docs: mtd: move it to the driver-api book

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>

4 files changed, 0 insertions, 931 deletions

diff --git a/Documentation/mtd/index.rst b/Documentation/mtd/index.rst
deleted file mode 100644
index 4fdae418ac97..000000000000
--- a/Documentation/mtd/index.rst
+++ /dev/null
@@ -1,12 +0,0 @@
-:orphan:
-
-==============================
-Memory Technology Device (MTD)
-==============================
-
-.. toctree::
-   :maxdepth: 1
-
-   intel-spi
-   nand_ecc
-   spi-nor
diff --git a/Documentation/mtd/intel-spi.rst b/Documentation/mtd/intel-spi.rst
deleted file mode 100644
index 0e6d9cd5388d..000000000000
--- a/Documentation/mtd/intel-spi.rst
+++ /dev/null
@@ -1,90 +0,0 @@
-==============================
-Upgrading BIOS using intel-spi
-==============================
-
-Many Intel CPUs like Baytrail and Braswell include SPI serial flash host
-controller which is used to hold BIOS and other platform specific data.
-Since contents of the SPI serial flash is crucial for machine to function,
-it is typically protected by different hardware protection mechanisms to
-avoid accidental (or on purpose) overwrite of the content.
-
-Not all manufacturers protect the SPI serial flash, mainly because it
-allows upgrading the BIOS image directly from an OS.
-
-The intel-spi driver makes it possible to read and write the SPI serial
-flash, if certain protection bits are not set and locked. If it finds
-any of them set, the whole MTD device is made read-only to prevent
-partial overwrites. By default the driver exposes SPI serial flash
-contents as read-only but it can be changed from kernel command line,
-passing "intel-spi.writeable=1".
-
-Please keep in mind that overwriting the BIOS image on SPI serial flash
-might render the machine unbootable and requires special equipment like
-Dediprog to revive. You have been warned!
-
-Below are the steps how to upgrade MinnowBoard MAX BIOS directly from
-Linux.
-
- 1) Download and extract the latest Minnowboard MAX BIOS SPI image
-    [1]. At the time writing this the latest image is v92.
-
- 2) Install mtd-utils package [2]. We need this in order to erase the SPI
-    serial flash. Distros like Debian and Fedora have this prepackaged with
-    name "mtd-utils".
-
- 3) Add "intel-spi.writeable=1" to the kernel command line and reboot
-    the board (you can also reload the driver passing "writeable=1" as
-    module parameter to modprobe).
-
- 4) Once the board is up and running again, find the right MTD partition
-    (it is named as "BIOS")::
-
-	# cat /proc/mtd
-	dev:    size   erasesize  name
-	mtd0: 00800000 00001000 "BIOS"
-
-    So here it will be /dev/mtd0 but it may vary.
-
- 5) Make backup of the existing image first::
-
-	# dd if=/dev/mtd0ro of=bios.bak
-	16384+0 records in
-	16384+0 records out
-	8388608 bytes (8.4 MB) copied, 10.0269 s, 837 kB/s
-
- 6) Verify the backup:
-
-	# sha1sum /dev/mtd0ro bios.bak
-	fdbb011920572ca6c991377c4b418a0502668b73  /dev/mtd0ro
-	fdbb011920572ca6c991377c4b418a0502668b73  bios.bak
-
-    The SHA1 sums must match. Otherwise do not continue any further!
-
- 7) Erase the SPI serial flash. After this step, do not reboot the
-    board! Otherwise it will not start anymore::
-
-	# flash_erase /dev/mtd0 0 0
-	Erasing 4 Kibyte @ 7ff000 -- 100 % complete
-
- 8) Once completed without errors you can write the new BIOS image:
-
-    # dd if=MNW2MAX1.X64.0092.R01.1605221712.bin of=/dev/mtd0
-
- 9) Verify that the new content of the SPI serial flash matches the new
-    BIOS image::
-
-	# sha1sum /dev/mtd0ro MNW2MAX1.X64.0092.R01.1605221712.bin
-	9b4df9e4be2057fceec3a5529ec3d950836c87a2  /dev/mtd0ro
-	9b4df9e4be2057fceec3a5529ec3d950836c87a2 MNW2MAX1.X64.0092.R01.1605221712.bin
-
-    The SHA1 sums should match.
-
- 10) Now you can reboot your board and observe the new BIOS starting up
-     properly.
-
-References
-----------
-
-[1] https://firmware.intel.com/sites/default/files/MinnowBoard%2EMAX_%2EX64%2E92%2ER01%2Ezip
-
-[2] http://www.linux-mtd.infradead.org/
diff --git a/Documentation/mtd/nand_ecc.rst b/Documentation/mtd/nand_ecc.rst
deleted file mode 100644
index e8d3c53a5056..000000000000
--- a/Documentation/mtd/nand_ecc.rst
+++ /dev/null
@@ -1,763 +0,0 @@
-==========================
-NAND Error-correction Code
-==========================
-
-Introduction
-============
-
-Having looked at the linux mtd/nand driver and more specific at nand_ecc.c
-I felt there was room for optimisation. I bashed the code for a few hours
-performing tricks like table lookup removing superfluous code etc.
-After that the speed was increased by 35-40%.
-Still I was not too happy as I felt there was additional room for improvement.
-
-Bad! I was hooked.
-I decided to annotate my steps in this file. Perhaps it is useful to someone
-or someone learns something from it.
-
-
-The problem
-===========
-
-NAND flash (at least SLC one) typically has sectors of 256 bytes.
-However NAND flash is not extremely reliable so some error detection
-(and sometimes correction) is needed.
-
-This is done by means of a Hamming code. I'll try to explain it in
-laymans terms (and apologies to all the pro's in the field in case I do
-not use the right terminology, my coding theory class was almost 30
-years ago, and I must admit it was not one of my favourites).
-
-As I said before the ecc calculation is performed on sectors of 256
-bytes. This is done by calculating several parity bits over the rows and
-columns. The parity used is even parity which means that the parity bit = 1
-if the data over which the parity is calculated is 1 and the parity bit = 0
-if the data over which the parity is calculated is 0. So the total
-number of bits over the data over which the parity is calculated + the
-parity bit is even. (see wikipedia if you can't follow this).
-Parity is often calculated by means of an exclusive or operation,
-sometimes also referred to as xor. In C the operator for xor is ^
-
-Back to ecc.
-Let's give a small figure:
-
-=========  ==== ==== ==== ==== ==== ==== ==== ====   === === === === ====
-byte   0:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp0 rp2 rp4 ... rp14
-byte   1:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp1 rp2 rp4 ... rp14
-byte   2:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp0 rp3 rp4 ... rp14
-byte   3:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp1 rp3 rp4 ... rp14
-byte   4:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp0 rp2 rp5 ... rp14
-...
-byte 254:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp0 rp3 rp5 ... rp15
-byte 255:  bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0   rp1 rp3 rp5 ... rp15
-           cp1  cp0  cp1  cp0  cp1  cp0  cp1  cp0
-           cp3  cp3  cp2  cp2  cp3  cp3  cp2  cp2
-           cp5  cp5  cp5  cp5  cp4  cp4  cp4  cp4
-=========  ==== ==== ==== ==== ==== ==== ==== ====   === === === === ====
-
-This figure represents a sector of 256 bytes.
-cp is my abbreviation for column parity, rp for row parity.
-
-Let's start to explain column parity.
-
-- cp0 is the parity that belongs to all bit0, bit2, bit4, bit6.
-
-  so the sum of all bit0, bit2, bit4 and bit6 values + cp0 itself is even.
-
-Similarly cp1 is the sum of all bit1, bit3, bit5 and bit7.
-
-- cp2 is the parity over bit0, bit1, bit4 and bit5
-- cp3 is the parity over bit2, bit3, bit6 and bit7.
-- cp4 is the parity over bit0, bit1, bit2 and bit3.
-- cp5 is the parity over bit4, bit5, bit6 and bit7.
-
-Note that each of cp0 .. cp5 is exactly one bit.
-
-Row parity actually works almost the same.
-
-- rp0 is the parity of all even bytes (0, 2, 4, 6, ... 252, 254)
-- rp1 is the parity of all odd bytes (1, 3, 5, 7, ..., 253, 255)
-- rp2 is the parity of all bytes 0, 1, 4, 5, 8, 9, ...
-  (so handle two bytes, then skip 2 bytes).
-- rp3 is covers the half rp2 does not cover (bytes 2, 3, 6, 7, 10, 11, ...)
-- for rp4 the rule is cover 4 bytes, skip 4 bytes, cover 4 bytes, skip 4 etc.
-
-  so rp4 calculates parity over bytes 0, 1, 2, 3, 8, 9, 10, 11, 16, ...)
-- and rp5 covers the other half, so bytes 4, 5, 6, 7, 12, 13, 14, 15, 20, ..
-
-The story now becomes quite boring. I guess you get the idea.
-
-- rp6 covers 8 bytes then skips 8 etc
-- rp7 skips 8 bytes then covers 8 etc
-- rp8 covers 16 bytes then skips 16 etc
-- rp9 skips 16 bytes then covers 16 etc
-- rp10 covers 32 bytes then skips 32 etc
-- rp11 skips 32 bytes then covers 32 etc
-- rp12 covers 64 bytes then skips 64 etc
-- rp13 skips 64 bytes then covers 64 etc
-- rp14 covers 128 bytes then skips 128
-- rp15 skips 128 bytes then covers 128
-
-In the end the parity bits are grouped together in three bytes as
-follows:
-
-=====  ===== ===== ===== ===== ===== ===== ===== =====
-ECC    Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
-=====  ===== ===== ===== ===== ===== ===== ===== =====
-ECC 0   rp07  rp06  rp05  rp04  rp03  rp02  rp01  rp00
-ECC 1   rp15  rp14  rp13  rp12  rp11  rp10  rp09  rp08
-ECC 2   cp5   cp4   cp3   cp2   cp1   cp0      1     1
-=====  ===== ===== ===== ===== ===== ===== ===== =====
-
-I detected after writing this that ST application note AN1823
-(http://www.st.com/stonline/) gives a much
-nicer picture.(but they use line parity as term where I use row parity)
-Oh well, I'm graphically challenged, so suffer with me for a moment :-)
-
-And I could not reuse the ST picture anyway for copyright reasons.
-
-
-Attempt 0
-=========
-
-Implementing the parity calculation is pretty simple.
-In C pseudocode::
-
-  for (i = 0; i < 256; i++)
-  {
-    if (i & 0x01)
-       rp1 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp1;
-    else
-       rp0 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp0;
-    if (i & 0x02)
-       rp3 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp3;
-    else
-       rp2 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp2;
-    if (i & 0x04)
-      rp5 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp5;
-    else
-      rp4 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp4;
-    if (i & 0x08)
-      rp7 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp7;
-    else
-      rp6 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp6;
-    if (i & 0x10)
-      rp9 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp9;
-    else
-      rp8 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp8;
-    if (i & 0x20)
-      rp11 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp11;
-    else
-      rp10 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp10;
-    if (i & 0x40)
-      rp13 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp13;
-    else
-      rp12 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp12;
-    if (i & 0x80)
-      rp15 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp15;
-    else
-      rp14 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp14;
-    cp0 = bit6 ^ bit4 ^ bit2 ^ bit0 ^ cp0;
-    cp1 = bit7 ^ bit5 ^ bit3 ^ bit1 ^ cp1;
-    cp2 = bit5 ^ bit4 ^ bit1 ^ bit0 ^ cp2;
-    cp3 = bit7 ^ bit6 ^ bit3 ^ bit2 ^ cp3
-    cp4 = bit3 ^ bit2 ^ bit1 ^ bit0 ^ cp4
-    cp5 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ cp5
-  }
-
-
-Analysis 0
-==========
-
-C does have bitwise operators but not really operators to do the above
-efficiently (and most hardware has no such instructions either).
-Therefore without implementing this it was clear that the code above was
-not going to bring me a Nobel prize :-)
-
-Fortunately the exclusive or operation is commutative, so we can combine
-the values in any order. So instead of calculating all the bits
-individually, let us try to rearrange things.
-For the column parity this is easy. We can just xor the bytes and in the
-end filter out the relevant bits. This is pretty nice as it will bring
-all cp calculation out of the for loop.
-
-Similarly we can first xor the bytes for the various rows.
-This leads to:
-
-
-Attempt 1
-=========
-
-::
-
-  const char parity[256] = {
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
-      0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0
-  };
-
-  void ecc1(const unsigned char *buf, unsigned char *code)
-  {
-      int i;
-      const unsigned char *bp = buf;
-      unsigned char cur;
-      unsigned char rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
-      unsigned char rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
-      unsigned char par;
-
-      par = 0;
-      rp0 = 0; rp1 = 0; rp2 = 0; rp3 = 0;
-      rp4 = 0; rp5 = 0; rp6 = 0; rp7 = 0;
-      rp8 = 0; rp9 = 0; rp10 = 0; rp11 = 0;
-      rp12 = 0; rp13 = 0; rp14 = 0; rp15 = 0;
-
-      for (i = 0; i < 256; i++)
-      {
-          cur = *bp++;
-          par ^= cur;
-          if (i & 0x01) rp1 ^= cur; else rp0 ^= cur;
-          if (i & 0x02) rp3 ^= cur; else rp2 ^= cur;
-          if (i & 0x04) rp5 ^= cur; else rp4 ^= cur;
-          if (i & 0x08) rp7 ^= cur; else rp6 ^= cur;
-          if (i & 0x10) rp9 ^= cur; else rp8 ^= cur;
-          if (i & 0x20) rp11 ^= cur; else rp10 ^= cur;
-          if (i & 0x40) rp13 ^= cur; else rp12 ^= cur;
-          if (i & 0x80) rp15 ^= cur; else rp14 ^= cur;
-      }
-      code[0] =
-          (parity[rp7] << 7) |
-          (parity[rp6] << 6) |
-          (parity[rp5] << 5) |
-          (parity[rp4] << 4) |
-          (parity[rp3] << 3) |
-          (parity[rp2] << 2) |
-          (parity[rp1] << 1) |
-          (parity[rp0]);
-      code[1] =
-          (parity[rp15] << 7) |
-          (parity[rp14] << 6) |
-          (parity[rp13] << 5) |
-          (parity[rp12] << 4) |
-          (parity[rp11] << 3) |
-          (parity[rp10] << 2) |
-          (parity[rp9]  << 1) |
-          (parity[rp8]);
-      code[2] =
-          (parity[par & 0xf0] << 7) |
-          (parity[par & 0x0f] << 6) |
-          (parity[par & 0xcc] << 5) |
-          (parity[par & 0x33] << 4) |
-          (parity[par & 0xaa] << 3) |
-          (parity[par & 0x55] << 2);
-      code[0] = ~code[0];
-      code[1] = ~code[1];
-      code[2] = ~code[2];
-  }
-
-Still pretty straightforward. The last three invert statements are there to
-give a checksum of 0xff 0xff 0xff for an empty flash. In an empty flash
-all data is 0xff, so the checksum then matches.
-
-I also introduced the parity lookup. I expected this to be the fastest
-way to calculate the parity, but I will investigate alternatives later
-on.
-
-
-Analysis 1
-==========
-
-The code works, but is not terribly efficient. On my system it took
-almost 4 times as much time as the linux driver code. But hey, if it was
-*that* easy this would have been done long before.
-No pain. no gain.
-
-Fortunately there is plenty of room for improvement.
-
-In step 1 we moved from bit-wise calculation to byte-wise calculation.
-However in C we can also use the unsigned long data type and virtually
-every modern microprocessor supports 32 bit operations, so why not try
-to write our code in such a way that we process data in 32 bit chunks.
-
-Of course this means some modification as the row parity is byte by
-byte. A quick analysis:
-for the column parity we use the par variable. When extending to 32 bits
-we can in the end easily calculate rp0 and rp1 from it.
-(because par now consists of 4 bytes, contributing to rp1, rp0, rp1, rp0
-respectively, from MSB to LSB)
-also rp2 and rp3 can be easily retrieved from par as rp3 covers the
-first two MSBs and rp2 covers the last two LSBs.
-
-Note that of course now the loop is executed only 64 times (256/4).
-And note that care must taken wrt byte ordering. The way bytes are
-ordered in a long is machine dependent, and might affect us.
-Anyway, if there is an issue: this code is developed on x86 (to be
-precise: a DELL PC with a D920 Intel CPU)
-
-And of course the performance might depend on alignment, but I expect
-that the I/O buffers in the nand driver are aligned properly (and
-otherwise that should be fixed to get maximum performance).
-
-Let's give it a try...
-
-
-Attempt 2
-=========
-
-::
-
-  extern const char parity[256];
-
-  void ecc2(const unsigned char *buf, unsigned char *code)
-  {
-      int i;
-      const unsigned long *bp = (unsigned long *)buf;
-      unsigned long cur;
-      unsigned long rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
-      unsigned long rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
-      unsigned long par;
-
-      par = 0;
-      rp0 = 0; rp1 = 0; rp2 = 0; rp3 = 0;
-      rp4 = 0; rp5 = 0; rp6 = 0; rp7 = 0;
-      rp8 = 0; rp9 = 0; rp10 = 0; rp11 = 0;
-      rp12 = 0; rp13 = 0; rp14 = 0; rp15 = 0;
-
-      for (i = 0; i < 64; i++)
-      {
-          cur = *bp++;
-          par ^= cur;
-          if (i & 0x01) rp5 ^= cur; else rp4 ^= cur;
-          if (i & 0x02) rp7 ^= cur; else rp6 ^= cur;
-          if (i & 0x04) rp9 ^= cur; else rp8 ^= cur;
-          if (i & 0x08) rp11 ^= cur; else rp10 ^= cur;
-          if (i & 0x10) rp13 ^= cur; else rp12 ^= cur;
-          if (i & 0x20) rp15 ^= cur; else rp14 ^= cur;
-      }
-      /*
-         we need to adapt the code generation for the fact that rp vars are now
-         long; also the column parity calculation needs to be changed.
-         we'll bring rp4 to 15 back to single byte entities by shifting and
-         xoring
-      */
-      rp4 ^= (rp4 >> 16); rp4 ^= (rp4 >> 8); rp4 &= 0xff;
-      rp5 ^= (rp5 >> 16); rp5 ^= (rp5 >> 8); rp5 &= 0xff;
-      rp6 ^= (rp6 >> 16); rp6 ^= (rp6 >> 8); rp6 &= 0xff;
-      rp7 ^= (rp7 >> 16); rp7 ^= (rp7 >> 8); rp7 &= 0xff;
-      rp8 ^= (rp8 >> 16); rp8 ^= (rp8 >> 8); rp8 &= 0xff;
-      rp9 ^= (rp9 >> 16); rp9 ^= (rp9 >> 8); rp9 &= 0xff;
-      rp10 ^= (rp10 >> 16); rp10 ^= (rp10 >> 8); rp10 &= 0xff;
-      rp11 ^= (rp11 >> 16); rp11 ^= (rp11 >> 8); rp11 &= 0xff;
-      rp12 ^= (rp12 >> 16); rp12 ^= (rp12 >> 8); rp12 &= 0xff;
-      rp13 ^= (rp13 >> 16); rp13 ^= (rp13 >> 8); rp13 &= 0xff;
-      rp14 ^= (rp14 >> 16); rp14 ^= (rp14 >> 8); rp14 &= 0xff;
-      rp15 ^= (rp15 >> 16); rp15 ^= (rp15 >> 8); rp15 &= 0xff;
-      rp3 = (par >> 16); rp3 ^= (rp3 >> 8); rp3 &= 0xff;
-      rp2 = par & 0xffff; rp2 ^= (rp2 >> 8); rp2 &= 0xff;
-      par ^= (par >> 16);
-      rp1 = (par >> 8); rp1 &= 0xff;
-      rp0 = (par & 0xff);
-      par ^= (par >> 8); par &= 0xff;
-
-      code[0] =
-          (parity[rp7] << 7) |
-          (parity[rp6] << 6) |
-          (parity[rp5] << 5) |
-          (parity[rp4] << 4) |
-          (parity[rp3] << 3) |
-          (parity[rp2] << 2) |
-          (parity[rp1] << 1) |
-          (parity[rp0]);
-      code[1] =
-          (parity[rp15] << 7) |
-          (parity[rp14] << 6) |
-          (parity[rp13] << 5) |
-          (parity[rp12] << 4) |
-          (parity[rp11] << 3) |
-          (parity[rp10] << 2) |
-          (parity[rp9]  << 1) |
-          (parity[rp8]);
-      code[2] =
-          (parity[par & 0xf0] << 7) |
-          (parity[par & 0x0f] << 6) |
-          (parity[par & 0xcc] << 5) |
-          (parity[par & 0x33] << 4) |
-          (parity[par & 0xaa] << 3) |
-          (parity[par & 0x55] << 2);
-      code[0] = ~code[0];
-      code[1] = ~code[1];
-      code[2] = ~code[2];
-  }
-
-The parity array is not shown any more. Note also that for these
-examples I kinda deviated from my regular programming style by allowing
-multiple statements on a line, not using { } in then and else blocks
-with only a single statement and by using operators like ^=
-
-
-Analysis 2
-==========
-
-The code (of course) works, and hurray: we are a little bit faster than
-the linux driver code (about 15%). But wait, don't cheer too quickly.
-There is more to be gained.
-If we look at e.g. rp14 and rp15 we see that we either xor our data with
-rp14 or with rp15. However we also have par which goes over all data.
-This means there is no need to calculate rp14 as it can be calculated from
-rp15 through rp14 = par ^ rp15, because par = rp14 ^ rp15;
-(or if desired we can avoid calculating rp15 and calculate it from
-rp14).  That is why some places refer to inverse parity.
-Of course the same thing holds for rp4/5, rp6/7, rp8/9, rp10/11 and rp12/13.
-Effectively this means we can eliminate the else clause from the if
-statements. Also we can optimise the calculation in the end a little bit
-by going from long to byte first. Actually we can even avoid the table
-lookups
-
-Attempt 3
-=========
-
-Odd replaced::
-
-          if (i & 0x01) rp5 ^= cur; else rp4 ^= cur;
-          if (i & 0x02) rp7 ^= cur; else rp6 ^= cur;
-          if (i & 0x04) rp9 ^= cur; else rp8 ^= cur;
-          if (i & 0x08) rp11 ^= cur; else rp10 ^= cur;
-          if (i & 0x10) rp13 ^= cur; else rp12 ^= cur;
-          if (i & 0x20) rp15 ^= cur; else rp14 ^= cur;
-
-with::
-
-          if (i & 0x01) rp5 ^= cur;
-          if (i & 0x02) rp7 ^= cur;
-          if (i & 0x04) rp9 ^= cur;
-          if (i & 0x08) rp11 ^= cur;
-          if (i & 0x10) rp13 ^= cur;
-          if (i & 0x20) rp15 ^= cur;
-
-and outside the loop added::
-
-          rp4  = par ^ rp5;
-          rp6  = par ^ rp7;
-          rp8  = par ^ rp9;
-          rp10  = par ^ rp11;
-          rp12  = par ^ rp13;
-          rp14  = par ^ rp15;
-
-And after that the code takes about 30% more time, although the number of
-statements is reduced. This is also reflected in the assembly code.
-
-
-Analysis 3
-==========
-
-Very weird. Guess it has to do with caching or instruction parallellism
-or so. I also tried on an eeePC (Celeron, clocked at 900 Mhz). Interesting
-observation was that this one is only 30% slower (according to time)
-executing the code as my 3Ghz D920 processor.
-
-Well, it was expected not to be easy so maybe instead move to a
-different track: let's move back to the code from attempt2 and do some
-loop unrolling. This will eliminate a few if statements. I'll try
-different amounts of unrolling to see what works best.
-
-
-Attempt 4
-=========
-
-Unrolled the loop 1, 2, 3 and 4 times.
-For 4 the code starts with::
-
-    for (i = 0; i < 4; i++)
-    {
-        cur = *bp++;
-        par ^= cur;
-        rp4 ^= cur;
-        rp6 ^= cur;
-        rp8 ^= cur;
-        rp10 ^= cur;
-        if (i & 0x1) rp13 ^= cur; else rp12 ^= cur;
-        if (i & 0x2) rp15 ^= cur; else rp14 ^= cur;
-        cur = *bp++;
-        par ^= cur;
-        rp5 ^= cur;
-        rp6 ^= cur;
-        ...
-
-
-Analysis 4
-==========
-
-Unrolling once gains about 15%
-
-Unrolling twice keeps the gain at about 15%
-
-Unrolling three times gives a gain of 30% compared to attempt 2.
-
-Unrolling four times gives a marginal improvement compared to unrolling
-three times.
-
-I decided to proceed with a four time unrolled loop anyway. It was my gut
-feeling that in the next steps I would obtain additional gain from it.
-
-The next step was triggered by the fact that par contains the xor of all
-bytes and rp4 and rp5 each contain the xor of half of the bytes.
-So in effect par = rp4 ^ rp5. But as xor is commutative we can also say
-that rp5 = par ^ rp4. So no need to keep both rp4 and rp5 around. We can
-eliminate rp5 (or rp4, but I already foresaw another optimisation).
-The same holds for rp6/7, rp8/9, rp10/11 rp12/13 and rp14/15.
-
-
-Attempt 5
-=========
-
-Effectively so all odd digit rp assignments in the loop were removed.
-This included the else clause of the if statements.
-Of course after the loop we need to correct things by adding code like::
-
-    rp5 = par ^ rp4;
-
-Also the initial assignments (rp5 = 0; etc) could be removed.
-Along the line I also removed the initialisation of rp0/1/2/3.
-
-
-Analysis 5
-==========
-
-Measurements showed this was a good move. The run-time roughly halved
-compared with attempt 4 with 4 times unrolled, and we only require 1/3rd
-of the processor time compared to the current code in the linux kernel.
-
-However, still I thought there was more. I didn't like all the if
-statements. Why not keep a running parity and only keep the last if
-statement. Time for yet another version!
-
-
-Attempt 6
-=========
-
-THe code within the for loop was changed to::
-
-    for (i = 0; i < 4; i++)
-    {
-        cur = *bp++; tmppar  = cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= tmppar;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp8 ^= tmppar;
-
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp10 ^= tmppar;
-
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp6 ^= cur; rp8 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= cur; rp8 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp8 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp8 ^= cur;
-
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur;
-
-        par ^= tmppar;
-        if ((i & 0x1) == 0) rp12 ^= tmppar;
-        if ((i & 0x2) == 0) rp14 ^= tmppar;
-    }
-
-As you can see tmppar is used to accumulate the parity within a for
-iteration. In the last 3 statements is added to par and, if needed,
-to rp12 and rp14.
-
-While making the changes I also found that I could exploit that tmppar
-contains the running parity for this iteration. So instead of having:
-rp4 ^= cur; rp6 ^= cur;
-I removed the rp6 ^= cur; statement and did rp6 ^= tmppar; on next
-statement. A similar change was done for rp8 and rp10
-
-
-Analysis 6
-==========
-
-Measuring this code again showed big gain. When executing the original
-linux code 1 million times, this took about 1 second on my system.
-(using time to measure the performance). After this iteration I was back
-to 0.075 sec. Actually I had to decide to start measuring over 10
-million iterations in order not to lose too much accuracy. This one
-definitely seemed to be the jackpot!
-
-There is a little bit more room for improvement though. There are three
-places with statements::
-
-	rp4 ^= cur; rp6 ^= cur;
-
-It seems more efficient to also maintain a variable rp4_6 in the while
-loop; This eliminates 3 statements per loop. Of course after the loop we
-need to correct by adding::
-
-	rp4 ^= rp4_6;
-	rp6 ^= rp4_6
-
-Furthermore there are 4 sequential assignments to rp8. This can be
-encoded slightly more efficiently by saving tmppar before those 4 lines
-and later do rp8 = rp8 ^ tmppar ^ notrp8;
-(where notrp8 is the value of rp8 before those 4 lines).
-Again a use of the commutative property of xor.
-Time for a new test!
-
-
-Attempt 7
-=========
-
-The new code now looks like::
-
-    for (i = 0; i < 4; i++)
-    {
-        cur = *bp++; tmppar  = cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= tmppar;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp8 ^= tmppar;
-
-        cur = *bp++; tmppar ^= cur; rp4_6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp10 ^= tmppar;
-
-        notrp8 = tmppar;
-        cur = *bp++; tmppar ^= cur; rp4_6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur;
-        rp8 = rp8 ^ tmppar ^ notrp8;
-
-        cur = *bp++; tmppar ^= cur; rp4_6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp6 ^= cur;
-        cur = *bp++; tmppar ^= cur; rp4 ^= cur;
-        cur = *bp++; tmppar ^= cur;
-
-        par ^= tmppar;
-        if ((i & 0x1) == 0) rp12 ^= tmppar;
-        if ((i & 0x2) == 0) rp14 ^= tmppar;
-    }
-    rp4 ^= rp4_6;
-    rp6 ^= rp4_6;
-
-
-Not a big change, but every penny counts :-)
-
-
-Analysis 7
-==========
-
-Actually this made things worse. Not very much, but I don't want to move
-into the wrong direction. Maybe something to investigate later. Could
-have to do with caching again.
-
-Guess that is what there is to win within the loop. Maybe unrolling one
-more time will help. I'll keep the optimisations from 7 for now.
-
-
-Attempt 8
-=========
-
-Unrolled the loop one more time.
-
-
-Analysis 8
-==========
-
-This makes things worse. Let's stick with attempt 6 and continue from there.
-Although it seems that the code within the loop cannot be optimised
-further there is still room to optimize the generation of the ecc codes.
-We can simply calculate the total parity. If this is 0 then rp4 = rp5
-etc. If the parity is 1, then rp4 = !rp5;
-
-But if rp4 = rp5 we do not need rp5 etc. We can just write the even bits
-in the result byte and then do something like::
-
-    code[0] |= (code[0] << 1);
-
-Lets test this.
-
-
-Attempt 9
-=========
-
-Changed the code but again this slightly degrades performance. Tried all
-kind of other things, like having dedicated parity arrays to avoid the
-shift after parity[rp7] << 7; No gain.
-Change the lookup using the parity array by using shift operators (e.g.
-replace parity[rp7] << 7 with::
-
-	rp7 ^= (rp7 << 4);
-	rp7 ^= (rp7 << 2);
-	rp7 ^= (rp7 << 1);
-	rp7 &= 0x80;
-
-No gain.
-
-The only marginal change was inverting the parity bits, so we can remove
-the last three invert statements.
-
-Ah well, pity this does not deliver more. Then again 10 million
-iterations using the linux driver code takes between 13 and 13.5
-seconds, whereas my code now takes about 0.73 seconds for those 10
-million iterations. So basically I've improved the performance by a
-factor 18 on my system. Not that bad. Of course on different hardware
-you will get different results. No warranties!
-
-But of course there is no such thing as a free lunch. The codesize almost
-tripled (from 562 bytes to 1434 bytes). Then again, it is not that much.
-
-
-Correcting errors
-=================
-
-For correcting errors I again used the ST application note as a starter,
-but I also peeked at the existing code.
-
-The algorithm itself is pretty straightforward. Just xor the given and
-the calculated ecc. If all bytes are 0 there is no problem. If 11 bits
-are 1 we have one correctable bit error. If there is 1 bit 1, we have an
-error in the given ecc code.
-
-It proved to be fastest to do some table lookups. Performance gain
-introduced by this is about a factor 2 on my system when a repair had to
-be done, and 1% or so if no repair had to be done.
-
-Code size increased from 330 bytes to 686 bytes for this function.
-(gcc 4.2, -O3)
-
-
-Conclusion
-==========
-
-The gain when calculating the ecc is tremendous. Om my development hardware
-a speedup of a factor of 18 for ecc calculation was achieved. On a test on an
-embedded system with a MIPS core a factor 7 was obtained.
-
-On a test with a Linksys NSLU2 (ARMv5TE processor) the speedup was a factor
-5 (big endian mode, gcc 4.1.2, -O3)
-
-For correction not much gain could be obtained (as bitflips are rare). Then
-again there are also much less cycles spent there.
-
-It seems there is not much more gain possible in this, at least when
-programmed in C. Of course it might be possible to squeeze something more
-out of it with an assembler program, but due to pipeline behaviour etc
-this is very tricky (at least for intel hw).
-
-Author: Frans Meulenbroeks
-
-Copyright (C) 2008 Koninklijke Philips Electronics NV.
diff --git a/Documentation/mtd/spi-nor.rst b/Documentation/mtd/spi-nor.rst
deleted file mode 100644
index f5333e3bf486..000000000000
--- a/Documentation/mtd/spi-nor.rst
+++ /dev/null
@@ -1,66 +0,0 @@
-=================
-SPI NOR framework
-=================
-
-Part I - Why do we need this framework?
----------------------------------------
-
-SPI bus controllers (drivers/spi/) only deal with streams of bytes; the bus
-controller operates agnostic of the specific device attached. However, some
-controllers (such as Freescale's QuadSPI controller) cannot easily handle
-arbitrary streams of bytes, but rather are designed specifically for SPI NOR.
-
-In particular, Freescale's QuadSPI controller must know the NOR commands to
-find the right LUT sequence. Unfortunately, the SPI subsystem has no notion of
-opcodes, addresses, or data payloads; a SPI controller simply knows to send or
-receive bytes (Tx and Rx). Therefore, we must define a new layering scheme under
-which the controller driver is aware of the opcodes, addressing, and other
-details of the SPI NOR protocol.
-
-Part II - How does the framework work?
---------------------------------------
-
-This framework just adds a new layer between the MTD and the SPI bus driver.
-With this new layer, the SPI NOR controller driver does not depend on the
-m25p80 code anymore.
-
-Before this framework, the layer is like::
-
-                   MTD
-         ------------------------
-                  m25p80
-         ------------------------
-	       SPI bus driver
-         ------------------------
-	        SPI NOR chip
-
-   After this framework, the layer is like:
-                   MTD
-         ------------------------
-              SPI NOR framework
-         ------------------------
-                  m25p80
-         ------------------------
-	       SPI bus driver
-         ------------------------
-	       SPI NOR chip
-
-  With the SPI NOR controller driver (Freescale QuadSPI), it looks like:
-                   MTD
-         ------------------------
-              SPI NOR framework
-         ------------------------
-                fsl-quadSPI
-         ------------------------
-	       SPI NOR chip
-
-Part III - How can drivers use the framework?
----------------------------------------------
-
-The main API is spi_nor_scan(). Before you call the hook, a driver should
-initialize the necessary fields for spi_nor{}. Please see
-drivers/mtd/spi-nor/spi-nor.c for detail. Please also refer to fsl-quadspi.c
-when you want to write a new driver for a SPI NOR controller.
-Another API is spi_nor_restore(), this is used to restore the status of SPI
-flash chip such as addressing mode. Call it whenever detach the driver from
-device or reboot the system.