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2020-05-24lib/bch: Allow easy bit swappingMiquel Raynal
It seems that several hardware ECC engine use a swapped representation of bytes compared to software. This might having to do with how the ECC engine is wired to the NAND controller or the order the bits are passed to the hardware BCH logic. This means that when the software BCH engine is working in conjunction with data generated with hardware, sometimes we might need to swap the bits inside bytes, eg: 0x0A = b0000_1010 -> b0101_0000 = 0x50 Make it possible by adding a boolean to the BCH initialization routine. Regarding the implementation itself, this is a rather simple approach that can probably be enhanced in the future by preparing the ->a_{mod,pow}_tab tables with the swapping in mind. Suggested-by: Boris Brezillon <boris.brezillon@collabora.com> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-3-miquel.raynal@bootlin.com
2020-05-24lib/bch: Rework a little bit the exported function namesMiquel Raynal
There are four exported functions, all suffixed by _bch, which is clearly not the norm. Let's rename them by prefixing them with bch_ instead. This is a mechanical change: init_bch -> bch_init free_bch -> bch_free encode_bch -> bch_encode decode_bch -> bch_decode Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> Link: https://lore.kernel.org/linux-mtd/20200519074549.23673-2-miquel.raynal@bootlin.com
2019-06-05treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 336Thomas Gleixner
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not write to the free software foundation inc 51 franklin st fifth floor boston ma 02110 1301 usa extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 246 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190530000436.674189849@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2011-03-11lib: add shared BCH ECC libraryIvan Djelic
This is a new software BCH encoding/decoding library, similar to the shared Reed-Solomon library. Binary BCH (Bose-Chaudhuri-Hocquenghem) codes are widely used to correct errors in NAND flash devices requiring more than 1-bit ecc correction; they are generally better suited for NAND flash than RS codes because NAND bit errors do not occur in bursts. Latest SLC NAND devices typically require at least 4-bit ecc protection per 512 bytes block. This library provides software encoding/decoding, but may also be used with ASIC/SoC hardware BCH engines to perform error correction. It is being currently used for this purpose on an OMAP3630 board (4bit/8bit HW BCH). It has also been used to decode raw dumps of NAND devices with on-die BCH ecc engines (e.g. Micron 4bit ecc SLC devices). Latest NAND devices (including SLC) can exhibit high error rates (typically a dozen or more bitflips per hour during stress tests); in order to minimize the performance impact of error correction, this library implements recently developed algorithms for fast polynomial root finding (see bch.c header for details) instead of the traditional exhaustive Chien root search; a few performance figures are provided below: Platform: arm926ejs @ 468 MHz, 32 KiB icache, 16 KiB dcache BCH ecc : 4-bit per 512 bytes Encoding average throughput: 250 Mbits/s Error correction time (compared with Chien search): average worst average (Chien) worst (Chien) ---------------------------------------------------------- 1 bit 8.5 µs 11 µs 200 µs 383 µs 2 bit 9.7 µs 12.5 µs 477 µs 728 µs 3 bit 18.1 µs 20.6 µs 758 µs 1010 µs 4 bit 19.5 µs 23 µs 1028 µs 1280 µs In the above figures, "worst" is meant in terms of error pattern, not in terms of cache miss / page faults effects (not taken into account here). The library has been extensively tested on the following platforms: x86, x86_64, arm926ejs, omap3630, qemu-ppc64, qemu-mips. Signed-off-by: Ivan Djelic <ivan.djelic@parrot.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>