at91: add hwecc method for nand

This is a patch to use the hardware ECC controller of
the AT91SAM9260 for the AT91 nand. Taken from the kernel 2.6.33.

Signed-off-by: Nikolay Petukhov <Nikolay.Petukhov@gmail.com>

drivers/mtd/nand/atmel_nand.c

@@ -31,6 +31,209 @@
 
 #include <nand.h>
 
+#ifdef CONFIG_ATMEL_NAND_HWECC
+
+/* Register access macros */
+#define ecc_readl(add, reg)				\
+	readl(AT91_BASE_SYS + add + ATMEL_ECC_##reg)
+#define ecc_writel(add, reg, value)			\
+	writel((value), AT91_BASE_SYS + add + ATMEL_ECC_##reg)
+
+#include "atmel_nand_ecc.h"	/* Hardware ECC registers */
+
+/* oob layout for large page size
+ * bad block info is on bytes 0 and 1
+ * the bytes have to be consecutives to avoid
+ * several NAND_CMD_RNDOUT during read
+ */
+static struct nand_ecclayout atmel_oobinfo_large = {
+	.eccbytes = 4,
+	.eccpos = {60, 61, 62, 63},
+	.oobfree = {
+		{2, 58}
+	},
+};
+
+/* oob layout for small page size
+ * bad block info is on bytes 4 and 5
+ * the bytes have to be consecutives to avoid
+ * several NAND_CMD_RNDOUT during read
+ */
+static struct nand_ecclayout atmel_oobinfo_small = {
+	.eccbytes = 4,
+	.eccpos = {0, 1, 2, 3},
+	.oobfree = {
+		{6, 10}
+	},
+};
+
+/*
+ * Calculate HW ECC
+ *
+ * function called after a write
+ *
+ * mtd:        MTD block structure
+ * dat:        raw data (unused)
+ * ecc_code:   buffer for ECC
+ */
+static int atmel_nand_calculate(struct mtd_info *mtd,
+		const u_char *dat, unsigned char *ecc_code)
+{
+	struct nand_chip *nand_chip = mtd->priv;
+	unsigned int ecc_value;
+
+	/* get the first 2 ECC bytes */
+	ecc_value = ecc_readl(CONFIG_SYS_NAND_ECC_BASE, PR);
+
+	ecc_code[0] = ecc_value & 0xFF;
+	ecc_code[1] = (ecc_value >> 8) & 0xFF;
+
+	/* get the last 2 ECC bytes */
+	ecc_value = ecc_readl(CONFIG_SYS_NAND_ECC_BASE, NPR) & ATMEL_ECC_NPARITY;
+
+	ecc_code[2] = ecc_value & 0xFF;
+	ecc_code[3] = (ecc_value >> 8) & 0xFF;
+
+	return 0;
+}
+
+/*
+ * HW ECC read page function
+ *
+ * mtd:        mtd info structure
+ * chip:       nand chip info structure
+ * buf:        buffer to store read data
+ */
+static int atmel_nand_read_page(struct mtd_info *mtd,
+		struct nand_chip *chip, uint8_t *buf, int page)
+{
+	int eccsize = chip->ecc.size;
+	int eccbytes = chip->ecc.bytes;
+	uint32_t *eccpos = chip->ecc.layout->eccpos;
+	uint8_t *p = buf;
+	uint8_t *oob = chip->oob_poi;
+	uint8_t *ecc_pos;
+	int stat;
+
+	/* read the page */
+	chip->read_buf(mtd, p, eccsize);
+
+	/* move to ECC position if needed */
+	if (eccpos[0] != 0) {
+		/* This only works on large pages
+		 * because the ECC controller waits for
+		 * NAND_CMD_RNDOUTSTART after the
+		 * NAND_CMD_RNDOUT.
+		 * anyway, for small pages, the eccpos[0] == 0
+		 */
+		chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
+				mtd->writesize + eccpos[0], -1);
+	}
+
+	/* the ECC controller needs to read the ECC just after the data */
+	ecc_pos = oob + eccpos[0];
+	chip->read_buf(mtd, ecc_pos, eccbytes);
+
+	/* check if there's an error */
+	stat = chip->ecc.correct(mtd, p, oob, NULL);
+
+	if (stat < 0)
+		mtd->ecc_stats.failed++;
+	else
+		mtd->ecc_stats.corrected += stat;
+
+	/* get back to oob start (end of page) */
+	chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize, -1);
+
+	/* read the oob */
+	chip->read_buf(mtd, oob, mtd->oobsize);
+
+	return 0;
+}
+
+/*
+ * HW ECC Correction
+ *
+ * function called after a read
+ *
+ * mtd:        MTD block structure
+ * dat:        raw data read from the chip
+ * read_ecc:   ECC from the chip (unused)
+ * isnull:     unused
+ *
+ * Detect and correct a 1 bit error for a page
+ */
+static int atmel_nand_correct(struct mtd_info *mtd, u_char *dat,
+		u_char *read_ecc, u_char *isnull)
+{
+	struct nand_chip *nand_chip = mtd->priv;
+	unsigned int ecc_status, ecc_parity, ecc_mode;
+	unsigned int ecc_word, ecc_bit;
+
+	/* get the status from the Status Register */
+	ecc_status = ecc_readl(CONFIG_SYS_NAND_ECC_BASE, SR);
+
+	/* if there's no error */
+	if (likely(!(ecc_status & ATMEL_ECC_RECERR)))
+		return 0;
+
+	/* get error bit offset (4 bits) */
+	ecc_bit = ecc_readl(CONFIG_SYS_NAND_ECC_BASE, PR) & ATMEL_ECC_BITADDR;
+	/* get word address (12 bits) */
+	ecc_word = ecc_readl(CONFIG_SYS_NAND_ECC_BASE, PR) & ATMEL_ECC_WORDADDR;
+	ecc_word >>= 4;
+
+	/* if there are multiple errors */
+	if (ecc_status & ATMEL_ECC_MULERR) {
+		/* check if it is a freshly erased block
+		 * (filled with 0xff) */
+		if ((ecc_bit == ATMEL_ECC_BITADDR)
+				&& (ecc_word == (ATMEL_ECC_WORDADDR >> 4))) {
+			/* the block has just been erased, return OK */
+			return 0;
+		}
+		/* it doesn't seems to be a freshly
+		 * erased block.
+		 * We can't correct so many errors */
+		printk(KERN_WARNING "atmel_nand : multiple errors detected."
+				" Unable to correct.\n");
+		return -EIO;
+	}
+
+	/* if there's a single bit error : we can correct it */
+	if (ecc_status & ATMEL_ECC_ECCERR) {
+		/* there's nothing much to do here.
+		 * the bit error is on the ECC itself.
+		 */
+		printk(KERN_WARNING "atmel_nand : one bit error on ECC code."
+				" Nothing to correct\n");
+		return 0;
+	}
+
+	printk(KERN_WARNING "atmel_nand : one bit error on data."
+			" (word offset in the page :"
+			" 0x%x bit offset : 0x%x)\n",
+			ecc_word, ecc_bit);
+	/* correct the error */
+	if (nand_chip->options & NAND_BUSWIDTH_16) {
+		/* 16 bits words */
+		((unsigned short *) dat)[ecc_word] ^= (1 << ecc_bit);
+	} else {
+		/* 8 bits words */
+		dat[ecc_word] ^= (1 << ecc_bit);
+	}
+	printk(KERN_WARNING "atmel_nand : error corrected\n");
+	return 1;
+}
+
+/*
+ * Enable HW ECC : unused on most chips
+ */
+static void atmel_nand_hwctl(struct mtd_info *mtd, int mode)
+{
+}
+#endif
+
 static void at91_nand_hwcontrol(struct mtd_info *mtd,
 					 int cmd, unsigned int ctrl)
 {
@@ -64,6 +267,11 @@ static int at91_nand_ready(struct mtd_info *mtd)
 
 int board_nand_init(struct nand_chip *nand)
 {
+#ifdef CONFIG_ATMEL_NAND_HWECC
+	static int chip_nr = 0;
+	struct mtd_info *mtd;
+#endif
+
 	nand->ecc.mode = NAND_ECC_SOFT;
 #ifdef CONFIG_SYS_NAND_DBW_16
 	nand->options = NAND_BUSWIDTH_16;
@@ -74,5 +282,62 @@ int board_nand_init(struct nand_chip *nand)
 #endif
 	nand->chip_delay = 20;
 
+#ifdef CONFIG_ATMEL_NAND_HWECC
+	nand->ecc.mode = NAND_ECC_HW;
+	nand->ecc.calculate = atmel_nand_calculate;
+	nand->ecc.correct = atmel_nand_correct;
+	nand->ecc.hwctl = atmel_nand_hwctl;
+	nand->ecc.read_page = atmel_nand_read_page;
+	nand->ecc.bytes = 4;
+#endif
+
+#ifdef CONFIG_ATMEL_NAND_HWECC
+	mtd = &nand_info[chip_nr++];
+	mtd->priv = nand;
+
+	/* Detect NAND chips */
+	if (nand_scan_ident(mtd, 1)) {
+		printk(KERN_WARNING "NAND Flash not found !\n");
+		return -ENXIO;
+	}
+
+	if (nand->ecc.mode == NAND_ECC_HW) {
+		/* ECC is calculated for the whole page (1 step) */
+		nand->ecc.size = mtd->writesize;
+
+		/* set ECC page size and oob layout */
+		switch (mtd->writesize) {
+		case 512:
+			nand->ecc.layout = &atmel_oobinfo_small;
+			ecc_writel(CONFIG_SYS_NAND_ECC_BASE, MR, ATMEL_ECC_PAGESIZE_528);
+			break;
+		case 1024:
+			nand->ecc.layout = &atmel_oobinfo_large;
+			ecc_writel(CONFIG_SYS_NAND_ECC_BASE, MR, ATMEL_ECC_PAGESIZE_1056);
+			break;
+		case 2048:
+			nand->ecc.layout = &atmel_oobinfo_large;
+			ecc_writel(CONFIG_SYS_NAND_ECC_BASE, MR, ATMEL_ECC_PAGESIZE_2112);
+			break;
+		case 4096:
+			nand->ecc.layout = &atmel_oobinfo_large;
+			ecc_writel(CONFIG_SYS_NAND_ECC_BASE, MR, ATMEL_ECC_PAGESIZE_4224);
+			break;
+		default:
+			/* page size not handled by HW ECC */
+			/* switching back to soft ECC */
+			nand->ecc.mode = NAND_ECC_SOFT;
+			nand->ecc.calculate = NULL;
+			nand->ecc.correct = NULL;
+			nand->ecc.hwctl = NULL;
+			nand->ecc.read_page = NULL;
+			nand->ecc.postpad = 0;
+			nand->ecc.prepad = 0;
+			nand->ecc.bytes = 0;
+			break;
+		}
+	}
+#endif
+
 	return 0;
 }

drivers/mtd/nand/atmel_nand_ecc.h

@@ -0,0 +1,36 @@
+/*
+ * Error Corrected Code Controller (ECC) - System peripherals regsters.
+ * Based on AT91SAM9260 datasheet revision B.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#ifndef ATMEL_NAND_ECC_H
+#define ATMEL_NAND_ECC_H
+
+#define ATMEL_ECC_CR		0x00			/* Control register */
+#define		ATMEL_ECC_RST		(1 << 0)		/* Reset parity */
+
+#define ATMEL_ECC_MR		0x04			/* Mode register */
+#define		ATMEL_ECC_PAGESIZE	(3 << 0)		/* Page Size */
+#define			ATMEL_ECC_PAGESIZE_528		(0)
+#define			ATMEL_ECC_PAGESIZE_1056		(1)
+#define			ATMEL_ECC_PAGESIZE_2112		(2)
+#define			ATMEL_ECC_PAGESIZE_4224		(3)
+
+#define ATMEL_ECC_SR		0x08			/* Status register */
+#define		ATMEL_ECC_RECERR		(1 << 0)		/* Recoverable Error */
+#define		ATMEL_ECC_ECCERR		(1 << 1)		/* ECC Single Bit Error */
+#define		ATMEL_ECC_MULERR		(1 << 2)		/* Multiple Errors */
+
+#define ATMEL_ECC_PR		0x0c			/* Parity register */
+#define		ATMEL_ECC_BITADDR	(0xf << 0)		/* Bit Error Address */
+#define		ATMEL_ECC_WORDADDR	(0xfff << 4)		/* Word Error Address */
+
+#define ATMEL_ECC_NPR		0x10			/* NParity register */
+#define		ATMEL_ECC_NPARITY	(0xffff << 0)		/* NParity */
+
+#endif