text: /*
   * This file provides ECC correction for more than 1 bit per block of data,
   * using binary BCH codes. It relies on the generic BCH library lib/bch.c.
   *
   * Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
   *
    * SPDX-License-Identifier:	GPL-2.0+
   */
  
  #include <common.h>
  /*#include <asm/io.h>*/
  #include <linux/types.h>
  
  #include <linux/bitops.h>
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/rawnand.h>
  #include <linux/mtd/nand_bch.h>
  #include <linux/bch.h>
  #include <malloc.h>
  
  /**
   * struct nand_bch_control - private NAND BCH control structure
   * @bch:       BCH control structure
   * @ecclayout: private ecc layout for this BCH configuration
   * @errloc:    error location array
   * @eccmask:   XOR ecc mask, allows erased pages to be decoded as valid
   */
  struct nand_bch_control {
  	struct bch_control   *bch;
  	struct nand_ecclayout ecclayout;
  	unsigned int         *errloc;
  	unsigned char        *eccmask;
  };
  
  /**
   * nand_bch_calculate_ecc - [NAND Interface] Calculate ECC for data block
   * @mtd:	MTD block structure
   * @buf:	input buffer with raw data
   * @code:	output buffer with ECC
   */
  int nand_bch_calculate_ecc(struct mtd_info *mtd, const unsigned char *buf,
  			   unsigned char *code)
  {
  	const struct nand_chip *chip = mtd_to_nand(mtd);
  	struct nand_bch_control *nbc = chip->ecc.priv;
  	unsigned int i;
  
  	memset(code, 0, chip->ecc.bytes);
  	encode_bch(nbc->bch, buf, chip->ecc.size, code);
  
  	/* apply mask so that an erased page is a valid codeword */
  	for (i = 0; i < chip->ecc.bytes; i++)
  		code[i] ^= nbc->eccmask[i];
  
  	return 0;
  }
  
  /**
   * nand_bch_correct_data - [NAND Interface] Detect and correct bit error(s)
   * @mtd:	MTD block structure
   * @buf:	raw data read from the chip
   * @read_ecc:	ECC from the chip
   * @calc_ecc:	the ECC calculated from raw data
   *
   * Detect and correct bit errors for a data byte block
   */
  int nand_bch_correct_data(struct mtd_info *mtd, unsigned char *buf,
  			  unsigned char *read_ecc, unsigned char *calc_ecc)
  {
  	const struct nand_chip *chip = mtd_to_nand(mtd);
  	struct nand_bch_control *nbc = chip->ecc.priv;
  	unsigned int *errloc = nbc->errloc;
  	int i, count;
  
  	count = decode_bch(nbc->bch, NULL, chip->ecc.size, read_ecc, calc_ecc,
  			   NULL, errloc);
  	if (count > 0) {
  		for (i = 0; i < count; i++) {
  			if (errloc[i] < (chip->ecc.size*8))
  				/* error is located in data, correct it */
  				buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));
  			/* else error in ecc, no action needed */
  
  			pr_debug("%s: corrected bitflip %u\n",
  				 __func__, errloc[i]);
  		}
  	} else if (count < 0) {
  		printk(KERN_ERR "ecc unrecoverable error\n");
  		count = -EBADMSG;
  	}
  	return count;
  }
  
  /**
   * nand_bch_init - [NAND Interface] Initialize NAND BCH error correction
   * @mtd:	MTD block structure
   *
   * Returns:
   *  a pointer to a new NAND BCH control structure, or NULL upon failure
   *
   * Initialize NAND BCH error correction. Parameters @eccsize and @eccbytes
   * are used to compute BCH parameters m (Galois field order) and t (error
   * correction capability). @eccbytes should be equal to the number of bytes
   * required to store m*t bits, where m is such that 2^m-1 > @eccsize*8.
   *
   * Example: to configure 4 bit correction per 512 bytes, you should pass
   * @eccsize = 512  (thus, m=13 is the smallest integer such that 2^m-1 > 512*8)
   * @eccbytes = 7   (7 bytes are required to store m*t = 13*4 = 52 bits)
   */
  struct nand_bch_control *nand_bch_init(struct mtd_info *mtd)
  {
  	struct nand_chip *nand = mtd_to_nand(mtd);
  	unsigned int m, t, eccsteps, i;
  	struct nand_ecclayout *layout = nand->ecc.layout;
  	struct nand_bch_control *nbc = NULL;
  	unsigned char *erased_page;
  	unsigned int eccsize = nand->ecc.size;
  	unsigned int eccbytes = nand->ecc.bytes;
  	unsigned int eccstrength = nand->ecc.strength;
  
  	if (!eccbytes && eccstrength) {
  		eccbytes = DIV_ROUND_UP(eccstrength * fls(8 * eccsize), 8);
  		nand->ecc.bytes = eccbytes;
  	}
  
  	if (!eccsize || !eccbytes) {
  		printk(KERN_WARNING "ecc parameters not supplied\n");
  		goto fail;
  	}
  
  	m = fls(1+8*eccsize);
  	t = (eccbytes*8)/m;
  
  	nbc = kzalloc(sizeof(*nbc), GFP_KERNEL);
  	if (!nbc)
  		goto fail;
  
  	nbc->bch = init_bch(m, t, 0);
  	if (!nbc->bch)
  		goto fail;
  
  	/* verify that eccbytes has the expected value */
  	if (nbc->bch->ecc_bytes != eccbytes) {
  		printk(KERN_WARNING "invalid eccbytes %u, should be %u\n",
  		       eccbytes, nbc->bch->ecc_bytes);
  		goto fail;
  	}
  
  	eccsteps = mtd->writesize/eccsize;
  
  	/* if no ecc placement scheme was provided, build one */
  	if (!layout) {
  
  		/* handle large page devices only */
  		if (mtd->oobsize < 64) {
  			printk(KERN_WARNING "must provide an oob scheme for "
  			       "oobsize %d\n", mtd->oobsize);
  			goto fail;
  		}
  
  		layout = &nbc->ecclayout;
  		layout->eccbytes = eccsteps*eccbytes;
  
  		/* reserve 2 bytes for bad block marker */
  		if (layout->eccbytes+2 > mtd->oobsize) {
  			printk(KERN_WARNING "no suitable oob scheme available "
  			       "for oobsize %d eccbytes %u\n", mtd->oobsize,
  			       eccbytes);
  			goto fail;
  		}
  		/* put ecc bytes at oob tail */
  		for (i = 0; i < layout->eccbytes; i++)
  			layout->eccpos[i] = mtd->oobsize-layout->eccbytes+i;
  
  		layout->oobfree[0].offset = 2;
  		layout->oobfree[0].length = mtd->oobsize-2-layout->eccbytes;
  
  		nand->ecc.layout = layout;
  	}
  
  	/* sanity checks */
  	if (8*(eccsize+eccbytes) >= (1 << m)) {
  		printk(KERN_WARNING "eccsize %u is too large\n", eccsize);
  		goto fail;
  	}
  	if (layout->eccbytes != (eccsteps*eccbytes)) {
  		printk(KERN_WARNING "invalid ecc layout\n");
  		goto fail;
  	}
  
  	nbc->eccmask = kmalloc(eccbytes, GFP_KERNEL);
  	nbc->errloc = kmalloc(t*sizeof(*nbc->errloc), GFP_KERNEL);
  	if (!nbc->eccmask || !nbc->errloc)
  		goto fail;
  	/*
  	 * compute and store the inverted ecc of an erased ecc block
  	 */
  	erased_page = kmalloc(eccsize, GFP_KERNEL);
  	if (!erased_page)
  		goto fail;
  
  	memset(erased_page, 0xff, eccsize);
  	memset(nbc->eccmask, 0, eccbytes);
  	encode_bch(nbc->bch, erased_page, eccsize, nbc->eccmask);
  	kfree(erased_page);
  
  	for (i = 0; i < eccbytes; i++)
  		nbc->eccmask[i] ^= 0xff;
  
  	if (!eccstrength)
  		nand->ecc.strength = (eccbytes * 8) / fls(8 * eccsize);
  
  	return nbc;
  fail:
  	nand_bch_free(nbc);
  	return NULL;
  }
  
  /**
   * nand_bch_free - [NAND Interface] Release NAND BCH ECC resources
   * @nbc:	NAND BCH control structure
   */
  void nand_bch_free(struct nand_bch_control *nbc)
  {
  	if (nbc) {
  		free_bch(nbc->bch);
  		kfree(nbc->errloc);
  		kfree(nbc->eccmask);
  		kfree(nbc);
  	}
  }
  