// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright 2016 General Electric Company
 */

#include "vpd_reader.h"

#include <i2c.h>
#include <linux/bch.h>
#include <stdlib.h>

/* BCH configuration */

const struct {
        int header_ecc_capability_bits;
        int data_ecc_capability_bits;
        unsigned int prim_poly;
        struct {
                int min;
                int max;
        } galois_field_order;
} bch_configuration = {
        .header_ecc_capability_bits = 4,
        .data_ecc_capability_bits = 16,
        .prim_poly = 0,
        .galois_field_order = {
                .min = 5,
                .max = 15,
        },
};

static int calculate_galois_field_order(size_t source_length)
{
        int gfo = bch_configuration.galois_field_order.min;

        for (; gfo < bch_configuration.galois_field_order.max &&
             ((((1 << gfo) - 1) - ((int)source_length * 8)) < 0);
             gfo++) {
        }

        if (gfo == bch_configuration.galois_field_order.max)
                return -1;

        return gfo + 1;
}

static int verify_bch(int ecc_bits, unsigned int prim_poly, u8 *data,
                      size_t data_length, const u8 *ecc, size_t ecc_length)
{
        int gfo = calculate_galois_field_order(data_length);

        if (gfo < 0)
                return -1;

        struct bch_control *bch = init_bch(gfo, ecc_bits, prim_poly);

        if (!bch)
                return -1;

        if (bch->ecc_bytes != ecc_length) {
                free_bch(bch);
                return -1;
        }

        unsigned int *errloc = (unsigned int *)calloc(data_length,
                                                      sizeof(unsigned int));
        int errors = decode_bch(bch, data, data_length, ecc, NULL, NULL,
                                errloc);

        free_bch(bch);
        if (errors < 0) {
                free(errloc);
                return -1;
        }

        if (errors > 0) {
                for (int n = 0; n < errors; n++) {
                        if (errloc[n] >= 8 * data_length) {
                                /*
                                 * n-th error located in ecc (no need for data
                                 * correction)
                                 */
                        } else {
                                /* n-th error located in data */
                                data[errloc[n] / 8] ^= 1 << (errloc[n] % 8);
                        }
                }
        }

        free(errloc);
        return 0;
}

static const int ID;
static const int LEN = 1;
static const int VER = 2;
static const int TYP = 3;
static const int BLOCK_SIZE = 4;

static const u8 HEADER_BLOCK_ID;
static const u8 HEADER_BLOCK_LEN = 18;
static const u32 HEADER_BLOCK_MAGIC = 0xca53ca53;
static const size_t HEADER_BLOCK_VERIFY_LEN = 14;
static const size_t HEADER_BLOCK_ECC_OFF = 14;
static const size_t HEADER_BLOCK_ECC_LEN = 4;

static const u8 ECC_BLOCK_ID = 0xFF;

static int vpd_reader(size_t size, u8 *data, struct vpd_cache *userdata,
                      int (*fn)(struct vpd_cache *, u8 id, u8 version, u8 type,
                                size_t size, u8 const *data))
{
        if (size < HEADER_BLOCK_LEN || !data || !fn)
                return -EINVAL;

        /*
         * +--------------------+----------------+--//--+--------------------+
         * | header block       | data block     | ...  | ecc block          |
         * +--------------------+----------------+--//--+--------------------+
         * :                    :                       :
         * +------+-------+-----+                       +------+-------------+
         * | id   | magic | ecc |                       | ...  | ecc         |
         * | len  | off   |     |                       +------+-------------+
         * | ver  | size  |     |                       :
         * | type |       |     |                       :
         * +------+-------+-----+                       :
         * :              :     :                       :
         * <----- [1] ---->     <--------- [2] --------->
         *
         * Repair (if necessary) the contents of header block [1] by using a
         * 4 byte ECC located at the end of the header block.  A successful
         * return value means that we can trust the header.
         */
        int ret = verify_bch(bch_configuration.header_ecc_capability_bits,
                             bch_configuration.prim_poly, data,
                             HEADER_BLOCK_VERIFY_LEN,
                             &data[HEADER_BLOCK_ECC_OFF], HEADER_BLOCK_ECC_LEN);
        if (ret < 0)
                return ret;

        /* Validate header block { id, length, version, type }. */
        if (data[ID] != HEADER_BLOCK_ID || data[LEN] != HEADER_BLOCK_LEN ||
            data[VER] != 0 || data[TYP] != 0 ||
            ntohl(*(u32 *)(&data[4])) != HEADER_BLOCK_MAGIC)
                return -EINVAL;

        u32 offset = ntohl(*(u32 *)(&data[8]));
        u16 size_bits = ntohs(*(u16 *)(&data[12]));

        /* Check that ECC header fits. */
        if (offset + 3 >= size)
                return -EINVAL;

        /* Validate ECC block. */
        u8 *ecc = &data[offset];

        if (ecc[ID] != ECC_BLOCK_ID || ecc[LEN] < BLOCK_SIZE ||
            ecc[LEN] + offset > size ||
            ecc[LEN] - BLOCK_SIZE != size_bits / 8 || ecc[VER] != 1 ||
            ecc[TYP] != 1)
                return -EINVAL;

        /*
         * Use the header block to locate the ECC block and verify the data
         * blocks [2] against the ecc block ECC.
         */
        ret = verify_bch(bch_configuration.data_ecc_capability_bits,
                         bch_configuration.prim_poly, &data[data[LEN]],
                         offset - data[LEN], &data[offset + BLOCK_SIZE],
                         ecc[LEN] - BLOCK_SIZE);
        if (ret < 0)
                return ret;

        /* Stop after ECC.  Ignore possible zero padding. */
        size = offset;

        for (;;) {
                /* Move to next block. */
                size -= data[LEN];
                data += data[LEN];

                if (size == 0) {
                        /* Finished iterating through blocks. */
                        return 0;
                }

                if (size < BLOCK_SIZE || data[LEN] < BLOCK_SIZE) {
                        /* Not enough data for a header, or short header. */
                        return -EINVAL;
                }

                ret = fn(userdata, data[ID], data[VER], data[TYP],
                         data[LEN] - BLOCK_SIZE, &data[BLOCK_SIZE]);
                if (ret)
                        return ret;
        }
}

int read_vpd(struct vpd_cache *cache,
             int (*process_block)(struct vpd_cache *, u8 id, u8 version,
                                  u8 type, size_t size, u8 const *data))
{
        static const size_t size = CONFIG_SYS_VPD_EEPROM_SIZE;

        int res;
        u8 *data;
        unsigned int current_i2c_bus = i2c_get_bus_num();

        res = i2c_set_bus_num(CONFIG_SYS_VPD_EEPROM_I2C_BUS);
        if (res < 0)
                return res;

        data = malloc(size);
        if (!data)
                return -ENOMEM;

        res = i2c_read(CONFIG_SYS_VPD_EEPROM_I2C_ADDR, 0,
                       CONFIG_SYS_VPD_EEPROM_I2C_ADDR_LEN,
                       data, size);
        if (res == 0)
                res = vpd_reader(size, data, cache, process_block);

        free(data);

        i2c_set_bus_num(current_i2c_bus);
        return res;
}