openwrtv3/target/linux/ramips/patches-3.18/0043-mtd-ralink-add-mt7620-nand-driver.patch

From b915fe7cd934160bfaf2cd52f03c118abcae2419 Mon Sep 17 00:00:00 2001
From: John Crispin <blogic@openwrt.org>
Date: Sun, 17 Nov 2013 17:41:46 +0100
Subject: [PATCH 43/57] mtd: ralink: add mt7620 nand driver

Signed-off-by: John Crispin <blogic@openwrt.org>
---
 drivers/mtd/maps/Kconfig       |    4 +
 drivers/mtd/maps/Makefile      |    2 +
 drivers/mtd/maps/ralink_nand.c | 2136 ++++++++++++++++++++++++++++++++++++++++
 drivers/mtd/maps/ralink_nand.h |  232 +++++
 4 files changed, 2374 insertions(+)
 create mode 100644 drivers/mtd/maps/ralink_nand.c
 create mode 100644 drivers/mtd/maps/ralink_nand.h

--- a/drivers/mtd/maps/Kconfig
+++ b/drivers/mtd/maps/Kconfig
@@ -399,4 +399,8 @@ config MTD_LATCH_ADDR
 
           If compiled as a module, it will be called latch-addr-flash.
 
+config MTD_NAND_MT7620
+	tristate "Support for NAND on Mediatek MT7620"
+	depends on RALINK && SOC_MT7620
+
 endmenu
--- a/drivers/mtd/maps/Makefile
+++ b/drivers/mtd/maps/Makefile
@@ -43,3 +43,5 @@ obj-$(CONFIG_MTD_VMU)		+= vmu-flash.o
 obj-$(CONFIG_MTD_GPIO_ADDR)	+= gpio-addr-flash.o
 obj-$(CONFIG_MTD_LATCH_ADDR)	+= latch-addr-flash.o
 obj-$(CONFIG_MTD_LANTIQ)	+= lantiq-flash.o
+obj-$(CONFIG_MTD_NAND_MT7620)	+= ralink_nand.o
+
--- /dev/null
+++ b/drivers/mtd/maps/ralink_nand.c
@@ -0,0 +1,2136 @@
+#define DEBUG
+#include <linux/device.h>
+#undef DEBUG
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/dma-mapping.h>
+#include <linux/mtd/partitions.h>
+#include <asm/io.h>
+#include <linux/delay.h>
+#include <linux/sched.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#include "ralink_nand.h"
+#ifdef RANDOM_GEN_BAD_BLOCK
+#include <linux/random.h>
+#endif
+
+#define LARGE_MTD_BOOT_PART_SIZE       (CFG_BLOCKSIZE<<2)
+#define LARGE_MTD_CONFIG_PART_SIZE     (CFG_BLOCKSIZE<<2)
+#define LARGE_MTD_FACTORY_PART_SIZE    (CFG_BLOCKSIZE<<1)
+
+
+#define BLOCK_ALIGNED(a) ((a) & (CFG_BLOCKSIZE - 1))
+
+#define READ_STATUS_RETRY	1000
+
+struct mtd_info *ranfc_mtd = NULL;
+
+int skipbbt = 0;
+int ranfc_debug = 1;
+static int ranfc_bbt = 1;
+#if defined (WORKAROUND_RX_BUF_OV)
+static int ranfc_verify = 1;
+#endif
+static u32 nand_addrlen;
+
+#if 0
+module_param(ranfc_debug, int, 0644);
+module_param(ranfc_bbt, int, 0644);
+module_param(ranfc_verify, int, 0644);
+#endif
+
+#if 0
+#define ra_dbg(args...) do { if (ranfc_debug) printk(args); } while(0)
+#else
+#define ra_dbg(args...)
+#endif
+
+#define CLEAR_INT_STATUS()	ra_outl(NFC_INT_ST, ra_inl(NFC_INT_ST))
+#define NFC_TRANS_DONE()	(ra_inl(NFC_INT_ST) & INT_ST_ND_DONE)
+
+int is_nand_page_2048 = 0;
+const unsigned int nand_size_map[2][3] = {{25, 30, 30}, {20, 27, 30}};
+
+static int nfc_wait_ready(int snooze_ms);
+
+static const char * const mtk_probe_types[] = { "cmdlinepart", "ofpart", NULL };
+
+/**
+ * reset nand chip
+ */
+static int nfc_chip_reset(void)
+{
+	int status;
+
+	//ra_dbg("%s:\n", __func__);
+
+	// reset nand flash
+	ra_outl(NFC_CMD1, 0x0);
+	ra_outl(NFC_CMD2, 0xff);
+	ra_outl(NFC_ADDR, 0x0);
+	ra_outl(NFC_CONF, 0x0411);
+
+	status = nfc_wait_ready(5);  //erase wait 5us
+	if (status & NAND_STATUS_FAIL) {
+		printk("%s: fail \n", __func__);
+	}
+	
+	return (int)(status & NAND_STATUS_FAIL);
+
+}
+
+
+
+/** 
+ * clear NFC and flash chip.
+ */
+static int nfc_all_reset(void)
+{
+	int retry;
+
+	ra_dbg("%s: \n", __func__);
+
+	// reset controller
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) | 0x02); //clear data buffer
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) & ~0x02); //clear data buffer
+
+	CLEAR_INT_STATUS();
+
+	retry = READ_STATUS_RETRY;
+	while ((ra_inl(NFC_INT_ST) & 0x02) != 0x02 && retry--);
+	if (retry <= 0) {
+		printk("nfc_all_reset: clean buffer fail \n");
+		return -1;
+	}
+
+	retry = READ_STATUS_RETRY;
+	while ((ra_inl(NFC_STATUS) & 0x1) != 0x0 && retry--) { //fixme, controller is busy ?
+		udelay(1);
+	}
+
+	nfc_chip_reset();
+
+	return 0;
+}
+
+/** NOTICE: only called by nfc_wait_ready().
+ * @return -1, nfc can not get transction done 
+ * @return 0, ok.
+ */
+static int _nfc_read_status(char *status)
+{
+	unsigned long cmd1, conf;
+	int int_st, nfc_st;
+	int retry;
+
+	cmd1 = 0x70;
+	conf = 0x000101 | (1 << 20);
+
+	//fixme, should we check nfc status?
+	CLEAR_INT_STATUS();
+
+	ra_outl(NFC_CMD1, cmd1); 	
+	ra_outl(NFC_CONF, conf); 
+
+	/* FIXME, 
+	 * 1. since we have no wired ready signal, directly 
+	 * calling this function is not gurantee to read right status under ready state.
+	 * 2. the other side, we can not determine how long to become ready, this timeout retry is nonsense.
+	 * 3. SUGGESTION: call nfc_read_status() from nfc_wait_ready(),
+	 * that is aware about caller (in sementics) and has snooze plused nfc ND_DONE.
+	 */
+	retry = READ_STATUS_RETRY; 
+	do {
+		nfc_st = ra_inl(NFC_STATUS);
+		int_st = ra_inl(NFC_INT_ST);
+		
+		ndelay(10);
+	} while (!(int_st & INT_ST_RX_BUF_RDY) && retry--);
+
+	if (!(int_st & INT_ST_RX_BUF_RDY)) {
+		printk("nfc_read_status: NFC fail, int_st(%x), retry:%x. nfc:%x, reset nfc and flash. \n", 
+		       int_st, retry, nfc_st);
+		nfc_all_reset();
+		*status = NAND_STATUS_FAIL;
+		return -1;
+	}
+
+	*status = (char)(le32_to_cpu(ra_inl(NFC_DATA)) & 0x0ff);
+	return 0;
+}
+
+/**
+ * @return !0, chip protect.
+ * @return 0, chip not protected.
+ */
+static int nfc_check_wp(void)
+{
+	/* Check the WP bit */
+#if !defined CONFIG_NOT_SUPPORT_WP
+	return !!(ra_inl(NFC_CTRL) & 0x01);
+#else
+	char result = 0;
+	int ret;
+
+	ret = _nfc_read_status(&result);
+	//FIXME, if ret < 0
+
+	return !(result & NAND_STATUS_WP);
+#endif
+}
+
+#if !defined CONFIG_NOT_SUPPORT_RB
+/*
+ * @return !0, chip ready.
+ * @return 0, chip busy.
+ */
+static int nfc_device_ready(void)
+{
+	/* Check the ready  */
+	return !!(ra_inl(NFC_STATUS) & 0x04);
+}
+#endif
+
+
+/**
+ * generic function to get data from flash.
+ * @return data length reading from flash.
+ */
+static int _ra_nand_pull_data(char *buf, int len, int use_gdma)
+{
+#ifdef RW_DATA_BY_BYTE
+	char *p = buf;
+#else
+	__u32 *p = (__u32 *)buf;
+#endif
+	int retry, int_st;
+	unsigned int ret_data;
+	int ret_size;
+
+	// receive data by use_gdma 
+	if (use_gdma) { 
+		//if (_ra_nand_dma_pull((unsigned long)p, len)) {
+		if (1) {
+			printk("%s: fail \n", __func__);
+			len = -1; //return error
+		}
+
+		return len;
+	}
+
+	//fixme: retry count size?
+	retry = READ_STATUS_RETRY;
+	// no gdma
+	while (len > 0) {
+		int_st = ra_inl(NFC_INT_ST);
+		if (int_st & INT_ST_RX_BUF_RDY) {
+
+			ret_data = ra_inl(NFC_DATA);
+			ra_outl(NFC_INT_ST, INT_ST_RX_BUF_RDY); 
+#ifdef RW_DATA_BY_BYTE
+			ret_size = sizeof(unsigned int);
+			ret_size = min(ret_size, len);
+			len -= ret_size;
+			while (ret_size-- > 0) {
+				//nfc is little endian 
+				*p++ = ret_data & 0x0ff;
+				ret_data >>= 8; 
+			}
+#else
+			ret_size = min(len, 4);
+			len -= ret_size;
+			if (ret_size == 4)
+				*p++ = ret_data;
+			else {
+				__u8 *q = (__u8 *)p;
+				while (ret_size-- > 0) {
+					*q++ = ret_data & 0x0ff;
+					ret_data >>= 8; 
+				}
+				p = (__u32 *)q;
+			}
+#endif
+			retry = READ_STATUS_RETRY;
+		}
+		else if (int_st & INT_ST_ND_DONE) {
+			break;
+		}
+		else {
+			udelay(1);
+			if (retry-- < 0) 
+				break;
+		}
+	}
+
+#ifdef RW_DATA_BY_BYTE
+	return (int)(p - buf);
+#else
+	return ((int)p - (int)buf);
+#endif
+}
+
+/**
+ * generic function to put data into flash.
+ * @return data length writing into flash.
+ */
+static int _ra_nand_push_data(char *buf, int len, int use_gdma)
+{
+#ifdef RW_DATA_BY_BYTE
+	char *p = buf;
+#else
+	__u32 *p = (__u32 *)buf;
+#endif
+	int retry, int_st;
+	unsigned int tx_data = 0;
+	int tx_size, iter = 0;
+
+	// receive data by use_gdma 
+	if (use_gdma) { 
+		//if (_ra_nand_dma_push((unsigned long)p, len))
+		if (1)
+			len = 0;		
+		printk("%s: fail \n", __func__);
+		return len;
+	}
+
+	// no gdma
+	retry = READ_STATUS_RETRY;
+	while (len > 0) {
+		int_st = ra_inl(NFC_INT_ST);
+		if (int_st & INT_ST_TX_BUF_RDY) {
+#ifdef RW_DATA_BY_BYTE
+			tx_size = min(len, (int)sizeof(unsigned long));
+			for (iter = 0; iter < tx_size; iter++) {
+				tx_data |= (*p++ << (8*iter));
+			}
+#else
+			tx_size = min(len, 4);
+			if (tx_size == 4)
+				tx_data = (*p++);
+			else {
+				__u8 *q = (__u8 *)p;
+				for (iter = 0; iter < tx_size; iter++)
+					tx_data |= (*q++ << (8*iter));
+				p = (__u32 *)q;
+			}
+#endif
+			ra_outl(NFC_INT_ST, INT_ST_TX_BUF_RDY);
+			ra_outl(NFC_DATA, tx_data);
+			len -= tx_size;
+			retry = READ_STATUS_RETRY;
+		}
+		else if (int_st & INT_ST_ND_DONE) {
+			break;
+		}
+		else {
+			udelay(1);
+			if (retry-- < 0) {
+				ra_dbg("%s p:%p buf:%p \n", __func__, p, buf);
+				break;
+			}
+		}
+	}
+
+	
+#ifdef RW_DATA_BY_BYTE
+	return (int)(p - buf);
+#else
+	return ((int)p - (int)buf);
+#endif
+
+}
+
+static int nfc_select_chip(struct ra_nand_chip *ra, int chipnr)
+{
+#if (CONFIG_NUMCHIPS == 1)
+	if (!(chipnr < CONFIG_NUMCHIPS))
+		return -1;
+	return 0;
+#else
+	BUG();
+#endif
+}
+
+/** @return -1: chip_select fail
+ *	    0 : both CE and WP==0 are OK
+ * 	    1 : CE OK and WP==1
+ */
+static int nfc_enable_chip(struct ra_nand_chip *ra, unsigned int offs, int read_only)
+{
+	int chipnr = offs >> ra->chip_shift;
+
+	ra_dbg("%s: offs:%x read_only:%x \n", __func__, offs, read_only);
+
+	chipnr = nfc_select_chip(ra, chipnr);
+	if (chipnr < 0) {
+		printk("%s: chip select error, offs(%x)\n", __func__, offs);
+		return -1;
+	}
+
+	if (!read_only)
+		return nfc_check_wp();
+	
+	return 0;
+}
+
+/** wait nand chip becomeing ready and return queried status.
+ * @param snooze: sleep time in ms unit before polling device ready.
+ * @return status of nand chip
+ * @return NAN_STATUS_FAIL if something unexpected.
+ */
+static int nfc_wait_ready(int snooze_ms)
+{
+	int retry;
+	char status;
+
+	// wait nfc idle,
+	if (snooze_ms == 0)
+		snooze_ms = 1;
+	else
+		schedule_timeout(snooze_ms * HZ / 1000);
+	
+	snooze_ms = retry = snooze_ms *1000000 / 100 ;  // ndelay(100)
+
+	while (!NFC_TRANS_DONE() && retry--) {
+		if (!cond_resched())
+			ndelay(100);
+	}
+	
+	if (!NFC_TRANS_DONE()) {
+		printk("nfc_wait_ready: no transaction done \n");
+		return NAND_STATUS_FAIL;
+	}
+
+#if !defined (CONFIG_NOT_SUPPORT_RB)
+	//fixme
+	while(!(status = nfc_device_ready()) && retry--) {
+		ndelay(100);
+	}
+
+	if (status == 0) {
+		printk("nfc_wait_ready: no device ready. \n");	
+		return NAND_STATUS_FAIL;
+	}
+
+	_nfc_read_status(&status);
+	return status;
+#else
+
+	while(retry--) {
+		_nfc_read_status(&status);
+		if (status & NAND_STATUS_READY)
+			break;
+		ndelay(100);
+	}
+	if (retry<0)
+		printk("nfc_wait_ready 2: no device ready, status(%x). \n", status);	
+
+	return status;
+#endif
+}
+
+/**
+ * return 0: erase OK
+ * return -EIO: fail 
+ */
+int nfc_erase_block(struct ra_nand_chip *ra, int row_addr)
+{
+	unsigned long cmd1, cmd2, bus_addr, conf;
+	char status;
+
+	cmd1 = 0x60;
+	cmd2 = 0xd0;
+	bus_addr = row_addr;
+	conf = 0x00511 | ((CFG_ROW_ADDR_CYCLE)<<16);
+
+	// set NFC
+	ra_dbg("%s: cmd1: %lx, cmd2:%lx bus_addr: %lx, conf: %lx \n", 
+	       __func__, cmd1, cmd2, bus_addr, conf);
+
+	//fixme, should we check nfc status?
+	CLEAR_INT_STATUS();
+
+	ra_outl(NFC_CMD1, cmd1); 	
+	ra_outl(NFC_CMD2, cmd2);
+	ra_outl(NFC_ADDR, bus_addr);
+	ra_outl(NFC_CONF, conf); 
+
+	status = nfc_wait_ready(3);  //erase wait 3ms 
+	if (status & NAND_STATUS_FAIL) {
+		printk("%s: fail \n", __func__);
+		return -EIO;
+	}
+	
+	return 0;
+
+}
+
+static inline int _nfc_read_raw_data(int cmd1, int cmd2, int bus_addr, int bus_addr2, int conf, char *buf, int len, int flags)
+{
+	int ret;
+
+	CLEAR_INT_STATUS();
+	ra_outl(NFC_CMD1, cmd1); 	
+	ra_outl(NFC_CMD2, cmd2);
+	ra_outl(NFC_ADDR, bus_addr);
+#if defined (CONFIG_RALINK_RT6855) || defined (CONFIG_RALINK_RT6855A) || \
+    defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_MT7621)	
+	ra_outl(NFC_ADDR2, bus_addr2);
+#endif	
+	ra_outl(NFC_CONF, conf); 
+
+	ret = _ra_nand_pull_data(buf, len, 0);
+	if (ret != len) {
+		ra_dbg("%s: ret:%x (%x) \n", __func__, ret, len);
+		return NAND_STATUS_FAIL;
+	}
+
+	//FIXME, this section is not necessary
+	ret = nfc_wait_ready(0); //wait ready 
+	/* to prevent the DATA FIFO 's old data from next operation */
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) | 0x02); //clear data buffer
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) & ~0x02); //clear data buffer
+
+	if (ret & NAND_STATUS_FAIL) {
+		printk("%s: fail \n", __func__);
+		return NAND_STATUS_FAIL;
+	}
+
+	return 0;
+}
+
+static inline int _nfc_write_raw_data(int cmd1, int cmd3, int bus_addr, int bus_addr2, int conf, char *buf, int len, int flags)
+{
+	int ret;
+
+	CLEAR_INT_STATUS();
+	ra_outl(NFC_CMD1, cmd1); 	
+	ra_outl(NFC_CMD3, cmd3); 	
+	ra_outl(NFC_ADDR, bus_addr);
+#if defined (CONFIG_RALINK_RT6855) || defined (CONFIG_RALINK_RT6855A) || \
+    defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_MT7621)	
+	ra_outl(NFC_ADDR2, bus_addr2);
+#endif	
+	ra_outl(NFC_CONF, conf); 
+
+	ret = _ra_nand_push_data(buf, len, 0);
+	if (ret != len) {
+		ra_dbg("%s: ret:%x (%x) \n", __func__, ret, len);
+		return NAND_STATUS_FAIL;
+	}
+
+	ret = nfc_wait_ready(1); //write wait 1ms
+	/* to prevent the DATA FIFO 's old data from next operation */
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) | 0x02); //clear data buffer
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) & ~0x02); //clear data buffer
+
+	if (ret & NAND_STATUS_FAIL) {
+		printk("%s: fail \n", __func__);
+		return NAND_STATUS_FAIL;
+	}
+
+	return 0;
+}
+
+/**
+ * @return !0: fail
+ * @return 0: OK
+ */
+int nfc_read_oob(struct ra_nand_chip *ra, int page, unsigned int offs, char *buf, int len, int flags)
+{
+	unsigned int cmd1 = 0, cmd2 = 0, conf = 0;
+	unsigned int bus_addr = 0, bus_addr2 = 0;
+	unsigned int ecc_en;
+	int use_gdma;
+	int status;
+
+	int pages_perblock = 1<<(ra->erase_shift - ra->page_shift);
+	// constrain of nfc read function 
+
+#if defined (WORKAROUND_RX_BUF_OV)
+	BUG_ON (len > 60); 	//problem of rx-buffer overrun 
+#endif
+	BUG_ON (offs >> ra->oob_shift); //page boundry
+	BUG_ON ((unsigned int)(((offs + len) >> ra->oob_shift) + page) >
+		((page + pages_perblock) & ~(pages_perblock-1))); //block boundry
+
+	use_gdma = flags & FLAG_USE_GDMA;
+	ecc_en = flags & FLAG_ECC_EN;
+	bus_addr = (page << (CFG_COLUMN_ADDR_CYCLE*8)) | (offs & ((1<<CFG_COLUMN_ADDR_CYCLE*8) - 1));
+
+	if (is_nand_page_2048) {
+		bus_addr += CFG_PAGESIZE;
+		bus_addr2 = page >> (CFG_COLUMN_ADDR_CYCLE*8);
+		cmd1 = 0x0;
+		cmd2 = 0x30;
+		conf = 0x000511| ((CFG_ADDR_CYCLE)<<16) | (len << 20); 
+	}
+	else {
+		cmd1 = 0x50;
+		conf = 0x000141| ((CFG_ADDR_CYCLE)<<16) | (len << 20); 
+	}
+	if (ecc_en) 
+		conf |= (1<<3); 
+	if (use_gdma)
+		conf |= (1<<2);
+
+	ra_dbg("%s: cmd1:%x, bus_addr:%x, conf:%x, len:%x, flag:%x\n",
+	       __func__, cmd1, bus_addr, conf, len, flags);
+
+	status = _nfc_read_raw_data(cmd1, cmd2, bus_addr, bus_addr2, conf, buf, len, flags);
+	if (status & NAND_STATUS_FAIL) {
+		printk("%s: fail\n", __func__);
+		return -EIO;
+	}
+
+	return 0; 
+}
+
+/**
+ * @return !0: fail
+ * @return 0: OK
+ */
+int nfc_write_oob(struct ra_nand_chip *ra, int page, unsigned int offs, char *buf, int len, int flags)
+{
+	unsigned int cmd1 = 0, cmd3=0, conf = 0;
+	unsigned int bus_addr = 0, bus_addr2 = 0;
+	int use_gdma;
+	int status;
+
+	int pages_perblock = 1<<(ra->erase_shift - ra->page_shift);
+	// constrain of nfc read function 
+
+	BUG_ON (offs >> ra->oob_shift); //page boundry
+	BUG_ON ((unsigned int)(((offs + len) >> ra->oob_shift) + page) >
+		((page + pages_perblock) & ~(pages_perblock-1))); //block boundry 
+
+	use_gdma = flags & FLAG_USE_GDMA;
+	bus_addr = (page << (CFG_COLUMN_ADDR_CYCLE*8)) | (offs & ((1<<CFG_COLUMN_ADDR_CYCLE*8) - 1));
+
+	if (is_nand_page_2048) {
+		cmd1 = 0x80;
+		cmd3 = 0x10;
+		bus_addr += CFG_PAGESIZE;
+		bus_addr2 = page >> (CFG_COLUMN_ADDR_CYCLE*8);
+		conf = 0x001123 | ((CFG_ADDR_CYCLE)<<16) | ((len) << 20);
+	}
+	else {
+		cmd1 = 0x08050;
+		cmd3 = 0x10;
+		conf = 0x001223 | ((CFG_ADDR_CYCLE)<<16) | ((len) << 20); 
+	}
+	if (use_gdma)
+		conf |= (1<<2);
+
+	// set NFC
+	ra_dbg("%s: cmd1: %x, cmd3: %x bus_addr: %x, conf: %x, len:%x\n", 
+	       __func__, cmd1, cmd3, bus_addr, conf, len);
+
+	status = _nfc_write_raw_data(cmd1, cmd3, bus_addr, bus_addr2, conf, buf, len, flags);
+	if (status & NAND_STATUS_FAIL) {
+		printk("%s: fail \n", __func__);
+		return -EIO;
+	}
+
+	return 0; 
+}
+
+
+int nfc_read_page(struct ra_nand_chip *ra, char *buf, int page, int flags);
+int nfc_write_page(struct ra_nand_chip *ra, char *buf, int page, int flags);
+
+
+#if !defined (WORKAROUND_RX_BUF_OV)	
+static int one_bit_correction(char *ecc, char *expected, int *bytes, int *bits);
+int nfc_ecc_verify(struct ra_nand_chip *ra, char *buf, int page, int mode)
+{
+	int ret, i;
+	char *p, *e;
+	int ecc;
+	
+	//ra_dbg("%s, page:%x mode:%d\n", __func__, page, mode);
+
+	if (mode == FL_WRITING) {
+		int len = CFG_PAGESIZE + CFG_PAGE_OOBSIZE;
+		int conf = 0x000141| ((CFG_ADDR_CYCLE)<<16) | (len << 20); 
+		conf |= (1<<3); //(ecc_en) 
+		//conf |= (1<<2); // (use_gdma)
+
+		p = ra->readback_buffers;
+		ret = nfc_read_page(ra, ra->readback_buffers, page, FLAG_ECC_EN); 
+		if (ret == 0) 
+			goto ecc_check;
+		
+		//FIXME, double comfirm
+		printk("%s: read back fail, try again \n",__func__);
+		ret = nfc_read_page(ra, ra->readback_buffers, page, FLAG_ECC_EN); 
+		if (ret != 0) {
+			printk("\t%s: read back fail agian \n",__func__);
+			goto bad_block;
+		}
+	}
+	else if (mode == FL_READING) {
+		p = buf;
+	}	
+	else
+		return -2;
+
+ecc_check:
+	p += CFG_PAGESIZE;
+	if (!is_nand_page_2048) {
+		ecc = ra_inl(NFC_ECC); 
+		if (ecc == 0) //clean page.
+			return 0;
+		e = (char*)&ecc;
+		for (i=0; i<CONFIG_ECC_BYTES; i++) {
+			int eccpos = CONFIG_ECC_OFFSET + i;
+			if (*(p + eccpos) != (char)0xff)
+				break;
+			if (i == CONFIG_ECC_BYTES - 1) {
+				printk("skip ecc 0xff at page %x\n", page);
+				return 0;
+			}
+		}
+		for (i=0; i<CONFIG_ECC_BYTES; i++) {
+			int eccpos = CONFIG_ECC_OFFSET + i;
+			if (*(p + eccpos) != *(e + i)) {
+				printk("%s mode:%s, invalid ecc, page: %x read:%x %x %x, ecc:%x \n",
+						__func__, (mode == FL_READING)?"read":"write", page,	
+						*(p+ CONFIG_ECC_OFFSET), *(p+ CONFIG_ECC_OFFSET+1), *(p+ CONFIG_ECC_OFFSET +2), ecc);
+				return -1;
+			}
+		}
+	}
+#if defined (CONFIG_RALINK_RT6855) || defined (CONFIG_RALINK_RT6855A) || \
+    defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_MT7621)	
+	else {
+		int ecc2, ecc3, ecc4, qsz;
+		char *e2, *e3, *e4;
+		int correction_flag = 0;
+		ecc = ra_inl(NFC_ECC_P1);
+		ecc2 = ra_inl(NFC_ECC_P2);
+		ecc3 = ra_inl(NFC_ECC_P3);
+		ecc4 = ra_inl(NFC_ECC_P4);
+		e = (char*)&ecc;
+		e2 = (char*)&ecc2;
+		e3 = (char*)&ecc3;
+		e4 = (char*)&ecc4;
+		qsz = CFG_PAGE_OOBSIZE / 4;
+		if (ecc == 0 && ecc2 == 0 && ecc3 == 0 && ecc4 == 0)
+			return 0;
+		for (i=0; i<CONFIG_ECC_BYTES; i++) {
+			int eccpos = CONFIG_ECC_OFFSET + i;
+			if (*(p + eccpos) != (char)0xff)
+				break;
+			else if (*(p + eccpos + qsz) != (char)0xff)
+				break;
+			else if (*(p + eccpos + qsz*2) != (char)0xff)
+				break;
+			else if (*(p + eccpos + qsz*3) != (char)0xff)
+				break;
+			if (i == CONFIG_ECC_BYTES - 1) {
+				printk("skip ecc 0xff at page %x\n", page);
+				return 0;
+			}
+		}
+		for (i=0; i<CONFIG_ECC_BYTES; i++) {
+			int eccpos = CONFIG_ECC_OFFSET + i;
+			if (*(p + eccpos) != *(e + i)) {
+				printk("%s mode:%s, invalid ecc, page: %x read:%x %x %x, ecc:%x \n",
+						__func__, (mode == FL_READING)?"read":"write", page,
+						*(p+ CONFIG_ECC_OFFSET), *(p+ CONFIG_ECC_OFFSET+1), *(p+ CONFIG_ECC_OFFSET +2), ecc);
+				correction_flag |= 0x1;
+			}
+			if (*(p + eccpos + qsz) != *(e2 + i)) {
+				printk("%s mode:%s, invalid ecc2, page: %x read:%x %x %x, ecc2:%x \n",
+						__func__, (mode == FL_READING)?"read":"write", page,
+						*(p+CONFIG_ECC_OFFSET+qsz), *(p+ CONFIG_ECC_OFFSET+1+qsz), *(p+ CONFIG_ECC_OFFSET+2+qsz), ecc2);
+				correction_flag |= 0x2;
+			}
+			if (*(p + eccpos + qsz*2) != *(e3 + i)) {
+				printk("%s mode:%s, invalid ecc3, page: %x read:%x %x %x, ecc3:%x \n",
+						__func__, (mode == FL_READING)?"read":"write", page,
+						*(p+CONFIG_ECC_OFFSET+qsz*2), *(p+ CONFIG_ECC_OFFSET+1+qsz*2), *(p+ CONFIG_ECC_OFFSET+2+qsz*2), ecc3);
+				correction_flag |= 0x4;
+			}
+			if (*(p + eccpos + qsz*3) != *(e4 + i)) {
+				printk("%s mode:%s, invalid ecc4, page: %x read:%x %x %x, ecc4:%x \n",
+						__func__, (mode == FL_READING)?"read":"write", page,
+						*(p+CONFIG_ECC_OFFSET+qsz*3), *(p+ CONFIG_ECC_OFFSET+1+qsz*3), *(p+ CONFIG_ECC_OFFSET+2+qsz*3), ecc4);
+				correction_flag |= 0x8;
+			}
+		}
+
+		if (correction_flag)
+		{
+			printk("trying to do correction!\n");
+			if (correction_flag & 0x1)
+			{
+				int bytes, bits;
+				char *pBuf = p - CFG_PAGESIZE;
+			
+				if (one_bit_correction(p + CONFIG_ECC_OFFSET, e, &bytes, &bits) == 0)
+				{
+					pBuf[bytes] = pBuf[bytes] ^ (1 << bits);
+					printk("1. correct byte %d, bit %d!\n", bytes, bits);
+				}
+				else
+				{
+					printk("failed to correct!\n");
+					return -1;
+				}
+			}
+
+			if (correction_flag & 0x2)
+			{
+				int bytes, bits;
+				char *pBuf = (p - CFG_PAGESIZE) + CFG_PAGESIZE/4;
+			
+				if (one_bit_correction((p + CONFIG_ECC_OFFSET + qsz), e2, &bytes, &bits) == 0)
+				{
+					pBuf[bytes] = pBuf[bytes] ^ (1 << bits);
+					printk("2. correct byte %d, bit %d!\n", bytes, bits);
+				}
+				else
+				{
+					printk("failed to correct!\n");
+					return -1;
+				}
+			}
+			if (correction_flag & 0x4)
+			{
+				int bytes, bits;
+				char *pBuf = (p - CFG_PAGESIZE) + CFG_PAGESIZE/2;
+			
+				if (one_bit_correction((p + CONFIG_ECC_OFFSET + qsz * 2), e3, &bytes, &bits) == 0)
+				{
+					pBuf[bytes] = pBuf[bytes] ^ (1 << bits);
+					printk("3. correct byte %d, bit %d!\n", bytes, bits);
+				}
+				else
+				{
+					printk("failed to correct!\n");
+					return -1;
+				}
+			}
+			if (correction_flag & 0x8)
+			{
+				int bytes, bits;
+				char *pBuf = (p - CFG_PAGESIZE) + CFG_PAGESIZE*3/4;
+			
+				if (one_bit_correction((p + CONFIG_ECC_OFFSET + qsz * 3), e4, &bytes, &bits) == 0)
+				{
+					pBuf[bytes] = pBuf[bytes] ^ (1 << bits);
+					printk("4. correct byte %d, bit %d!\n", bytes, bits);
+				}
+				else
+				{
+					printk("failed to correct!\n");
+					return -1;
+				}
+			}
+		}
+
+	}
+#endif	
+	return 0;
+
+bad_block:
+	return -1;
+}
+
+#else
+
+void ranfc_dump(void) 
+{	
+	int i;
+	for (i=0; i<11; i++) {
+		if (i==6) 
+			continue;
+		printk("%x: %x \n", NFC_BASE + i*4, ra_inl(NFC_BASE + i*4));
+	}
+}
+
+/**
+ * @return 0, ecc OK or corrected.
+ * @return NAND_STATUS_FAIL, ecc fail.   
+ */
+
+int nfc_ecc_verify(struct ra_nand_chip *ra, char *buf, int page, int mode)
+{
+	int ret, i;
+	char *p, *e;
+	int ecc;
+	
+	if (ranfc_verify == 0)
+		return 0;
+
+	ra_dbg("%s, page:%x mode:%d\n", __func__, page, mode);
+
+	if (mode == FL_WRITING) { // read back and memcmp
+		ret = nfc_read_page(ra, ra->readback_buffers, page, FLAG_NONE); 
+		if (ret != 0) //double comfirm
+			ret = nfc_read_page(ra, ra->readback_buffers, page, FLAG_NONE); 
+
+		if (ret != 0) {
+			printk("%s: mode:%x read back fail \n", __func__, mode);
+			return -1;
+		}
+		return memcmp(buf, ra->readback_buffers, 1<<ra->page_shift);
+	}
+	
+	if (mode == FL_READING) { 
+#if 0
+		if (ra->sandbox_page == 0)
+			return 0;
+
+		ret = nfc_write_page(ra, buf, ra->sandbox_page, FLAG_USE_GDMA | FLAG_ECC_EN);
+		if (ret != 0) {
+			printk("%s, fail write sandbox_page \n", __func__);
+			return -1;
+		}
+#else
+		/** @note: 
+		 * The following command is actually not 'write' command to drive NFC to write flash.
+		 * However, it can make NFC to calculate ECC, that will be used to compare with original ones.
+		 * --YT
+		 */
+		unsigned int conf = 0x001223| (CFG_ADDR_CYCLE<<16) | (0x200 << 20) | (1<<3) | (1<<2); 
+		_nfc_write_raw_data(0xff, 0xff, ra->sandbox_page<<ra->page_shift, conf, buf, 0x200, FLAG_USE_GDMA);
+#endif
+
+		ecc = ra_inl(NFC_ECC); 
+		if (ecc == 0) //clean page.
+			return 0;
+		e = (char*)&ecc;
+		p = buf + (1<<ra->page_shift);
+		for (i=0; i<CONFIG_ECC_BYTES; i++) {
+			int eccpos = CONFIG_ECC_OFFSET + i;
+			if (*(p + eccpos) != *(e + i)) {
+				printk("%s mode:%s, invalid ecc, page: %x read:%x %x %x, write:%x \n",
+				       __func__, (mode == FL_READING)?"read":"write", page,	
+				       *(p+ CONFIG_ECC_OFFSET), *(p+ CONFIG_ECC_OFFSET+1), *(p+ CONFIG_ECC_OFFSET +2), ecc);
+
+				for (i=0; i<528; i++)
+					printk("%-2x \n", *(buf + i));
+				return -1;
+			}
+		}
+		return 0;
+	}
+
+	return -1;
+
+}
+
+#endif
+
+
+/**
+ * @return -EIO, writing size is less than a page 
+ * @return 0, OK
+ */
+int nfc_read_page(struct ra_nand_chip *ra, char *buf, int page, int flags)
+{
+	unsigned int cmd1 = 0, cmd2 = 0, conf = 0;
+	unsigned int bus_addr = 0, bus_addr2 = 0;
+	unsigned int ecc_en;
+	int use_gdma;
+	int size, offs;
+	int status = 0;
+
+	use_gdma = flags & FLAG_USE_GDMA;
+	ecc_en = flags & FLAG_ECC_EN;
+
+	page = page & (CFG_CHIPSIZE - 1); // chip boundary
+	size = CFG_PAGESIZE + CFG_PAGE_OOBSIZE; //add oobsize
+	offs = 0;
+
+	while (size > 0) {
+		int len;
+#if defined (WORKAROUND_RX_BUF_OV)
+		len = min(60, size);
+#else
+		len = size;
+#endif		
+		bus_addr = (page << (CFG_COLUMN_ADDR_CYCLE*8)) | (offs & ((1<<CFG_COLUMN_ADDR_CYCLE*8)-1)); 
+		if (is_nand_page_2048) {
+			bus_addr2 = page >> (CFG_COLUMN_ADDR_CYCLE*8);
+			cmd1 = 0x0;
+			cmd2 = 0x30;
+			conf = 0x000511| ((CFG_ADDR_CYCLE)<<16) | (len << 20); 
+		}
+		else {
+			if (offs & ~(CFG_PAGESIZE-1))
+				cmd1 = 0x50;
+			else if (offs & ~((1<<CFG_COLUMN_ADDR_CYCLE*8)-1))
+				cmd1 = 0x01;
+			else
+				cmd1 = 0;
+
+			conf = 0x000141| ((CFG_ADDR_CYCLE)<<16) | (len << 20); 
+		}
+#if !defined (WORKAROUND_RX_BUF_OV)
+		if (ecc_en) 
+			conf |= (1<<3); 
+#endif
+		if (use_gdma)
+			conf |= (1<<2);
+
+		status = _nfc_read_raw_data(cmd1, cmd2, bus_addr, bus_addr2, conf, buf+offs, len, flags);
+		if (status & NAND_STATUS_FAIL) {
+			printk("%s: fail \n", __func__);
+			return -EIO;
+		}
+
+		offs += len;
+		size -= len;
+	}
+
+	// verify and correct ecc
+	if ((flags & (FLAG_VERIFY | FLAG_ECC_EN)) == (FLAG_VERIFY | FLAG_ECC_EN)) {
+		status = nfc_ecc_verify(ra, buf, page, FL_READING);	
+		if (status != 0) {
+			printk("%s: fail, buf:%x, page:%x, flag:%x\n", 
+			       __func__, (unsigned int)buf, page, flags);
+			return -EBADMSG;
+		}
+	}
+	else {
+		// fix,e not yet support
+		ra->buffers_page = -1; //cached
+	}
+
+	return 0;
+}
+
+
+/** 
+ * @return -EIO, fail to write
+ * @return 0, OK
+ */
+int nfc_write_page(struct ra_nand_chip *ra, char *buf, int page, int flags)
+{
+	unsigned int cmd1 = 0, cmd3, conf = 0;
+	unsigned int bus_addr = 0, bus_addr2 = 0;
+	unsigned int ecc_en;
+	int use_gdma;
+	int size;
+	char status;
+	uint8_t *oob = buf + (1<<ra->page_shift);
+
+	use_gdma = flags & FLAG_USE_GDMA;
+	ecc_en = flags & FLAG_ECC_EN;
+
+	oob[ra->badblockpos] = 0xff;	//tag as good block.
+	ra->buffers_page = -1; //cached
+
+	page = page & (CFG_CHIPSIZE-1); //chip boundary
+	size = CFG_PAGESIZE + CFG_PAGE_OOBSIZE; //add oobsize
+	bus_addr = (page << (CFG_COLUMN_ADDR_CYCLE*8)); //write_page always write from offset 0.
+
+	if (is_nand_page_2048) {
+	bus_addr2 = page >> (CFG_COLUMN_ADDR_CYCLE*8);
+		cmd1 = 0x80;
+		cmd3 = 0x10;
+		conf = 0x001123| ((CFG_ADDR_CYCLE)<<16) | (size << 20); 
+	}
+	else {
+	cmd1 = 0x8000;
+	cmd3 = 0x10;
+	conf = 0x001223| ((CFG_ADDR_CYCLE)<<16) | (size << 20); 
+}
+	if (ecc_en) 
+		conf |= (1<<3); //enable ecc
+	if (use_gdma)
+		conf |= (1<<2);
+
+	// set NFC
+	ra_dbg("nfc_write_page: cmd1: %x, cmd3: %x bus_addr: %x, conf: %x, len:%x\n", 
+	       cmd1, cmd3, bus_addr, conf, size);
+
+	status = _nfc_write_raw_data(cmd1, cmd3, bus_addr, bus_addr2, conf, buf, size, flags);
+	if (status & NAND_STATUS_FAIL) {
+		printk("%s: fail \n", __func__);
+		return -EIO;
+	}
+	
+
+	if (flags & FLAG_VERIFY) { // verify and correct ecc
+		status = nfc_ecc_verify(ra, buf, page, FL_WRITING);
+
+#ifdef RANDOM_GEN_BAD_BLOCK
+		if (((random32() & 0x1ff) == 0x0) && (page >= 0x100)) // randomly create bad block
+		{
+			printk("hmm... create a bad block at page %x\n", (bus_addr >> 16));
+			status = -1;
+		}
+#endif
+
+		if (status != 0) {
+			printk("%s: ecc_verify fail: ret:%x \n", __func__, status);
+			oob[ra->badblockpos] = 0x33; 
+			page -= page % (CFG_BLOCKSIZE/CFG_PAGESIZE);
+			printk("create a bad block at page %x\n", page);
+			if (!is_nand_page_2048)
+				status = nfc_write_oob(ra, page, ra->badblockpos, oob+ra->badblockpos, 1, flags);
+			else
+			{
+				status = _nfc_write_raw_data(cmd1, cmd3, bus_addr, bus_addr2, conf, buf, size, flags);
+				nfc_write_oob(ra, page, 0, oob, 16, FLAG_NONE);
+			}
+			return -EBADMSG;
+		}
+	}
+
+
+	ra->buffers_page = page; //cached
+	return 0;
+}
+
+
+
+/*************************************************************
+ * nand internal process 
+ *************************************************************/
+
+/**
+ * nand_release_device - [GENERIC] release chip
+ * @mtd:	MTD device structure
+ *
+ * Deselect, release chip lock and wake up anyone waiting on the device
+ */
+static void nand_release_device(struct ra_nand_chip *ra)
+{
+	/* De-select the NAND device */
+	nfc_select_chip(ra, -1);
+
+	/* Release the controller and the chip */
+	ra->state = FL_READY;
+
+	mutex_unlock(ra->controller);
+}
+
+/**
+ * nand_get_device - [GENERIC] Get chip for selected access
+ * @chip:	the nand chip descriptor
+ * @mtd:	MTD device structure
+ * @new_state:	the state which is requested
+ *
+ * Get the device and lock it for exclusive access
+ */
+static int
+nand_get_device(struct ra_nand_chip *ra, int new_state)
+{
+	int ret = 0;
+
+	ret = mutex_lock_interruptible(ra->controller);
+	if (!ret) 
+		ra->state = new_state;
+
+	return ret;
+
+}
+
+
+
+/*************************************************************
+ * nand internal process 
+ *************************************************************/
+
+int nand_bbt_get(struct ra_nand_chip *ra, int block)
+{
+	int byte, bits;
+	bits = block * BBTTAG_BITS;
+
+	byte = bits / 8;
+	bits = bits % 8;
+	
+	return (ra->bbt[byte] >> bits) & BBTTAG_BITS_MASK;
+}
+
+int nand_bbt_set(struct ra_nand_chip *ra, int block, int tag)
+{
+	int byte, bits;
+	bits = block * BBTTAG_BITS;
+
+	byte = bits / 8;
+	bits = bits % 8;
+
+	// If previous tag is bad, dont overwrite it	
+	if (((ra->bbt[byte] >> bits) & BBTTAG_BITS_MASK) == BBT_TAG_BAD)
+	{
+		return BBT_TAG_BAD;
+	}
+
+	ra->bbt[byte] = (ra->bbt[byte] & ~(BBTTAG_BITS_MASK << bits)) | ((tag & BBTTAG_BITS_MASK) << bits);
+		
+	return tag;
+}
+
+/**
+ * nand_block_checkbad - [GENERIC] Check if a block is marked bad
+ * @mtd:	MTD device structure
+ * @ofs:	offset from device start
+ *
+ * Check, if the block is bad. Either by reading the bad block table or
+ * calling of the scan function.
+ */
+int nand_block_checkbad(struct ra_nand_chip *ra, loff_t offs)
+{
+	int page, block;
+	int ret = 4;
+	unsigned int tag;
+	char *str[]= {"UNK", "RES", "BAD", "GOOD"};
+
+	if (ranfc_bbt == 0)
+		return 0;
+
+	{
+		// align with chip
+
+		offs = offs & ((1<<ra->chip_shift) -1);
+
+		page = offs >> ra->page_shift;
+		block = offs >> ra->erase_shift;
+	}
+
+	tag = nand_bbt_get(ra, block);
+
+	if (tag == BBT_TAG_UNKNOWN) {
+		ret = nfc_read_oob(ra, page, ra->badblockpos, (char*)&tag, 1, FLAG_NONE);
+		if (ret == 0)
+			tag = ((le32_to_cpu(tag) & 0x0ff) == 0x0ff) ? BBT_TAG_GOOD : BBT_TAG_BAD;
+		else
+			tag = BBT_TAG_BAD;
+
+		nand_bbt_set(ra, block, tag);
+	}
+
+	if (tag != BBT_TAG_GOOD) {
+		printk("%s: offs:%x tag: %s \n", __func__, (unsigned int)offs, str[tag]);
+		return 1;
+	}
+	else 
+		return 0;
+	
+}
+
+
+
+/**
+ * nand_block_markbad -
+ */
+int nand_block_markbad(struct ra_nand_chip *ra, loff_t offs)
+{
+	int page, block;
+	int ret = 4;
+	unsigned int tag;
+	char *ecc;
+
+	// align with chip
+	ra_dbg("%s offs: %x \n", __func__, (int)offs);
+
+	offs = offs & ((1<<ra->chip_shift) -1);
+
+	page = offs >> ra->page_shift;
+	block = offs >> ra->erase_shift;
+
+	tag = nand_bbt_get(ra, block);
+
+	if (tag == BBT_TAG_BAD) {
+		printk("%s: mark repeatedly \n", __func__);
+		return 0;
+	}
+
+	// new tag as bad
+	tag =BBT_TAG_BAD;
+	ret = nfc_read_page(ra, ra->buffers, page, FLAG_NONE);
+	if (ret != 0) {
+		printk("%s: fail to read bad block tag \n", __func__);
+		goto tag_bbt;
+	}
+
+	ecc = &ra->buffers[(1<<ra->page_shift)+ra->badblockpos];
+	if (*ecc == (char)0x0ff) {
+		//tag into flash
+		*ecc = (char)tag;
+		ret = nfc_write_page(ra, ra->buffers, page, FLAG_USE_GDMA);
+		if (ret)
+			printk("%s: fail to write bad block tag \n", __func__);
+		
+	}	
+
+tag_bbt:
+	//update bbt
+	nand_bbt_set(ra, block, tag);
+
+	return 0;
+}
+
+
+#if defined (WORKAROUND_RX_BUF_OV)
+/**
+ * to find a bad block for ecc verify of read_page
+ */
+unsigned int nand_bbt_find_sandbox(struct ra_nand_chip *ra)
+{
+	loff_t offs = 0;
+	int chipsize = 1 << ra->chip_shift;
+	int blocksize = 1 << ra->erase_shift;
+
+	
+	while (offs < chipsize) {
+		if (nand_block_checkbad(ra, offs)) //scan and verify the unknown tag
+			break;
+		offs += blocksize;
+	}
+
+	if (offs >= chipsize) {
+		offs = chipsize - blocksize;
+	}
+
+	nand_bbt_set(ra, (unsigned int)offs>>ra->erase_shift, BBT_TAG_RES);	 // tag bbt only, instead of update badblockpos of flash.
+	return (offs >> ra->page_shift);
+}
+#endif
+
+
+
+/**
+ * nand_erase_nand - [Internal] erase block(s)
+ * @mtd:	MTD device structure
+ * @instr:	erase instruction
+ * @allowbbt:	allow erasing the bbt area
+ *
+ * Erase one ore more blocks
+ */
+int _nand_erase_nand(struct ra_nand_chip *ra, struct erase_info *instr)
+{
+	int page, len, status, ret;
+	unsigned int addr, blocksize = 1<<ra->erase_shift;
+
+	ra_dbg("%s: start:%x, len:%x \n", __func__, 
+	       (unsigned int)instr->addr, (unsigned int)instr->len);
+
+//#define BLOCK_ALIGNED(a) ((a) & (blocksize - 1)) // already defined
+
+	if (BLOCK_ALIGNED(instr->addr) || BLOCK_ALIGNED(instr->len)) {
+		ra_dbg("%s: erase block not aligned, addr:%x len:%x\n", __func__, instr->addr, instr->len);
+		return -EINVAL;
+	}
+
+	instr->fail_addr = 0xffffffff;
+
+	len = instr->len;
+	addr = instr->addr;
+	instr->state = MTD_ERASING;
+
+	while (len) {
+
+		page = (int)(addr >> ra->page_shift);
+
+		/* select device and check wp */
+		if (nfc_enable_chip(ra, addr, 0)) {
+			printk("%s: nand is write protected \n", __func__);
+			instr->state = MTD_ERASE_FAILED;
+			goto erase_exit;
+		}
+
+		/* if we have a bad block, we do not erase bad blocks */
+		if (nand_block_checkbad(ra, addr)) {
+			printk(KERN_WARNING "nand_erase: attempt to erase a "
+			       "bad block at 0x%08x\n", addr);
+			instr->state = MTD_ERASE_FAILED;
+			goto erase_exit;
+		}
+
+		/*
+		 * Invalidate the page cache, if we erase the block which
+		 * contains the current cached page
+		 */
+		if (BLOCK_ALIGNED(addr) == BLOCK_ALIGNED(ra->buffers_page << ra->page_shift))
+			ra->buffers_page = -1;
+
+		status = nfc_erase_block(ra, page);
+		/* See if block erase succeeded */
+		if (status) {
+			printk("%s: failed erase, page 0x%08x\n", __func__, page);
+			instr->state = MTD_ERASE_FAILED;
+			instr->fail_addr = (page << ra->page_shift);
+			goto erase_exit;
+		}
+
+
+		/* Increment page address and decrement length */
+		len -= blocksize;
+		addr += blocksize;
+
+	}
+	instr->state = MTD_ERASE_DONE;
+
+erase_exit:
+
+	ret = ((instr->state == MTD_ERASE_DONE) ? 0 : -EIO);
+	/* Do call back function */
+	if (!ret)
+		mtd_erase_callback(instr);
+
+	if (ret) {
+		nand_bbt_set(ra, addr >> ra->erase_shift, BBT_TAG_BAD);
+	}
+
+	/* Return more or less happy */
+	return ret;
+}
+
+static int
+nand_write_oob_buf(struct ra_nand_chip *ra, uint8_t *buf, uint8_t *oob, size_t size,
+		   int mode, int ooboffs)
+{
+	size_t oobsize = 1<<ra->oob_shift;
+	struct nand_oobfree *free;
+	uint32_t woffs = ooboffs;
+	int retsize = 0;
+
+	ra_dbg("%s: size:%x, mode:%x, offs:%x  \n", __func__, size, mode, ooboffs);
+
+	switch(mode) {
+	case MTD_OPS_PLACE_OOB:
+	case MTD_OPS_RAW:
+		if (ooboffs > oobsize)
+			return -1;
+
+		size = min(size, oobsize - ooboffs);
+		memcpy(buf + ooboffs, oob, size);
+		retsize = size;
+		break;
+
+	case MTD_OPS_AUTO_OOB:
+		if (ooboffs > ra->oob->oobavail)
+			return -1;
+
+		while (size) {
+			for(free = ra->oob->oobfree; free->length && size; free++) {
+				int wlen = free->length - woffs;
+				int bytes = 0;
+
+				/* Write request not from offset 0 ? */
+				if (wlen <= 0) {
+					woffs = -wlen;
+					continue;
+				}
+
+				bytes = min_t(size_t, size, wlen);
+				memcpy (buf + free->offset + woffs, oob, bytes);
+				woffs = 0;
+				oob += bytes;
+				size -= bytes;
+				retsize += bytes;
+			}
+			buf += oobsize;
+		}
+		break;
+
+	default:
+		BUG();
+	}
+
+	return retsize;
+}
+
+static int nand_read_oob_buf(struct ra_nand_chip *ra, uint8_t *oob, size_t size, 
+			     int mode, int ooboffs) 
+{
+	size_t oobsize = 1<<ra->oob_shift;
+	uint8_t *buf = ra->buffers + (1<<ra->page_shift);
+	int retsize=0;
+
+	ra_dbg("%s: size:%x, mode:%x, offs:%x  \n", __func__, size, mode, ooboffs);
+
+	switch(mode) {
+	case MTD_OPS_PLACE_OOB:
+	case MTD_OPS_RAW:
+		if (ooboffs > oobsize)
+			return -1;
+
+		size = min(size, oobsize - ooboffs);
+		memcpy(oob, buf + ooboffs, size);
+		return size;
+
+	case MTD_OPS_AUTO_OOB: {
+		struct nand_oobfree *free;
+		uint32_t woffs = ooboffs;
+
+		if (ooboffs > ra->oob->oobavail) 
+			return -1;
+		
+		size = min(size, ra->oob->oobavail - ooboffs);
+		for(free = ra->oob->oobfree; free->length && size; free++) {
+			int wlen = free->length - woffs;
+			int bytes = 0;
+
+			/* Write request not from offset 0 ? */
+			if (wlen <= 0) {
+				woffs = -wlen;
+				continue;
+			}
+			
+			bytes = min_t(size_t, size, wlen);
+			memcpy (oob, buf + free->offset + woffs, bytes);
+			woffs = 0;
+			oob += bytes;
+			size -= bytes;
+			retsize += bytes;
+		}
+		return retsize;
+	}
+	default:
+		BUG();
+	}
+	
+	return -1;
+}
+
+/**
+ * nand_do_write_ops - [Internal] NAND write with ECC
+ * @mtd:	MTD device structure
+ * @to:		offset to write to
+ * @ops:	oob operations description structure
+ *
+ * NAND write with ECC
+ */
+static int nand_do_write_ops(struct ra_nand_chip *ra, loff_t to,
+			     struct mtd_oob_ops *ops)
+{
+	int page;
+	uint32_t datalen = ops->len;
+	uint32_t ooblen = ops->ooblen;
+	uint8_t *oob = ops->oobbuf;
+	uint8_t *data = ops->datbuf;
+	int pagesize = (1<<ra->page_shift);
+	int pagemask = (pagesize -1);
+	int oobsize = 1<<ra->oob_shift;
+	loff_t addr = to;
+	//int i = 0; //for ra_dbg only
+
+	ra_dbg("%s: to:%x, ops data:%p, oob:%p datalen:%x ooblen:%x, ooboffs:%x oobmode:%x \n", 
+	       __func__, (unsigned int)to, data, oob, datalen, ooblen, ops->ooboffs, ops->mode);
+
+	ops->retlen = 0;
+	ops->oobretlen = 0;
+
+
+	/* Invalidate the page cache, when we write to the cached page */
+	ra->buffers_page = -1;
+
+	
+	if (data ==0)
+		datalen = 0;
+	
+	// oob sequential (burst) write
+	if (datalen == 0 && ooblen) {
+		int len = ((ooblen + ops->ooboffs) + (ra->oob->oobavail - 1)) / ra->oob->oobavail * oobsize;
+
+		/* select chip, and check if it is write protected */
+		if (nfc_enable_chip(ra, addr, 0))
+			return -EIO;
+
+		//FIXME, need sanity check of block boundary
+		page = (int)((to & ((1<<ra->chip_shift)-1)) >> ra->page_shift); //chip boundary
+		memset(ra->buffers, 0x0ff, pagesize);
+		//fixme, should we reserve the original content?
+		if (ops->mode == MTD_OPS_AUTO_OOB) {
+			nfc_read_oob(ra, page, 0, ra->buffers, len, FLAG_NONE);
+		}
+		//prepare buffers
+		if (ooblen != 8)
+		{
+			nand_write_oob_buf(ra, ra->buffers, oob, ooblen, ops->mode, ops->ooboffs);
+			// write out buffer to chip
+			nfc_write_oob(ra, page, 0, ra->buffers, len, FLAG_USE_GDMA);
+		}
+
+		ops->oobretlen = ooblen;
+		ooblen = 0;
+	}
+
+	// data sequential (burst) write
+	if (datalen && ooblen == 0) {
+		// ranfc can not support write_data_burst, since hw-ecc and fifo constraints..
+	}
+
+	// page write
+	while(datalen || ooblen) {
+		int len;
+		int ret;
+		int offs;
+		int ecc_en = 0;
+
+		ra_dbg("%s (%d): addr:%x, ops data:%p, oob:%p datalen:%x ooblen:%x, ooboffs:%x \n", 
+		       __func__, i++, (unsigned int)addr, data, oob, datalen, ooblen, ops->ooboffs);
+
+		page = (int)((addr & ((1<<ra->chip_shift)-1)) >> ra->page_shift); //chip boundary
+		
+		/* select chip, and check if it is write protected */
+		if (nfc_enable_chip(ra, addr, 0))
+			return -EIO;
+
+		// oob write
+		if (ops->mode == MTD_OPS_AUTO_OOB) {
+			//fixme, this path is not yet varified 
+			nfc_read_oob(ra, page, 0, ra->buffers + pagesize, oobsize, FLAG_NONE);
+		}
+		if (oob && ooblen > 0) {
+			len = nand_write_oob_buf(ra, ra->buffers + pagesize, oob, ooblen, ops->mode, ops->ooboffs);
+			if (len < 0) 
+				return -EINVAL;
+			
+			oob += len;
+			ops->oobretlen += len;
+			ooblen -= len;
+		}
+
+		// data write
+		offs = addr & pagemask;
+		len = min_t(size_t, datalen, pagesize - offs);
+		if (data && len > 0) {
+			memcpy(ra->buffers + offs, data, len);	// we can not sure ops->buf wether is DMA-able.
+
+			data += len;
+			datalen -= len;
+			ops->retlen += len;
+
+			ecc_en = FLAG_ECC_EN;
+		}
+		ret = nfc_write_page(ra, ra->buffers, page, FLAG_USE_GDMA | FLAG_VERIFY |
+				     ((ops->mode == MTD_OPS_RAW || ops->mode == MTD_OPS_PLACE_OOB) ? 0 : ecc_en ));
+		if (ret) {
+			nand_bbt_set(ra, addr >> ra->erase_shift, BBT_TAG_BAD);
+			return ret;
+		}
+
+		nand_bbt_set(ra, addr >> ra->erase_shift, BBT_TAG_GOOD);
+
+		addr = (page+1) << ra->page_shift;
+
+	}
+	return 0;
+}
+
+/**
+ * nand_do_read_ops - [Internal] Read data with ECC
+ *
+ * @mtd:	MTD device structure
+ * @from:	offset to read from
+ * @ops:	oob ops structure
+ *
+ * Internal function. Called with chip held.
+ */
+static int nand_do_read_ops(struct ra_nand_chip *ra, loff_t from,
+			    struct mtd_oob_ops *ops)
+{
+	int page;
+	uint32_t datalen = ops->len;
+	uint32_t ooblen = ops->ooblen;
+	uint8_t *oob = ops->oobbuf;
+	uint8_t *data = ops->datbuf;
+	int pagesize = (1<<ra->page_shift);
+	int pagemask = (pagesize -1);
+	loff_t addr = from;
+	//int i = 0; //for ra_dbg only
+
+	ra_dbg("%s: addr:%x, ops data:%p, oob:%p datalen:%x ooblen:%x, ooboffs:%x \n", 
+	       __func__, (unsigned int)addr, data, oob, datalen, ooblen, ops->ooboffs);
+
+	ops->retlen = 0;
+	ops->oobretlen = 0;
+	if (data == 0)
+		datalen = 0;
+
+
+	while(datalen || ooblen) {
+		int len;
+		int ret;
+		int offs;
+
+		ra_dbg("%s (%d): addr:%x, ops data:%p, oob:%p datalen:%x ooblen:%x, ooboffs:%x \n", 
+		       __func__, i++, (unsigned int)addr, data, oob, datalen, ooblen, ops->ooboffs);
+		/* select chip */
+		if (nfc_enable_chip(ra, addr, 1) < 0)
+			return -EIO;
+
+		page = (int)((addr & ((1<<ra->chip_shift)-1)) >> ra->page_shift); 
+
+		ret = nfc_read_page(ra, ra->buffers, page, FLAG_VERIFY | 
+				    ((ops->mode == MTD_OPS_RAW || ops->mode == MTD_OPS_PLACE_OOB) ? 0: FLAG_ECC_EN ));
+		//FIXME, something strange here, some page needs 2 more tries to guarantee read success.
+		if (ret) {
+			printk("read again:\n");
+			ret = nfc_read_page(ra, ra->buffers, page, FLAG_VERIFY | 
+					    ((ops->mode == MTD_OPS_RAW || ops->mode == MTD_OPS_PLACE_OOB) ? 0: FLAG_ECC_EN ));
+
+			if (ret) {
+				printk("read again fail \n");
+				nand_bbt_set(ra, addr >> ra->erase_shift, BBT_TAG_BAD);
+				if ((ret != -EUCLEAN) && (ret != -EBADMSG)) {
+					return ret;
+				}
+				else {
+					/* ecc verification fail, but data need to be returned. */
+				}
+			}
+			else {
+				printk(" read agian susccess \n");
+			}
+		}
+
+		// oob read
+		if (oob && ooblen > 0) {
+			len = nand_read_oob_buf(ra, oob, ooblen, ops->mode, ops->ooboffs);
+			if (len < 0) {
+				printk("nand_read_oob_buf: fail return %x \n", len);
+				return -EINVAL;
+			}
+
+			oob += len;
+			ops->oobretlen += len;
+			ooblen -= len;
+		}
+
+		// data read
+		offs = addr & pagemask;
+		len = min_t(size_t, datalen, pagesize - offs);
+		if (data && len > 0) {
+			memcpy(data, ra->buffers + offs, len);	// we can not sure ops->buf wether is DMA-able.
+
+			data += len;
+			datalen -= len;
+			ops->retlen += len;
+			if (ret)
+				return ret;
+		}
+
+
+		nand_bbt_set(ra, addr >> ra->erase_shift, BBT_TAG_GOOD);
+		// address go further to next page, instead of increasing of length of write. This avoids some special cases wrong.
+		addr = (page+1) << ra->page_shift;
+	}
+	return 0;
+}
+
+static int
+ramtd_nand_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	struct ra_nand_chip *ra = (struct ra_nand_chip *)mtd->priv;
+	int ret;
+
+	ra_dbg("%s: start:%x, len:%x \n", __func__,
+		(unsigned int)instr->addr, (unsigned int)instr->len);
+
+	nand_get_device(ra, FL_ERASING);
+	ret = _nand_erase_nand((struct ra_nand_chip *)mtd->priv, instr);
+	nand_release_device(ra);
+
+	return ret;
+}
+
+static int
+ramtd_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
+		size_t *retlen, const uint8_t *buf)
+{
+	struct ra_nand_chip *ra = mtd->priv;
+	struct mtd_oob_ops ops;
+	int ret;
+
+	ra_dbg("%s: to 0x%x len=0x%x\n", __func__, to, len);
+
+	if ((to + len) > mtd->size)
+		return -EINVAL;
+
+	if (!len)
+		return 0;
+
+	nand_get_device(ra, FL_WRITING);
+
+	memset(&ops, 0, sizeof(ops));
+	ops.len = len;
+	ops.datbuf = (uint8_t *)buf;
+	ops.oobbuf = NULL;
+	ops.mode =  MTD_OPS_AUTO_OOB;
+
+	ret = nand_do_write_ops(ra, to, &ops);
+
+	*retlen = ops.retlen;
+
+	nand_release_device(ra);
+
+	return ret;
+}
+
+static int
+ramtd_nand_read(struct mtd_info *mtd, loff_t from, size_t len,
+		size_t *retlen, uint8_t *buf)
+{
+
+	struct ra_nand_chip *ra = mtd->priv;
+	int ret;
+	struct mtd_oob_ops ops;
+
+	ra_dbg("%s: mtd:%p from:%x, len:%x, buf:%p \n", __func__, mtd, (unsigned int)from, len, buf);
+
+	/* Do not allow reads past end of device */
+	if ((from + len) > mtd->size)
+		return -EINVAL;
+	if (!len)
+		return 0;
+
+	nand_get_device(ra, FL_READING);
+
+	memset(&ops, 0, sizeof(ops));
+	ops.len = len;
+	ops.datbuf = buf;
+	ops.oobbuf = NULL;
+	ops.mode = MTD_OPS_AUTO_OOB;
+
+	ret = nand_do_read_ops(ra, from, &ops);
+
+	*retlen = ops.retlen;
+
+	nand_release_device(ra);
+
+	return ret;
+
+}
+
+static int
+ramtd_nand_readoob(struct mtd_info *mtd, loff_t from,
+			struct mtd_oob_ops *ops)
+{
+	struct ra_nand_chip *ra = mtd->priv;
+	int ret;
+
+	ra_dbg("%s: \n", __func__);
+
+	nand_get_device(ra, FL_READING);
+
+	ret = nand_do_read_ops(ra, from, ops);
+
+	nand_release_device(ra);
+
+	return ret;
+}
+
+static int
+ramtd_nand_writeoob(struct mtd_info *mtd, loff_t to,
+			struct mtd_oob_ops *ops)
+{
+	struct ra_nand_chip *ra = mtd->priv;
+	int ret;
+
+	nand_get_device(ra, FL_READING);
+	ret = nand_do_write_ops(ra, to, ops);
+	nand_release_device(ra);
+
+	return ret;
+}
+
+static int
+ramtd_nand_block_isbad(struct mtd_info *mtd, loff_t offs)
+{
+	if (offs > mtd->size)
+		return -EINVAL;
+
+	return nand_block_checkbad((struct ra_nand_chip *)mtd->priv, offs);
+}
+
+static int
+ramtd_nand_block_markbad(struct mtd_info *mtd, loff_t ofs)
+{
+	struct ra_nand_chip *ra = mtd->priv;
+	int ret;
+
+	ra_dbg("%s: \n", __func__);
+	nand_get_device(ra, FL_WRITING);
+	ret = nand_block_markbad(ra, ofs);
+	nand_release_device(ra);
+
+	return ret;
+}
+
+// 1-bit error detection
+static int one_bit_correction(char *ecc1, char *ecc2, int *bytes, int *bits)
+{
+	// check if ecc and expected are all valid
+	char *p, nibble, crumb;
+	int i, xor, iecc1 = 0, iecc2 = 0;
+
+	printk("correction : %x %x %x\n", ecc1[0], ecc1[1], ecc1[2]);
+	printk("correction : %x %x %x\n", ecc2[0], ecc2[1], ecc2[2]);
+
+	p = (char *)ecc1;
+	for (i = 0; i < CONFIG_ECC_BYTES; i++)
+	{
+		nibble = *(p+i) & 0xf;
+		if ((nibble != 0x0) && (nibble != 0xf) && (nibble != 0x3) && (nibble != 0xc) &&
+			(nibble != 0x5) && (nibble != 0xa) && (nibble != 0x6) && (nibble != 0x9))
+			return -1;
+		nibble = ((*(p+i)) >> 4) & 0xf;
+		if ((nibble != 0x0) && (nibble != 0xf) && (nibble != 0x3) && (nibble != 0xc) &&
+			(nibble != 0x5) && (nibble != 0xa) && (nibble != 0x6) && (nibble != 0x9))
+			return -1;
+	}
+
+	p = (char *)ecc2;
+	for (i = 0; i < CONFIG_ECC_BYTES; i++)
+	{
+		nibble = *(p+i) & 0xf;
+		if ((nibble != 0x0) && (nibble != 0xf) && (nibble != 0x3) && (nibble != 0xc) &&
+			(nibble != 0x5) && (nibble != 0xa) && (nibble != 0x6) && (nibble != 0x9))
+			return -1;
+		nibble = ((*(p+i)) >> 4) & 0xf;
+		if ((nibble != 0x0) && (nibble != 0xf) && (nibble != 0x3) && (nibble != 0xc) &&
+			(nibble != 0x5) && (nibble != 0xa) && (nibble != 0x6) && (nibble != 0x9))
+			return -1;
+	}
+
+	memcpy(&iecc1, ecc1, 3);
+	memcpy(&iecc2, ecc2, 3);
+
+	xor = iecc1 ^ iecc2;
+	printk("xor = %x (%x %x)\n", xor, iecc1, iecc2);
+
+	*bytes = 0;
+	for (i = 0; i < 9; i++)
+	{
+		crumb = (xor >> (2*i)) & 0x3;
+		if ((crumb == 0x0) || (crumb == 0x3))
+			return -1;
+		if (crumb == 0x2)
+			*bytes += (1 << i);
+	}
+
+	*bits = 0;
+	for (i = 0; i < 3; i++)
+	{
+		crumb = (xor >> (18 + 2*i)) & 0x3;
+		if ((crumb == 0x0) || (crumb == 0x3))
+			return -1;
+		if (crumb == 0x2)
+			*bits += (1 << i);
+	}
+
+	return 0;
+}
+
+
+
+/************************************************************
+ * the init/exit section.
+ */
+
+static struct nand_ecclayout ra_oob_layout = {
+	.eccbytes = CONFIG_ECC_BYTES,
+	.eccpos = {5, 6, 7},
+	.oobfree = {
+		 {.offset = 0, .length = 4},
+		 {.offset = 8, .length = 8},
+		 {.offset = 0, .length = 0}
+	 },
+#define RA_CHIP_OOB_AVAIL (4+8)
+	.oobavail = RA_CHIP_OOB_AVAIL,
+	// 5th byte is bad-block flag.
+};
+
+static int
+mtk_nand_probe(struct platform_device *pdev)
+{
+        struct mtd_part_parser_data ppdata;
+	struct ra_nand_chip *ra;
+	int alloc_size, bbt_size, buffers_size, reg, err;
+	unsigned char chip_mode = 12;
+
+/*	if(ra_check_flash_type()!=BOOT_FROM_NAND) {
+		return 0;
+	}*/
+
+	//FIXME: config 512 or 2048-byte page according to HWCONF
+#if defined (CONFIG_RALINK_RT6855A)
+	reg = ra_inl(RALINK_SYSCTL_BASE+0x8c);
+	chip_mode = ((reg>>28) & 0x3)|(((reg>>22) & 0x3)<<2);
+	if (chip_mode == 1) {
+		printk("! nand 2048\n");
+		ra_or(NFC_CONF1, 1);
+		is_nand_page_2048 = 1;
+		nand_addrlen = 5;
+	}
+	else {
+		printk("! nand 512\n");
+		ra_and(NFC_CONF1, ~1);
+		is_nand_page_2048 = 0;
+		nand_addrlen = 4;
+	}	
+#elif (defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_RT6855))
+	ra_outl(RALINK_SYSCTL_BASE+0x60, ra_inl(RALINK_SYSCTL_BASE+0x60) & ~(0x3<<18));
+	reg = ra_inl(RALINK_SYSCTL_BASE+0x10);
+	chip_mode = (reg & 0x0F);
+	if((chip_mode==1)||(chip_mode==11)) {
+		ra_or(NFC_CONF1, 1);
+		is_nand_page_2048 = 1;
+		nand_addrlen = ((chip_mode!=11) ? 4 : 5);
+		printk("!!! nand page size = 2048, addr len=%d\n", nand_addrlen);
+	}
+	else {
+		ra_and(NFC_CONF1, ~1);
+		is_nand_page_2048 = 0;
+		nand_addrlen = ((chip_mode!=10) ? 3 : 4);
+		printk("!!! nand page size = 512, addr len=%d\n", nand_addrlen);
+	}			
+#else
+	is_nand_page_2048 = 0;
+	nand_addrlen = 3;
+	printk("!!! nand page size = 512, addr len=%d\n", nand_addrlen);
+#endif			
+
+#if defined (CONFIG_RALINK_RT6855A) || defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_RT6855) 
+	//config ECC location
+    ra_and(NFC_CONF1, 0xfff000ff);
+	ra_or(NFC_CONF1, ((CONFIG_ECC_OFFSET + 2) << 16) +
+						((CONFIG_ECC_OFFSET + 1) << 12) +
+						(CONFIG_ECC_OFFSET << 8));
+#endif
+
+#define ALIGNE_16(a) (((unsigned long)(a)+15) & ~15)
+	buffers_size = ALIGNE_16((1<<CONFIG_PAGE_SIZE_BIT) + (1<<CONFIG_OOBSIZE_PER_PAGE_BIT)); //ra->buffers
+	bbt_size = BBTTAG_BITS * (1<<(CONFIG_CHIP_SIZE_BIT - (CONFIG_PAGE_SIZE_BIT + CONFIG_NUMPAGE_PER_BLOCK_BIT))) / 8; //ra->bbt
+	bbt_size = ALIGNE_16(bbt_size);
+
+	alloc_size = buffers_size + bbt_size;
+	alloc_size += buffers_size; //for ra->readback_buffers
+	alloc_size += sizeof(*ra); 
+	alloc_size += sizeof(*ranfc_mtd);
+
+	//make sure gpio-0 is input
+	ra_outl(RALINK_PIO_BASE+0x24, ra_inl(RALINK_PIO_BASE+0x24) & ~0x01);
+
+	ra = (struct ra_nand_chip *)kzalloc(alloc_size, GFP_KERNEL | GFP_DMA);
+	if (!ra) {
+		printk("%s: mem alloc fail \n", __func__);
+		return -ENOMEM;
+	}
+	memset(ra, 0, alloc_size);
+
+	//dynamic
+	ra->buffers = (char *)((char *)ra + sizeof(*ra));
+	ra->readback_buffers = ra->buffers + buffers_size; 
+	ra->bbt = ra->readback_buffers + buffers_size; 
+	ranfc_mtd = (struct mtd_info *)(ra->bbt + bbt_size);
+
+	//static 
+	ra->numchips		= CONFIG_NUMCHIPS;
+	ra->chip_shift		= CONFIG_CHIP_SIZE_BIT;
+	ra->page_shift		= CONFIG_PAGE_SIZE_BIT;
+	ra->oob_shift		= CONFIG_OOBSIZE_PER_PAGE_BIT;
+	ra->erase_shift		= (CONFIG_PAGE_SIZE_BIT + CONFIG_NUMPAGE_PER_BLOCK_BIT);
+	ra->badblockpos		= CONFIG_BAD_BLOCK_POS;
+	ra_oob_layout.eccpos[0] = CONFIG_ECC_OFFSET;
+	ra_oob_layout.eccpos[1] = CONFIG_ECC_OFFSET + 1;
+	ra_oob_layout.eccpos[2] = CONFIG_ECC_OFFSET + 2;
+	ra->oob			= &ra_oob_layout;
+	ra->buffers_page	= -1;
+
+#if defined (WORKAROUND_RX_BUF_OV)
+	if (ranfc_verify) {
+		ra->sandbox_page = nand_bbt_find_sandbox(ra);
+	}
+#endif
+	ra_outl(NFC_CTRL, ra_inl(NFC_CTRL) | 0x01); //set wp to high
+	nfc_all_reset();
+
+	ranfc_mtd->type		= MTD_NANDFLASH;
+	ranfc_mtd->flags	= MTD_CAP_NANDFLASH;
+	ranfc_mtd->size		= CONFIG_NUMCHIPS * CFG_CHIPSIZE;
+	ranfc_mtd->erasesize	= CFG_BLOCKSIZE;
+	ranfc_mtd->writesize	= CFG_PAGESIZE;
+	ranfc_mtd->oobsize 	= CFG_PAGE_OOBSIZE;
+	ranfc_mtd->oobavail	= RA_CHIP_OOB_AVAIL;
+	ranfc_mtd->name		= "ra_nfc";
+	//ranfc_mtd->index
+	ranfc_mtd->ecclayout	= &ra_oob_layout;
+	//ranfc_mtd->numberaseregions
+	//ranfc_mtd->eraseregions
+	//ranfc_mtd->bansize
+	ranfc_mtd->_erase 	= ramtd_nand_erase;
+	//ranfc_mtd->point
+	//ranfc_mtd->unpoint
+	ranfc_mtd->_read		= ramtd_nand_read;
+	ranfc_mtd->_write	= ramtd_nand_write;
+	ranfc_mtd->_read_oob	= ramtd_nand_readoob;
+	ranfc_mtd->_write_oob	= ramtd_nand_writeoob;
+	//ranfc_mtd->get_fact_prot_info; ranfc_mtd->read_fact_prot_reg; 
+	//ranfc_mtd->get_user_prot_info; ranfc_mtd->read_user_prot_reg;
+	//ranfc_mtd->write_user_prot_reg; ranfc_mtd->lock_user_prot_reg;
+	//ranfc_mtd->writev; ranfc_mtd->sync; ranfc_mtd->lock; ranfc_mtd->unlock; ranfc_mtd->suspend; ranfc_mtd->resume;
+	ranfc_mtd->_block_isbad		= ramtd_nand_block_isbad;
+	ranfc_mtd->_block_markbad	= ramtd_nand_block_markbad;
+	//ranfc_mtd->reboot_notifier
+	//ranfc_mtd->ecc_stats;
+	// subpage_sht;
+
+	//ranfc_mtd->get_device; ranfc_mtd->put_device
+	ranfc_mtd->priv = ra;
+
+	ranfc_mtd->owner = THIS_MODULE;
+	ra->controller = &ra->hwcontrol;
+	mutex_init(ra->controller);
+
+	printk("%s: alloc %x, at %p , btt(%p, %x), ranfc_mtd:%p\n", 
+	       __func__ , alloc_size, ra, ra->bbt, bbt_size, ranfc_mtd);
+
+	ppdata.of_node = pdev->dev.of_node;
+	err = mtd_device_parse_register(ranfc_mtd, mtk_probe_types,
+			&ppdata, NULL, 0);
+
+	return err;
+}
+
+static int
+mtk_nand_remove(struct platform_device *pdev)
+{
+	struct ra_nand_chip *ra;
+
+	if (ranfc_mtd) {
+		ra = (struct ra_nand_chip  *)ranfc_mtd->priv;
+
+		/* Deregister partitions */
+		//del_mtd_partitions(ranfc_mtd);
+		kfree(ra);
+	}
+	return 0;
+}
+
+static const struct of_device_id mtk_nand_match[] = {
+	{ .compatible = "mtk,mt7620-nand" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mtk_nand_match);
+
+static struct platform_driver mtk_nand_driver = {
+	.probe = mtk_nand_probe,
+	.remove = mtk_nand_remove,
+	.driver = {
+		.name = "mt7620_nand",
+		.owner = THIS_MODULE,
+		.of_match_table = mtk_nand_match,
+	},
+};
+
+module_platform_driver(mtk_nand_driver);
+
+
+MODULE_LICENSE("GPL");
--- /dev/null
+++ b/drivers/mtd/maps/ralink_nand.h
@@ -0,0 +1,232 @@
+#ifndef RT2880_NAND_H
+#define RT2880_NAND_H
+
+#include <linux/mtd/mtd.h>
+
+//#include "gdma.h"
+
+#define RALINK_SYSCTL_BASE		0xB0000000
+#define RALINK_PIO_BASE			0xB0000600
+#define RALINK_NAND_CTRL_BASE		0xB0000810
+#define CONFIG_RALINK_MT7620
+
+#define SKIP_BAD_BLOCK
+//#define RANDOM_GEN_BAD_BLOCK
+
+#define ra_inl(addr)  (*(volatile unsigned int *)(addr))
+#define ra_outl(addr, value)  (*(volatile unsigned int *)(addr) = (value))
+#define ra_aor(addr, a_mask, o_value)  ra_outl(addr, (ra_inl(addr) & (a_mask)) | (o_value))
+#define ra_and(addr, a_mask)  ra_aor(addr, a_mask, 0)
+#define ra_or(addr, o_value)  ra_aor(addr, -1, o_value)
+
+
+#define CONFIG_NUMCHIPS 1
+#define CONFIG_NOT_SUPPORT_WP //rt3052 has no WP signal for chip.
+//#define CONFIG_NOT_SUPPORT_RB
+
+extern int is_nand_page_2048;
+extern const unsigned int nand_size_map[2][3];
+
+//chip
+// chip geometry: SAMSUNG small size 32MB.
+#define CONFIG_CHIP_SIZE_BIT (nand_size_map[is_nand_page_2048][nand_addrlen-3]) //! (1<<NAND_SIZE_BYTE) MB
+//#define CONFIG_CHIP_SIZE_BIT (is_nand_page_2048? 29 : 25)	//! (1<<NAND_SIZE_BYTE) MB
+#define CONFIG_PAGE_SIZE_BIT (is_nand_page_2048? 11 : 9)	//! (1<<PAGE_SIZE) MB
+//#define CONFIG_SUBPAGE_BIT 1		//! these bits will be compensate by command cycle
+#define CONFIG_NUMPAGE_PER_BLOCK_BIT (is_nand_page_2048? 6 : 5)	//! order of number of pages a block. 
+#define CONFIG_OOBSIZE_PER_PAGE_BIT (is_nand_page_2048? 6 : 4)	//! byte number of oob a page.
+#define CONFIG_BAD_BLOCK_POS (is_nand_page_2048? 0 : 4)     //! offset of byte to denote bad block.
+#define CONFIG_ECC_BYTES 3      //! ecc has 3 bytes
+#define CONFIG_ECC_OFFSET (is_nand_page_2048? 6 : 5)        //! ecc starts from offset 5.
+
+//this section should not be modified.
+//#define CFG_COLUMN_ADDR_MASK ((1 << (CONFIG_PAGE_SIZE_BIT - CONFIG_SUBPAGE_BIT)) - 1)
+//#define CFG_COLUMN_ADDR_CYCLE (((CONFIG_PAGE_SIZE_BIT - CONFIG_SUBPAGE_BIT) + 7)/8) 
+//#define CFG_ROW_ADDR_CYCLE ((CONFIG_CHIP_SIZE_BIT - CONFIG_PAGE_SIZE_BIT + 7)/8) 
+//#define CFG_ADDR_CYCLE (CFG_COLUMN_ADDR_CYCLE + CFG_ROW_ADDR_CYCLE)
+
+#define CFG_COLUMN_ADDR_CYCLE   (is_nand_page_2048? 2 : 1)
+#define CFG_ROW_ADDR_CYCLE      (nand_addrlen - CFG_COLUMN_ADDR_CYCLE)
+#define CFG_ADDR_CYCLE (CFG_COLUMN_ADDR_CYCLE + CFG_ROW_ADDR_CYCLE)
+
+#define CFG_CHIPSIZE    (1 << ((CONFIG_CHIP_SIZE_BIT>=32)? 31 : CONFIG_CHIP_SIZE_BIT))
+//#define CFG_CHIPSIZE  	(1 << CONFIG_CHIP_SIZE_BIT)
+#define CFG_PAGESIZE	(1 << CONFIG_PAGE_SIZE_BIT)
+#define CFG_BLOCKSIZE 	(CFG_PAGESIZE << CONFIG_NUMPAGE_PER_BLOCK_BIT)
+#define CFG_NUMPAGE	(1 << (CONFIG_CHIP_SIZE_BIT - CONFIG_PAGE_SIZE_BIT))
+#define CFG_NUMBLOCK	(CFG_NUMPAGE >> CONFIG_NUMPAGE_PER_BLOCK_BIT)
+#define CFG_BLOCK_OOBSIZE	(1 << (CONFIG_OOBSIZE_PER_PAGE_BIT + CONFIG_NUMPAGE_PER_BLOCK_BIT))	
+#define CFG_PAGE_OOBSIZE	(1 << CONFIG_OOBSIZE_PER_PAGE_BIT)	
+
+#define NAND_BLOCK_ALIGN(addr) ((addr) & (CFG_BLOCKSIZE-1))
+#define NAND_PAGE_ALIGN(addr) ((addr) & (CFG_PAGESIZE-1))
+
+
+#define NFC_BASE 	RALINK_NAND_CTRL_BASE
+#define NFC_CTRL	(NFC_BASE + 0x0)
+#define NFC_CONF	(NFC_BASE + 0x4)
+#define NFC_CMD1	(NFC_BASE + 0x8)
+#define NFC_CMD2	(NFC_BASE + 0xc)
+#define NFC_CMD3	(NFC_BASE + 0x10)
+#define NFC_ADDR	(NFC_BASE + 0x14)
+#define NFC_DATA	(NFC_BASE + 0x18)
+#if defined (CONFIG_RALINK_RT6855) || defined (CONFIG_RALINK_RT6855A) || \
+	defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_MT7621)
+#define NFC_ECC		(NFC_BASE + 0x30)
+#else
+#define NFC_ECC		(NFC_BASE + 0x1c)
+#endif
+#define NFC_STATUS	(NFC_BASE + 0x20)
+#define NFC_INT_EN	(NFC_BASE + 0x24)
+#define NFC_INT_ST	(NFC_BASE + 0x28)
+#if defined (CONFIG_RALINK_RT6855) || defined (CONFIG_RALINK_RT6855A) || \
+	defined (CONFIG_RALINK_MT7620) || defined (CONFIG_RALINK_MT7621)
+#define NFC_CONF1	(NFC_BASE + 0x2c)
+#define NFC_ECC_P1	(NFC_BASE + 0x30)
+#define NFC_ECC_P2	(NFC_BASE + 0x34)
+#define NFC_ECC_P3	(NFC_BASE + 0x38)
+#define NFC_ECC_P4	(NFC_BASE + 0x3c)
+#define NFC_ECC_ERR1	(NFC_BASE + 0x40)
+#define NFC_ECC_ERR2	(NFC_BASE + 0x44)
+#define NFC_ECC_ERR3	(NFC_BASE + 0x48)
+#define NFC_ECC_ERR4	(NFC_BASE + 0x4c)
+#define NFC_ADDR2	(NFC_BASE + 0x50)
+#endif
+
+enum _int_stat {
+	INT_ST_ND_DONE 	= 1<<0,
+	INT_ST_TX_BUF_RDY       = 1<<1,
+	INT_ST_RX_BUF_RDY	= 1<<2,
+	INT_ST_ECC_ERR		= 1<<3,
+	INT_ST_TX_TRAS_ERR	= 1<<4,
+	INT_ST_RX_TRAS_ERR	= 1<<5,
+	INT_ST_TX_KICK_ERR	= 1<<6,
+	INT_ST_RX_KICK_ERR      = 1<<7
+};
+
+
+//#define WORKAROUND_RX_BUF_OV 1
+
+
+/*************************************************************
+ * stolen from nand.h
+ *************************************************************/
+
+/*
+ * Standard NAND flash commands
+ */
+#define NAND_CMD_READ0		0
+#define NAND_CMD_READ1		1
+#define NAND_CMD_RNDOUT		5
+#define NAND_CMD_PAGEPROG	0x10
+#define NAND_CMD_READOOB	0x50
+#define NAND_CMD_ERASE1		0x60
+#define NAND_CMD_STATUS		0x70
+#define NAND_CMD_STATUS_MULTI	0x71
+#define NAND_CMD_SEQIN		0x80
+#define NAND_CMD_RNDIN		0x85
+#define NAND_CMD_READID		0x90
+#define NAND_CMD_ERASE2		0xd0
+#define NAND_CMD_RESET		0xff
+
+/* Extended commands for large page devices */
+#define NAND_CMD_READSTART	0x30
+#define NAND_CMD_RNDOUTSTART	0xE0
+#define NAND_CMD_CACHEDPROG	0x15
+
+/* Extended commands for AG-AND device */
+/*
+ * Note: the command for NAND_CMD_DEPLETE1 is really 0x00 but
+ *       there is no way to distinguish that from NAND_CMD_READ0
+ *       until the remaining sequence of commands has been completed
+ *       so add a high order bit and mask it off in the command.
+ */
+#define NAND_CMD_DEPLETE1	0x100
+#define NAND_CMD_DEPLETE2	0x38
+#define NAND_CMD_STATUS_MULTI	0x71
+#define NAND_CMD_STATUS_ERROR	0x72
+/* multi-bank error status (banks 0-3) */
+#define NAND_CMD_STATUS_ERROR0	0x73
+#define NAND_CMD_STATUS_ERROR1	0x74
+#define NAND_CMD_STATUS_ERROR2	0x75
+#define NAND_CMD_STATUS_ERROR3	0x76
+#define NAND_CMD_STATUS_RESET	0x7f
+#define NAND_CMD_STATUS_CLEAR	0xff
+
+#define NAND_CMD_NONE		-1
+
+/* Status bits */
+#define NAND_STATUS_FAIL	0x01
+#define NAND_STATUS_FAIL_N1	0x02
+#define NAND_STATUS_TRUE_READY	0x20
+#define NAND_STATUS_READY	0x40
+#define NAND_STATUS_WP		0x80
+
+typedef enum {
+	FL_READY,
+	FL_READING,
+	FL_WRITING,
+	FL_ERASING,
+	FL_SYNCING,
+	FL_CACHEDPRG,
+	FL_PM_SUSPENDED,
+} nand_state_t;
+
+/*************************************************************/
+
+
+
+typedef enum _ra_flags {
+	FLAG_NONE	= 0,
+	FLAG_ECC_EN 	= (1<<0),
+	FLAG_USE_GDMA 	= (1<<1),
+	FLAG_VERIFY 	= (1<<2),
+} RA_FLAGS;
+
+
+#define BBTTAG_BITS		2
+#define BBTTAG_BITS_MASK	((1<<BBTTAG_BITS) -1)
+enum BBT_TAG {
+	BBT_TAG_UNKNOWN = 0, //2'b01
+	BBT_TAG_GOOD	= 3, //2'b11
+	BBT_TAG_BAD	= 2, //2'b10
+	BBT_TAG_RES	= 1, //2'b01
+};
+
+struct ra_nand_chip {
+	int	numchips;
+	int 	chip_shift;
+	int	page_shift;
+	int 	erase_shift;
+	int 	oob_shift;
+	int	badblockpos;
+#if !defined (__UBOOT__)
+	struct mutex hwcontrol;
+	struct mutex *controller;
+#endif
+	struct nand_ecclayout	*oob;
+	int 	state;
+	unsigned int 	buffers_page;
+	char	*buffers; //[CFG_PAGESIZE + CFG_PAGE_OOBSIZE];
+	char 	*readback_buffers;
+	unsigned char 	*bbt;
+#if defined (WORKAROUND_RX_BUF_OV)
+	unsigned int	 sandbox_page;	// steal a page (block) for read ECC verification
+#endif
+
+};
+
+
+
+//fixme, gdma api 
+int nand_dma_sync(void);
+void release_dma_buf(void);
+int set_gdma_ch(unsigned long dst, 
+		unsigned long src, unsigned int len, int burst_size,
+		int soft_mode, int src_req_type, int dst_req_type,
+		int src_burst_mode, int dst_burst_mode);
+
+
+
+
+#endif