// SPDX-License-Identifier: GPL-2.0+
/*
 * Generic Error-Correcting Code (ECC) engine
 *
 * Copyright (C) 2019 Macronix
 * Author:
 *     Miquèl RAYNAL <miquel.raynal@bootlin.com>
 *
 *
 * This file describes the abstraction of any NAND ECC engine. It has been
 * designed to fit most cases, including parallel NANDs and SPI-NANDs.
 *
 * There are three main situations where instantiating this ECC engine makes
 * sense:
 *   - external: The ECC engine is outside the NAND pipeline, typically this
 *               is a software ECC engine, or an hardware engine that is
 *               outside the NAND controller pipeline.
 *   - pipelined: The ECC engine is inside the NAND pipeline, ie. on the
 *                controller's side. This is the case of most of the raw NAND
 *                controllers. In the pipeline case, the ECC bytes are
 *                generated/data corrected on the fly when a page is
 *                written/read.
 *   - ondie: The ECC engine is inside the NAND pipeline, on the chip's side.
 *            Some NAND chips can correct themselves the data.
 *
 * Besides the initial setup and final cleanups, the interfaces are rather
 * simple:
 *   - prepare: Prepare an I/O request. Enable/disable the ECC engine based on
 *              the I/O request type. In case of software correction or external
 *              engine, this step may involve to derive the ECC bytes and place
 *              them in the OOB area before a write.
 *   - finish: Finish an I/O request. Correct the data in case of a read
 *             request and report the number of corrected bits/uncorrectable
 *             errors. Most likely empty for write operations, unless you have
 *             hardware specific stuff to do, like shutting down the engine to
 *             save power.
 *
 * The I/O request should be enclosed in a prepare()/finish() pair of calls
 * and will behave differently depending on the requested I/O type:
 *   - raw: Correction disabled
 *   - ecc: Correction enabled
 *
 * The request direction is impacting the logic as well:
 *   - read: Load data from the NAND chip
 *   - write: Store data in the NAND chip
 *
 * Mixing all this combinations together gives the following behavior.
 * Those are just examples, drivers are free to add custom steps in their
 * prepare/finish hook.
 *
 * [external ECC engine]
 *   - external + prepare + raw + read: do nothing
 *   - external + finish  + raw + read: do nothing
 *   - external + prepare + raw + write: do nothing
 *   - external + finish  + raw + write: do nothing
 *   - external + prepare + ecc + read: do nothing
 *   - external + finish  + ecc + read: calculate expected ECC bytes, extract
 *                                      ECC bytes from OOB buffer, correct
 *                                      and report any bitflip/error
 *   - external + prepare + ecc + write: calculate ECC bytes and store them at
 *                                       the right place in the OOB buffer based
 *                                       on the OOB layout
 *   - external + finish  + ecc + write: do nothing
 *
 * [pipelined ECC engine]
 *   - pipelined + prepare + raw + read: disable the controller's ECC engine if
 *                                       activated
 *   - pipelined + finish  + raw + read: do nothing
 *   - pipelined + prepare + raw + write: disable the controller's ECC engine if
 *                                        activated
 *   - pipelined + finish  + raw + write: do nothing
 *   - pipelined + prepare + ecc + read: enable the controller's ECC engine if
 *                                       deactivated
 *   - pipelined + finish  + ecc + read: check the status, report any
 *                                       error/bitflip
 *   - pipelined + prepare + ecc + write: enable the controller's ECC engine if
 *                                        deactivated
 *   - pipelined + finish  + ecc + write: do nothing
 *
 * [ondie ECC engine]
 *   - ondie + prepare + raw + read: send commands to disable the on-chip ECC
 *                                   engine if activated
 *   - ondie + finish  + raw + read: do nothing
 *   - ondie + prepare + raw + write: send commands to disable the on-chip ECC
 *                                    engine if activated
 *   - ondie + finish  + raw + write: do nothing
 *   - ondie + prepare + ecc + read: send commands to enable the on-chip ECC
 *                                   engine if deactivated
 *   - ondie + finish  + ecc + read: send commands to check the status, report
 *                                   any error/bitflip
 *   - ondie + prepare + ecc + write: send commands to enable the on-chip ECC
 *                                    engine if deactivated
 *   - ondie + finish  + ecc + write: do nothing
 */

#include <linux/module.h>
#include <linux/mtd/nand.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_platform.h>

static LIST_HEAD(on_host_hw_engines);
static DEFINE_MUTEX(on_host_hw_engines_mutex);

/**
 * nand_ecc_init_ctx - Init the ECC engine context
 * @nand: the NAND device
 *
 * On success, the caller is responsible of calling @nand_ecc_cleanup_ctx().
 */
int nand_ecc_init_ctx(struct nand_device *nand)
{
        if (!nand->ecc.engine || !nand->ecc.engine->ops->init_ctx)
                return 0;

        return nand->ecc.engine->ops->init_ctx(nand);
}
EXPORT_SYMBOL(nand_ecc_init_ctx);

/**
 * nand_ecc_cleanup_ctx - Cleanup the ECC engine context
 * @nand: the NAND device
 */
void nand_ecc_cleanup_ctx(struct nand_device *nand)
{
        if (nand->ecc.engine && nand->ecc.engine->ops->cleanup_ctx)
                nand->ecc.engine->ops->cleanup_ctx(nand);
}
EXPORT_SYMBOL(nand_ecc_cleanup_ctx);

/**
 * nand_ecc_prepare_io_req - Prepare an I/O request
 * @nand: the NAND device
 * @req: the I/O request
 */
int nand_ecc_prepare_io_req(struct nand_device *nand,
                            struct nand_page_io_req *req)
{
        if (!nand->ecc.engine || !nand->ecc.engine->ops->prepare_io_req)
                return 0;

        return nand->ecc.engine->ops->prepare_io_req(nand, req);
}
EXPORT_SYMBOL(nand_ecc_prepare_io_req);

/**
 * nand_ecc_finish_io_req - Finish an I/O request
 * @nand: the NAND device
 * @req: the I/O request
 */
int nand_ecc_finish_io_req(struct nand_device *nand,
                           struct nand_page_io_req *req)
{
        if (!nand->ecc.engine || !nand->ecc.engine->ops->finish_io_req)
                return 0;

        return nand->ecc.engine->ops->finish_io_req(nand, req);
}
EXPORT_SYMBOL(nand_ecc_finish_io_req);

/* Define default OOB placement schemes for large and small page devices */
static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
                                 struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int total_ecc_bytes = nand->ecc.ctx.total;

        if (section > 1)
                return -ERANGE;

        if (!section) {
                oobregion->offset = 0;
                if (mtd->oobsize == 16)
                        oobregion->length = 4;
                else
                        oobregion->length = 3;
        } else {
                if (mtd->oobsize == 8)
                        return -ERANGE;

                oobregion->offset = 6;
                oobregion->length = total_ecc_bytes - 4;
        }

        return 0;
}

static int nand_ooblayout_free_sp(struct mtd_info *mtd, int section,
                                  struct mtd_oob_region *oobregion)
{
        if (section > 1)
                return -ERANGE;

        if (mtd->oobsize == 16) {
                if (section)
                        return -ERANGE;

                oobregion->length = 8;
                oobregion->offset = 8;
        } else {
                oobregion->length = 2;
                if (!section)
                        oobregion->offset = 3;
                else
                        oobregion->offset = 6;
        }

        return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_sp_ops = {
        .ecc = nand_ooblayout_ecc_sp,
        .free = nand_ooblayout_free_sp,
};

const struct mtd_ooblayout_ops *nand_get_small_page_ooblayout(void)
{
        return &nand_ooblayout_sp_ops;
}
EXPORT_SYMBOL_GPL(nand_get_small_page_ooblayout);

static int nand_ooblayout_ecc_lp(struct mtd_info *mtd, int section,
                                 struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int total_ecc_bytes = nand->ecc.ctx.total;

        if (section || !total_ecc_bytes)
                return -ERANGE;

        oobregion->length = total_ecc_bytes;
        oobregion->offset = mtd->oobsize - oobregion->length;

        return 0;
}

static int nand_ooblayout_free_lp(struct mtd_info *mtd, int section,
                                  struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int total_ecc_bytes = nand->ecc.ctx.total;

        if (section)
                return -ERANGE;

        oobregion->length = mtd->oobsize - total_ecc_bytes - 2;
        oobregion->offset = 2;

        return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_lp_ops = {
        .ecc = nand_ooblayout_ecc_lp,
        .free = nand_ooblayout_free_lp,
};

const struct mtd_ooblayout_ops *nand_get_large_page_ooblayout(void)
{
        return &nand_ooblayout_lp_ops;
}
EXPORT_SYMBOL_GPL(nand_get_large_page_ooblayout);

/*
 * Support the old "large page" layout used for 1-bit Hamming ECC where ECC
 * are placed at a fixed offset.
 */
static int nand_ooblayout_ecc_lp_hamming(struct mtd_info *mtd, int section,
                                         struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int total_ecc_bytes = nand->ecc.ctx.total;

        if (section)
                return -ERANGE;

        switch (mtd->oobsize) {
        case 64:
                oobregion->offset = 40;
                break;
        case 128:
                oobregion->offset = 80;
                break;
        default:
                return -EINVAL;
        }

        oobregion->length = total_ecc_bytes;
        if (oobregion->offset + oobregion->length > mtd->oobsize)
                return -ERANGE;

        return 0;
}

static int nand_ooblayout_free_lp_hamming(struct mtd_info *mtd, int section,
                                          struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int total_ecc_bytes = nand->ecc.ctx.total;
        int ecc_offset = 0;

        if (section < 0 || section > 1)
                return -ERANGE;

        switch (mtd->oobsize) {
        case 64:
                ecc_offset = 40;
                break;
        case 128:
                ecc_offset = 80;
                break;
        default:
                return -EINVAL;
        }

        if (section == 0) {
                oobregion->offset = 2;
                oobregion->length = ecc_offset - 2;
        } else {
                oobregion->offset = ecc_offset + total_ecc_bytes;
                oobregion->length = mtd->oobsize - oobregion->offset;
        }

        return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops = {
        .ecc = nand_ooblayout_ecc_lp_hamming,
        .free = nand_ooblayout_free_lp_hamming,
};

const struct mtd_ooblayout_ops *nand_get_large_page_hamming_ooblayout(void)
{
        return &nand_ooblayout_lp_hamming_ops;
}
EXPORT_SYMBOL_GPL(nand_get_large_page_hamming_ooblayout);

static enum nand_ecc_engine_type
of_get_nand_ecc_engine_type(struct device_node *np)
{
        struct device_node *eng_np;

        if (of_property_read_bool(np, "nand-no-ecc-engine"))
                return NAND_ECC_ENGINE_TYPE_NONE;

        if (of_property_read_bool(np, "nand-use-soft-ecc-engine"))
                return NAND_ECC_ENGINE_TYPE_SOFT;

        eng_np = of_parse_phandle(np, "nand-ecc-engine", 0);
        of_node_put(eng_np);

        if (eng_np) {
                if (eng_np == np)
                        return NAND_ECC_ENGINE_TYPE_ON_DIE;
                else
                        return NAND_ECC_ENGINE_TYPE_ON_HOST;
        }

        return NAND_ECC_ENGINE_TYPE_INVALID;
}

static const char * const nand_ecc_placement[] = {
        [NAND_ECC_PLACEMENT_OOB] = "oob",
        [NAND_ECC_PLACEMENT_INTERLEAVED] = "interleaved",
};

static enum nand_ecc_placement of_get_nand_ecc_placement(struct device_node *np)
{
        enum nand_ecc_placement placement;
        const char *pm;
        int err;

        err = of_property_read_string(np, "nand-ecc-placement", &pm);
        if (!err) {
                for (placement = NAND_ECC_PLACEMENT_OOB;
                     placement < ARRAY_SIZE(nand_ecc_placement); placement++) {
                        if (!strcasecmp(pm, nand_ecc_placement[placement]))
                                return placement;
                }
        }

        return NAND_ECC_PLACEMENT_UNKNOWN;
}

static const char * const nand_ecc_algos[] = {
        [NAND_ECC_ALGO_HAMMING] = "hamming",
        [NAND_ECC_ALGO_BCH] = "bch",
        [NAND_ECC_ALGO_RS] = "rs",
};

static enum nand_ecc_algo of_get_nand_ecc_algo(struct device_node *np)
{
        enum nand_ecc_algo ecc_algo;
        const char *pm;
        int err;

        err = of_property_read_string(np, "nand-ecc-algo", &pm);
        if (!err) {
                for (ecc_algo = NAND_ECC_ALGO_HAMMING;
                     ecc_algo < ARRAY_SIZE(nand_ecc_algos);
                     ecc_algo++) {
                        if (!strcasecmp(pm, nand_ecc_algos[ecc_algo]))
                                return ecc_algo;
                }
        }

        return NAND_ECC_ALGO_UNKNOWN;
}

static int of_get_nand_ecc_step_size(struct device_node *np)
{
        int ret;
        u32 val;

        ret = of_property_read_u32(np, "nand-ecc-step-size", &val);
        return ret ? ret : val;
}

static int of_get_nand_ecc_strength(struct device_node *np)
{
        int ret;
        u32 val;

        ret = of_property_read_u32(np, "nand-ecc-strength", &val);
        return ret ? ret : val;
}

void of_get_nand_ecc_user_config(struct nand_device *nand)
{
        struct device_node *dn = nanddev_get_of_node(nand);
        int strength, size;

        nand->ecc.user_conf.engine_type = of_get_nand_ecc_engine_type(dn);
        nand->ecc.user_conf.algo = of_get_nand_ecc_algo(dn);
        nand->ecc.user_conf.placement = of_get_nand_ecc_placement(dn);

        strength = of_get_nand_ecc_strength(dn);
        if (strength >= 0)
                nand->ecc.user_conf.strength = strength;

        size = of_get_nand_ecc_step_size(dn);
        if (size >= 0)
                nand->ecc.user_conf.step_size = size;

        if (of_property_read_bool(dn, "nand-ecc-maximize"))
                nand->ecc.user_conf.flags |= NAND_ECC_MAXIMIZE_STRENGTH;
}
EXPORT_SYMBOL(of_get_nand_ecc_user_config);

/**
 * nand_ecc_is_strong_enough - Check if the chip configuration meets the
 *                             datasheet requirements.
 *
 * @nand: Device to check
 *
 * If our configuration corrects A bits per B bytes and the minimum
 * required correction level is X bits per Y bytes, then we must ensure
 * both of the following are true:
 *
 * (1) A / B >= X / Y
 * (2) A >= X
 *
 * Requirement (1) ensures we can correct for the required bitflip density.
 * Requirement (2) ensures we can correct even when all bitflips are clumped
 * in the same sector.
 */
bool nand_ecc_is_strong_enough(struct nand_device *nand)
{
        const struct nand_ecc_props *reqs = nanddev_get_ecc_requirements(nand);
        const struct nand_ecc_props *conf = nanddev_get_ecc_conf(nand);
        struct mtd_info *mtd = nanddev_to_mtd(nand);
        int corr, ds_corr;

        if (conf->step_size == 0 || reqs->step_size == 0)
                /* Not enough information */
                return true;

        /*
         * We get the number of corrected bits per page to compare
         * the correction density.
         */
        corr = (mtd->writesize * conf->strength) / conf->step_size;
        ds_corr = (mtd->writesize * reqs->strength) / reqs->step_size;

        return corr >= ds_corr && conf->strength >= reqs->strength;
}
EXPORT_SYMBOL(nand_ecc_is_strong_enough);

/* ECC engine driver internal helpers */
int nand_ecc_init_req_tweaking(struct nand_ecc_req_tweak_ctx *ctx,
                               struct nand_device *nand)
{
        unsigned int total_buffer_size;

        ctx->nand = nand;

        /* Let the user decide the exact length of each buffer */
        if (!ctx->page_buffer_size)
                ctx->page_buffer_size = nanddev_page_size(nand);
        if (!ctx->oob_buffer_size)
                ctx->oob_buffer_size = nanddev_per_page_oobsize(nand);

        total_buffer_size = ctx->page_buffer_size + ctx->oob_buffer_size;

        ctx->spare_databuf = kzalloc(total_buffer_size, GFP_KERNEL);
        if (!ctx->spare_databuf)
                return -ENOMEM;

        ctx->spare_oobbuf = ctx->spare_databuf + ctx->page_buffer_size;

        return 0;
}
EXPORT_SYMBOL_GPL(nand_ecc_init_req_tweaking);

void nand_ecc_cleanup_req_tweaking(struct nand_ecc_req_tweak_ctx *ctx)
{
        kfree(ctx->spare_databuf);
}
EXPORT_SYMBOL_GPL(nand_ecc_cleanup_req_tweaking);

/*
 * Ensure data and OOB area is fully read/written otherwise the correction might
 * not work as expected.
 */
void nand_ecc_tweak_req(struct nand_ecc_req_tweak_ctx *ctx,
                        struct nand_page_io_req *req)
{
        struct nand_device *nand = ctx->nand;
        struct nand_page_io_req *orig, *tweak;

        /* Save the original request */
        ctx->orig_req = *req;
        ctx->bounce_data = false;
        ctx->bounce_oob = false;
        orig = &ctx->orig_req;
        tweak = req;

        /* Ensure the request covers the entire page */
        if (orig->datalen < nanddev_page_size(nand)) {
                ctx->bounce_data = true;
                tweak->dataoffs = 0;
                tweak->datalen = nanddev_page_size(nand);
                tweak->databuf.in = ctx->spare_databuf;
                memset(tweak->databuf.in, 0xFF, ctx->page_buffer_size);
        }

        if (orig->ooblen < nanddev_per_page_oobsize(nand)) {
                ctx->bounce_oob = true;
                tweak->ooboffs = 0;
                tweak->ooblen = nanddev_per_page_oobsize(nand);
                tweak->oobbuf.in = ctx->spare_oobbuf;
                memset(tweak->oobbuf.in, 0xFF, ctx->oob_buffer_size);
        }

        /* Copy the data that must be written in the bounce buffers, if needed */
        if (orig->type == NAND_PAGE_WRITE) {
                if (ctx->bounce_data)
                        memcpy((void *)tweak->databuf.out + orig->dataoffs,
                               orig->databuf.out, orig->datalen);

                if (ctx->bounce_oob)
                        memcpy((void *)tweak->oobbuf.out + orig->ooboffs,
                               orig->oobbuf.out, orig->ooblen);
        }
}
EXPORT_SYMBOL_GPL(nand_ecc_tweak_req);

void nand_ecc_restore_req(struct nand_ecc_req_tweak_ctx *ctx,
                          struct nand_page_io_req *req)
{
        struct nand_page_io_req *orig, *tweak;

        orig = &ctx->orig_req;
        tweak = req;

        /* Restore the data read from the bounce buffers, if needed */
        if (orig->type == NAND_PAGE_READ) {
                if (ctx->bounce_data)
                        memcpy(orig->databuf.in,
                               tweak->databuf.in + orig->dataoffs,
                               orig->datalen);

                if (ctx->bounce_oob)
                        memcpy(orig->oobbuf.in,
                               tweak->oobbuf.in + orig->ooboffs,
                               orig->ooblen);
        }

        /* Ensure the original request is restored */
        *req = *orig;
}
EXPORT_SYMBOL_GPL(nand_ecc_restore_req);

struct nand_ecc_engine *nand_ecc_get_sw_engine(struct nand_device *nand)
{
        unsigned int algo = nand->ecc.user_conf.algo;

        if (algo == NAND_ECC_ALGO_UNKNOWN)
                algo = nand->ecc.defaults.algo;

        switch (algo) {
        case NAND_ECC_ALGO_HAMMING:
                return nand_ecc_sw_hamming_get_engine();
        case NAND_ECC_ALGO_BCH:
                return nand_ecc_sw_bch_get_engine();
        default:
                break;
        }

        return NULL;
}
EXPORT_SYMBOL(nand_ecc_get_sw_engine);

struct nand_ecc_engine *nand_ecc_get_on_die_hw_engine(struct nand_device *nand)
{
        return nand->ecc.ondie_engine;
}
EXPORT_SYMBOL(nand_ecc_get_on_die_hw_engine);

int nand_ecc_register_on_host_hw_engine(struct nand_ecc_engine *engine)
{
        struct nand_ecc_engine *item;

        if (!engine)
                return -EINVAL;

        /* Prevent multiple registrations of one engine */
        list_for_each_entry(item, &on_host_hw_engines, node)
                if (item == engine)
                        return 0;

        mutex_lock(&on_host_hw_engines_mutex);
        list_add_tail(&engine->node, &on_host_hw_engines);
        mutex_unlock(&on_host_hw_engines_mutex);

        return 0;
}
EXPORT_SYMBOL(nand_ecc_register_on_host_hw_engine);

int nand_ecc_unregister_on_host_hw_engine(struct nand_ecc_engine *engine)
{
        if (!engine)
                return -EINVAL;

        mutex_lock(&on_host_hw_engines_mutex);
        list_del(&engine->node);
        mutex_unlock(&on_host_hw_engines_mutex);

        return 0;
}
EXPORT_SYMBOL(nand_ecc_unregister_on_host_hw_engine);

static struct nand_ecc_engine *nand_ecc_match_on_host_hw_engine(struct device *dev)
{
        struct nand_ecc_engine *item;

        list_for_each_entry(item, &on_host_hw_engines, node)
                if (item->dev == dev)
                        return item;

        return NULL;
}

struct nand_ecc_engine *nand_ecc_get_on_host_hw_engine(struct nand_device *nand)
{
        struct nand_ecc_engine *engine = NULL;
        struct device *dev = &nand->mtd.dev;
        struct platform_device *pdev;
        struct device_node *np;

        if (list_empty(&on_host_hw_engines))
                return NULL;

        /* Check for an explicit nand-ecc-engine property */
        np = of_parse_phandle(dev->of_node, "nand-ecc-engine", 0);
        if (np) {
                pdev = of_find_device_by_node(np);
                if (!pdev)
                        return ERR_PTR(-EPROBE_DEFER);

                engine = nand_ecc_match_on_host_hw_engine(&pdev->dev);
                platform_device_put(pdev);
                of_node_put(np);

                if (!engine)
                        return ERR_PTR(-EPROBE_DEFER);
        }

        if (engine)
                get_device(engine->dev);

        return engine;
}
EXPORT_SYMBOL(nand_ecc_get_on_host_hw_engine);

void nand_ecc_put_on_host_hw_engine(struct nand_device *nand)
{
        put_device(nand->ecc.engine->dev);
}
EXPORT_SYMBOL(nand_ecc_put_on_host_hw_engine);

/*
 * In the case of a pipelined engine, the device registering the ECC
 * engine is not necessarily the ECC engine itself but may be a host controller.
 * It is then useful to provide a helper to retrieve the right device object
 * which actually represents the ECC engine.
 */
struct device *nand_ecc_get_engine_dev(struct device *host)
{
        struct platform_device *ecc_pdev;
        struct device_node *np;

        /*
         * If the device node contains this property, it means we need to follow
         * it in order to get the right ECC engine device we are looking for.
         */
        np = of_parse_phandle(host->of_node, "nand-ecc-engine", 0);
        if (!np)
                return host;

        ecc_pdev = of_find_device_by_node(np);
        if (!ecc_pdev) {
                of_node_put(np);
                return NULL;
        }

        platform_device_put(ecc_pdev);
        of_node_put(np);

        return &ecc_pdev->dev;
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Miquel Raynal <miquel.raynal@bootlin.com>");
MODULE_DESCRIPTION("Generic ECC engine");