// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2017 Free Electrons
 * Copyright (C) 2017 NextThing Co
 *
 * Author: Boris Brezillon <boris.brezillon@free-electrons.com>
 */

#include <linux/slab.h>

#include "internals.h"

/*
 * Special Micron status bit 3 indicates that the block has been
 * corrected by on-die ECC and should be rewritten.
 */
#define NAND_ECC_STATUS_WRITE_RECOMMENDED       BIT(3)

/*
 * On chips with 8-bit ECC and additional bit can be used to distinguish
 * cases where a errors were corrected without needing a rewrite
 *
 * Bit 4 Bit 3 Bit 0 Description
 * ----- ----- ----- -----------
 * 0     0     0     No Errors
 * 0     0     1     Multiple uncorrected errors
 * 0     1     0     4 - 6 errors corrected, recommend rewrite
 * 0     1     1     Reserved
 * 1     0     0     1 - 3 errors corrected
 * 1     0     1     Reserved
 * 1     1     0     7 - 8 errors corrected, recommend rewrite
 */
#define NAND_ECC_STATUS_MASK            (BIT(4) | BIT(3) | BIT(0))
#define NAND_ECC_STATUS_UNCORRECTABLE   BIT(0)
#define NAND_ECC_STATUS_4_6_CORRECTED   BIT(3)
#define NAND_ECC_STATUS_1_3_CORRECTED   BIT(4)
#define NAND_ECC_STATUS_7_8_CORRECTED   (BIT(4) | BIT(3))

struct nand_onfi_vendor_micron {
        u8 two_plane_read;
        u8 read_cache;
        u8 read_unique_id;
        u8 dq_imped;
        u8 dq_imped_num_settings;
        u8 dq_imped_feat_addr;
        u8 rb_pulldown_strength;
        u8 rb_pulldown_strength_feat_addr;
        u8 rb_pulldown_strength_num_settings;
        u8 otp_mode;
        u8 otp_page_start;
        u8 otp_data_prot_addr;
        u8 otp_num_pages;
        u8 otp_feat_addr;
        u8 read_retry_options;
        u8 reserved[72];
        u8 param_revision;
} __packed;

struct micron_on_die_ecc {
        bool forced;
        bool enabled;
        void *rawbuf;
};

struct micron_nand {
        struct micron_on_die_ecc ecc;
};

static int micron_nand_setup_read_retry(struct nand_chip *chip, int retry_mode)
{
        u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = {retry_mode};

        return nand_set_features(chip, ONFI_FEATURE_ADDR_READ_RETRY, feature);
}

/*
 * Configure chip properties from Micron vendor-specific ONFI table
 */
static int micron_nand_onfi_init(struct nand_chip *chip)
{
        struct nand_parameters *p = &chip->parameters;

        if (p->onfi) {
                struct nand_onfi_vendor_micron *micron = (void *)p->onfi->vendor;

                chip->read_retries = micron->read_retry_options;
                chip->setup_read_retry = micron_nand_setup_read_retry;
        }

        if (p->supports_set_get_features) {
                set_bit(ONFI_FEATURE_ADDR_READ_RETRY, p->set_feature_list);
                set_bit(ONFI_FEATURE_ON_DIE_ECC, p->set_feature_list);
                set_bit(ONFI_FEATURE_ADDR_READ_RETRY, p->get_feature_list);
                set_bit(ONFI_FEATURE_ON_DIE_ECC, p->get_feature_list);
        }

        return 0;
}

static int micron_nand_on_die_4_ooblayout_ecc(struct mtd_info *mtd,
                                              int section,
                                              struct mtd_oob_region *oobregion)
{
        if (section >= 4)
                return -ERANGE;

        oobregion->offset = (section * 16) + 8;
        oobregion->length = 8;

        return 0;
}

static int micron_nand_on_die_4_ooblayout_free(struct mtd_info *mtd,
                                               int section,
                                               struct mtd_oob_region *oobregion)
{
        if (section >= 4)
                return -ERANGE;

        oobregion->offset = (section * 16) + 2;
        oobregion->length = 6;

        return 0;
}

static const struct mtd_ooblayout_ops micron_nand_on_die_4_ooblayout_ops = {
        .ecc = micron_nand_on_die_4_ooblayout_ecc,
        .free = micron_nand_on_die_4_ooblayout_free,
};

static int micron_nand_on_die_8_ooblayout_ecc(struct mtd_info *mtd,
                                              int section,
                                              struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (section)
                return -ERANGE;

        oobregion->offset = mtd->oobsize - chip->ecc.total;
        oobregion->length = chip->ecc.total;

        return 0;
}

static int micron_nand_on_die_8_ooblayout_free(struct mtd_info *mtd,
                                               int section,
                                               struct mtd_oob_region *oobregion)
{
        struct nand_chip *chip = mtd_to_nand(mtd);

        if (section)
                return -ERANGE;

        oobregion->offset = 2;
        oobregion->length = mtd->oobsize - chip->ecc.total - 2;

        return 0;
}

static const struct mtd_ooblayout_ops micron_nand_on_die_8_ooblayout_ops = {
        .ecc = micron_nand_on_die_8_ooblayout_ecc,
        .free = micron_nand_on_die_8_ooblayout_free,
};

static int micron_nand_on_die_ecc_setup(struct nand_chip *chip, bool enable)
{
        struct micron_nand *micron = nand_get_manufacturer_data(chip);
        u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = { 0, };
        int ret;

        if (micron->ecc.forced)
                return 0;

        if (micron->ecc.enabled == enable)
                return 0;

        if (enable)
                feature[0] |= ONFI_FEATURE_ON_DIE_ECC_EN;

        ret = nand_set_features(chip, ONFI_FEATURE_ON_DIE_ECC, feature);
        if (!ret)
                micron->ecc.enabled = enable;

        return ret;
}

static int micron_nand_on_die_ecc_status_4(struct nand_chip *chip, u8 status,
                                           void *buf, int page,
                                           int oob_required)
{
        struct micron_nand *micron = nand_get_manufacturer_data(chip);
        struct mtd_info *mtd = nand_to_mtd(chip);
        unsigned int step, max_bitflips = 0;
        int ret;

        if (!(status & NAND_ECC_STATUS_WRITE_RECOMMENDED)) {
                if (status & NAND_STATUS_FAIL)
                        mtd->ecc_stats.failed++;

                return 0;
        }

        /*
         * The internal ECC doesn't tell us the number of bitflips that have
         * been corrected, but tells us if it recommends to rewrite the block.
         * If it's the case, we need to read the page in raw mode and compare
         * its content to the corrected version to extract the actual number of
         * bitflips.
         * But before we do that, we must make sure we have all OOB bytes read
         * in non-raw mode, even if the user did not request those bytes.
         */
        if (!oob_required) {
                ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,
                                        false);
                if (ret)
                        return ret;
        }

        micron_nand_on_die_ecc_setup(chip, false);

        ret = nand_read_page_op(chip, page, 0, micron->ecc.rawbuf,
                                mtd->writesize + mtd->oobsize);
        if (ret)
                return ret;

        for (step = 0; step < chip->ecc.steps; step++) {
                unsigned int offs, i, nbitflips = 0;
                u8 *rawbuf, *corrbuf;

                offs = step * chip->ecc.size;
                rawbuf = micron->ecc.rawbuf + offs;
                corrbuf = buf + offs;

                for (i = 0; i < chip->ecc.size; i++)
                        nbitflips += hweight8(corrbuf[i] ^ rawbuf[i]);

                offs = (step * 16) + 4;
                rawbuf = micron->ecc.rawbuf + mtd->writesize + offs;
                corrbuf = chip->oob_poi + offs;

                for (i = 0; i < chip->ecc.bytes + 4; i++)
                        nbitflips += hweight8(corrbuf[i] ^ rawbuf[i]);

                if (WARN_ON(nbitflips > chip->ecc.strength))
                        return -EINVAL;

                max_bitflips = max(nbitflips, max_bitflips);
                mtd->ecc_stats.corrected += nbitflips;
        }

        return max_bitflips;
}

static int micron_nand_on_die_ecc_status_8(struct nand_chip *chip, u8 status)
{
        struct mtd_info *mtd = nand_to_mtd(chip);

        /*
         * With 8/512 we have more information but still don't know precisely
         * how many bit-flips were seen.
         */
        switch (status & NAND_ECC_STATUS_MASK) {
        case NAND_ECC_STATUS_UNCORRECTABLE:
                mtd->ecc_stats.failed++;
                return 0;
        case NAND_ECC_STATUS_1_3_CORRECTED:
                mtd->ecc_stats.corrected += 3;
                return 3;
        case NAND_ECC_STATUS_4_6_CORRECTED:
                mtd->ecc_stats.corrected += 6;
                /* rewrite recommended */
                return 6;
        case NAND_ECC_STATUS_7_8_CORRECTED:
                mtd->ecc_stats.corrected += 8;
                /* rewrite recommended */
                return 8;
        default:
                return 0;
        }
}

static int
micron_nand_read_page_on_die_ecc(struct nand_chip *chip, uint8_t *buf,
                                 int oob_required, int page)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        u8 status;
        int ret, max_bitflips = 0;

        ret = micron_nand_on_die_ecc_setup(chip, true);
        if (ret)
                return ret;

        ret = nand_read_page_op(chip, page, 0, NULL, 0);
        if (ret)
                goto out;

        ret = nand_status_op(chip, &status);
        if (ret)
                goto out;

        ret = nand_exit_status_op(chip);
        if (ret)
                goto out;

        ret = nand_read_data_op(chip, buf, mtd->writesize, false);
        if (!ret && oob_required)
                ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,
                                        false);

        if (chip->ecc.strength == 4)
                max_bitflips = micron_nand_on_die_ecc_status_4(chip, status,
                                                               buf, page,
                                                               oob_required);
        else
                max_bitflips = micron_nand_on_die_ecc_status_8(chip, status);

out:
        micron_nand_on_die_ecc_setup(chip, false);

        return ret ? ret : max_bitflips;
}

static int
micron_nand_write_page_on_die_ecc(struct nand_chip *chip, const uint8_t *buf,
                                  int oob_required, int page)
{
        int ret;

        ret = micron_nand_on_die_ecc_setup(chip, true);
        if (ret)
                return ret;

        ret = nand_write_page_raw(chip, buf, oob_required, page);
        micron_nand_on_die_ecc_setup(chip, false);

        return ret;
}

enum {
        /* The NAND flash doesn't support on-die ECC */
        MICRON_ON_DIE_UNSUPPORTED,

        /*
         * The NAND flash supports on-die ECC and it can be
         * enabled/disabled by a set features command.
         */
        MICRON_ON_DIE_SUPPORTED,

        /*
         * The NAND flash supports on-die ECC, and it cannot be
         * disabled.
         */
        MICRON_ON_DIE_MANDATORY,
};

#define MICRON_ID_INTERNAL_ECC_MASK     GENMASK(1, 0)
#define MICRON_ID_ECC_ENABLED           BIT(7)

/*
 * Try to detect if the NAND support on-die ECC. To do this, we enable
 * the feature, and read back if it has been enabled as expected. We
 * also check if it can be disabled, because some Micron NANDs do not
 * allow disabling the on-die ECC and we don't support such NANDs for
 * now.
 *
 * This function also has the side effect of disabling on-die ECC if
 * it had been left enabled by the firmware/bootloader.
 */
static int micron_supports_on_die_ecc(struct nand_chip *chip)
{
        u8 id[5];
        int ret;

        if (!chip->parameters.onfi)
                return MICRON_ON_DIE_UNSUPPORTED;

        if (nanddev_bits_per_cell(&chip->base) != 1)
                return MICRON_ON_DIE_UNSUPPORTED;

        /*
         * We only support on-die ECC of 4/512 or 8/512
         */
        if  (chip->base.eccreq.strength != 4 && chip->base.eccreq.strength != 8)
                return MICRON_ON_DIE_UNSUPPORTED;

        /* 0x2 means on-die ECC is available. */
        if (chip->id.len != 5 ||
            (chip->id.data[4] & MICRON_ID_INTERNAL_ECC_MASK) != 0x2)
                return MICRON_ON_DIE_UNSUPPORTED;

        /*
         * It seems that there are devices which do not support ECC officially.
         * At least the MT29F2G08ABAGA / MT29F2G08ABBGA devices supports
         * enabling the ECC feature but don't reflect that to the READ_ID table.
         * So we have to guarantee that we disable the ECC feature directly
         * after we did the READ_ID table command. Later we can evaluate the
         * ECC_ENABLE support.
         */
        ret = micron_nand_on_die_ecc_setup(chip, true);
        if (ret)
                return MICRON_ON_DIE_UNSUPPORTED;

        ret = nand_readid_op(chip, 0, id, sizeof(id));
        if (ret)
                return MICRON_ON_DIE_UNSUPPORTED;

        ret = micron_nand_on_die_ecc_setup(chip, false);
        if (ret)
                return MICRON_ON_DIE_UNSUPPORTED;

        if (!(id[4] & MICRON_ID_ECC_ENABLED))
                return MICRON_ON_DIE_UNSUPPORTED;

        ret = nand_readid_op(chip, 0, id, sizeof(id));
        if (ret)
                return MICRON_ON_DIE_UNSUPPORTED;

        if (id[4] & MICRON_ID_ECC_ENABLED)
                return MICRON_ON_DIE_MANDATORY;

        /*
         * We only support on-die ECC of 4/512 or 8/512
         */
        if  (chip->base.eccreq.strength != 4 && chip->base.eccreq.strength != 8)
                return MICRON_ON_DIE_UNSUPPORTED;

        return MICRON_ON_DIE_SUPPORTED;
}

static int micron_nand_init(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct micron_nand *micron;
        int ondie;
        int ret;

        micron = kzalloc(sizeof(*micron), GFP_KERNEL);
        if (!micron)
                return -ENOMEM;

        nand_set_manufacturer_data(chip, micron);

        ret = micron_nand_onfi_init(chip);
        if (ret)
                goto err_free_manuf_data;

        if (mtd->writesize == 2048)
                chip->options |= NAND_BBM_FIRSTPAGE | NAND_BBM_SECONDPAGE;

        ondie = micron_supports_on_die_ecc(chip);

        if (ondie == MICRON_ON_DIE_MANDATORY &&
            chip->ecc.mode != NAND_ECC_ON_DIE) {
                pr_err("On-die ECC forcefully enabled, not supported\n");
                ret = -EINVAL;
                goto err_free_manuf_data;
        }

        if (chip->ecc.mode == NAND_ECC_ON_DIE) {
                if (ondie == MICRON_ON_DIE_UNSUPPORTED) {
                        pr_err("On-die ECC selected but not supported\n");
                        ret = -EINVAL;
                        goto err_free_manuf_data;
                }

                if (ondie == MICRON_ON_DIE_MANDATORY) {
                        micron->ecc.forced = true;
                        micron->ecc.enabled = true;
                }

                /*
                 * In case of 4bit on-die ECC, we need a buffer to store a
                 * page dumped in raw mode so that we can compare its content
                 * to the same page after ECC correction happened and extract
                 * the real number of bitflips from this comparison.
                 * That's not needed for 8-bit ECC, because the status expose
                 * a better approximation of the number of bitflips in a page.
                 */
                if (chip->base.eccreq.strength == 4) {
                        micron->ecc.rawbuf = kmalloc(mtd->writesize +
                                                     mtd->oobsize,
                                                     GFP_KERNEL);
                        if (!micron->ecc.rawbuf) {
                                ret = -ENOMEM;
                                goto err_free_manuf_data;
                        }
                }

                if (chip->base.eccreq.strength == 4)
                        mtd_set_ooblayout(mtd,
                                          &micron_nand_on_die_4_ooblayout_ops);
                else
                        mtd_set_ooblayout(mtd,
                                          &micron_nand_on_die_8_ooblayout_ops);

                chip->ecc.bytes = chip->base.eccreq.strength * 2;
                chip->ecc.size = 512;
                chip->ecc.strength = chip->base.eccreq.strength;
                chip->ecc.algo = NAND_ECC_BCH;
                chip->ecc.read_page = micron_nand_read_page_on_die_ecc;
                chip->ecc.write_page = micron_nand_write_page_on_die_ecc;

                if (ondie == MICRON_ON_DIE_MANDATORY) {
                        chip->ecc.read_page_raw = nand_read_page_raw_notsupp;
                        chip->ecc.write_page_raw = nand_write_page_raw_notsupp;
                } else {
                        chip->ecc.read_page_raw = nand_read_page_raw;
                        chip->ecc.write_page_raw = nand_write_page_raw;
                }
        }

        return 0;

err_free_manuf_data:
        kfree(micron->ecc.rawbuf);
        kfree(micron);

        return ret;
}

static void micron_nand_cleanup(struct nand_chip *chip)
{
        struct micron_nand *micron = nand_get_manufacturer_data(chip);

        kfree(micron->ecc.rawbuf);
        kfree(micron);
}

static void micron_fixup_onfi_param_page(struct nand_chip *chip,
                                         struct nand_onfi_params *p)
{
        /*
         * MT29F1G08ABAFAWP-ITE:F and possibly others report 00 00 for the
         * revision number field of the ONFI parameter page. Assume ONFI
         * version 1.0 if the revision number is 00 00.
         */
        if (le16_to_cpu(p->revision) == 0)
                p->revision = cpu_to_le16(ONFI_VERSION_1_0);
}

const struct nand_manufacturer_ops micron_nand_manuf_ops = {
        .init = micron_nand_init,
        .cleanup = micron_nand_cleanup,
        .fixup_onfi_param_page = micron_fixup_onfi_param_page,
};