hw/nvram/aspeed_otp.c

/*
 *  ASPEED OTP (One-Time Programmable) memory
 *
 *  Copyright (C) 2025 Aspeed
 *
 *  SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "qemu/osdep.h"
#include "qemu/log.h"
#include "qapi/error.h"
#include "system/block-backend.h"
#include "hw/core/qdev-properties.h"
#include "hw/nvram/aspeed_otp.h"
#include "hw/nvram/trace.h"

static uint64_t aspeed_otp_read(void *opaque, hwaddr offset, unsigned size)
{
    AspeedOTPState *s = opaque;
    uint64_t val = 0;

    memcpy(&val, s->storage + offset, size);

    return val;
}

static bool valid_program_data(uint32_t otp_addr,
                                 uint32_t value, uint32_t prog_bit)
{
    uint32_t programmed_bits, has_programmable_bits;
    bool is_odd = otp_addr & 1;

    /*
     * prog_bit uses 0s to indicate target bits to program:
     *   - if OTP word is even-indexed, programmed bits flip 0->1
     *   - if odd, bits flip 1->0
     * Bit programming is one-way only and irreversible.
     */
    if (is_odd) {
        programmed_bits = ~value & prog_bit;
    } else {
        programmed_bits = value & (~prog_bit);
    }

    /* If any bit can be programmed, accept the request */
    has_programmable_bits = value ^ (~prog_bit);

    if (programmed_bits) {
        trace_aspeed_otp_prog_conflict(otp_addr, programmed_bits);
        for (int i = 0; i < 32; ++i) {
            if (programmed_bits & (1U << i)) {
                trace_aspeed_otp_prog_bit(i);
            }
        }
    }

    return has_programmable_bits != 0;
}

static bool program_otpmem_data(void *opaque, uint32_t otp_addr,
                             uint32_t prog_bit, uint32_t *value)
{
    AspeedOTPState *s = opaque;
    bool is_odd = otp_addr & 1;
    uint32_t otp_offset = otp_addr << 2;

    memcpy(value, s->storage + otp_offset, sizeof(uint32_t));

    if (!valid_program_data(otp_addr, *value, prog_bit)) {
        return false;
    }

    if (is_odd) {
        *value &= ~prog_bit;
    } else {
        *value |= ~prog_bit;
    }

    return true;
}

static void aspeed_otp_write(void *opaque, hwaddr otp_addr,
                                uint64_t val, unsigned size)
{
    AspeedOTPState *s = opaque;
    uint32_t otp_offset, value;

    if (!program_otpmem_data(s, otp_addr, val, &value)) {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "%s: Failed to program data, value = %x, bit = %"PRIx64"\n",
                      __func__, value, val);
        return;
    }

    otp_offset = otp_addr << 2;
    memcpy(s->storage + otp_offset, &value, size);

    if (s->blk) {
        if (blk_pwrite(s->blk, otp_offset, size, &value, 0) < 0) {
            qemu_log_mask(LOG_GUEST_ERROR,
                          "%s: Failed to write %x to %x\n",
                          __func__, value, otp_offset);

            return;
        }
    }
    trace_aspeed_otp_prog(otp_offset, val, value);
}

static bool aspeed_otp_init_storage(AspeedOTPState *s, Error **errp)
{
    uint32_t *p;
    int i, num;
    uint64_t perm;

    if (s->blk) {
        perm = BLK_PERM_CONSISTENT_READ |
               (blk_supports_write_perm(s->blk) ? BLK_PERM_WRITE : 0);
        if (blk_set_perm(s->blk, perm, BLK_PERM_ALL, errp) < 0) {
            return false;
        }
        if (blk_pread(s->blk, 0, s->size, s->storage, 0) < 0) {
            error_setg(errp, "Failed to read the initial flash content");
            return false;
        }
    } else {
        num = s->size / sizeof(uint32_t);
        p = (uint32_t *)s->storage;
        for (i = 0; i < num; i++) {
            p[i] = (i % 2 == 0) ? 0x00000000 : 0xFFFFFFFF;
        }
    }
    return true;
}

static const MemoryRegionOps aspeed_otp_ops = {
    .read = aspeed_otp_read,
    .write = aspeed_otp_write,
    .endianness = DEVICE_LITTLE_ENDIAN,
    .valid.min_access_size = 1,
    .valid.max_access_size = 4,
    .valid.unaligned = true,
    .impl.unaligned = true
};

static void aspeed_otp_realize(DeviceState *dev, Error **errp)
{
    AspeedOTPState *s = ASPEED_OTP(dev);

    if (s->size == 0) {
        error_setg(errp, "aspeed.otp: 'size' property must be set");
        return;
    }

    s->storage = blk_blockalign(s->blk, s->size);

    if (!aspeed_otp_init_storage(s, errp)) {
        return;
    }

    memory_region_init_io(&s->mmio, OBJECT(dev), &aspeed_otp_ops,
                          s, "aspeed.otp", s->size);
    address_space_init(&s->as, &s->mmio, NULL);
}

static const Property aspeed_otp_properties[] = {
    DEFINE_PROP_UINT64("size", AspeedOTPState, size, 0),
    DEFINE_PROP_DRIVE("drive", AspeedOTPState, blk),
};

static void aspeed_otp_class_init(ObjectClass *klass, const void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);
    dc->realize = aspeed_otp_realize;
    device_class_set_props(dc, aspeed_otp_properties);
}

static const TypeInfo aspeed_otp_info = {
    .name          = TYPE_ASPEED_OTP,
    .parent        = TYPE_DEVICE,
    .instance_size = sizeof(AspeedOTPState),
    .class_init    = aspeed_otp_class_init,
};

static void aspeed_otp_register_types(void)
{
    type_register_static(&aspeed_otp_info);
}

type_init(aspeed_otp_register_types)