hw/nvram/aspeed_otp: Add ASPEED OTP memory device model

Introduce a QEMU device model for ASPEED's One-Time Programmable (OTP)
memory.

This model simulates a word-addressable OTP region used for secure
fuse storage. The OTP memory can operate with an internal memory
buffer.

The OTP model provides a memory-like interface through a dedicated
AddressSpace, allowing other device models (e.g., SBC) to issue
transactions as if accessing a memory-mapped region.

Signed-off-by: Kane-Chen-AS <kane_chen@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250812094011.2617526-2-kane_chen@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/nvram/aspeed_otp.c

@@ -0,0 +1,99 @@
+/*
+ *  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/qdev-properties.h"
+#include "hw/nvram/aspeed_otp.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 void aspeed_otp_write(void *opaque, hwaddr otp_addr,
+                                uint64_t val, unsigned size)
+{
+    AspeedOTPState *s = opaque;
+
+    memcpy(s->storage + otp_addr, &val, size);
+}
+
+static bool aspeed_otp_init_storage(AspeedOTPState *s, Error **errp)
+{
+    uint32_t *p;
+    int i, num;
+
+        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,
+};
+
+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),
+};
+
+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)

hw/nvram/meson.build

@@ -19,3 +19,7 @@ system_ss.add(when: 'CONFIG_XLNX_BBRAM', if_true: files('xlnx-bbram.c'))
 
 specific_ss.add(when: 'CONFIG_PSERIES', if_true: files('spapr_nvram.c'))
 specific_ss.add(when: 'CONFIG_ACPI', if_true: files('fw_cfg-acpi.c'))
+
+system_ss.add(when: 'CONFIG_ASPEED_SOC', if_true: files(
+  'aspeed_otp.c',
+  ))

include/hw/nvram/aspeed_otp.h

@@ -0,0 +1,33 @@
+/*
+ *  ASPEED OTP (One-Time Programmable) memory
+ *
+ *  Copyright (C) 2025 Aspeed
+ *
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef ASPEED_OTP_H
+#define ASPEED_OTP_H
+
+#include "system/memory.h"
+#include "hw/block/block.h"
+#include "system/address-spaces.h"
+
+#define TYPE_ASPEED_OTP "aspeed-otp"
+OBJECT_DECLARE_SIMPLE_TYPE(AspeedOTPState, ASPEED_OTP)
+
+typedef struct AspeedOTPState {
+    DeviceState parent_obj;
+
+    BlockBackend *blk;
+
+    uint64_t size;
+
+    AddressSpace as;
+
+    MemoryRegion mmio;
+
+    uint8_t *storage;
+} AspeedOTPState;
+
+#endif /* ASPEED_OTP_H */