In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

This patch fixes the following warning:

drivers/mtd/nand/onenand/onenand_base.c: In function ‘onenand_check_features’:
drivers/mtd/nand/onenand/onenand_base.c:3264:17: warning: this statement may fall through [-Wimplicit-fallthrough=]
   this->options |= ONENAND_HAS_NOP_1;
drivers/mtd/nand/onenand/onenand_base.c:3265:2: note: here
  case ONENAND_DEVICE_DENSITY_4Gb:
  ^~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.

Cc: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

While I was tempted to move it to admin-guide, as some docs
there are more userspace-faced, there are some very technical
discussions about memory error correction code from the Kernel
implementer's PoV. So, let's place it inside the driver-api
book.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Rename the mtd documentation files to ReST, add an
index for them and adjust in order to produce a nice html
output via the Sphinx build system.

It should be noticed that Sphinx doesn't handle very well
URLs with dots in the middle. Thankfully, internally, the '.'
char is translated to %2E, so we can jus use %2E instead of
dots, and this will work fine on both text and processed files.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Pull MTD updates from Miquel Raynal:
 "This contains the following changes for MTD:

  MTD core changes:
   - New Hyperbus framework
   - New _is_locked (concat) implementation
   - Various cleanups

  NAND core changes:
   - use longest matching pattern in ->exec_op() default parser
   - export NAND operation tracer
   - add flag to indicate panic_write in MTD
   - use kzalloc() instead of kmalloc() and memset()

  Raw NAND controller drivers changes:
   - brcmnand:
       - fix BCH ECC layout for large page NAND parts
       - fallback to detected ecc-strength, ecc-step-size
       - when oops in progress use pio and interrupt polling
       - code refactor code to introduce helper functions
       - add support for v7.3 controller
   - FSMC:
       - use nand_op_trace for operation tracing
   - GPMI:
       - move all driver code into single file
       - various cleanups (including dmaengine changes)
       - use runtime PM to manage clocks
       - implement exec_op
   - MTK:
       - correct low level time calculation of r/w cycle
       - improve data sampling timing for read cycle
       - add validity check for CE# pin setting
       - fix wrongly assigned OOB buffer pointer issue
       - re-license MTK NAND driver as Dual MIT/GPL
   - STM32:
       - manage the get_irq error case
       - increase DMA completion timeouts

  Raw NAND chips drivers changes:
   - Macronix: add read-retry support

  Onenand driver changes:
   - add support for 8Gb datasize chips
   - avoid fall-through warnings

  SPI-NAND changes:
   - define macros for page-read ops with three-byte addresses
   - add support for two-byte device IDs and then for GigaDevice
     GD5F1GQ4UFxxG
   - add initial support for Paragon PN26G0xA
   - handle the case where the last page read has bitflips

  SPI-NOR core changes:
   - add support for the mt25ql02g and w25q16jv flashes
   - print error in case of jedec read id fails
   - is25lp256: add post BFPT fix to correct the addr_width

  SPI NOR controller drivers changes:
   - intel-spi: Add support for Intel Elkhart Lake SPI serial flash
   - smt32: remove the driver as the driver was replaced by spi-stm32-qspi.c
   - cadence-quadspi: add reset control"

* tag 'mtd/for-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux: (60 commits)
  mtd: concat: implement _is_locked mtd operation
  mtd: concat: refactor concat_lock/concat_unlock
  mtd: abi: do not use C++ style comments in uapi header
  mtd: afs: remove unneeded NULL check
  mtd: rawnand: stm32_fmc2: increase DMA completion timeouts
  mtd: rawnand: Use kzalloc() instead of kmalloc() and memset()
  mtd: hyperbus: Add driver for TI's HyperBus memory controller
  mtd: spinand: read returns badly if the last page has bitflips
  mtd: spinand: Add initial support for Paragon PN26G0xA
  mtd: rawnand: mtk: Re-license MTK NAND driver as Dual MIT/GPL
  mtd: rawnand: gpmi: remove double assignment to block_size
  dt-bindings: mtd: brcmnand: Add brcmnand, brcmnand-v7.3 support
  mtd: rawnand: brcmnand: Add support for v7.3 controller
  mtd: rawnand: brcmnand: Refactored code to introduce helper functions
  mtd: rawnand: brcmnand: When oops in progress use pio and interrupt polling
  mtd: Add flag to indicate panic_write
  mtd: rawnand: Add Macronix NAND read retry support
  mtd: onenand: Avoid fall-through warnings
  mtd: spinand: Add support for GigaDevice GD5F1GQ4UFxxG
  mtd: spinand: Add support for two-byte device IDs
  ...

Pull Documentation updates from Jonathan Corbet:
 "It's been a relatively busy cycle for docs:

   - A fair pile of RST conversions, many from Mauro. These create more
     than the usual number of simple but annoying merge conflicts with
     other trees, unfortunately. He has a lot more of these waiting on
     the wings that, I think, will go to you directly later on.

   - A new document on how to use merges and rebases in kernel repos,
     and one on Spectre vulnerabilities.

   - Various improvements to the build system, including automatic
     markup of function() references because some people, for reasons I
     will never understand, were of the opinion that
     :c:func:``function()`` is unattractive and not fun to type.

   - We now recommend using sphinx 1.7, but still support back to 1.4.

   - Lots of smaller improvements, warning fixes, typo fixes, etc"

* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
  docs: automarkup.py: ignore exceptions when seeking for xrefs
  docs: Move binderfs to admin-guide
  Disable Sphinx SmartyPants in HTML output
  doc: RCU callback locks need only _bh, not necessarily _irq
  docs: format kernel-parameters -- as code
  Doc : doc-guide : Fix a typo
  platform: x86: get rid of a non-existent document
  Add the RCU docs to the core-api manual
  Documentation: RCU: Add TOC tree hooks
  Documentation: RCU: Rename txt files to rst
  Documentation: RCU: Convert RCU UP systems to reST
  Documentation: RCU: Convert RCU linked list to reST
  Documentation: RCU: Convert RCU basic concepts to reST
  docs: filesystems: Remove uneeded .rst extension on toctables
  scripts/sphinx-pre-install: fix out-of-tree build
  docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
  Documentation: PGP: update for newer HW devices
  Documentation: Add section about CPU vulnerabilities for Spectre
  Documentation: platform: Delete x86-laptop-drivers.txt
  docs: Note that :c:func: should no longer be used
  ...

SPI-NOR core changes:
- add support for the mt25ql02g and w25q16jv flashes
- print error in case of jedec read id fails
- is25lp256: add post BFPT fix to correct the addr_width

SPI NOR controller drivers changes:
- intel-spi: Add support for Intel Elkhart Lake SPI serial flash
- smt32: remove the driver as the driver was replaced by spi-stm32-qspi.c
- cadence-quadspi: add reset control

Add an implementation of the _is_locked operation for concatenated mtd
devices. This doesn't handle getting the lock status of a range that
spans chips, which is consistent with cfi_ppb_is_locked and
cfi_intelext_is_locked which only look at the first block in the range.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Richard Weinberger <richard@nod.at>

concat_lock() and concat_unlock() only differed in terms of the mtd_xx
operation they called. Refactor them to use a common helper function and
pass a boolean flag to indicate whether lock or unlock is needed.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Richard Weinberger <richard@nod.at>

NULL check before kfree is unneeded, so remove it.

Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

NAND core changes:
- use longest matching pattern in ->exec_op() default parser
- export NAND operation tracer
- add flag to indicate panic_write in MTD
- use kzalloc() instead of kmalloc() and memset()

Raw NAND controller drivers changes:
- brcmnand:
  * fix BCH ECC layout for large page NAND parts
  * fallback to detected ecc-strength, ecc-step-size
  * when oops in progress use pio and interrupt polling
  * code refactor code to introduce helper functions
  * add support for v7.3 controller
- FSMC:
  * use nand_op_trace for operation tracing
- GPMI:
  * move all driver code into single file
  * various cleanups (including dmaengine changes)
  * use runtime PM to manage clocks
  * implement exec_op
- MTK:
  * correct low level time calculation of r/w cycle
  * improve data sampling timing for read cycle
  * add validity check for CE# pin setting
  * fix wrongly assigned OOB buffer pointer issue
  * re-license MTK NAND driver as Dual MIT/GPL
- STM32:
  * manage the get_irq error case
  * increase DMA completion timeouts

Raw NAND chips drivers changes:
- Macronix: add read-retry support

Onenand driver changes:
- add support for 8Gb datasize chips
- avoid fall-through warnings

SPI-NAND changes:
- define macros for page-read ops with three-byte addresses
- add support for two-byte device IDs and then for GigaDevice
  GD5F1GQ4UFxxG
- add initial support for Paragon PN26G0xA
- handle the case where the last page read has bitflips