path: root/drivers/mtd/spi-nor/intel-spi.c

/*
 * Intel PCH/PCU SPI flash driver.
 *
 * Copyright (C) 2016, Intel Corporation
 * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/err.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sizes.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/spi-nor.h>
#include <linux/platform_data/intel-spi.h>

#include "intel-spi.h"

/* Offsets are from @ispi->base */
#define BFPREG				0x00

#define HSFSTS_CTL			0x04
#define HSFSTS_CTL_FSMIE		BIT(31)
#define HSFSTS_CTL_FDBC_SHIFT		24
#define HSFSTS_CTL_FDBC_MASK		(0x3f << HSFSTS_CTL_FDBC_SHIFT)

#define HSFSTS_CTL_FCYCLE_SHIFT		17
#define HSFSTS_CTL_FCYCLE_MASK		(0x0f << HSFSTS_CTL_FCYCLE_SHIFT)
/* HW sequencer opcodes */
#define HSFSTS_CTL_FCYCLE_READ		(0x00 << HSFSTS_CTL_FCYCLE_SHIFT)
#define HSFSTS_CTL_FCYCLE_WRITE		(0x02 << HSFSTS_CTL_FCYCLE_SHIFT)
#define HSFSTS_CTL_FCYCLE_ERASE		(0x03 << HSFSTS_CTL_FCYCLE_SHIFT)
#define HSFSTS_CTL_FCYCLE_ERASE_64K	(0x04 << HSFSTS_CTL_FCYCLE_SHIFT)
#define HSFSTS_CTL_FCYCLE_RDID		(0x06 << HSFSTS_CTL_FCYCLE_SHIFT)
#define HSFSTS_CTL_FCYCLE_WRSR		(0x07 << HSFSTS_CTL_FCYCLE_SHIFT)
#define HSFSTS_CTL_FCYCLE_RDSR		(0x08 << HSFSTS_CTL_FCYCLE_SHIFT)

#define HSFSTS_CTL_FGO			BIT(16)
#define HSFSTS_CTL_FLOCKDN		BIT(15)
#define HSFSTS_CTL_FDV			BIT(14)
#define HSFSTS_CTL_SCIP			BIT(5)
#define HSFSTS_CTL_AEL			BIT(2)
#define HSFSTS_CTL_FCERR		BIT(1)
#define HSFSTS_CTL_FDONE		BIT(0)

#define FADDR				0x08
#define DLOCK				0x0c
#define FDATA(n)			(0x10 + ((n) * 4))

#define FRACC				0x50

#define FREG(n)				(0x54 + ((n) * 4))
#define FREG_BASE_MASK			0x3fff
#define FREG_LIMIT_SHIFT		16
#define FREG_LIMIT_MASK			(0x03fff << FREG_LIMIT_SHIFT)

/* Offset is from @ispi->pregs */
#define PR(n)				((n) * 4)
#define PR_WPE				BIT(31)
#define PR_LIMIT_SHIFT			16
#define PR_LIMIT_MASK			(0x3fff << PR_LIMIT_SHIFT)
#define PR_RPE				BIT(15)
#define PR_BASE_MASK			0x3fff

/* Offsets are from @ispi->sregs */
#define SSFSTS_CTL			0x00
#define SSFSTS_CTL_FSMIE		BIT(23)
#define SSFSTS_CTL_DS			BIT(22)
#define SSFSTS_CTL_DBC_SHIFT		16
#define SSFSTS_CTL_SPOP			BIT(11)
#define SSFSTS_CTL_ACS			BIT(10)
#define SSFSTS_CTL_SCGO			BIT(9)
#define SSFSTS_CTL_COP_SHIFT		12
#define SSFSTS_CTL_FRS			BIT(7)
#define SSFSTS_CTL_DOFRS		BIT(6)
#define SSFSTS_CTL_AEL			BIT(4)
#define SSFSTS_CTL_FCERR		BIT(3)
#define SSFSTS_CTL_FDONE		BIT(2)
#define SSFSTS_CTL_SCIP			BIT(0)

#define PREOP_OPTYPE			0x04
#define OPMENU0				0x08
#define OPMENU1				0x0c

#define OPTYPE_READ_NO_ADDR		0
#define OPTYPE_WRITE_NO_ADDR		1
#define OPTYPE_READ_WITH_ADDR		2
#define OPTYPE_WRITE_WITH_ADDR		3

/* CPU specifics */
#define BYT_PR				0x74
#define BYT_SSFSTS_CTL			0x90
#define BYT_BCR				0xfc
#define BYT_BCR_WPD			BIT(0)
#define BYT_FREG_NUM			5
#define BYT_PR_NUM			5

#define LPT_PR				0x74
#define LPT_SSFSTS_CTL			0x90
#define LPT_FREG_NUM			5
#define LPT_PR_NUM			5

#define BXT_PR				0x84
#define BXT_SSFSTS_CTL			0xa0
#define BXT_FREG_NUM			12
#define BXT_PR_NUM			6

#define INTEL_SPI_TIMEOUT		5000 /* ms */
#define INTEL_SPI_FIFO_SZ		64

/**
 * struct intel_spi - Driver private data
 * @dev: Device pointer
 * @info: Pointer to board specific info
 * @nor: SPI NOR layer structure
 * @base: Beginning of MMIO space
 * @pregs: Start of protection registers
 * @sregs: Start of software sequencer registers
 * @nregions: Maximum number of regions
 * @pr_num: Maximum number of protected range registers
 * @writeable: Is the chip writeable
 * @locked: Is SPI setting locked
 * @swseq_reg: Use SW sequencer in register reads/writes
 * @erase_64k: 64k erase supported
 * @opcodes: Opcodes which are supported. This are programmed by BIOS
 *           before it locks down the controller.
 * @preopcodes: Preopcodes which are supported.
 */
struct intel_spi {
	struct device *dev;
	const struct intel_spi_boardinfo *info;
	struct spi_nor nor;
	void __iomem *base;
	void __iomem *pregs;
	void __iomem *sregs;
	size_t nregions;
	size_t pr_num;
	bool writeable;
	bool locked;
	bool swseq_reg;
	bool erase_64k;
	u8 opcodes[8];
	u8 preopcodes[2];
};

static bool writeable;
module_param(writeable, bool, 0);
MODULE_PARM_DESC(writeable, "Enable write access to SPI flash chip (default=0)");

static void intel_spi_dump_regs(struct intel_spi *ispi)
{
	u32 value;
	int i;

	dev_dbg(ispi->dev, "BFPREG=0x%08x\n", readl(ispi->base + BFPREG));

	value = readl(ispi->base + HSFSTS_CTL);
	dev_dbg(ispi->dev, "HSFSTS_CTL=0x%08x\n", value);
	if (value & HSFSTS_CTL_FLOCKDN)
		dev_dbg(ispi->dev, "-> Locked\n");

	dev_dbg(ispi->dev, "FADDR=0x%08x\n", readl(ispi->base + FADDR));
	dev_dbg(ispi->dev, "DLOCK=0x%08x\n", readl(ispi->base + DLOCK));

	for (i = 0; i < 16; i++)
		dev_dbg(ispi->dev, "FDATA(%d)=0x%08x\n",
			i, readl(ispi->base + FDATA(i)));

	dev_dbg(ispi->dev, "FRACC=0x%08x\n", readl(ispi->base + FRACC));

	for (i = 0; i < ispi->nregions; i++)
		dev_dbg(ispi->dev, "FREG(%d)=0x%08x\n", i,
			readl(ispi->base + FREG(i)));
	for (i = 0; i < ispi->pr_num; i++)
		dev_dbg(ispi->dev, "PR(%d)=0x%08x\n", i,
			readl(ispi->pregs + PR(i)));

	value = readl(ispi->sregs + SSFSTS_CTL);
	dev_dbg(ispi->dev, "SSFSTS_CTL=0x%08x\n", value);
	dev_dbg(ispi->dev, "PREOP_OPTYPE=0x%08x\n",
		readl(ispi->sregs + PREOP_OPTYPE));
	dev_dbg(ispi->dev, "OPMENU0=0x%08x\n", readl(ispi->sregs + OPMENU0));
	dev_dbg(ispi->dev, "OPMENU1=0x%08x\n", readl(ispi->sregs + OPMENU1));

	if (ispi->info->type == INTEL_SPI_BYT)
		dev_dbg(ispi->dev, "BCR=0x%08x\n", readl(ispi->base + BYT_BCR));

	dev_dbg(ispi->dev, "Protected regions:\n");
	for (i = 0; i < ispi->pr_num; i++) {
		u32 base, limit;

		value = readl(ispi->pregs + PR(i));
		if (!(value & (PR_WPE | PR_RPE)))
			continue;

		limit = (value & PR_LIMIT_MASK) >> PR_LIMIT_SHIFT;
		base = value & PR_BASE_MASK;

		dev_dbg(ispi->dev, " %02d base: 0x%08x limit: 0x%08x [%c%c]\n",
			 i, base << 12, (limit << 12) | 0xfff,
			 value & PR_WPE ? 'W' : '.',
			 value & PR_RPE ? 'R' : '.');
	}

	dev_dbg(ispi->dev, "Flash regions:\n");
	for (i = 0; i < ispi->nregions; i++) {
		u32 region, base, limit;

		region = readl(ispi->base + FREG(i));
		base = region & FREG_BASE_MASK;
		limit = (region & FREG_LIMIT_MASK) >> FREG_LIMIT_SHIFT;

		if (base >= limit || (i > 0 && limit == 0))
			dev_dbg(ispi->dev, " %02d disabled\n", i);
		else
			dev_dbg(ispi->dev, " %02d base: 0x%08x limit: 0x%08x\n",
				 i, base << 12, (limit << 12) | 0xfff);
	}

	dev_dbg(ispi->dev, "Using %cW sequencer for register access\n",
		ispi->swseq_reg ? 'S' : 'H');
}

/* Reads max INTEL_SPI_FIFO_SZ bytes from the device fifo */
static int intel_spi_read_block(struct intel_spi *ispi, void *buf, size_t size)
{
	size_t bytes;
	int i = 0;

	if (size > INTEL_SPI_FIFO_SZ)
		return -EINVAL;

	while (size > 0) {
		bytes = min_t(size_t, size, 4);
		memcpy_fromio(buf, ispi->base + FDATA(i), bytes);
		size -= bytes;
		buf += bytes;
		i++;
	}

	return 0;
}

/* Writes max INTEL_SPI_FIFO_SZ bytes to the device fifo */
static int intel_spi_write_block(struct intel_spi *ispi, const void *buf,
				 size_t size)
{
	size_t bytes;
	int i = 0;

	if (size > INTEL_SPI_FIFO_SZ)
		return -EINVAL;

	while (size > 0) {
		bytes = min_t(size_t, size, 4);
		memcpy_toio(ispi->base + FDATA(i), buf, bytes);
		size -= bytes;
		buf += bytes;
		i++;
	}

	return 0;
}

static int intel_spi_wait_hw_busy(struct intel_spi *ispi)
{
	u32 val;

	return readl_poll_timeout(ispi->base + HSFSTS_CTL, val,
				  !(val & HSFSTS_CTL_SCIP), 0,
				  INTEL_SPI_TIMEOUT * 1000);
}

static int intel_spi_wait_sw_busy(struct intel_spi *ispi)
{
	u32 val;

	return readl_poll_timeout(ispi->sregs + SSFSTS_CTL, val,
				  !(val & SSFSTS_CTL_SCIP), 0,
				  INTEL_SPI_TIMEOUT * 1000);
}

static int intel_spi_init(struct intel_spi *ispi)
{
	u32 opmenu0, opmenu1, val;
	int i;

	switch (ispi->info->type) {
	case INTEL_SPI_BYT:
		ispi->sregs = ispi->base + BYT_SSFSTS_CTL;
		ispi->pregs = ispi->base + BYT_PR;
		ispi->nregions = BYT_FREG_NUM;
		ispi->pr_num = BYT_PR_NUM;
		ispi->swseq_reg = true;

		if (writeable) {
			/* Disable write protection */
			val = readl(ispi->base + BYT_BCR);
			if (!(val & BYT_BCR_WPD)) {
				val |= BYT_BCR_WPD;
				writel(val, ispi->base + BYT_BCR);
				val = readl(ispi->base + BYT_BCR);
			}

			ispi->writeable = !!(val & BYT_BCR_WPD);
		}

		break;

	case INTEL_SPI_LPT:
		ispi->sregs = ispi->base + LPT_SSFSTS_CTL;
		ispi->pregs = ispi->base + LPT_PR;
		ispi->nregions = LPT_FREG_NUM;
		ispi->pr_num = LPT_PR_NUM;
		ispi->swseq_reg = true;
		break;

	case INTEL_SPI_BXT:
		ispi->sregs = ispi->base + BXT_SSFSTS_CTL;
		ispi->pregs = ispi->base + BXT_PR;
		ispi->nregions = BXT_FREG_NUM;
		ispi->pr_num = BXT_PR_NUM;
		ispi->erase_64k = true;
		break;

	default:
		return -EINVAL;
	}

	/* Disable #SMI generation from HW sequencer */
	val = readl(ispi->base + HSFSTS_CTL);
	val &= ~HSFSTS_CTL_FSMIE;
	writel(val, ispi->base + HSFSTS_CTL);

	/*
	 * Some controllers can only do basic operations using hardware
	 * sequencer. All other operations are supposed to be carried out
	 * using software sequencer.
	 */
	if (ispi->swseq_reg) {
		/* Disable #SMI generation from SW sequencer */
		val = readl(ispi->sregs + SSFSTS_CTL);
		val &= ~SSFSTS_CTL_FSMIE;
		writel(val, ispi->sregs + SSFSTS_CTL);
	}

	/* Check controller's lock status */
	val = readl(ispi->base + HSFSTS_CTL);
	ispi->locked = !!(val & HSFSTS_CTL_FLOCKDN);

	if (ispi->locked) {
		/*
		 * BIOS programs allowed opcodes and then locks down the
		 * register. So read back what opcodes it decided to support.
		 * That's the set we are going to support as well.
		 */
		opmenu0 = readl(ispi->sregs + OPMENU0);
		opmenu1 = readl(ispi->sregs + OPMENU1);

		if (opmenu0 && opmenu1) {
			for (i = 0; i < ARRAY_SIZE(ispi->opcodes) / 2; i++) {
				ispi->opcodes[i] = opmenu0 >> i * 8;
				ispi->opcodes[i + 4] = opmenu1 >> i * 8;
			}

			val = readl(ispi->sregs + PREOP_OPTYPE);
			ispi->preopcodes[0] = val;
			ispi->preopcodes[1] = val >> 8;
		}
	}

	intel_spi_dump_regs(ispi);

	return 0;
}

static int intel_spi_opcode_index(struct intel_spi *ispi, u8 opcode, int optype)
{
	int i;
	int preop;

	if (ispi->locked) {
		for (i = 0; i < ARRAY_SIZE(ispi->opcodes); i++)
			if (ispi->opcodes[i] == opcode)
				return i;

		return -EINVAL;
	}

	/* The lock is off, so just use index 0 */
	writel(opcode, ispi->sregs + OPMENU0);
	preop = readw(ispi->sregs + PREOP_OPTYPE);
	writel(optype << 16 | preop, ispi->sregs + PREOP_OPTYPE);

	return 0;
}

static int intel_spi_hw_cycle(struct intel_spi *ispi, u8 opcode, int len)
{
	u32 val, status;
	int ret;

	val = readl(ispi->base + HSFSTS_CTL);
	val &= ~(HSFSTS_CTL_FCYCLE_MASK | HSFSTS_CTL_FDBC_MASK);

	switch (opcode) {
	case SPINOR_OP_RDID:
		val |= HSFSTS_CTL_FCYCLE_RDID;
		break;
	case SPINOR_OP_WRSR:
		val |= HSFSTS_CTL_FCYCLE_WRSR;
		break;
	case SPINOR_OP_RDSR:
		val |= HSFSTS_CTL_FCYCLE_RDSR;
		break;
	default:
		return -EINVAL;
	}

	if (len > INTEL_SPI_FIFO_SZ)
		return -EINVAL;

	val |= (len - 1) << HSFSTS_CTL_FDBC_SHIFT;
	val |= HSFSTS_CTL_FCERR | HSFSTS_CTL_FDONE;
	val |= HSFSTS_CTL_FGO;
	writel(val, ispi->base + HSFSTS_CTL);

	ret = intel_spi_wait_hw_busy(ispi);
	if (ret)
		return ret;

	status = readl(ispi->base + HSFSTS_CTL);
	if (status & HSFSTS_CTL_FCERR)
		return -EIO;
	else if (status & HSFSTS_CTL_AEL)
		return -EACCES;

	return 0;
}

static int intel_spi_sw_cycle(struct intel_spi *ispi, u8 opcode, int len,
			      int optype)
{
	u32 val = 0, status;
	u16 preop;
	int ret;

	ret = intel_spi_opcode_index(ispi, opcode, optype);
	if (ret < 0)
		return ret;

	if (len > INTEL_SPI_FIFO_SZ)
		return -EINVAL;

	/* Only mark 'Data Cycle' bit when there is data to be transferred */
	if (len > 0)
		val = ((len - 1) << SSFSTS_CTL_DBC_SHIFT) | SSFSTS_CTL_DS;
	val |= ret << SSFSTS_CTL_COP_SHIFT;
	val |= SSFSTS_CTL_FCERR | SSFSTS_CTL_FDONE;
	val |= SSFSTS_CTL_SCGO;
	preop = readw(ispi->sregs + PREOP_OPTYPE);
	if (preop) {
		val |= SSFSTS_CTL_ACS;
		if (preop >> 8)
			val |= SSFSTS_CTL_SPOP;
	}
	writel(val, ispi->sregs + SSFSTS_CTL);

	ret = intel_spi_wait_sw_busy(ispi);
	if (ret)
		return ret;

	status = readl(ispi->sregs + SSFSTS_CTL);
	if (status & SSFSTS_CTL_FCERR)
		return -EIO;
	else if (status & SSFSTS_CTL_AEL)
		return -EACCES;

	return 0;
}

static int intel_spi_read_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
{
	struct intel_spi *ispi = nor->priv;
	int ret;

	/* Address of the first chip */
	writel(0, ispi->base + FADDR);

	if (ispi->swseq_reg)
		ret = intel_spi_sw_cycle(ispi, opcode, len,
					 OPTYPE_READ_NO_ADDR);
	else
		ret = intel_spi_hw_cycle(ispi, opcode, len);

	if (ret)
		return ret;

	return intel_spi_read_block(ispi, buf, len);
}

static int intel_spi_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
{
	struct intel_spi *ispi = nor->priv;
	int ret;

	/*
	 * This is handled with atomic operation and preop code in Intel
	 * controller so skip it here now. If the controller is not locked,
	 * program the opcode to the PREOP register for later use.
	 */
	if (opcode == SPINOR_OP_WREN) {
		if (!ispi->locked)
			writel(opcode, ispi->sregs + PREOP_OPTYPE);

		return 0;
	}

	writel(0, ispi->base + FADDR);

	/* Write the value beforehand */
	ret = intel_spi_write_block(ispi, buf, len);
	if (ret)
		return ret;

	if (ispi->swseq_reg)
		return intel_spi_sw_cycle(ispi, opcode, len,
					  OPTYPE_WRITE_NO_ADDR);
	return intel_spi_hw_cycle(ispi, opcode, len);
}

static ssize_t intel_spi_read(struct spi_nor *nor, loff_t from, size_t len,
			      u_char *read_buf)
{
	struct intel_spi *ispi = nor->priv;
	size_t block_size, retlen = 0;
	u32 val, status;
	ssize_t ret;

	switch (nor->read_opcode) {
	case SPINOR_OP_READ:
	case SPINOR_OP_READ_FAST:
		break;
	default:
		return -EINVAL;
	}

	while (len > 0) {
		block_size = min_t(size_t, len, INTEL_SPI_FIFO_SZ);

		writel(from, ispi->base + FADDR);

		val = readl(ispi->base + HSFSTS_CTL);
		val &= ~(HSFSTS_CTL_FDBC_MASK | HSFSTS_CTL_FCYCLE_MASK);
		val |= HSFSTS_CTL_AEL | HSFSTS_CTL_FCERR | HSFSTS_CTL_FDONE;
		val |= (block_size - 1) << HSFSTS_CTL_FDBC_SHIFT;
		val |= HSFSTS_CTL_FCYCLE_READ;
		val |= HSFSTS_CTL_FGO;
		writel(val, ispi->base + HSFSTS_CTL);

		ret = intel_spi_wait_hw_busy(ispi);
		if (ret)
			return ret;

		status = readl(ispi->base + HSFSTS_CTL);
		if (status & HSFSTS_CTL_FCERR)
			ret = -EIO;
		else if (status & HSFSTS_CTL_AEL)
			ret = -EACCES;

		if (ret < 0) {
			dev_err(ispi->dev, "read error: %llx: %#x\n", from,
				status);
			return ret;
		}

		ret = intel_spi_read_block(ispi, read_buf, block_size);
		if (ret)
			return ret;

		len -= block_size;
		from += block_size;
		retlen += block_size;
		read_buf += block_size;
	}

	return retlen;
}

static ssize_t intel_spi_write(struct spi_nor *nor, loff_t to, size_t len,
			       const u_char *write_buf)
{
	struct intel_spi *ispi = nor->priv;
	size_t block_size, retlen = 0;
	u32 val, status;
	ssize_t ret;

	while (len > 0) {
		block_size = min_t(size_t, len, INTEL_SPI_FIFO_SZ);

		writel(to, ispi->base + FADDR);

		val = readl(ispi->base + HSFSTS_CTL);
		val &= ~(HSFSTS_CTL_FDBC_MASK | HSFSTS_CTL_FCYCLE_MASK);
		val |= HSFSTS_CTL_AEL | HSFSTS_CTL_FCERR | HSFSTS_CTL_FDONE;
		val |= (block_size - 1) << HSFSTS_CTL_FDBC_SHIFT;
		val |= HSFSTS_CTL_FCYCLE_WRITE;

		ret = intel_spi_write_block(ispi, write_buf, block_size);
		if (ret) {
			dev_err(ispi->dev, "failed to write block\n");
			return ret;
		}

		/* Start the write now */
		val |= HSFSTS_CTL_FGO;
		writel(val, ispi->base + HSFSTS_CTL);

		ret = intel_spi_wait_hw_busy(ispi);
		if (ret) {
			dev_err(ispi->dev, "timeout\n");
			return ret;
		}

		status = readl(ispi->base + HSFSTS_CTL);
		if (status & HSFSTS_CTL_FCERR)
			ret = -EIO;
		else if (status & HSFSTS_CTL_AEL)
			ret = -EACCES;

		if (ret < 0) {
			dev_err(ispi->dev, "write error: %llx: %#x\n", to,
				status);
			return ret;
		}

		len -= block_size;
		to += block_size;
		retlen += block_size;
		write_buf += block_size;
	}

	return retlen;
}

static int intel_spi_erase(struct spi_nor *nor, loff_t offs)
{
	size_t erase_size, len = nor->mtd.erasesize;
	struct intel_spi *ispi = nor->priv;
	u32 val, status, cmd;
	int ret;

	/* If the hardware can do 64k erase use that when possible */
	if (len >= SZ_64K && ispi->erase_64k) {
		cmd = HSFSTS_CTL_FCYCLE_ERASE_64K;
		erase_size = SZ_64K;
	} else {
		cmd = HSFSTS_CTL_FCYCLE_ERASE;
		erase_size = SZ_4K;
	}

	while (len > 0) {
		writel(offs, ispi->base + FADDR);

		val = readl(ispi->base + HSFSTS_CTL);
		val &= ~(HSFSTS_CTL_FDBC_MASK | HSFSTS_CTL_FCYCLE_MASK);
		val |= HSFSTS_CTL_AEL | HSFSTS_CTL_FCERR | HSFSTS_CTL_FDONE;
		val |= cmd;
		val |= HSFSTS_CTL_FGO;
		writel(val, ispi->base + HSFSTS_CTL);

		ret = intel_spi_wait_hw_busy(ispi);
		if (ret)
			return ret;

		status = readl(ispi->base + HSFSTS_CTL);
		if (status & HSFSTS_CTL_FCERR)
			return -EIO;
		else if (status & HSFSTS_CTL_AEL)
			return -EACCES;

		offs += erase_size;
		len -= erase_size;
	}

	return 0;
}

static bool intel_spi_is_protected(const struct intel_spi *ispi,
				   unsigned int base, unsigned int limit)
{
	int i;

	for (i = 0; i < ispi->pr_num; i++) {
		u32 pr_base, pr_limit, pr_value;

		pr_value = readl(ispi->pregs + PR(i));
		if (!(pr_value & (PR_WPE | PR_RPE)))
			continue;

		pr_limit = (pr_value & PR_LIMIT_MASK) >> PR_LIMIT_SHIFT;
		pr_base = pr_value & PR_BASE_MASK;

		if (pr_base >= base && pr_limit <= limit)
			return true;
	}

	return false;
}

/*
 * There will be a single partition holding all enabled flash regions. We
 * call this "BIOS".
 */
static void intel_spi_fill_partition(struct intel_spi *ispi,
				     struct mtd_partition *part)
{
	u64 end;
	int i;

	memset(part, 0, sizeof(*part));

	/* Start from the mandatory descriptor region */
	part->size = 4096;
	part->name = "BIOS";

	/*
	 * Now try to find where this partition ends based on the flash
	 * region registers.
	 */
	for (i = 1; i < ispi->nregions; i++) {
		u32 region, base, limit;

		region = readl(ispi->base + FREG(i));
		base = region & FREG_BASE_MASK;
		limit = (region & FREG_LIMIT_MASK) >> FREG_LIMIT_SHIFT;

		if (base >= limit || limit == 0)
			continue;

		/*
		 * If any of the regions have protection bits set, make the
		 * whole partition read-only to be on the safe side.
		 */
		if (intel_spi_is_protected(ispi, base, limit))
			ispi->writeable = false;

		end = (limit << 12) + 4096;
		if (end > part->size)
			part->size = end;
	}
}

struct intel_spi *intel_spi_probe(struct device *dev,
	struct resource *mem, const struct intel_spi_boardinfo *info)
{
	const struct spi_nor_hwcaps hwcaps = {
		.mask = SNOR_HWCAPS_READ |
			SNOR_HWCAPS_READ_FAST |
			SNOR_HWCAPS_PP,
	};
	struct mtd_partition part;
	struct intel_spi *ispi;
	int ret;

	if (!info || !mem)
		return ERR_PTR(-EINVAL);

	ispi = devm_kzalloc(dev, sizeof(*ispi), GFP_KERNEL);
	if (!ispi)
		return ERR_PTR(-ENOMEM);

	ispi->base = devm_ioremap_resource(dev, mem);
	if (IS_ERR(ispi->base))
		return ERR_CAST(ispi->base);

	ispi->dev = dev;
	ispi->info = info;
	ispi->writeable = info->writeable;

	ret = intel_spi_init(ispi);
	if (ret)
		return ERR_PTR(ret);

	ispi->nor.dev = ispi->dev;
	ispi->nor.priv = ispi;
	ispi->nor.read_reg = intel_spi_read_reg;
	ispi->nor.write_reg = intel_spi_write_reg;
	ispi->nor.read = intel_spi_read;
	ispi->nor.write = intel_spi_write;
	ispi->nor.erase = intel_spi_erase;

	ret = spi_nor_scan(&ispi->nor, NULL, &hwcaps);
	if (ret) {
		dev_info(dev, "failed to locate the chip\n");
		return ERR_PTR(ret);
	}

	intel_spi_fill_partition(ispi, &part);

	/* Prevent writes if not explicitly enabled */
	if (!ispi->writeable || !writeable)
		ispi->nor.mtd.flags &= ~MTD_WRITEABLE;

	ret = mtd_device_parse_register(&ispi->nor.mtd, NULL, NULL, &part, 1);
	if (ret)
		return ERR_PTR(ret);

	return ispi;
}
EXPORT_SYMBOL_GPL(intel_spi_probe);

int intel_spi_remove(struct intel_spi *ispi)
{
	return mtd_device_unregister(&ispi->nor.mtd);
}
EXPORT_SYMBOL_GPL(intel_spi_remove);

MODULE_DESCRIPTION("Intel PCH/PCU SPI flash core driver");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
MODULE_LICENSE("GPL v2");