[PATCH v2 00/36] Introduce the generic ECC engine abstraction

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

As of today, only raw NAND controllers used to feature an integrated
ECC engine and so controller drivers always embedded some code to
enable/disable the correction.

This statement is no longer correct as SPI-NAND devices might not
embed an on-die ECC engine and must make use of an external ECC
engine. We figured there are three possible situations for (generic)
NAND device: either the engine is 'on-die' (most of the SPI-NANDs, a
few raw NANDs), or the engine is part of the host controller (most raw
NANDs), or the engine may be external (SPI controllers might feature
an ECC engine, or there are still the possibility to use software
correction).


To solve this situation, this is a proposal on how to make things
work. We want to create an ECC engine object which has simple
callbacks:
* init/cleanup its context
* prepare an I/O operation
* finish an I/O operation
Details about what is going to happen in these callbacks is described
in drivers/mtd/nand/ecc/engine.c.

The logic in this series is:
1/ Use the generic NAND core for all NAND devices (raw and SPI).
2/ Create the ECC engine interface in drivers/mtd/nand/ecc/
3/ Move code in driver/mtd/nand/ecc.
4/ Make both software engines (Hamming and BCH) generic, move them in
   the ecc/ directory, clean them a bit and instantiate ECC
   engines. Write raw NAND helpers to use these two new engines.
5/ Isolate SPI-NAND on-die ECC engine in its own driver.
6/ Make use from the SPI-NAND layer of all the ECC engines listed
   above (on user request, people can now make use of soft BCH if they
   don't have an ECC-engine).

This work is still WIP, I expect a few 0-day regressions, maybe the
naming is not perfect but it gives an idea of what I would like to
introduce. The next steps are:
1/ Migrate the raw NAND core to make a proper use of these ECC
   engines.
2/ Deprecate in the raw NAND subsystem the interfaces used until now
   (I expect we should get rid of a lot of boilerplate).
3/ Introduce an external hardware ECC engine driver.


Thanks,
Miquèl

Changes in v2
=============
* SPDX license identifiers for soft BCH and Hamming: the license macro
  was right, "GPL" means "GPLv2 or higher", so do not change this
  portion. Also update the commit messages to fit the actual change.
* Do not compile-in the NAND core by default, do it only for raw
  NAND. Remove the dependencies on CONFIG_MTD in a different
  patch. Also, keep an extra level of hierarchy in Kconfig for the
  NAND bits by adding a menu instead of a config.
* Moved the standard OOB layouts in the ecc/engine.c driver instead of
  in the NAND core.
* Used the nand_ecc_ prefix in most of the engines functions instead
  of just ecc_, which is now reserved for bare helpers. Get rid of the
  __ecc prefix.
* In the sunxi NAND controller driver: moved the ECC structure from
  sunxi_nfc to sunxi_nand_chip as the ECC engine is per-chip and not
  per controller.
* Software Hamming ECC engine is only enabled by default if raw NAND
  is also enabled. NDFC now selects the software Hamming ECC engine
  (instead of depending on it).
* Mention in software BCH and Hamming Kconfig entries that booting
  from NAND is very likely to fail if the user selects these symbols
  as modules.
* Added Boris Reviewed-by tag on the SPI-NAND typo fixing patch.
* Renamed the "mode" into a "provider" entry in the ECC configuration
  structures.
* Moved the "total" entry of the ECC configuration directly in the
  context structure (should probably not be public but let's keep it
  as is for now).
* Split the generic ECC engine introduction into smaller patches to do
  some renaming aside.
* Drop the "maximize" entry in the ECC engine configuration structure,
  keep using a flag like before.
* Canceled the move of the SPI-NAND specific ECC engine out of the
  core file.
* Amended the root ECC structures to have three nand_ecc_conf
  structures: one for the defaults, one for the chip requirements, one
  for the user desires.
* Created a *ondie_engine pointer in the nand_ecc structure to save
  the on-die ECC engine, if any. For instance, saving a reference to
  this engine is done by the SPI-NAND core.
* Dropped the SPI-NAND flag that was used to distinguish between NAND
  flavors from the NAND core, it should not be needed anymore.
* Added an helper in the NAND core to put a reference on an ECC
  engine. This will be used by the hardware engines only.
* Renamed the files ecc/sw-{bch,hamming}.c and their headers
  include/linux/mtd/nand-ecc-sw-{bch,hamming}-engine.h.
* Created a MTD_NAND_ECC invisible Kconfig symbol.
* Added plenty of missing EXPORT_SYMBOL{,_GPL}().
* Minor modifications so that everything still compiles even when
  modules and built-in drivers are mixed in Kconfig in the whole NAND
  directory.


Miquel Raynal (36):
  mtd: nand: Move nand_device forward declaration to the top
  mtd: nand: Add an extra level in the Kconfig hierarchy
  mtd: nand: Drop useless 'depends on' in Kconfig
  mtd: rawnand: Use the NAND core
  mtd: nand: Add a NAND page I/O request type
  mtd: nand: Rename a core structure
  mtd: rawnand: Avoid a typedef
  mtd: rawnand: Add an invalid ECC mode to discriminate with valid ones
  mtd: rawnand: Clarify the values for invalid ECC mode/algo
  mtd: nand: Introduce the ECC engine abstraction
  mtd: Fix typo in mtd_ooblayout_set_databytes() description
  mtd: nand: Move standard OOB layouts to the generic ECC core
  mtd: nand: Move ECC specific functions to ecc/engine.c
  mtd: nand: ecc: Move BCH code into the ecc/ directory
  mtd: nand: ecc: Use SPDX license identifier for the software BCH code
  mtd: nand: ecc: Turn the software BCH implementation generic
  mtd: rawnand: Get rid of chip->ecc.priv
  mtd: nand: ecc: Move Hamming code into the ecc/ directory
  mtd: nand: ecc: Use SPDX license identifier for the software Hamming
    code
  mtd: nand: ecc: Clarify the software Hamming introductory line
  mtd: nand: ecc: Turn the software Hamming implementation generic
  mtd: nand: Remove useless include about software Hamming ECC
  mtd: nand: ecc: Let the software BCH ECC engine be a module
  mtd: nand: ecc: Let the software Hamming ECC engine be unselected
  mtd: nand: ecc: Create the software BCH engine instance
  mtd: nand: ecc: Create the software Hamming engine instance
  mtd: nand: Let software ECC engines be retrieved from the NAND core
  mtd: spinand: Fix typo in comment
  mtd: spinand: Move ECC related definitions earlier in the driver
  mtd: spinand: Instantiate a SPI-NAND on-die ECC engine
  mtd: nand: Let on-die ECC engines be retrieved from the NAND core
  mtd: rawnand: Fill a default ECC provider/algorithm
  mtd: spinand: Fill a default ECC provider/algorithm
  mtd: nand: Add helpers to manage ECC engines and configurations
  mtd: spinand: Use the external ECC engine logic
  mtd: spinand: Propagate ECC information to the MTD structure

 arch/arm/mach-s3c24xx/common-smdk.c           |   1 -
 arch/arm/mach-s3c24xx/mach-anubis.c           |   1 -
 arch/arm/mach-s3c24xx/mach-at2440evb.c        |   1 -
 arch/arm/mach-s3c24xx/mach-bast.c             |   1 -
 arch/arm/mach-s3c24xx/mach-gta02.c            |   1 -
 arch/arm/mach-s3c24xx/mach-jive.c             |   1 -
 arch/arm/mach-s3c24xx/mach-mini2440.c         |   1 -
 arch/arm/mach-s3c24xx/mach-osiris.c           |   1 -
 arch/arm/mach-s3c24xx/mach-qt2410.c           |   1 -
 arch/arm/mach-s3c24xx/mach-rx3715.c           |   1 -
 arch/arm/mach-s3c24xx/mach-vstms.c            |   1 -
 drivers/mtd/mtdcore.c                         |   2 +-
 drivers/mtd/nand/Kconfig                      |   5 +
 drivers/mtd/nand/Makefile                     |   1 +
 drivers/mtd/nand/core.c                       | 124 ++++
 drivers/mtd/nand/ecc/Kconfig                  |  41 ++
 drivers/mtd/nand/ecc/Makefile                 |   5 +
 drivers/mtd/nand/ecc/engine.c                 | 481 +++++++++++++++
 drivers/mtd/nand/ecc/sw-bch.c                 | 424 ++++++++++++++
 .../nand/{raw/nand_ecc.c => ecc/sw-hamming.c} | 347 ++++++++---
 drivers/mtd/nand/onenand/Kconfig              |   1 -
 drivers/mtd/nand/raw/Kconfig                  |  26 +-
 drivers/mtd/nand/raw/Makefile                 |   2 -
 drivers/mtd/nand/raw/atmel/nand-controller.c  |  12 +-
 drivers/mtd/nand/raw/cs553x_nand.c            |   3 +-
 drivers/mtd/nand/raw/denali.c                 |   3 +
 drivers/mtd/nand/raw/denali_pci.c             |   1 -
 drivers/mtd/nand/raw/fsl_elbc_nand.c          |   1 -
 drivers/mtd/nand/raw/fsl_ifc_nand.c           |   1 -
 drivers/mtd/nand/raw/fsl_upm.c                |   1 -
 drivers/mtd/nand/raw/fsmc_nand.c              |   3 +-
 drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c    |  12 +-
 drivers/mtd/nand/raw/lpc32xx_mlc.c            |   1 -
 drivers/mtd/nand/raw/lpc32xx_slc.c            |   3 +-
 drivers/mtd/nand/raw/marvell_nand.c           |   7 +-
 drivers/mtd/nand/raw/mtk_nand.c               |   4 +-
 drivers/mtd/nand/raw/nand_base.c              | 551 ++++++------------
 drivers/mtd/nand/raw/nand_bch.c               | 232 --------
 drivers/mtd/nand/raw/nand_esmt.c              |  11 +-
 drivers/mtd/nand/raw/nand_hynix.c             |  41 +-
 drivers/mtd/nand/raw/nand_jedec.c             |   4 +-
 drivers/mtd/nand/raw/nand_micron.c            |  14 +-
 drivers/mtd/nand/raw/nand_onfi.c              |   8 +-
 drivers/mtd/nand/raw/nand_samsung.c           |  19 +-
 drivers/mtd/nand/raw/nand_toshiba.c           |  13 +-
 drivers/mtd/nand/raw/nandsim.c                |   3 +-
 drivers/mtd/nand/raw/ndfc.c                   |   3 +-
 drivers/mtd/nand/raw/omap2.c                  |  32 +-
 drivers/mtd/nand/raw/pasemi_nand.c            |   1 -
 drivers/mtd/nand/raw/s3c2410.c                |   1 -
 drivers/mtd/nand/raw/sharpsl.c                |   3 +-
 drivers/mtd/nand/raw/sunxi_nand.c             |  38 +-
 drivers/mtd/nand/raw/tegra_nand.c             |  12 +-
 drivers/mtd/nand/raw/tmio_nand.c              |   7 +-
 drivers/mtd/nand/raw/txx9ndfmc.c              |   5 +-
 drivers/mtd/nand/spi/Kconfig                  |   1 +
 drivers/mtd/nand/spi/core.c                   | 301 ++++++----
 drivers/mtd/nand/spi/macronix.c               |   6 +-
 drivers/mtd/nand/spi/on-die-ecc-engine.c      |   0
 drivers/mtd/nand/spi/toshiba.c                |   6 +-
 drivers/mtd/sm_ftl.c                          |  30 +-
 drivers/mtd/tests/mtd_nandecctest.c           |  31 +-
 include/linux/mtd/nand-ecc-sw-bch.h           |  80 +++
 include/linux/mtd/nand-ecc-sw-hamming.h       |  99 ++++
 include/linux/mtd/nand.h                      | 150 ++++-
 include/linux/mtd/nand_bch.h                  |  69 ---
 include/linux/mtd/nand_ecc.h                  |  42 --
 include/linux/mtd/rawnand.h                   |  42 +-
 include/linux/mtd/sharpsl.h                   |   1 -
 include/linux/mtd/spinand.h                   |  13 +-
 include/linux/platform_data/mtd-davinci.h     |   2 +-
 .../linux/platform_data/mtd-nand-s3c2410.h    |   2 +-
 72 files changed, 2240 insertions(+), 1155 deletions(-)
 create mode 100644 drivers/mtd/nand/ecc/Kconfig
 create mode 100644 drivers/mtd/nand/ecc/Makefile
 create mode 100644 drivers/mtd/nand/ecc/engine.c
 create mode 100644 drivers/mtd/nand/ecc/sw-bch.c
 rename drivers/mtd/nand/{raw/nand_ecc.c => ecc/sw-hamming.c} (59%)
 delete mode 100644 drivers/mtd/nand/raw/nand_bch.c
 create mode 100644 drivers/mtd/nand/spi/on-die-ecc-engine.c
 create mode 100644 include/linux/mtd/nand-ecc-sw-bch.h
 create mode 100644 include/linux/mtd/nand-ecc-sw-hamming.h
 delete mode 100644 include/linux/mtd/nand_bch.h
 delete mode 100644 include/linux/mtd/nand_ecc.h

-- 
2.19.1


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