[PATCH v3 04/18] hw/arm/aspeed: Add AST1700 LTPI expander device model

[Kane Chen via <qemu-devel@nongnu.org>]

From: Kane-Chen-AS <kane_chen@aspeedtech.com>

Introduce a minimal QEMU device model for the ASPEED AST1700, an
MCU-less I/O expander used in the LTPI topology defined by the
DC-SCM 2.0 specification (see figure 2):
https://www.opencompute.org/documents/ocp-dc-scm-2-0-ltpi-ver-1-0-pdf

This initial implementation includes:

* Definition of aspeed.ast1700 as a SysBusDevice

* Setup of a basic memory region to reserve I/O space for future
  peripheral modeling

This stub establishes the foundation for LTPI-related device emulation,
without implementing any functional peripherals at this stage.

Signed-off-by: Kane-Chen-AS <kane_chen@aspeedtech.com>
---
 include/hw/arm/aspeed_ast1700.h | 23 ++++++++++++++++
 hw/arm/aspeed_ast1700.c         | 48 +++++++++++++++++++++++++++++++++
 hw/arm/meson.build              |  1 +
 3 files changed, 72 insertions(+)
 create mode 100644 include/hw/arm/aspeed_ast1700.h
 create mode 100644 hw/arm/aspeed_ast1700.c

diff --git a/include/hw/arm/aspeed_ast1700.h b/include/hw/arm/aspeed_ast1700.h
new file mode 100644
index 0000000000..2a95ebfe89
--- /dev/null
+++ b/include/hw/arm/aspeed_ast1700.h
@@ -0,0 +1,23 @@
+/*
+ * ASPEED AST1700 IO Expander
+ *
+ * Copyright (C) 2025 ASPEED Technology Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef ASPEED_AST1700_H
+#define ASPEED_AST1700_H
+
+#include "hw/sysbus.h"
+
+#define TYPE_ASPEED_AST1700 "aspeed.ast1700"
+
+OBJECT_DECLARE_SIMPLE_TYPE(AspeedAST1700SoCState, ASPEED_AST1700)
+
+struct AspeedAST1700SoCState {
+    SysBusDevice parent_obj;
+
+    MemoryRegion iomem;
+};
+
+#endif /* ASPEED_AST1700_H */
diff --git a/hw/arm/aspeed_ast1700.c b/hw/arm/aspeed_ast1700.c
new file mode 100644
index 0000000000..f564b9b242
--- /dev/null
+++ b/hw/arm/aspeed_ast1700.c
@@ -0,0 +1,48 @@
+/*
+ * ASPEED AST1700 IO Expander
+ *
+ * Copyright (C) 2025 ASPEED Technology Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/boards.h"
+#include "hw/qdev-core.h"
+#include "qom/object.h"
+#include "hw/arm/aspeed_ast1700.h"
+
+#define AST2700_SOC_LTPI_SIZE        0x01000000
+
+static void aspeed_ast1700_realize(DeviceState *dev, Error **errp)
+{
+    AspeedAST1700SoCState *s = ASPEED_AST1700(dev);
+    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
+
+    /* Occupy memory space for all controllers in AST1700 */
+    memory_region_init(&s->iomem, OBJECT(s), TYPE_ASPEED_AST1700,
+                       AST2700_SOC_LTPI_SIZE);
+    sysbus_init_mmio(sbd, &s->iomem);
+}
+
+static void aspeed_ast1700_class_init(ObjectClass *klass, const void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = aspeed_ast1700_realize;
+}
+
+static const TypeInfo aspeed_ast1700_info = {
+    .name          = TYPE_ASPEED_AST1700,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(AspeedAST1700SoCState),
+    .class_init    = aspeed_ast1700_class_init,
+    .abstract      = false,
+};
+
+static void aspeed_ast1700_register_types(void)
+{
+    type_register_static(&aspeed_ast1700_info);
+}
+
+type_init(aspeed_ast1700_register_types);
diff --git a/hw/arm/meson.build b/hw/arm/meson.build
index aeaf654790..ee26a05dc9 100644
--- a/hw/arm/meson.build
+++ b/hw/arm/meson.build
@@ -42,6 +42,7 @@ arm_common_ss.add(when: 'CONFIG_FSL_IMX31', if_true: files('fsl-imx31.c', 'kzm.c
 arm_common_ss.add(when: 'CONFIG_FSL_IMX6', if_true: files('fsl-imx6.c'))
 arm_ss.add(when: 'CONFIG_ASPEED_SOC', if_true: files(
   'aspeed.c',
+  'aspeed_ast1700.c',
   'aspeed_soc_common.c',
   'aspeed_ast2400.c',
   'aspeed_ast2400_palmetto.c',
-- 
2.43.0