// SPDX-License-Identifier: GPL-2.0
/*
 * OTP support for SPI NOR flashes
 *
 * Copyright (C) 2021 Michael Walle <michael@walle.cc>
 */

#include <linux/log2.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/spi-nor.h>

#include "core.h"

#define spi_nor_otp_region_len(nor) ((nor)->params->otp.org->len)
#define spi_nor_otp_n_regions(nor) ((nor)->params->otp.org->n_regions)

/**
 * spi_nor_otp_read_secr() - read security register
 * @nor:        pointer to 'struct spi_nor'
 * @addr:       offset to read from
 * @len:        number of bytes to read
 * @buf:        pointer to dst buffer
 *
 * Read a security register by using the SPINOR_OP_RSECR commands.
 *
 * In Winbond/GigaDevice datasheets the term "security register" stands for
 * an one-time-programmable memory area, consisting of multiple bytes (usually
 * 256). Thus one "security register" maps to one OTP region.
 *
 * This method is used on GigaDevice and Winbond flashes.
 *
 * Please note, the read must not span multiple registers.
 *
 * Return: number of bytes read successfully, -errno otherwise
 */
int spi_nor_otp_read_secr(struct spi_nor *nor, loff_t addr, size_t len, u8 *buf)
{
        u8 addr_width, read_opcode, read_dummy;
        struct spi_mem_dirmap_desc *rdesc;
        enum spi_nor_protocol read_proto;
        int ret;

        read_opcode = nor->read_opcode;
        addr_width = nor->addr_width;
        read_dummy = nor->read_dummy;
        read_proto = nor->read_proto;
        rdesc = nor->dirmap.rdesc;

        nor->read_opcode = SPINOR_OP_RSECR;
        nor->read_dummy = 8;
        nor->read_proto = SNOR_PROTO_1_1_1;
        nor->dirmap.rdesc = NULL;

        ret = spi_nor_read_data(nor, addr, len, buf);

        nor->read_opcode = read_opcode;
        nor->addr_width = addr_width;
        nor->read_dummy = read_dummy;
        nor->read_proto = read_proto;
        nor->dirmap.rdesc = rdesc;

        return ret;
}

/**
 * spi_nor_otp_write_secr() - write security register
 * @nor:        pointer to 'struct spi_nor'
 * @addr:       offset to write to
 * @len:        number of bytes to write
 * @buf:        pointer to src buffer
 *
 * Write a security register by using the SPINOR_OP_PSECR commands.
 *
 * For more information on the term "security register", see the documentation
 * of spi_nor_otp_read_secr().
 *
 * This method is used on GigaDevice and Winbond flashes.
 *
 * Please note, the write must not span multiple registers.
 *
 * Return: number of bytes written successfully, -errno otherwise
 */
int spi_nor_otp_write_secr(struct spi_nor *nor, loff_t addr, size_t len,
                           const u8 *buf)
{
        enum spi_nor_protocol write_proto;
        struct spi_mem_dirmap_desc *wdesc;
        u8 addr_width, program_opcode;
        int ret, written;

        program_opcode = nor->program_opcode;
        addr_width = nor->addr_width;
        write_proto = nor->write_proto;
        wdesc = nor->dirmap.wdesc;

        nor->program_opcode = SPINOR_OP_PSECR;
        nor->write_proto = SNOR_PROTO_1_1_1;
        nor->dirmap.wdesc = NULL;

        /*
         * We only support a write to one single page. For now all winbond
         * flashes only have one page per security register.
         */
        ret = spi_nor_write_enable(nor);
        if (ret)
                goto out;

        written = spi_nor_write_data(nor, addr, len, buf);
        if (written < 0)
                goto out;

        ret = spi_nor_wait_till_ready(nor);

out:
        nor->program_opcode = program_opcode;
        nor->addr_width = addr_width;
        nor->write_proto = write_proto;
        nor->dirmap.wdesc = wdesc;

        return ret ?: written;
}

/**
 * spi_nor_otp_erase_secr() - erase a security register
 * @nor:        pointer to 'struct spi_nor'
 * @addr:       offset of the security register to be erased
 *
 * Erase a security register by using the SPINOR_OP_ESECR command.
 *
 * For more information on the term "security register", see the documentation
 * of spi_nor_otp_read_secr().
 *
 * This method is used on GigaDevice and Winbond flashes.
 *
 * Return: 0 on success, -errno otherwise
 */
int spi_nor_otp_erase_secr(struct spi_nor *nor, loff_t addr)
{
        u8 erase_opcode = nor->erase_opcode;
        int ret;

        ret = spi_nor_write_enable(nor);
        if (ret)
                return ret;

        nor->erase_opcode = SPINOR_OP_ESECR;
        ret = spi_nor_erase_sector(nor, addr);
        nor->erase_opcode = erase_opcode;
        if (ret)
                return ret;

        return spi_nor_wait_till_ready(nor);
}

static int spi_nor_otp_lock_bit_cr(unsigned int region)
{
        static const int lock_bits[] = { SR2_LB1, SR2_LB2, SR2_LB3 };

        if (region >= ARRAY_SIZE(lock_bits))
                return -EINVAL;

        return lock_bits[region];
}

/**
 * spi_nor_otp_lock_sr2() - lock the OTP region
 * @nor:        pointer to 'struct spi_nor'
 * @region:     OTP region
 *
 * Lock the OTP region by writing the status register-2. This method is used on
 * GigaDevice and Winbond flashes.
 *
 * Return: 0 on success, -errno otherwise.
 */
int spi_nor_otp_lock_sr2(struct spi_nor *nor, unsigned int region)
{
        u8 *cr = nor->bouncebuf;
        int ret, lock_bit;

        lock_bit = spi_nor_otp_lock_bit_cr(region);
        if (lock_bit < 0)
                return lock_bit;

        ret = spi_nor_read_cr(nor, cr);
        if (ret)
                return ret;

        /* no need to write the register if region is already locked */
        if (cr[0] & lock_bit)
                return 0;

        cr[0] |= lock_bit;

        return spi_nor_write_16bit_cr_and_check(nor, cr[0]);
}

/**
 * spi_nor_otp_is_locked_sr2() - get the OTP region lock status
 * @nor:        pointer to 'struct spi_nor'
 * @region:     OTP region
 *
 * Retrieve the OTP region lock bit by reading the status register-2. This
 * method is used on GigaDevice and Winbond flashes.
 *
 * Return: 0 on success, -errno otherwise.
 */
int spi_nor_otp_is_locked_sr2(struct spi_nor *nor, unsigned int region)
{
        u8 *cr = nor->bouncebuf;
        int ret, lock_bit;

        lock_bit = spi_nor_otp_lock_bit_cr(region);
        if (lock_bit < 0)
                return lock_bit;

        ret = spi_nor_read_cr(nor, cr);
        if (ret)
                return ret;

        return cr[0] & lock_bit;
}

static loff_t spi_nor_otp_region_start(const struct spi_nor *nor, unsigned int region)
{
        const struct spi_nor_otp_organization *org = nor->params->otp.org;

        return org->base + region * org->offset;
}

static size_t spi_nor_otp_size(struct spi_nor *nor)
{
        return spi_nor_otp_n_regions(nor) * spi_nor_otp_region_len(nor);
}

/* Translate the file offsets from and to OTP regions. */
static loff_t spi_nor_otp_region_to_offset(struct spi_nor *nor, unsigned int region)
{
        return region * spi_nor_otp_region_len(nor);
}

static unsigned int spi_nor_otp_offset_to_region(struct spi_nor *nor, loff_t ofs)
{
        return div64_u64(ofs, spi_nor_otp_region_len(nor));
}

static int spi_nor_mtd_otp_info(struct mtd_info *mtd, size_t len,
                                size_t *retlen, struct otp_info *buf)
{
        struct spi_nor *nor = mtd_to_spi_nor(mtd);
        const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
        unsigned int n_regions = spi_nor_otp_n_regions(nor);
        unsigned int i;
        int ret, locked;

        if (len < n_regions * sizeof(*buf))
                return -ENOSPC;

        ret = spi_nor_lock_and_prep(nor);
        if (ret)
                return ret;

        for (i = 0; i < n_regions; i++) {
                buf->start = spi_nor_otp_region_to_offset(nor, i);
                buf->length = spi_nor_otp_region_len(nor);

                locked = ops->is_locked(nor, i);
                if (locked < 0) {
                        ret = locked;
                        goto out;
                }

                buf->locked = !!locked;
                buf++;
        }

        *retlen = n_regions * sizeof(*buf);

out:
        spi_nor_unlock_and_unprep(nor);

        return ret;
}

static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, loff_t ofs,
                                           size_t len)
{
        const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
        unsigned int region;
        int locked;

        /*
         * If any of the affected OTP regions are locked the entire range is
         * considered locked.
         */
        for (region = spi_nor_otp_offset_to_region(nor, ofs);
             region <= spi_nor_otp_offset_to_region(nor, ofs + len - 1);
             region++) {
                locked = ops->is_locked(nor, region);
                /* take the branch it is locked or in case of an error */
                if (locked)
                        return locked;
        }

        return 0;
}

static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
                                      size_t total_len, size_t *retlen,
                                      const u8 *buf, bool is_write)
{
        struct spi_nor *nor = mtd_to_spi_nor(mtd);
        const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
        const size_t rlen = spi_nor_otp_region_len(nor);
        loff_t rstart, rofs;
        unsigned int region;
        size_t len;
        int ret;

        if (ofs < 0 || ofs >= spi_nor_otp_size(nor))
                return 0;

        /* don't access beyond the end */
        total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);

        if (!total_len)
                return 0;

        ret = spi_nor_lock_and_prep(nor);
        if (ret)
                return ret;

        if (is_write) {
                ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, total_len);
                if (ret < 0) {
                        goto out;
                } else if (ret) {
                        ret = -EROFS;
                        goto out;
                }
        }

        while (total_len) {
                /*
                 * The OTP regions are mapped into a contiguous area starting
                 * at 0 as expected by the MTD layer. This will map the MTD
                 * file offsets to the address of an OTP region as used in the
                 * actual SPI commands.
                 */
                region = spi_nor_otp_offset_to_region(nor, ofs);
                rstart = spi_nor_otp_region_start(nor, region);

                /*
                 * The size of a OTP region is expected to be a power of two,
                 * thus we can just mask the lower bits and get the offset into
                 * a region.
                 */
                rofs = ofs & (rlen - 1);

                /* don't access beyond one OTP region */
                len = min_t(size_t, total_len, rlen - rofs);

                if (is_write)
                        ret = ops->write(nor, rstart + rofs, len, buf);
                else
                        ret = ops->read(nor, rstart + rofs, len, (u8 *)buf);
                if (ret == 0)
                        ret = -EIO;
                if (ret < 0)
                        goto out;

                *retlen += ret;
                ofs += ret;
                buf += ret;
                total_len -= ret;
        }
        ret = 0;

out:
        spi_nor_unlock_and_unprep(nor);
        return ret;
}

static int spi_nor_mtd_otp_read(struct mtd_info *mtd, loff_t from, size_t len,
                                size_t *retlen, u8 *buf)
{
        return spi_nor_mtd_otp_read_write(mtd, from, len, retlen, buf, false);
}

static int spi_nor_mtd_otp_write(struct mtd_info *mtd, loff_t to, size_t len,
                                 size_t *retlen, const u8 *buf)
{
        return spi_nor_mtd_otp_read_write(mtd, to, len, retlen, buf, true);
}

static int spi_nor_mtd_otp_erase(struct mtd_info *mtd, loff_t from, size_t len)
{
        struct spi_nor *nor = mtd_to_spi_nor(mtd);
        const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
        const size_t rlen = spi_nor_otp_region_len(nor);
        unsigned int region;
        loff_t rstart;
        int ret;

        /* OTP erase is optional */
        if (!ops->erase)
                return -EOPNOTSUPP;

        if (!len)
                return 0;

        if (from < 0 || (from + len) > spi_nor_otp_size(nor))
                return -EINVAL;

        /* the user has to explicitly ask for whole regions */
        if (!IS_ALIGNED(len, rlen) || !IS_ALIGNED(from, rlen))
                return -EINVAL;

        ret = spi_nor_lock_and_prep(nor);
        if (ret)
                return ret;

        ret = spi_nor_mtd_otp_range_is_locked(nor, from, len);
        if (ret < 0) {
                goto out;
        } else if (ret) {
                ret = -EROFS;
                goto out;
        }

        while (len) {
                region = spi_nor_otp_offset_to_region(nor, from);
                rstart = spi_nor_otp_region_start(nor, region);

                ret = ops->erase(nor, rstart);
                if (ret)
                        goto out;

                len -= rlen;
                from += rlen;
        }

out:
        spi_nor_unlock_and_unprep(nor);

        return ret;
}

static int spi_nor_mtd_otp_lock(struct mtd_info *mtd, loff_t from, size_t len)
{
        struct spi_nor *nor = mtd_to_spi_nor(mtd);
        const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
        const size_t rlen = spi_nor_otp_region_len(nor);
        unsigned int region;
        int ret;

        if (from < 0 || (from + len) > spi_nor_otp_size(nor))
                return -EINVAL;

        /* the user has to explicitly ask for whole regions */
        if (!IS_ALIGNED(len, rlen) || !IS_ALIGNED(from, rlen))
                return -EINVAL;

        ret = spi_nor_lock_and_prep(nor);
        if (ret)
                return ret;

        while (len) {
                region = spi_nor_otp_offset_to_region(nor, from);
                ret = ops->lock(nor, region);
                if (ret)
                        goto out;

                len -= rlen;
                from += rlen;
        }

out:
        spi_nor_unlock_and_unprep(nor);

        return ret;
}

void spi_nor_otp_init(struct spi_nor *nor)
{
        struct mtd_info *mtd = &nor->mtd;

        if (!nor->params->otp.ops)
                return;

        if (WARN_ON(!is_power_of_2(spi_nor_otp_region_len(nor))))
                return;

        /*
         * We only support user_prot callbacks (yet).
         *
         * Some SPI NOR flashes like Macronix ones can be ordered in two
         * different variants. One with a factory locked OTP area and one where
         * it is left to the user to write to it. The factory locked OTP is
         * usually preprogrammed with an "electrical serial number". We don't
         * support these for now.
         */
        mtd->_get_user_prot_info = spi_nor_mtd_otp_info;
        mtd->_read_user_prot_reg = spi_nor_mtd_otp_read;
        mtd->_write_user_prot_reg = spi_nor_mtd_otp_write;
        mtd->_lock_user_prot_reg = spi_nor_mtd_otp_lock;
        mtd->_erase_user_prot_reg = spi_nor_mtd_otp_erase;
}