Commit 69db4aa4 authored by Brian Norris's avatar Brian Norris

Merge tag '4.9/mtd-pairing-scheme' of github.com:linux-nand/linux

Introduction of the MTD pairing scheme concept.
parents f5b88de2 477b0229
......@@ -375,6 +375,110 @@ static int mtd_reboot_notifier(struct notifier_block *n, unsigned long state,
return NOTIFY_DONE;
}
/**
* 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)
{
int npairs = mtd_wunit_per_eb(mtd) / mtd_pairing_groups(mtd);
if (wunit < 0 || wunit >= npairs)
return -EINVAL;
if (mtd->pairing && mtd->pairing->get_info)
return mtd->pairing->get_info(mtd, wunit, info);
info->group = 0;
info->pair = wunit;
return 0;
}
EXPORT_SYMBOL_GPL(mtd_wunit_to_pairing_info);
/**
* mtd_wunit_to_pairing_info - 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)
{
int ngroups = mtd_pairing_groups(mtd);
int npairs = mtd_wunit_per_eb(mtd) / ngroups;
if (!info || info->pair < 0 || info->pair >= npairs ||
info->group < 0 || info->group >= ngroups)
return -EINVAL;
if (mtd->pairing && mtd->pairing->get_wunit)
return mtd->pairing->get_wunit(mtd, 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)
{
if (!mtd->pairing || !mtd->pairing->ngroups)
return 1;
return mtd->pairing->ngroups;
}
EXPORT_SYMBOL_GPL(mtd_pairing_groups);
/**
* add_mtd_device - register an MTD device
* @mtd: pointer to new MTD device info structure
......
......@@ -409,6 +409,7 @@ static struct mtd_part *allocate_partition(struct mtd_info *master,
slave->mtd.oobsize = master->oobsize;
slave->mtd.oobavail = master->oobavail;
slave->mtd.subpage_sft = master->subpage_sft;
slave->mtd.pairing = master->pairing;
slave->mtd.name = name;
slave->mtd.owner = master->owner;
......
......@@ -127,6 +127,82 @@ 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);
};
struct module; /* only needed for owner field in mtd_info */
struct mtd_info {
......@@ -188,6 +264,9 @@ 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;
/* the ecc step size. */
unsigned int ecc_step_size;
......@@ -296,6 +375,12 @@ 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 void mtd_set_of_node(struct mtd_info *mtd,
struct device_node *np)
{
......@@ -312,6 +397,11 @@ static inline int 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);
int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
void **virt, resource_size_t *phys);
......@@ -397,6 +487,23 @@ 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)
{
return mtd->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;
......
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