drivers/mtd/nand/raw/sunxi_nand_spl.c - u-boot-mtk - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (c) 2014-2015, Antmicro Ltd <www.antmicro.com>
  * Copyright (c) 2015, AW-SOM Technologies <www.aw-som.com>
  */

 #include <asm/arch/clock.h>
 #include <asm/io.h>
 #include <common.h>
 #include <config.h>
 #include <nand.h>
 #include <linux/ctype.h>

 /* registers */
 #define NFC_CTL                    0x00000000
 #define NFC_ST                     0x00000004
 #define NFC_INT                    0x00000008
 #define NFC_TIMING_CTL             0x0000000C
 #define NFC_TIMING_CFG             0x00000010
 #define NFC_ADDR_LOW               0x00000014
 #define NFC_ADDR_HIGH              0x00000018
 #define NFC_SECTOR_NUM             0x0000001C
 #define NFC_CNT                    0x00000020
 #define NFC_CMD                    0x00000024
 #define NFC_RCMD_SET               0x00000028
 #define NFC_WCMD_SET               0x0000002C
 #define NFC_IO_DATA                0x00000030
 #define NFC_ECC_CTL                0x00000034
 #define NFC_ECC_ST                 0x00000038
 #define NFC_DEBUG                  0x0000003C
 #define NFC_ECC_CNT0               0x00000040
 #define NFC_ECC_CNT1               0x00000044
 #define NFC_ECC_CNT2               0x00000048
 #define NFC_ECC_CNT3               0x0000004C
 #define NFC_USER_DATA_BASE         0x00000050
 #define NFC_EFNAND_STATUS          0x00000090
 #define NFC_SPARE_AREA             0x000000A0
 #define NFC_PATTERN_ID             0x000000A4
 #define NFC_RAM0_BASE              0x00000400
 #define NFC_RAM1_BASE              0x00000800

 #define NFC_CTL_EN                 (1 << 0)
 #define NFC_CTL_RESET              (1 << 1)
 #define NFC_CTL_RAM_METHOD         (1 << 14)
 #define NFC_CTL_PAGE_SIZE_MASK     (0xf << 8)
 #define NFC_CTL_PAGE_SIZE(a)       ((fls(a) - 11) << 8)


 #define NFC_ECC_EN                 (1 << 0)
 #define NFC_ECC_PIPELINE           (1 << 3)
 #define NFC_ECC_EXCEPTION          (1 << 4)
 #define NFC_ECC_BLOCK_SIZE         (1 << 5)
 #define NFC_ECC_RANDOM_EN          (1 << 9)
 #define NFC_ECC_RANDOM_DIRECTION   (1 << 10)


 #define NFC_ADDR_NUM_OFFSET        16
 #define NFC_SEND_ADDR              (1 << 19)
 #define NFC_ACCESS_DIR             (1 << 20)
 #define NFC_DATA_TRANS             (1 << 21)
 #define NFC_SEND_CMD1              (1 << 22)
 #define NFC_WAIT_FLAG              (1 << 23)
 #define NFC_SEND_CMD2              (1 << 24)
 #define NFC_SEQ                    (1 << 25)
 #define NFC_DATA_SWAP_METHOD       (1 << 26)
 #define NFC_ROW_AUTO_INC           (1 << 27)
 #define NFC_SEND_CMD3              (1 << 28)
 #define NFC_SEND_CMD4              (1 << 29)
 #define NFC_RAW_CMD                (0 << 30)
 #define NFC_ECC_CMD                (1 << 30)
 #define NFC_PAGE_CMD               (2 << 30)

 #define NFC_ST_CMD_INT_FLAG        (1 << 1)
 #define NFC_ST_DMA_INT_FLAG        (1 << 2)
 #define NFC_ST_CMD_FIFO_STAT       (1 << 3)

 #define NFC_READ_CMD_OFFSET         0
 #define NFC_RANDOM_READ_CMD0_OFFSET 8
 #define NFC_RANDOM_READ_CMD1_OFFSET 16

 #define NFC_CMD_RNDOUTSTART        0xE0
 #define NFC_CMD_RNDOUT             0x05
 #define NFC_CMD_READSTART          0x30

 struct nfc_config {
 	int page_size;
 	int ecc_strength;
 	int ecc_size;
 	int addr_cycles;
 	int nseeds;
 	bool randomize;
 	bool valid;
 };

 /* minimal "boot0" style NAND support for Allwinner A20 */

 /* random seed used by linux */
 const uint16_t random_seed[128] = {
 	0x2b75, 0x0bd0, 0x5ca3, 0x62d1, 0x1c93, 0x07e9, 0x2162, 0x3a72,
 	0x0d67, 0x67f9, 0x1be7, 0x077d, 0x032f, 0x0dac, 0x2716, 0x2436,
 	0x7922, 0x1510, 0x3860, 0x5287, 0x480f, 0x4252, 0x1789, 0x5a2d,
 	0x2a49, 0x5e10, 0x437f, 0x4b4e, 0x2f45, 0x216e, 0x5cb7, 0x7130,
 	0x2a3f, 0x60e4, 0x4dc9, 0x0ef0, 0x0f52, 0x1bb9, 0x6211, 0x7a56,
 	0x226d, 0x4ea7, 0x6f36, 0x3692, 0x38bf, 0x0c62, 0x05eb, 0x4c55,
 	0x60f4, 0x728c, 0x3b6f, 0x2037, 0x7f69, 0x0936, 0x651a, 0x4ceb,
 	0x6218, 0x79f3, 0x383f, 0x18d9, 0x4f05, 0x5c82, 0x2912, 0x6f17,
 	0x6856, 0x5938, 0x1007, 0x61ab, 0x3e7f, 0x57c2, 0x542f, 0x4f62,
 	0x7454, 0x2eac, 0x7739, 0x42d4, 0x2f90, 0x435a, 0x2e52, 0x2064,
 	0x637c, 0x66ad, 0x2c90, 0x0bad, 0x759c, 0x0029, 0x0986, 0x7126,
 	0x1ca7, 0x1605, 0x386a, 0x27f5, 0x1380, 0x6d75, 0x24c3, 0x0f8e,
 	0x2b7a, 0x1418, 0x1fd1, 0x7dc1, 0x2d8e, 0x43af, 0x2267, 0x7da3,
 	0x4e3d, 0x1338, 0x50db, 0x454d, 0x764d, 0x40a3, 0x42e6, 0x262b,
 	0x2d2e, 0x1aea, 0x2e17, 0x173d, 0x3a6e, 0x71bf, 0x25f9, 0x0a5d,
 	0x7c57, 0x0fbe, 0x46ce, 0x4939, 0x6b17, 0x37bb, 0x3e91, 0x76db,
 };

 #define DEFAULT_TIMEOUT_US	100000

 static int check_value_inner(int offset, int expected_bits,
 			     int timeout_us, int negation)
 {
 	do {
 		int val = readl(offset) & expected_bits;
 		if (negation ? !val : val)
 			return 1;
 		udelay(1);
 	} while (--timeout_us);

 	return 0;
 }

 static inline int check_value(int offset, int expected_bits,
 			      int timeout_us)
 {
 	return check_value_inner(offset, expected_bits, timeout_us, 0);
 }

 static inline int check_value_negated(int offset, int unexpected_bits,
 				      int timeout_us)
 {
 	return check_value_inner(offset, unexpected_bits, timeout_us, 1);
 }

 static int nand_wait_cmd_fifo_empty(void)
 {
 	if (!check_value_negated(SUNXI_NFC_BASE + NFC_ST, NFC_ST_CMD_FIFO_STAT,
 				 DEFAULT_TIMEOUT_US)) {
 		printf("nand: timeout waiting for empty cmd FIFO\n");
 		return -ETIMEDOUT;
 	}

 	return 0;
 }

 static int nand_wait_int(void)
 {
 	if (!check_value(SUNXI_NFC_BASE + NFC_ST, NFC_ST_CMD_INT_FLAG,
 			 DEFAULT_TIMEOUT_US)) {
 		printf("nand: timeout waiting for interruption\n");
 		return -ETIMEDOUT;
 	}

 	return 0;
 }

 static int nand_exec_cmd(u32 cmd)
 {
 	int ret;

 	ret = nand_wait_cmd_fifo_empty();
 	if (ret)
 		return ret;

 	writel(NFC_ST_CMD_INT_FLAG, SUNXI_NFC_BASE + NFC_ST);
 	writel(cmd, SUNXI_NFC_BASE + NFC_CMD);

 	return nand_wait_int();
 }

 void nand_init(void)
 {
 	uint32_t val;

 	board_nand_init();

 	val = readl(SUNXI_NFC_BASE + NFC_CTL);
 	/* enable and reset CTL */
 	writel(val | NFC_CTL_EN | NFC_CTL_RESET,
 	       SUNXI_NFC_BASE + NFC_CTL);

 	if (!check_value_negated(SUNXI_NFC_BASE + NFC_CTL,
 				 NFC_CTL_RESET, DEFAULT_TIMEOUT_US)) {
 		printf("Couldn't initialize nand\n");
 	}

 	/* reset NAND */
 	nand_exec_cmd(NFC_SEND_CMD1 | NFC_WAIT_FLAG | NAND_CMD_RESET);
 }

 static void nand_apply_config(const struct nfc_config *conf)
 {
 	u32 val;

 	nand_wait_cmd_fifo_empty();

 	val = readl(SUNXI_NFC_BASE + NFC_CTL);
 	val &= ~NFC_CTL_PAGE_SIZE_MASK;
 	writel(val | NFC_CTL_RAM_METHOD | NFC_CTL_PAGE_SIZE(conf->page_size),
 	       SUNXI_NFC_BASE + NFC_CTL);
 	writel(conf->ecc_size, SUNXI_NFC_BASE + NFC_CNT);
 	writel(conf->page_size, SUNXI_NFC_BASE + NFC_SPARE_AREA);
 }

 static int nand_load_page(const struct nfc_config *conf, u32 offs)
 {
 	int page = offs / conf->page_size;

 	writel((NFC_CMD_RNDOUTSTART << NFC_RANDOM_READ_CMD1_OFFSET) |
 	       (NFC_CMD_RNDOUT << NFC_RANDOM_READ_CMD0_OFFSET) |
 	       (NFC_CMD_READSTART << NFC_READ_CMD_OFFSET),
 	       SUNXI_NFC_BASE + NFC_RCMD_SET);
 	writel(((page & 0xFFFF) << 16), SUNXI_NFC_BASE + NFC_ADDR_LOW);
 	writel((page >> 16) & 0xFF, SUNXI_NFC_BASE + NFC_ADDR_HIGH);

 	return nand_exec_cmd(NFC_SEND_CMD1 | NFC_SEND_CMD2 | NFC_RAW_CMD |
 			     NFC_SEND_ADDR | NFC_WAIT_FLAG |
 			     ((conf->addr_cycles - 1) << NFC_ADDR_NUM_OFFSET));
 }

 static int nand_change_column(u16 column)
 {
 	int ret;

 	writel((NFC_CMD_RNDOUTSTART << NFC_RANDOM_READ_CMD1_OFFSET) |
 	       (NFC_CMD_RNDOUT << NFC_RANDOM_READ_CMD0_OFFSET) |
 	       (NFC_CMD_RNDOUTSTART << NFC_READ_CMD_OFFSET),
 	       SUNXI_NFC_BASE + NFC_RCMD_SET);
 	writel(column, SUNXI_NFC_BASE + NFC_ADDR_LOW);

 	ret = nand_exec_cmd(NFC_SEND_CMD1 | NFC_SEND_CMD2 | NFC_RAW_CMD |
 			    (1 << NFC_ADDR_NUM_OFFSET) | NFC_SEND_ADDR |
 			    NFC_CMD_RNDOUT);
 	if (ret)
 		return ret;

 	/* Ensure tCCS has passed before reading data */
 	udelay(1);

 	return 0;
 }

 static const int ecc_bytes[] = {32, 46, 54, 60, 74, 88, 102, 110, 116};

 static int nand_read_page(const struct nfc_config *conf, u32 offs,
 			  void *dest, int len)
 {
 	int nsectors = len / conf->ecc_size;
 	u16 rand_seed = 0;
 	int oob_chunk_sz = ecc_bytes[conf->ecc_strength];
 	int page = offs / conf->page_size;
 	u32 ecc_st;
 	int i;

 	if (offs % conf->page_size || len % conf->ecc_size ||
 	    len > conf->page_size || len < 0)
 		return -EINVAL;

 	/* Choose correct seed if randomized */
 	if (conf->randomize)
 		rand_seed = random_seed[page % conf->nseeds];

 	/* Retrieve data from SRAM (PIO) */
 	for (i = 0; i < nsectors; i++) {
 		int data_off = i * conf->ecc_size;
 		int oob_off = conf->page_size + (i * oob_chunk_sz);
 		u8 *data = dest + data_off;

 		/* Clear ECC status and restart ECC engine */
 		writel(0, SUNXI_NFC_BASE + NFC_ECC_ST);
 		writel((rand_seed << 16) | (conf->ecc_strength << 12) |
 		       (conf->randomize ? NFC_ECC_RANDOM_EN : 0) |
 		       (conf->ecc_size == 512 ? NFC_ECC_BLOCK_SIZE : 0) |
 		       NFC_ECC_EN | NFC_ECC_EXCEPTION,
 		       SUNXI_NFC_BASE + NFC_ECC_CTL);

 		/* Move the data in SRAM */
 		nand_change_column(data_off);
 		writel(conf->ecc_size, SUNXI_NFC_BASE + NFC_CNT);
 		nand_exec_cmd(NFC_DATA_TRANS);

 		/*
 		 * Let the ECC engine consume the ECC bytes and possibly correct
 		 * the data.
 		 */
 		nand_change_column(oob_off);
 		nand_exec_cmd(NFC_DATA_TRANS | NFC_ECC_CMD);

 		/* Get the ECC status */
 		ecc_st = readl(SUNXI_NFC_BASE + NFC_ECC_ST);

 		/* ECC error detected. */
 		if (ecc_st & 0xffff)
 			return -EIO;

 		/*
 		 * Return 1 if the first chunk is empty (needed for
 		 * configuration detection).
 		 */
 		if (!i && (ecc_st & 0x10000))
 			return 1;

 		/* Retrieve the data from SRAM */
 		memcpy_fromio(data, SUNXI_NFC_BASE + NFC_RAM0_BASE,
 			      conf->ecc_size);

 		/* Stop the ECC engine */
 		writel(readl(SUNXI_NFC_BASE + NFC_ECC_CTL) & ~NFC_ECC_EN,
 		       SUNXI_NFC_BASE + NFC_ECC_CTL);

 		if (data_off + conf->ecc_size >= len)
 			break;
 	}

 	return 0;
 }

 static int nand_max_ecc_strength(struct nfc_config *conf)
 {
 	int max_oobsize, max_ecc_bytes;
 	int nsectors = conf->page_size / conf->ecc_size;
 	int i;

 	/*
 	 * ECC strength is limited by the size of the OOB area which is
 	 * correlated with the page size.
 	 */
 	switch (conf->page_size) {
 	case 2048:
 		max_oobsize = 64;
 		break;
 	case 4096:
 		max_oobsize = 256;
 		break;
 	case 8192:
 		max_oobsize = 640;
 		break;
 	case 16384:
 		max_oobsize = 1664;
 		break;
 	default:
 		return -EINVAL;
 	}

 	max_ecc_bytes = max_oobsize / nsectors;

 	for (i = 0; i < ARRAY_SIZE(ecc_bytes); i++) {
 		if (ecc_bytes[i] > max_ecc_bytes)
 			break;
 	}

 	if (!i)
 		return -EINVAL;

 	return i - 1;
 }

 static int nand_detect_ecc_config(struct nfc_config *conf, u32 offs,
 				  void *dest)
 {
 	/* NAND with pages > 4k will likely require 1k sector size. */
 	int min_ecc_size = conf->page_size > 4096 ? 1024 : 512;
 	int page = offs / conf->page_size;
 	int ret;

 	/*
 	 * In most cases, 1k sectors are preferred over 512b ones, start
 	 * testing this config first.
 	 */
 	for (conf->ecc_size = 1024; conf->ecc_size >= min_ecc_size;
 	     conf->ecc_size >>= 1) {
 		int max_ecc_strength = nand_max_ecc_strength(conf);

 		nand_apply_config(conf);

 		/*
 		 * We are starting from the maximum ECC strength because
 		 * most of the time NAND vendors provide an OOB area that
 		 * barely meets the ECC requirements.
 		 */
 		for (conf->ecc_strength = max_ecc_strength;
 		     conf->ecc_strength >= 0;
 		     conf->ecc_strength--) {
 			conf->randomize = false;
 			if (nand_change_column(0))
 				return -EIO;

 			/*
 			 * Only read the first sector to speedup detection.
 			 */
 			ret = nand_read_page(conf, offs, dest, conf->ecc_size);
 			if (!ret) {
 				return 0;
 			} else if (ret > 0) {
 				/*
 				 * If page is empty we can't deduce anything
 				 * about the ECC config => stop the detection.
 				 */
 				return -EINVAL;
 			}

 			conf->randomize = true;
 			conf->nseeds = ARRAY_SIZE(random_seed);
 			do {
 				if (nand_change_column(0))
 					return -EIO;

 				if (!nand_read_page(conf, offs, dest,
 						    conf->ecc_size))
 					return 0;

 				/*
 				 * Find the next ->nseeds value that would
 				 * change the randomizer seed for the page
 				 * we're trying to read.
 				 */
 				while (conf->nseeds >= 16) {
 					int seed = page % conf->nseeds;

 					conf->nseeds >>= 1;
 					if (seed != page % conf->nseeds)
 						break;
 				}
 			} while (conf->nseeds >= 16);
 		}
 	}

 	return -EINVAL;
 }

 static int nand_detect_config(struct nfc_config *conf, u32 offs, void *dest)
 {
 	if (conf->valid)
 		return 0;

 	/*
 	 * Modern NANDs are more likely than legacy ones, so we start testing
 	 * with 5 address cycles.
 	 */
 	for (conf->addr_cycles = 5;
 	     conf->addr_cycles >= 4;
 	     conf->addr_cycles--) {
 		int max_page_size = conf->addr_cycles == 4 ? 2048 : 16384;

 		/*
 		 * Ignoring 1k pages cause I'm not even sure this case exist
 		 * in the real world.
 		 */
 		for (conf->page_size = 2048; conf->page_size <= max_page_size;
 		     conf->page_size <<= 1) {
 			if (nand_load_page(conf, offs))
 				return -1;

 			if (!nand_detect_ecc_config(conf, offs, dest)) {
 				conf->valid = true;
 				return 0;
 			}
 		}
 	}

 	return -EINVAL;
 }

 static int nand_read_buffer(struct nfc_config *conf, uint32_t offs,
 			    unsigned int size, void *dest)
 {
 	int first_seed = 0, page, ret;

 	size = ALIGN(size, conf->page_size);
 	page = offs / conf->page_size;
 	if (conf->randomize)
 		first_seed = page % conf->nseeds;

 	for (; size; size -= conf->page_size) {
 		if (nand_load_page(conf, offs))
 			return -1;

 		ret = nand_read_page(conf, offs, dest, conf->page_size);
 		/*
 		 * The ->nseeds value should be equal to the number of pages
 		 * in an eraseblock. Since we don't know this information in
 		 * advance we might have picked a wrong value.
 		 */
 		if (ret < 0 && conf->randomize) {
 			int cur_seed = page % conf->nseeds;

 			/*
 			 * We already tried all the seed values => we are
 			 * facing a real corruption.
 			 */
 			if (cur_seed < first_seed)
 				return -EIO;

 			/* Try to adjust ->nseeds and read the page again... */
 			conf->nseeds = cur_seed;

 			if (nand_change_column(0))
 				return -EIO;

 			/* ... it still fails => it's a real corruption. */
 			if (nand_read_page(conf, offs, dest, conf->page_size))
 				return -EIO;
 		} else if (ret && conf->randomize) {
 			memset(dest, 0xff, conf->page_size);
 		}

 		page++;
 		offs += conf->page_size;
 		dest += conf->page_size;
 	}

 	return 0;
 }

 int nand_spl_load_image(uint32_t offs, unsigned int size, void *dest)
 {
 	static struct nfc_config conf = { };
 	int ret;

 	ret = nand_detect_config(&conf, offs, dest);
 	if (ret)
 		return ret;

 	return nand_read_buffer(&conf, offs, size, dest);
 }

 void nand_deselect(void)
 {
 	struct sunxi_ccm_reg *const ccm =
 		(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;

 	clrbits_le32(&ccm->ahb_gate0, (CLK_GATE_OPEN << AHB_GATE_OFFSET_NAND0));
 #ifdef CONFIG_MACH_SUN9I
 	clrbits_le32(&ccm->ahb_gate1, (1 << AHB_GATE_OFFSET_DMA));
 #else
 	clrbits_le32(&ccm->ahb_gate0, (1 << AHB_GATE_OFFSET_DMA));
 #endif
 	clrbits_le32(&ccm->nand0_clk_cfg, CCM_NAND_CTRL_ENABLE | AHB_DIV_1);
 }
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (c) 2014-2015, Antmicro Ltd <www.antmicro.com>
	* Copyright (c) 2015, AW-SOM Technologies <www.aw-som.com>
	*/

	#include <asm/arch/clock.h>
	#include <asm/io.h>
	#include <common.h>
	#include <config.h>
	#include <nand.h>
	#include <linux/ctype.h>

	/* registers */
	#define NFC_CTL 0x00000000
	#define NFC_ST 0x00000004
	#define NFC_INT 0x00000008
	#define NFC_TIMING_CTL 0x0000000C
	#define NFC_TIMING_CFG 0x00000010
	#define NFC_ADDR_LOW 0x00000014
	#define NFC_ADDR_HIGH 0x00000018
	#define NFC_SECTOR_NUM 0x0000001C
	#define NFC_CNT 0x00000020
	#define NFC_CMD 0x00000024
	#define NFC_RCMD_SET 0x00000028
	#define NFC_WCMD_SET 0x0000002C
	#define NFC_IO_DATA 0x00000030
	#define NFC_ECC_CTL 0x00000034
	#define NFC_ECC_ST 0x00000038
	#define NFC_DEBUG 0x0000003C
	#define NFC_ECC_CNT0 0x00000040
	#define NFC_ECC_CNT1 0x00000044
	#define NFC_ECC_CNT2 0x00000048
	#define NFC_ECC_CNT3 0x0000004C
	#define NFC_USER_DATA_BASE 0x00000050
	#define NFC_EFNAND_STATUS 0x00000090
	#define NFC_SPARE_AREA 0x000000A0
	#define NFC_PATTERN_ID 0x000000A4
	#define NFC_RAM0_BASE 0x00000400
	#define NFC_RAM1_BASE 0x00000800

	#define NFC_CTL_EN (1 << 0)
	#define NFC_CTL_RESET (1 << 1)
	#define NFC_CTL_RAM_METHOD (1 << 14)
	#define NFC_CTL_PAGE_SIZE_MASK (0xf << 8)
	#define NFC_CTL_PAGE_SIZE(a) ((fls(a) - 11) << 8)


	#define NFC_ECC_EN (1 << 0)
	#define NFC_ECC_PIPELINE (1 << 3)
	#define NFC_ECC_EXCEPTION (1 << 4)
	#define NFC_ECC_BLOCK_SIZE (1 << 5)
	#define NFC_ECC_RANDOM_EN (1 << 9)
	#define NFC_ECC_RANDOM_DIRECTION (1 << 10)


	#define NFC_ADDR_NUM_OFFSET 16
	#define NFC_SEND_ADDR (1 << 19)
	#define NFC_ACCESS_DIR (1 << 20)
	#define NFC_DATA_TRANS (1 << 21)
	#define NFC_SEND_CMD1 (1 << 22)
	#define NFC_WAIT_FLAG (1 << 23)
	#define NFC_SEND_CMD2 (1 << 24)
	#define NFC_SEQ (1 << 25)
	#define NFC_DATA_SWAP_METHOD (1 << 26)
	#define NFC_ROW_AUTO_INC (1 << 27)
	#define NFC_SEND_CMD3 (1 << 28)
	#define NFC_SEND_CMD4 (1 << 29)
	#define NFC_RAW_CMD (0 << 30)
	#define NFC_ECC_CMD (1 << 30)
	#define NFC_PAGE_CMD (2 << 30)

	#define NFC_ST_CMD_INT_FLAG (1 << 1)
	#define NFC_ST_DMA_INT_FLAG (1 << 2)
	#define NFC_ST_CMD_FIFO_STAT (1 << 3)

	#define NFC_READ_CMD_OFFSET 0
	#define NFC_RANDOM_READ_CMD0_OFFSET 8
	#define NFC_RANDOM_READ_CMD1_OFFSET 16

	#define NFC_CMD_RNDOUTSTART 0xE0
	#define NFC_CMD_RNDOUT 0x05
	#define NFC_CMD_READSTART 0x30

	struct nfc_config {
	int page_size;
	int ecc_strength;
	int ecc_size;
	int addr_cycles;
	int nseeds;
	bool randomize;
	bool valid;
	};

	/* minimal "boot0" style NAND support for Allwinner A20 */

	/* random seed used by linux */
	const uint16_t random_seed[128] = {
	0x2b75, 0x0bd0, 0x5ca3, 0x62d1, 0x1c93, 0x07e9, 0x2162, 0x3a72,
	0x0d67, 0x67f9, 0x1be7, 0x077d, 0x032f, 0x0dac, 0x2716, 0x2436,
	0x7922, 0x1510, 0x3860, 0x5287, 0x480f, 0x4252, 0x1789, 0x5a2d,
	0x2a49, 0x5e10, 0x437f, 0x4b4e, 0x2f45, 0x216e, 0x5cb7, 0x7130,
	0x2a3f, 0x60e4, 0x4dc9, 0x0ef0, 0x0f52, 0x1bb9, 0x6211, 0x7a56,
	0x226d, 0x4ea7, 0x6f36, 0x3692, 0x38bf, 0x0c62, 0x05eb, 0x4c55,
	0x60f4, 0x728c, 0x3b6f, 0x2037, 0x7f69, 0x0936, 0x651a, 0x4ceb,
	0x6218, 0x79f3, 0x383f, 0x18d9, 0x4f05, 0x5c82, 0x2912, 0x6f17,
	0x6856, 0x5938, 0x1007, 0x61ab, 0x3e7f, 0x57c2, 0x542f, 0x4f62,
	0x7454, 0x2eac, 0x7739, 0x42d4, 0x2f90, 0x435a, 0x2e52, 0x2064,
	0x637c, 0x66ad, 0x2c90, 0x0bad, 0x759c, 0x0029, 0x0986, 0x7126,
	0x1ca7, 0x1605, 0x386a, 0x27f5, 0x1380, 0x6d75, 0x24c3, 0x0f8e,
	0x2b7a, 0x1418, 0x1fd1, 0x7dc1, 0x2d8e, 0x43af, 0x2267, 0x7da3,
	0x4e3d, 0x1338, 0x50db, 0x454d, 0x764d, 0x40a3, 0x42e6, 0x262b,
	0x2d2e, 0x1aea, 0x2e17, 0x173d, 0x3a6e, 0x71bf, 0x25f9, 0x0a5d,
	0x7c57, 0x0fbe, 0x46ce, 0x4939, 0x6b17, 0x37bb, 0x3e91, 0x76db,
	};

	#define DEFAULT_TIMEOUT_US 100000

	static int check_value_inner(int offset, int expected_bits,
	int timeout_us, int negation)
	{
	do {
	int val = readl(offset) & expected_bits;
	if (negation ? !val : val)
	return 1;
	udelay(1);
	} while (--timeout_us);

	return 0;
	}

	static inline int check_value(int offset, int expected_bits,
	int timeout_us)
	{
	return check_value_inner(offset, expected_bits, timeout_us, 0);
	}

	static inline int check_value_negated(int offset, int unexpected_bits,
	int timeout_us)
	{
	return check_value_inner(offset, unexpected_bits, timeout_us, 1);
	}

	static int nand_wait_cmd_fifo_empty(void)
	{
	if (!check_value_negated(SUNXI_NFC_BASE + NFC_ST, NFC_ST_CMD_FIFO_STAT,
	DEFAULT_TIMEOUT_US)) {
	printf("nand: timeout waiting for empty cmd FIFO\n");
	return -ETIMEDOUT;
	}

	return 0;
	}

	static int nand_wait_int(void)
	{
	if (!check_value(SUNXI_NFC_BASE + NFC_ST, NFC_ST_CMD_INT_FLAG,
	DEFAULT_TIMEOUT_US)) {
	printf("nand: timeout waiting for interruption\n");
	return -ETIMEDOUT;
	}

	return 0;
	}

	static int nand_exec_cmd(u32 cmd)
	{
	int ret;

	ret = nand_wait_cmd_fifo_empty();
	if (ret)
	return ret;

	writel(NFC_ST_CMD_INT_FLAG, SUNXI_NFC_BASE + NFC_ST);
	writel(cmd, SUNXI_NFC_BASE + NFC_CMD);

	return nand_wait_int();
	}

	void nand_init(void)
	{
	uint32_t val;

	board_nand_init();

	val = readl(SUNXI_NFC_BASE + NFC_CTL);
	/* enable and reset CTL */
	writel(val \| NFC_CTL_EN \| NFC_CTL_RESET,
	SUNXI_NFC_BASE + NFC_CTL);

	if (!check_value_negated(SUNXI_NFC_BASE + NFC_CTL,
	NFC_CTL_RESET, DEFAULT_TIMEOUT_US)) {
	printf("Couldn't initialize nand\n");
	}

	/* reset NAND */
	nand_exec_cmd(NFC_SEND_CMD1 \| NFC_WAIT_FLAG \| NAND_CMD_RESET);
	}

	static void nand_apply_config(const struct nfc_config *conf)
	{
	u32 val;

	nand_wait_cmd_fifo_empty();

	val = readl(SUNXI_NFC_BASE + NFC_CTL);
	val &= ~NFC_CTL_PAGE_SIZE_MASK;
	writel(val \| NFC_CTL_RAM_METHOD \| NFC_CTL_PAGE_SIZE(conf->page_size),
	SUNXI_NFC_BASE + NFC_CTL);
	writel(conf->ecc_size, SUNXI_NFC_BASE + NFC_CNT);
	writel(conf->page_size, SUNXI_NFC_BASE + NFC_SPARE_AREA);
	}

	static int nand_load_page(const struct nfc_config *conf, u32 offs)
	{
	int page = offs / conf->page_size;

	writel((NFC_CMD_RNDOUTSTART << NFC_RANDOM_READ_CMD1_OFFSET) \|
	(NFC_CMD_RNDOUT << NFC_RANDOM_READ_CMD0_OFFSET) \|
	(NFC_CMD_READSTART << NFC_READ_CMD_OFFSET),
	SUNXI_NFC_BASE + NFC_RCMD_SET);
	writel(((page & 0xFFFF) << 16), SUNXI_NFC_BASE + NFC_ADDR_LOW);
	writel((page >> 16) & 0xFF, SUNXI_NFC_BASE + NFC_ADDR_HIGH);

	return nand_exec_cmd(NFC_SEND_CMD1 \| NFC_SEND_CMD2 \| NFC_RAW_CMD \|
	NFC_SEND_ADDR \| NFC_WAIT_FLAG \|
	((conf->addr_cycles - 1) << NFC_ADDR_NUM_OFFSET));
	}

	static int nand_change_column(u16 column)
	{
	int ret;

	writel((NFC_CMD_RNDOUTSTART << NFC_RANDOM_READ_CMD1_OFFSET) \|
	(NFC_CMD_RNDOUT << NFC_RANDOM_READ_CMD0_OFFSET) \|
	(NFC_CMD_RNDOUTSTART << NFC_READ_CMD_OFFSET),
	SUNXI_NFC_BASE + NFC_RCMD_SET);
	writel(column, SUNXI_NFC_BASE + NFC_ADDR_LOW);

	ret = nand_exec_cmd(NFC_SEND_CMD1 \| NFC_SEND_CMD2 \| NFC_RAW_CMD \|
	(1 << NFC_ADDR_NUM_OFFSET) \| NFC_SEND_ADDR \|
	NFC_CMD_RNDOUT);
	if (ret)
	return ret;

	/* Ensure tCCS has passed before reading data */
	udelay(1);

	return 0;
	}

	static const int ecc_bytes[] = {32, 46, 54, 60, 74, 88, 102, 110, 116};

	static int nand_read_page(const struct nfc_config *conf, u32 offs,
	void *dest, int len)
	{
	int nsectors = len / conf->ecc_size;
	u16 rand_seed = 0;
	int oob_chunk_sz = ecc_bytes[conf->ecc_strength];
	int page = offs / conf->page_size;
	u32 ecc_st;
	int i;

	if (offs % conf->page_size \|\| len % conf->ecc_size \|\|
	len > conf->page_size \|\| len < 0)
	return -EINVAL;

	/* Choose correct seed if randomized */
	if (conf->randomize)
	rand_seed = random_seed[page % conf->nseeds];

	/* Retrieve data from SRAM (PIO) */
	for (i = 0; i < nsectors; i++) {
	int data_off = i * conf->ecc_size;
	int oob_off = conf->page_size + (i * oob_chunk_sz);
	u8 *data = dest + data_off;

	/* Clear ECC status and restart ECC engine */
	writel(0, SUNXI_NFC_BASE + NFC_ECC_ST);
	writel((rand_seed << 16) \| (conf->ecc_strength << 12) \|
	(conf->randomize ? NFC_ECC_RANDOM_EN : 0) \|
	(conf->ecc_size == 512 ? NFC_ECC_BLOCK_SIZE : 0) \|
	NFC_ECC_EN \| NFC_ECC_EXCEPTION,
	SUNXI_NFC_BASE + NFC_ECC_CTL);

	/* Move the data in SRAM */
	nand_change_column(data_off);
	writel(conf->ecc_size, SUNXI_NFC_BASE + NFC_CNT);
	nand_exec_cmd(NFC_DATA_TRANS);

	/*
	* Let the ECC engine consume the ECC bytes and possibly correct
	* the data.
	*/
	nand_change_column(oob_off);
	nand_exec_cmd(NFC_DATA_TRANS \| NFC_ECC_CMD);

	/* Get the ECC status */
	ecc_st = readl(SUNXI_NFC_BASE + NFC_ECC_ST);

	/* ECC error detected. */
	if (ecc_st & 0xffff)
	return -EIO;

	/*
	* Return 1 if the first chunk is empty (needed for
	* configuration detection).
	*/
	if (!i && (ecc_st & 0x10000))
	return 1;

	/* Retrieve the data from SRAM */
	memcpy_fromio(data, SUNXI_NFC_BASE + NFC_RAM0_BASE,
	conf->ecc_size);

	/* Stop the ECC engine */
	writel(readl(SUNXI_NFC_BASE + NFC_ECC_CTL) & ~NFC_ECC_EN,
	SUNXI_NFC_BASE + NFC_ECC_CTL);

	if (data_off + conf->ecc_size >= len)
	break;
	}

	return 0;
	}

	static int nand_max_ecc_strength(struct nfc_config *conf)
	{
	int max_oobsize, max_ecc_bytes;
	int nsectors = conf->page_size / conf->ecc_size;
	int i;

	/*
	* ECC strength is limited by the size of the OOB area which is
	* correlated with the page size.
	*/
	switch (conf->page_size) {
	case 2048:
	max_oobsize = 64;
	break;
	case 4096:
	max_oobsize = 256;
	break;
	case 8192:
	max_oobsize = 640;
	break;
	case 16384:
	max_oobsize = 1664;
	break;
	default:
	return -EINVAL;
	}

	max_ecc_bytes = max_oobsize / nsectors;

	for (i = 0; i < ARRAY_SIZE(ecc_bytes); i++) {
	if (ecc_bytes[i] > max_ecc_bytes)
	break;
	}

	if (!i)
	return -EINVAL;

	return i - 1;
	}

	static int nand_detect_ecc_config(struct nfc_config *conf, u32 offs,
	void *dest)
	{
	/* NAND with pages > 4k will likely require 1k sector size. */
	int min_ecc_size = conf->page_size > 4096 ? 1024 : 512;
	int page = offs / conf->page_size;
	int ret;

	/*
	* In most cases, 1k sectors are preferred over 512b ones, start
	* testing this config first.
	*/
	for (conf->ecc_size = 1024; conf->ecc_size >= min_ecc_size;
	conf->ecc_size >>= 1) {
	int max_ecc_strength = nand_max_ecc_strength(conf);

	nand_apply_config(conf);

	/*
	* We are starting from the maximum ECC strength because
	* most of the time NAND vendors provide an OOB area that
	* barely meets the ECC requirements.
	*/
	for (conf->ecc_strength = max_ecc_strength;
	conf->ecc_strength >= 0;
	conf->ecc_strength--) {
	conf->randomize = false;
	if (nand_change_column(0))
	return -EIO;

	/*
	* Only read the first sector to speedup detection.
	*/
	ret = nand_read_page(conf, offs, dest, conf->ecc_size);
	if (!ret) {
	return 0;
	} else if (ret > 0) {
	/*
	* If page is empty we can't deduce anything
	* about the ECC config => stop the detection.
	*/
	return -EINVAL;
	}

	conf->randomize = true;
	conf->nseeds = ARRAY_SIZE(random_seed);
	do {
	if (nand_change_column(0))
	return -EIO;

	if (!nand_read_page(conf, offs, dest,
	conf->ecc_size))
	return 0;

	/*
	* Find the next ->nseeds value that would
	* change the randomizer seed for the page
	* we're trying to read.
	*/
	while (conf->nseeds >= 16) {
	int seed = page % conf->nseeds;

	conf->nseeds >>= 1;
	if (seed != page % conf->nseeds)
	break;
	}
	} while (conf->nseeds >= 16);
	}
	}

	return -EINVAL;
	}

	static int nand_detect_config(struct nfc_config conf, u32 offs, void dest)
	{
	if (conf->valid)
	return 0;

	/*
	* Modern NANDs are more likely than legacy ones, so we start testing
	* with 5 address cycles.
	*/
	for (conf->addr_cycles = 5;
	conf->addr_cycles >= 4;
	conf->addr_cycles--) {
	int max_page_size = conf->addr_cycles == 4 ? 2048 : 16384;

	/*
	* Ignoring 1k pages cause I'm not even sure this case exist
	* in the real world.
	*/
	for (conf->page_size = 2048; conf->page_size <= max_page_size;
	conf->page_size <<= 1) {
	if (nand_load_page(conf, offs))
	return -1;

	if (!nand_detect_ecc_config(conf, offs, dest)) {
	conf->valid = true;
	return 0;
	}
	}
	}

	return -EINVAL;
	}

	static int nand_read_buffer(struct nfc_config *conf, uint32_t offs,
	unsigned int size, void *dest)
	{
	int first_seed = 0, page, ret;

	size = ALIGN(size, conf->page_size);
	page = offs / conf->page_size;
	if (conf->randomize)
	first_seed = page % conf->nseeds;

	for (; size; size -= conf->page_size) {
	if (nand_load_page(conf, offs))
	return -1;

	ret = nand_read_page(conf, offs, dest, conf->page_size);
	/*
	* The ->nseeds value should be equal to the number of pages
	* in an eraseblock. Since we don't know this information in
	* advance we might have picked a wrong value.
	*/
	if (ret < 0 && conf->randomize) {
	int cur_seed = page % conf->nseeds;

	/*
	* We already tried all the seed values => we are
	* facing a real corruption.
	*/
	if (cur_seed < first_seed)
	return -EIO;

	/* Try to adjust ->nseeds and read the page again... */
	conf->nseeds = cur_seed;

	if (nand_change_column(0))
	return -EIO;

	/* ... it still fails => it's a real corruption. */
	if (nand_read_page(conf, offs, dest, conf->page_size))
	return -EIO;
	} else if (ret && conf->randomize) {
	memset(dest, 0xff, conf->page_size);
	}

	page++;
	offs += conf->page_size;
	dest += conf->page_size;
	}

	return 0;
	}

	int nand_spl_load_image(uint32_t offs, unsigned int size, void *dest)
	{
	static struct nfc_config conf = { };
	int ret;

	ret = nand_detect_config(&conf, offs, dest);
	if (ret)
	return ret;

	return nand_read_buffer(&conf, offs, size, dest);
	}

	void nand_deselect(void)
	{
	struct sunxi_ccm_reg *const ccm =
	(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;

	clrbits_le32(&ccm->ahb_gate0, (CLK_GATE_OPEN << AHB_GATE_OFFSET_NAND0));
	#ifdef CONFIG_MACH_SUN9I
	clrbits_le32(&ccm->ahb_gate1, (1 << AHB_GATE_OFFSET_DMA));
	#else
	clrbits_le32(&ccm->ahb_gate0, (1 << AHB_GATE_OFFSET_DMA));
	#endif
	clrbits_le32(&ccm->nand0_clk_cfg, CCM_NAND_CTRL_ENABLE \| AHB_DIV_1);
	}