtd->_read || ops->oobbuf))
 		return -EOPNOTSUPP;
 
-	if (mtd->_read_oob)
-		ret_code = mtd->_read_oob(mtd, from, ops);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
+		ret_code = mtd_io_emulated_slc(mtd, from, true, ops);
 	else
-		ret_code = mtd->_read(mtd, from, ops->len, &ops->retlen,
-				      ops->datbuf);
+		ret_code = mtd_read_oob_std(mtd, from, ops);
 
 	/*
 	 * In cases where ops->datbuf != NULL, mtd->_read_oob() has semantics
@@ -1117,11 +1354,11 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to,
 	if (!mtd->_write_oob && (!mtd->_write || ops->oobbuf))
 		return -EOPNOTSUPP;
 
-	if (mtd->_write_oob)
-		return mtd->_write_oob(mtd, to, ops);
-	else
-		return mtd->_write(mtd, to, ops->len, &ops->retlen,
-				   ops->datbuf);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
+		return mtd_io_emulated_slc(mtd, to, false, ops);
+
+	return mtd_write_oob_std(mtd, to, ops);
+
 }
 EXPORT_SYMBOL_GPL(mtd_write_oob);
 
@@ -1571,69 +1808,104 @@ EXPORT_SYMBOL_GPL(mtd_lock_user_prot_reg);
 /* Chip-supported device locking */
 int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
-	if (!mtd->_lock)
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->_lock)
 		return -EOPNOTSUPP;
 	if (ofs < 0 || ofs > mtd->size || len > mtd->size - ofs)
 		return -EINVAL;
 	if (!len)
 		return 0;
-	return mtd->_lock(mtd, ofs, len);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
+		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
+		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
+	}
+
+	return master->_lock(master, mtd_get_master_ofs(mtd, ofs), len);
 }
 EXPORT_SYMBOL_GPL(mtd_lock);
 
 int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
-	if (!mtd->_unlock)
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->_unlock)
 		return -EOPNOTSUPP;
 	if (ofs < 0 || ofs > mtd->size || len > mtd->size - ofs)
 		return -EINVAL;
 	if (!len)
 		return 0;
-	return mtd->_unlock(mtd, ofs, len);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
+		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
+		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
+	}
+
+	return master->_unlock(master, mtd_get_master_ofs(mtd, ofs), len);
 }
 EXPORT_SYMBOL_GPL(mtd_unlock);
 
 int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
-	if (!mtd->_is_locked)
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->_is_locked)
 		return -EOPNOTSUPP;
 	if (ofs < 0 || ofs > mtd->size || len > mtd->size - ofs)
 		return -EINVAL;
 	if (!len)
 		return 0;
-	return mtd->_is_locked(mtd, ofs, len);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
+		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
+		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
+	}
+
+	return master->_is_locked(master, mtd_get_master_ofs(mtd, ofs), len);
 }
 EXPORT_SYMBOL_GPL(mtd_is_locked);
 
 int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
 {
+	struct mtd_info *master = mtd_get_master(mtd);
+
 	if (ofs < 0 || ofs > mtd->size)
 		return -EINVAL;
-	if (!mtd->_block_isreserved)
+	if (!master->_block_isreserved)
 		return 0;
-	return mtd->_block_isreserved(mtd, ofs);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
+		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
+	return master->_block_isreserved(master, mtd_get_master_ofs(mtd, ofs));
 }
 EXPORT_SYMBOL_GPL(mtd_block_isreserved);
 
 int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
 {
+	struct mtd_info *master = mtd_get_master(mtd);
+
 	if (ofs < 0 || ofs > mtd->size)
 		return -EINVAL;
-	if (!mtd->_block_isbad)
+	if (!master->_block_isbad)
 		return 0;
-	return mtd->_block_isbad(mtd, ofs);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
+		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
+
+	return master->_block_isbad(master, mtd_get_master_ofs(mtd, ofs));
 }
 EXPORT_SYMBOL_GPL(mtd_block_isbad);
 
 int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
 {
-	if (!mtd->_block_markbad)
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	if (!master->_block_markbad)
 		return -EOPNOTSUPP;
 	if (ofs < 0 || ofs > mtd->size)
 		return -EINVAL;
 	if (!(mtd->flags & MTD_WRITEABLE))
 		return -EROFS;
-	return mtd->_block_markbad(mtd, ofs);
+	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
+		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
+
+	return master->_block_markbad(master, mtd_get_master_ofs(mtd, ofs));
 }
 EXPORT_SYMBOL_GPL(mtd_block_markbad);
 
diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index d064ac3048..63d14467d4 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -148,6 +148,12 @@ static int mtd_parse_partition(const char **_mtdparts,
 		mtdparts += 2;
 	}
 
+	/* if slc is found use emulated SLC mode on this partition*/
+	if (!strncmp(mtdparts, "slc", 3)) {
+		partition->add_flags |= MTD_SLC_ON_MLC_EMULATION;
+		mtdparts += 3;
+	}
+
 	/* Check for a potential next partition definition */
 	if (*mtdparts == ',') {
 		if (partition->size == MTD_SIZE_REMAINING) {
@@ -591,6 +597,7 @@ static struct mtd_info *allocate_partition(struct mtd_info *master,
 	/* set up the MTD object for this partition */
 	slave->type = master->type;
 	slave->flags = master->flags & ~part->mask_flags;
+	slave->flags |= part->add_flags;
 	slave->size = part->size;
 	slave->writesize = master->writesize;
 	slave->writebufsize = master->writebufsize;
diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 3679ee727e..845bf57c53 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -108,6 +108,56 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
  */
 DEFINE_LED_TRIGGER(nand_led_trigger);
 
+static int nand_pairing_dist3_get_info(struct mtd_info *mtd, int page,
+				       struct mtd_pairing_info *info)
+{
+	int lastpage = (mtd->erasesize / mtd->writesize) - 1;
+	int dist = 3;
+
+	if (page == lastpage)
+		dist = 2;
+
+	if (!page || (page & 1)) {
+		info->group = 0;
+		info->pair = (page + 1) / 2;
+	} else {
+		info->group = 1;
+		info->pair = (page + 1 - dist) / 2;
+	}
+
+	return 0;
+}
+
+static int nand_pairing_dist3_get_wunit(struct mtd_info *mtd,
+					const struct mtd_pairing_info *info)
+{
+	int lastpair = ((mtd->erasesize / mtd->writesize) - 1) / 2;
+	int page = info->pair * 2;
+	int dist = 3;
+
+	if (!info->group && !info->pair)
+		return 0;
+
+	if (info->pair == lastpair && info->group)
+		dist = 2;
+
+	if (!info->group)
+		page--;
+	else if (info->pair)
+		page += dist - 1;
+
+	if (page >= mtd->erasesize / mtd->writesize)
+		return -EINVAL;
+
+	return page;
+}
+
+const struct mtd_pairing_scheme dist3_pairing_scheme = {
+	.ngroups = 2,
+	.get_info = nand_pairing_dist3_get_info,
+	.get_wunit = nand_pairing_dist3_get_wunit,
+};
+
 static int check_offs_len(struct mtd_info *mtd,
 					loff_t ofs, uint64_t len)
 {
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 927854950a..7d63df4130 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -133,6 +133,82 @@ struct mtd_ooblayout_ops {
 		     struct mtd_oob_region *oobfree);
 };
 
+/**
+ * struct mtd_pairing_info - page pairing information
+ *
+ * @pair: pair id
+ * @group: group id
+ *
+ * The term "pair" is used here, even though TLC NANDs might group pages by 3
+ * (3 bits in a single cell). A pair should regroup all pages that are sharing
+ * the same cell. Pairs are then indexed in ascending order.
+ *
+ * @group is defining the position of a page in a given pair. It can also be
+ * seen as the bit position in the cell: page attached to bit 0 belongs to
+ * group 0, page attached to bit 1 belongs to group 1, etc.
+ *
+ * Example:
+ * The H27UCG8T2BTR-BC datasheet describes the following pairing scheme:
+ *
+ *		group-0		group-1
+ *
+ *  pair-0	page-0		page-4
+ *  pair-1	page-1		page-5
+ *  pair-2	page-2		page-8
+ *  ...
+ *  pair-127	page-251	page-255
+ *
+ *
+ * Note that the "group" and "pair" terms were extracted from Samsung and
+ * Hynix datasheets, and might be referenced under other names in other
+ * datasheets (Micron is describing this concept as "shared pages").
+ */
+struct mtd_pairing_info {
+	int pair;
+	int group;
+};
+
+/**
+ * struct mtd_pairing_scheme - page pairing scheme description
+ *
+ * @ngroups: number of groups. Should be related to the number of bits
+ *	     per cell.
+ * @get_info: converts a write-unit (page number within an erase block) into
+ *	      mtd_pairing information (pair + group). This function should
+ *	      fill the info parameter based on the wunit index or return
+ *	      -EINVAL if the wunit parameter is invalid.
+ * @get_wunit: converts pairing information into a write-unit (page) number.
+ *	       This function should return the wunit index pointed by the
+ *	       pairing information described in the info argument. It should
+ *	       return -EINVAL, if there's no wunit corresponding to the
+ *	       passed pairing information.
+ *
+ * See mtd_pairing_info documentation for a detailed explanation of the
+ * pair and group concepts.
+ *
+ * The mtd_pairing_scheme structure provides a generic solution to represent
+ * NAND page pairing scheme. Instead of exposing two big tables to do the
+ * write-unit <-> (pair + group) conversions, we ask the MTD drivers to
+ * implement the ->get_info() and ->get_wunit() functions.
+ *
+ * MTD users will then be able to query these information by using the
+ * mtd_pairing_info_to_wunit() and mtd_wunit_to_pairing_info() helpers.
+ *
+ * @ngroups is here to help MTD users iterating over all the pages in a
+ * given pair. This value can be retrieved by MTD users using the
+ * mtd_pairing_groups() helper.
+ *
+ * Examples are given in the mtd_pairing_info_to_wunit() and
+ * mtd_wunit_to_pairing_info() documentation.
+ */
+struct mtd_pairing_scheme {
+	int ngroups;
+	int (*get_info)(struct mtd_info *mtd, int wunit,
+			struct mtd_pairing_info *info);
+	int (*get_wunit)(struct mtd_info *mtd,
+			 const struct mtd_pairing_info *info);
+};
+
 /*
  * Internal ECC layout control structure. For historical reasons, there is a
  * similar, smaller struct nand_ecclayout_user (in mtd-abi.h) that is retained
@@ -211,6 +287,9 @@ struct mtd_info {
 	/* OOB layout description */
 	const struct mtd_ooblayout_ops *ooblayout;
 
+	/* NAND pairing scheme, only provided for MLC/TLC NANDs */
+	const struct mtd_pairing_scheme *pairing;
+
 	/* ECC layout structure pointer - read only! */
 	struct nand_ecclayout *ecclayout;
 
@@ -331,6 +410,24 @@ struct mtd_info {
 	struct list_head partitions;
 };
 
+static inline struct mtd_info *mtd_get_master(struct mtd_info *mtd)
+{
+	while (mtd->parent)
+		mtd = mtd->parent;
+
+	return mtd;
+}
+
+static inline u64 mtd_get_master_ofs(struct mtd_info *mtd, u64 ofs)
+{
+	while (mtd->parent) {
+		ofs += mtd->offset;
+		mtd = mtd->parent;
+	}
+
+	return ofs;
+}
+
 #if IS_ENABLED(CONFIG_DM)
 static inline void mtd_set_ofnode(struct mtd_info *mtd, ofnode node)
 {
@@ -391,11 +488,22 @@ static inline void mtd_set_ooblayout(struct mtd_info *mtd,
 	mtd->ooblayout = ooblayout;
 }
 
+static inline void mtd_set_pairing_scheme(struct mtd_info *mtd,
+				const struct mtd_pairing_scheme *pairing)
+{
+	mtd->pairing = pairing;
+}
+
 static inline u32 mtd_oobavail(struct mtd_info *mtd, struct mtd_oob_ops *ops)
 {
 	return ops->mode == MTD_OPS_AUTO_OOB ? mtd->oobavail : mtd->oobsize;
 }
 
+int mtd_wunit_to_pairing_info(struct mtd_info *mtd, int wunit,
+			      struct mtd_pairing_info *info);
+int mtd_pairing_info_to_wunit(struct mtd_info *mtd,
+			      const struct mtd_pairing_info *info);
+int mtd_pairing_groups(struct mtd_info *mtd);
 int mtd_erase(struct mtd_info *mtd, struct erase_info *instr);
 #ifndef __UBOOT__
 int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
@@ -487,6 +595,24 @@ static inline uint32_t mtd_mod_by_ws(uint64_t sz, struct mtd_info *mtd)
 	return do_div(sz, mtd->writesize);
 }
 
+static inline int mtd_wunit_per_eb(struct mtd_info *mtd)
+{
+	struct mtd_info *master = mtd_get_master(mtd);
+
+	return master->erasesize / mtd->writesize;
+}
+
+static inline int mtd_offset_to_wunit(struct mtd_info *mtd, loff_t offs)
+{
+	return mtd_div_by_ws(mtd_mod_by_eb(offs, mtd), mtd);
+}
+
+static inline loff_t mtd_wunit_to_offset(struct mtd_info *mtd, loff_t base,
+					 int wunit)
+{
+	return base + (wunit * mtd->writesize);
+}
+
 static inline int mtd_has_oob(const struct mtd_info *mtd)
 {
 	return mtd->_read_oob && mtd->_write_oob;
diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
index 3822237f2a..8e0f35ce25 100644
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -31,6 +31,7 @@
  * 	master MTD flag set for the corresponding MTD partition.
  * 	For example, to force a read-only partition, simply adding
  * 	MTD_WRITEABLE to the mask_flags will do the trick.
+ * add_flags: contains flags to add to the parent flags
  *
  * Note: writeable partitions require their size and offset be
  * erasesize aligned (e.g. use MTDPART_OFS_NEXTBLK).
@@ -41,6 +42,7 @@ struct mtd_partition {
 	uint64_t size;			/* partition size */
 	uint64_t offset;		/* offset within the master MTD space */
 	uint32_t mask_flags;		/* master MTD flags to mask out for this partition */
+	uint32_t add_flags;		/* flags to add to the partition */
 	struct nand_ecclayout *ecclayout;	/* out of band layout for this partition (NAND only) */
 };
 
diff --git a/include/mtd/mtd-abi.h b/include/mtd/mtd-abi.h
index 8d9761050f..2f6ce18795 100644
--- a/include/mtd/mtd-abi.h
+++ b/include/mtd/mtd-abi.h
@@ -94,6 +94,7 @@ struct mtd_write_req {
 #define MTD_BIT_WRITEABLE	0x800	/* Single bits can be flipped */
 #define MTD_NO_ERASE		0x1000	/* No erase necessary */
 #define MTD_POWERUP_LOCK	0x2000	/* Always locked after reset */
+#define MTD_SLC_ON_MLC_EMULATION 0x4000	/* Emulate SLC behavior on MLC NANDs */
 
 /* Some common devices / combinations of capabilities */
 #define MTD_CAP_ROM		0
-- 
2.30.2

[RFC 2/2] mtd: Add pairing info for Toshiba TC58TEG5DCLTA00 NAND

[Chris Morgan]

From: Chris Morgan <macromorgan@hotmail.com>

Add pairing info for the Toshiba TC58TEG5DCLTA00 NAND so that we may
utilize slc-mode emulation for enhanced reliability and compatibility
with upstream Linux.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
---
 drivers/mtd/nand/raw/nand_base.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 845bf57c53..ac5b17af70 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -4549,6 +4549,15 @@ ident_done:
 			break;
 	}
 
+	/* Special handling for TC58TEG5DCLTA00 to match upstream Linux */
+	if (id_data[0] == NAND_MFR_TOSHIBA && id_data[1] == 0xd7
+	    && id_data[2] == 0x84 && id_data[3] == 0x93
+	    && id_data[4] == 0x72 && id_data[5] == 0x51
+	    && id_data[6] == 0x08 && id_data[7] == 0x04) {
+		chip->options |= NAND_NEED_SCRAMBLING;
+		mtd_set_pairing_scheme(mtd, &dist3_pairing_scheme);
+	}
+
 	if (chip->options & NAND_BUSWIDTH_AUTO) {
 		WARN_ON(chip->options & NAND_BUSWIDTH_16);
 		chip->options |= busw;
-- 
2.30.2