mtd: spi: Add lightweight SPI flash stack for SPL

Add a tiny SPI flash stack that just supports reading data/images from
SPI flash. This is useful for boards that have SPL size constraints and
would need to use SPI flash framework just to read images/data from
flash. There is approximately 1.5 to 2KB savings with this.

Based on prior work of reducing spi flash id table by
Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>

Signed-off-by: Vignesh R <vigneshr@ti.com>
Tested-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Tested-by: Stefan Roese <sr@denx.de>
Tested-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com> #zynq-microzed

1 files changed, 804 insertions, 0 deletions

diff --git a/drivers/mtd/spi/spi-nor-tiny.c b/drivers/mtd/spi/spi-nor-tiny.c
new file mode 100644
index 0000000000..c19d468d62
--- /dev/null
+++ b/drivers/mtd/spi/spi-nor-tiny.c
@@ -0,0 +1,804 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Based on m25p80.c, by Mike Lavender (mike@steroidmicros.com), with
+ * influence from lart.c (Abraham Van Der Merwe) and mtd_dataflash.c
+ *
+ * Copyright (C) 2005, Intec Automation Inc.
+ * Copyright (C) 2014, Freescale Semiconductor, Inc.
+ *
+ * Synced from Linux v4.19
+ */
+
+#include <common.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/log2.h>
+#include <linux/math64.h>
+#include <linux/sizes.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/spi-nor.h>
+#include <spi-mem.h>
+#include <spi.h>
+
+#include "sf_internal.h"
+
+/* Define max times to check status register before we give up. */
+
+/*
+ * For everything but full-chip erase; probably could be much smaller, but kept
+ * around for safety for now
+ */
+
+#define HZ					CONFIG_SYS_HZ
+
+#define DEFAULT_READY_WAIT_JIFFIES		(40UL * HZ)
+
+static int spi_nor_read_write_reg(struct spi_nor *nor, struct spi_mem_op
+		*op, void *buf)
+{
+	if (op->data.dir == SPI_MEM_DATA_IN)
+		op->data.buf.in = buf;
+	else
+		op->data.buf.out = buf;
+	return spi_mem_exec_op(nor->spi, op);
+}
+
+static int spi_nor_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
+{
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(code, 1),
+					  SPI_MEM_OP_NO_ADDR,
+					  SPI_MEM_OP_NO_DUMMY,
+					  SPI_MEM_OP_DATA_IN(len, NULL, 1));
+	int ret;
+
+	ret = spi_nor_read_write_reg(nor, &op, val);
+	if (ret < 0)
+		dev_dbg(&flash->spimem->spi->dev, "error %d reading %x\n", ret,
+			code);
+
+	return ret;
+}
+
+static int spi_nor_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
+{
+	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(opcode, 1),
+					  SPI_MEM_OP_NO_ADDR,
+					  SPI_MEM_OP_NO_DUMMY,
+					  SPI_MEM_OP_DATA_OUT(len, NULL, 1));
+
+	return spi_nor_read_write_reg(nor, &op, buf);
+}
+
+static ssize_t spi_nor_read_data(struct spi_nor *nor, loff_t from, size_t len,
+				 u_char *buf)
+{
+	struct spi_mem_op op =
+			SPI_MEM_OP(SPI_MEM_OP_CMD(nor->read_opcode, 1),
+				   SPI_MEM_OP_ADDR(nor->addr_width, from, 1),
+				   SPI_MEM_OP_DUMMY(nor->read_dummy, 1),
+				   SPI_MEM_OP_DATA_IN(len, buf, 1));
+	size_t remaining = len;
+	int ret;
+
+	/* get transfer protocols. */
+	op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->read_proto);
+	op.addr.buswidth = spi_nor_get_protocol_addr_nbits(nor->read_proto);
+	op.dummy.buswidth = op.addr.buswidth;
+	op.data.buswidth = spi_nor_get_protocol_data_nbits(nor->read_proto);
+
+	/* convert the dummy cycles to the number of bytes */
+	op.dummy.nbytes = (nor->read_dummy * op.dummy.buswidth) / 8;
+
+	while (remaining) {
+		op.data.nbytes = remaining < UINT_MAX ? remaining : UINT_MAX;
+		ret = spi_mem_adjust_op_size(nor->spi, &op);
+		if (ret)
+			return ret;
+
+		ret = spi_mem_exec_op(nor->spi, &op);
+		if (ret)
+			return ret;
+
+		op.addr.val += op.data.nbytes;
+		remaining -= op.data.nbytes;
+		op.data.buf.in += op.data.nbytes;
+	}
+
+	return len;
+}
+
+#if defined(CONFIG_SPI_FLASH_SPANSION) || defined(CONFIG_SPI_FLASH_WINBOND)
+/*
+ * Read configuration register, returning its value in the
+ * location. Return the configuration register value.
+ * Returns negative if error occurred.
+ */
+static int read_cr(struct spi_nor *nor)
+{
+	int ret;
+	u8 val;
+
+	ret = spi_nor_read_reg(nor, SPINOR_OP_RDCR, &val, 1);
+	if (ret < 0) {
+		dev_dbg(nor->dev, "error %d reading CR\n", ret);
+		return ret;
+	}
+
+	return val;
+}
+#endif
+
+/*
+ * Write status register 1 byte
+ * Returns negative if error occurred.
+ */
+static inline int write_sr(struct spi_nor *nor, u8 val)
+{
+	nor->cmd_buf[0] = val;
+	return spi_nor_write_reg(nor, SPINOR_OP_WRSR, nor->cmd_buf, 1);
+}
+
+/*
+ * Set write enable latch with Write Enable command.
+ * Returns negative if error occurred.
+ */
+static inline int write_enable(struct spi_nor *nor)
+{
+	return spi_nor_write_reg(nor, SPINOR_OP_WREN, NULL, 0);
+}
+
+/*
+ * Send write disable instruction to the chip.
+ */
+static inline int write_disable(struct spi_nor *nor)
+{
+	return spi_nor_write_reg(nor, SPINOR_OP_WRDI, NULL, 0);
+}
+
+static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)
+{
+	return mtd->priv;
+}
+
+static u8 spi_nor_convert_opcode(u8 opcode, const u8 table[][2], size_t size)
+{
+	size_t i;
+
+	for (i = 0; i < size; i++)
+		if (table[i][0] == opcode)
+			return table[i][1];
+
+	/* No conversion found, keep input op code. */
+	return opcode;
+}
+
+static inline u8 spi_nor_convert_3to4_read(u8 opcode)
+{
+	static const u8 spi_nor_3to4_read[][2] = {
+		{ SPINOR_OP_READ,	SPINOR_OP_READ_4B },
+		{ SPINOR_OP_READ_FAST,	SPINOR_OP_READ_FAST_4B },
+		{ SPINOR_OP_READ_1_1_2,	SPINOR_OP_READ_1_1_2_4B },
+		{ SPINOR_OP_READ_1_2_2,	SPINOR_OP_READ_1_2_2_4B },
+		{ SPINOR_OP_READ_1_1_4,	SPINOR_OP_READ_1_1_4_4B },
+		{ SPINOR_OP_READ_1_4_4,	SPINOR_OP_READ_1_4_4_4B },
+	};
+
+	return spi_nor_convert_opcode(opcode, spi_nor_3to4_read,
+				      ARRAY_SIZE(spi_nor_3to4_read));
+}
+
+static void spi_nor_set_4byte_opcodes(struct spi_nor *nor,
+				      const struct flash_info *info)
+{
+	nor->read_opcode = spi_nor_convert_3to4_read(nor->read_opcode);
+}
+
+/* Enable/disable 4-byte addressing mode. */
+static inline int set_4byte(struct spi_nor *nor, const struct flash_info *info,
+			    int enable)
+{
+	int status;
+	bool need_wren = false;
+	u8 cmd;
+
+	switch (JEDEC_MFR(info)) {
+	case SNOR_MFR_ST:
+	case SNOR_MFR_MICRON:
+		/* Some Micron need WREN command; all will accept it */
+		need_wren = true;
+	case SNOR_MFR_MACRONIX:
+	case SNOR_MFR_WINBOND:
+		if (need_wren)
+			write_enable(nor);
+
+		cmd = enable ? SPINOR_OP_EN4B : SPINOR_OP_EX4B;
+		status = spi_nor_write_reg(nor, cmd, NULL, 0);
+		if (need_wren)
+			write_disable(nor);
+
+		if (!status && !enable &&
+		    JEDEC_MFR(info) == SNOR_MFR_WINBOND) {
+			/*
+			 * On Winbond W25Q256FV, leaving 4byte mode causes
+			 * the Extended Address Register to be set to 1, so all
+			 * 3-byte-address reads come from the second 16M.
+			 * We must clear the register to enable normal behavior.
+			 */
+			write_enable(nor);
+			nor->cmd_buf[0] = 0;
+			spi_nor_write_reg(nor, SPINOR_OP_WREAR,
+					  nor->cmd_buf, 1);
+			write_disable(nor);
+		}
+
+		return status;
+	default:
+		/* Spansion style */
+		nor->cmd_buf[0] = enable << 7;
+		return spi_nor_write_reg(nor, SPINOR_OP_BRWR, nor->cmd_buf, 1);
+	}
+}
+
+#if defined(CONFIG_SPI_FLASH_SPANSION) ||	\
+	defined(CONFIG_SPI_FLASH_WINBOND) ||	\
+	defined(CONFIG_SPI_FLASH_MACRONIX)
+/*
+ * Read the status register, returning its value in the location
+ * Return the status register value.
+ * Returns negative if error occurred.
+ */
+static int read_sr(struct spi_nor *nor)
+{
+	int ret;
+	u8 val;
+
+	ret = spi_nor_read_reg(nor, SPINOR_OP_RDSR, &val, 1);
+	if (ret < 0) {
+		pr_debug("error %d reading SR\n", (int)ret);
+		return ret;
+	}
+
+	return val;
+}
+
+/*
+ * Read the flag status register, returning its value in the location
+ * Return the status register value.
+ * Returns negative if error occurred.
+ */
+static int read_fsr(struct spi_nor *nor)
+{
+	int ret;
+	u8 val;
+
+	ret = spi_nor_read_reg(nor, SPINOR_OP_RDFSR, &val, 1);
+	if (ret < 0) {
+		pr_debug("error %d reading FSR\n", ret);
+		return ret;
+	}
+
+	return val;
+}
+
+static int spi_nor_sr_ready(struct spi_nor *nor)
+{
+	int sr = read_sr(nor);
+
+	if (sr < 0)
+		return sr;
+
+	return !(sr & SR_WIP);
+}
+
+static int spi_nor_fsr_ready(struct spi_nor *nor)
+{
+	int fsr = read_fsr(nor);
+
+	if (fsr < 0)
+		return fsr;
+	return fsr & FSR_READY;
+}
+
+static int spi_nor_ready(struct spi_nor *nor)
+{
+	int sr, fsr;
+
+	sr = spi_nor_sr_ready(nor);
+	if (sr < 0)
+		return sr;
+	fsr = nor->flags & SNOR_F_USE_FSR ? spi_nor_fsr_ready(nor) : 1;
+	if (fsr < 0)
+		return fsr;
+	return sr && fsr;
+}
+
+/*
+ * Service routine to read status register until ready, or timeout occurs.
+ * Returns non-zero if error.
+ */
+static int spi_nor_wait_till_ready_with_timeout(struct spi_nor *nor,
+						unsigned long timeout)
+{
+	unsigned long timebase;
+	int ret;
+
+	timebase = get_timer(0);
+
+	while (get_timer(timebase) < timeout) {
+		ret = spi_nor_ready(nor);
+		if (ret < 0)
+			return ret;
+		if (ret)
+			return 0;
+	}
+
+	dev_err(nor->dev, "flash operation timed out\n");
+
+	return -ETIMEDOUT;
+}
+
+static int spi_nor_wait_till_ready(struct spi_nor *nor)
+{
+	return spi_nor_wait_till_ready_with_timeout(nor,
+						    DEFAULT_READY_WAIT_JIFFIES);
+}
+#endif /* CONFIG_SPI_FLASH_SPANSION */
+
+/*
+ * Erase an address range on the nor chip.  The address range may extend
+ * one or more erase sectors.  Return an error is there is a problem erasing.
+ */
+static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	return -ENOTSUPP;
+}
+
+static const struct flash_info *spi_nor_read_id(struct spi_nor *nor)
+{
+	int			tmp;
+	u8			id[SPI_NOR_MAX_ID_LEN];
+	const struct flash_info	*info;
+
+	tmp = spi_nor_read_reg(nor, SPINOR_OP_RDID, id, SPI_NOR_MAX_ID_LEN);
+	if (tmp < 0) {
+		dev_dbg(nor->dev, "error %d reading JEDEC ID\n", tmp);
+		return ERR_PTR(tmp);
+	}
+
+	info = spi_nor_ids;
+	for (; info->sector_size != 0; info++) {
+		if (info->id_len) {
+			if (!memcmp(info->id, id, info->id_len))
+				return info;
+		}
+	}
+	dev_dbg(nor->dev, "unrecognized JEDEC id bytes: %02x, %02x, %02x\n",
+		id[0], id[1], id[2]);
+	return ERR_PTR(-ENODEV);
+}
+
+static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len,
+			size_t *retlen, u_char *buf)
+{
+	struct spi_nor *nor = mtd_to_spi_nor(mtd);
+	int ret;
+
+	dev_dbg(nor->dev, "from 0x%08x, len %zd\n", (u32)from, len);
+
+	while (len) {
+		loff_t addr = from;
+
+		ret = spi_nor_read_data(nor, addr, len, buf);
+		if (ret == 0) {
+			/* We shouldn't see 0-length reads */
+			ret = -EIO;
+			goto read_err;
+		}
+		if (ret < 0)
+			goto read_err;
+
+		*retlen += ret;
+		buf += ret;
+		from += ret;
+		len -= ret;
+	}
+	ret = 0;
+
+read_err:
+	return ret;
+}
+
+/*
+ * Write an address range to the nor chip.  Data must be written in
+ * FLASH_PAGESIZE chunks.  The address range may be any size provided
+ * it is within the physical boundaries.
+ */
+static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
+			 size_t *retlen, const u_char *buf)
+{
+	return -ENOTSUPP;
+}
+
+#ifdef CONFIG_SPI_FLASH_MACRONIX
+/**
+ * macronix_quad_enable() - set QE bit in Status Register.
+ * @nor:	pointer to a 'struct spi_nor'
+ *
+ * Set the Quad Enable (QE) bit in the Status Register.
+ *
+ * bit 6 of the Status Register is the QE bit for Macronix like QSPI memories.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int macronix_quad_enable(struct spi_nor *nor)
+{
+	int ret, val;
+
+	val = read_sr(nor);
+	if (val < 0)
+		return val;
+	if (val & SR_QUAD_EN_MX)
+		return 0;
+
+	write_enable(nor);
+
+	write_sr(nor, val | SR_QUAD_EN_MX);
+
+	ret = spi_nor_wait_till_ready(nor);
+	if (ret)
+		return ret;
+
+	ret = read_sr(nor);
+	if (!(ret > 0 && (ret & SR_QUAD_EN_MX))) {
+		dev_err(nor->dev, "Macronix Quad bit not set\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#endif
+
+#if defined(CONFIG_SPI_FLASH_SPANSION) || defined(CONFIG_SPI_FLASH_WINBOND)
+/*
+ * Write status Register and configuration register with 2 bytes
+ * The first byte will be written to the status register, while the
+ * second byte will be written to the configuration register.
+ * Return negative if error occurred.
+ */
+static int write_sr_cr(struct spi_nor *nor, u8 *sr_cr)
+{
+	int ret;
+
+	write_enable(nor);
+
+	ret = spi_nor_write_reg(nor, SPINOR_OP_WRSR, sr_cr, 2);
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while writing configuration register\n");
+		return -EINVAL;
+	}
+
+	ret = spi_nor_wait_till_ready(nor);
+	if (ret) {
+		dev_dbg(nor->dev,
+			"timeout while writing configuration register\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * spansion_read_cr_quad_enable() - set QE bit in Configuration Register.
+ * @nor:	pointer to a 'struct spi_nor'
+ *
+ * Set the Quad Enable (QE) bit in the Configuration Register.
+ * This function should be used with QSPI memories supporting the Read
+ * Configuration Register (35h) instruction.
+ *
+ * bit 1 of the Configuration Register is the QE bit for Spansion like QSPI
+ * memories.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spansion_read_cr_quad_enable(struct spi_nor *nor)
+{
+	u8 sr_cr[2];
+	int ret;
+
+	/* Check current Quad Enable bit value. */
+	ret = read_cr(nor);
+	if (ret < 0) {
+		dev_dbg(dev, "error while reading configuration register\n");
+		return -EINVAL;
+	}
+
+	if (ret & CR_QUAD_EN_SPAN)
+		return 0;
+
+	sr_cr[1] = ret | CR_QUAD_EN_SPAN;
+
+	/* Keep the current value of the Status Register. */
+	ret = read_sr(nor);
+	if (ret < 0) {
+		dev_dbg(dev, "error while reading status register\n");
+		return -EINVAL;
+	}
+	sr_cr[0] = ret;
+
+	ret = write_sr_cr(nor, sr_cr);
+	if (ret)
+		return ret;
+
+	/* Read back and check it. */
+	ret = read_cr(nor);
+	if (!(ret > 0 && (ret & CR_QUAD_EN_SPAN))) {
+		dev_dbg(nor->dev, "Spansion Quad bit not set\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#endif /* CONFIG_SPI_FLASH_SPANSION */
+
+struct spi_nor_read_command {
+	u8			num_mode_clocks;
+	u8			num_wait_states;
+	u8			opcode;
+	enum spi_nor_protocol	proto;
+};
+
+enum spi_nor_read_command_index {
+	SNOR_CMD_READ,
+	SNOR_CMD_READ_FAST,
+
+	/* Quad SPI */
+	SNOR_CMD_READ_1_1_4,
+
+	SNOR_CMD_READ_MAX
+};
+
+struct spi_nor_flash_parameter {
+	struct spi_nor_hwcaps		hwcaps;
+	struct spi_nor_read_command	reads[SNOR_CMD_READ_MAX];
+};
+
+static void
+spi_nor_set_read_settings(struct spi_nor_read_command *read,
+			  u8 num_mode_clocks,
+			  u8 num_wait_states,
+			  u8 opcode,
+			  enum spi_nor_protocol proto)
+{
+	read->num_mode_clocks = num_mode_clocks;
+	read->num_wait_states = num_wait_states;
+	read->opcode = opcode;
+	read->proto = proto;
+}
+
+static int spi_nor_init_params(struct spi_nor *nor,
+			       const struct flash_info *info,
+			       struct spi_nor_flash_parameter *params)
+{
+	/* (Fast) Read settings. */
+	params->hwcaps.mask = SNOR_HWCAPS_READ;
+	spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ],
+				  0, 0, SPINOR_OP_READ,
+				  SNOR_PROTO_1_1_1);
+
+	if (!(info->flags & SPI_NOR_NO_FR)) {
+		params->hwcaps.mask |= SNOR_HWCAPS_READ_FAST;
+		spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ_FAST],
+					  0, 8, SPINOR_OP_READ_FAST,
+					  SNOR_PROTO_1_1_1);
+	}
+
+	if (info->flags & SPI_NOR_QUAD_READ) {
+		params->hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;
+		spi_nor_set_read_settings(&params->reads[SNOR_CMD_READ_1_1_4],
+					  0, 8, SPINOR_OP_READ_1_1_4,
+					  SNOR_PROTO_1_1_4);
+	}
+
+	return 0;
+}
+
+static int spi_nor_select_read(struct spi_nor *nor,
+			       const struct spi_nor_flash_parameter *params,
+			       u32 shared_hwcaps)
+{
+	int best_match = shared_hwcaps & SNOR_HWCAPS_READ_MASK;
+	int cmd;
+	const struct spi_nor_read_command *read;
+
+	if (best_match < 0)
+		return -EINVAL;
+
+	if (best_match & SNOR_HWCAPS_READ_1_1_4)
+		cmd = SNOR_CMD_READ_1_1_4;
+	else if (best_match & SNOR_HWCAPS_READ_FAST)
+		cmd = SNOR_CMD_READ_FAST;
+	else
+		cmd = SNOR_CMD_READ;
+
+	read = &params->reads[cmd];
+	nor->read_opcode = read->opcode;
+	nor->read_proto = read->proto;
+
+	/*
+	 * In the spi-nor framework, we don't need to make the difference
+	 * between mode clock cycles and wait state clock cycles.
+	 * Indeed, the value of the mode clock cycles is used by a QSPI
+	 * flash memory to know whether it should enter or leave its 0-4-4
+	 * (Continuous Read / XIP) mode.
+	 * eXecution In Place is out of the scope of the mtd sub-system.
+	 * Hence we choose to merge both mode and wait state clock cycles
+	 * into the so called dummy clock cycles.
+	 */
+	nor->read_dummy = read->num_mode_clocks + read->num_wait_states;
+	return 0;
+}
+
+static int spi_nor_setup(struct spi_nor *nor, const struct flash_info *info,
+			 const struct spi_nor_flash_parameter *params,
+			 const struct spi_nor_hwcaps *hwcaps)
+{
+	u32 shared_mask;
+	int err;
+
+	/*
+	 * Keep only the hardware capabilities supported by both the SPI
+	 * controller and the SPI flash memory.
+	 */
+	shared_mask = hwcaps->mask & params->hwcaps.mask;
+
+	/* Select the (Fast) Read command. */
+	err = spi_nor_select_read(nor, params, shared_mask);
+	if (err) {
+		dev_dbg(nor->dev,
+			"can't select read settings supported by both the SPI controller and memory.\n");
+		return err;
+	}
+
+	/* Enable Quad I/O if needed. */
+	if (spi_nor_get_protocol_width(nor->read_proto) == 4) {
+		switch (JEDEC_MFR(info)) {
+#ifdef CONFIG_SPI_FLASH_MACRONIX
+		case SNOR_MFR_MACRONIX:
+			err = macronix_quad_enable(nor);
+			break;
+#endif
+		case SNOR_MFR_ST:
+		case SNOR_MFR_MICRON:
+			break;
+
+		default:
+#if defined(CONFIG_SPI_FLASH_SPANSION) || defined(CONFIG_SPI_FLASH_WINBOND)
+			/* Kept only for backward compatibility purpose. */
+			err = spansion_read_cr_quad_enable(nor);
+#endif
+			break;
+		}
+	}
+	if (err) {
+		dev_dbg(nor->dev, "quad mode not supported\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int spi_nor_init(struct spi_nor *nor)
+{
+	if (nor->addr_width == 4 &&
+	    (JEDEC_MFR(nor->info) != SNOR_MFR_SPANSION) &&
+	    !(nor->info->flags & SPI_NOR_4B_OPCODES)) {
+		/*
+		 * If the RESET# pin isn't hooked up properly, or the system
+		 * otherwise doesn't perform a reset command in the boot
+		 * sequence, it's impossible to 100% protect against unexpected
+		 * reboots (e.g., crashes). Warn the user (or hopefully, system
+		 * designer) that this is bad.
+		 */
+		if (nor->flags & SNOR_F_BROKEN_RESET)
+			printf("enabling reset hack; may not recover from unexpected reboots\n");
+		set_4byte(nor, nor->info, 1);
+	}
+
+	return 0;
+}
+
+int spi_nor_scan(struct spi_nor *nor)
+{
+	struct spi_nor_flash_parameter params;
+	const struct flash_info *info = NULL;
+	struct mtd_info *mtd = &nor->mtd;
+	struct spi_nor_hwcaps hwcaps = {
+		.mask = SNOR_HWCAPS_READ |
+			SNOR_HWCAPS_READ_FAST
+	};
+	struct spi_slave *spi = nor->spi;
+	int ret;
+
+	/* Reset SPI protocol for all commands. */
+	nor->reg_proto = SNOR_PROTO_1_1_1;
+	nor->read_proto = SNOR_PROTO_1_1_1;
+	nor->write_proto = SNOR_PROTO_1_1_1;
+
+	if (spi->mode & SPI_RX_QUAD)
+		hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;
+
+	info = spi_nor_read_id(nor);
+	if (IS_ERR_OR_NULL(info))
+		return -ENOENT;
+	/* Parse the Serial Flash Discoverable Parameters table. */
+	ret = spi_nor_init_params(nor, info, &params);
+	if (ret)
+		return ret;
+
+	mtd->name = "spi-flash";
+	mtd->priv = nor;
+	mtd->type = MTD_NORFLASH;
+	mtd->writesize = 1;
+	mtd->flags = MTD_CAP_NORFLASH;
+	mtd->size = info->sector_size * info->n_sectors;
+	mtd->_erase = spi_nor_erase;
+	mtd->_read = spi_nor_read;
+	mtd->_write = spi_nor_write;
+
+	nor->size = mtd->size;
+
+	if (info->flags & USE_FSR)
+		nor->flags |= SNOR_F_USE_FSR;
+	if (info->flags & USE_CLSR)
+		nor->flags |= SNOR_F_USE_CLSR;
+
+	if (info->flags & SPI_NOR_NO_FR)
+		params.hwcaps.mask &= ~SNOR_HWCAPS_READ_FAST;
+
+	/*
+	 * Configure the SPI memory:
+	 * - select op codes for (Fast) Read, Page Program and Sector Erase.
+	 * - set the number of dummy cycles (mode cycles + wait states).
+	 * - set the SPI protocols for register and memory accesses.
+	 * - set the Quad Enable bit if needed (required by SPI x-y-4 protos).
+	 */
+	ret = spi_nor_setup(nor, info, &params, &hwcaps);
+	if (ret)
+		return ret;
+
+	if (nor->addr_width) {
+		/* already configured from SFDP */
+	} else if (info->addr_width) {
+		nor->addr_width = info->addr_width;
+	} else if (mtd->size > 0x1000000) {
+		/* enable 4-byte addressing if the device exceeds 16MiB */
+		nor->addr_width = 4;
+		if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
+		    info->flags & SPI_NOR_4B_OPCODES)
+			spi_nor_set_4byte_opcodes(nor, info);
+	} else {
+		nor->addr_width = 3;
+	}
+
+	if (nor->addr_width > SPI_NOR_MAX_ADDR_WIDTH) {
+		dev_dbg(dev, "address width is too large: %u\n",
+			nor->addr_width);
+		return -EINVAL;
+	}
+
+	/* Send all the required SPI flash commands to initialize device */
+	nor->info = info;
+	ret = spi_nor_init(nor);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/* U-Boot specific functions, need to extend MTD to support these */
+int spi_flash_cmd_get_sw_write_prot(struct spi_nor *nor)
+{
+	return -ENOTSUPP;
+}