[PATCH v2 2/7] hw/fsi: Introduce IBM's scratchpad

[Ninad Palsule <ninad@linux.ibm.com>]

This is a part of patchset where IBM's Flexible Service Interface is
introduced.

The LBUS device is embeded inside the scratchpad. The scratchpad
provides a non-functional registers. There is a 1-1 relation between
scratchpad and LBUS devices. Each LBUS device has 1K memory mapped in
the LBUS.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
---
v2:
- Incorporated Joel's review comments.
---
 hw/fsi/Kconfig                     |   4 ++
 hw/fsi/engine-scratchpad.c         | 100 +++++++++++++++++++++++++++++
 hw/fsi/meson.build                 |   1 +
 include/hw/fsi/engine-scratchpad.h |  33 ++++++++++
 4 files changed, 138 insertions(+)
 create mode 100644 hw/fsi/engine-scratchpad.c
 create mode 100644 include/hw/fsi/engine-scratchpad.h

diff --git a/hw/fsi/Kconfig b/hw/fsi/Kconfig
index 687449e14e..2a9c49f2c9 100644
--- a/hw/fsi/Kconfig
+++ b/hw/fsi/Kconfig
@@ -1,2 +1,6 @@
+config SCRATCHPAD
+    bool
+    select LBUS
+
 config LBUS
     bool
diff --git a/hw/fsi/engine-scratchpad.c b/hw/fsi/engine-scratchpad.c
new file mode 100644
index 0000000000..15a8f8cc66
--- /dev/null
+++ b/hw/fsi/engine-scratchpad.c
@@ -0,0 +1,100 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM scratchpad engine
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+#include "qemu/log.h"
+
+#include "hw/fsi/engine-scratchpad.h"
+
+static uint64_t scratchpad_read(void *opaque, hwaddr addr, unsigned size)
+{
+    ScratchPad *s = SCRATCHPAD(opaque);
+
+    qemu_log_mask(LOG_UNIMP, "%s: read @0x%" HWADDR_PRIx " size=%d\n",
+                  __func__, addr, size);
+
+    if (addr) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Out of bounds read: 0x%"HWADDR_PRIx" for %u\n",
+                      __func__, addr, size);
+        return 0;
+    }
+
+    return s->reg;
+}
+
+static void scratchpad_write(void *opaque, hwaddr addr, uint64_t data,
+                                 unsigned size)
+{
+    ScratchPad *s = SCRATCHPAD(opaque);
+
+    qemu_log_mask(LOG_UNIMP, "%s: write @0x%" HWADDR_PRIx " size=%d "
+                  "value=%"PRIx64"\n", __func__, addr, size, data);
+
+    if (addr) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: Out of bounds write: 0x%"HWADDR_PRIx" for %u\n",
+                      __func__, addr, size);
+        return;
+    }
+
+    s->reg = data;
+}
+
+static const struct MemoryRegionOps scratchpad_ops = {
+    .read = scratchpad_read,
+    .write = scratchpad_write,
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static void scratchpad_realize(DeviceState *dev, Error **errp)
+{
+    LBusDevice *ldev = LBUS_DEVICE(dev);
+
+    memory_region_init_io(&ldev->iomem, OBJECT(ldev), &scratchpad_ops,
+                          ldev, TYPE_SCRATCHPAD, 0x400);
+}
+
+static void scratchpad_reset(DeviceState *dev)
+{
+    ScratchPad *s = SCRATCHPAD(dev);
+
+    s->reg = 0;
+}
+
+static void scratchpad_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    LBusDeviceClass *ldc = LBUS_DEVICE_CLASS(klass);
+
+    dc->realize = scratchpad_realize;
+    dc->reset = scratchpad_reset;
+
+    ldc->config =
+          ENGINE_CONFIG_NEXT            /* valid */
+        | 0x00010000                    /* slots */
+        | 0x00001000                    /* version */
+        | ENGINE_CONFIG_TYPE_SCRATCHPAD /* type */
+        | 0x00000007;                   /* crc */
+}
+
+static const TypeInfo scratchpad_info = {
+    .name = TYPE_SCRATCHPAD,
+    .parent = TYPE_LBUS_DEVICE,
+    .instance_size = sizeof(ScratchPad),
+    .class_init = scratchpad_class_init,
+    .class_size = sizeof(LBusDeviceClass),
+};
+
+static void scratchpad_register_types(void)
+{
+    type_register_static(&scratchpad_info);
+}
+
+type_init(scratchpad_register_types);
diff --git a/hw/fsi/meson.build b/hw/fsi/meson.build
index e1007d5fea..f90e09ddab 100644
--- a/hw/fsi/meson.build
+++ b/hw/fsi/meson.build
@@ -1 +1,2 @@
 system_ss.add(when: 'CONFIG_LBUS', if_true: files('lbus.c'))
+system_ss.add(when: 'CONFIG_SCRATCHPAD', if_true: files('engine-scratchpad.c'))
diff --git a/include/hw/fsi/engine-scratchpad.h b/include/hw/fsi/engine-scratchpad.h
new file mode 100644
index 0000000000..63bf89ac5a
--- /dev/null
+++ b/include/hw/fsi/engine-scratchpad.h
@@ -0,0 +1,33 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM scratchpad engne
+ */
+#ifndef FSI_ENGINE_SCRATCHPAD_H
+#define FSI_ENGINE_SCRATCHPAD_H
+
+#include "qemu/bitops.h"
+
+#include "hw/fsi/lbus.h"
+
+#define ENGINE_CONFIG_NEXT              BE_BIT(0)
+#define ENGINE_CONFIG_VPD               BE_BIT(1)
+#define ENGINE_CONFIG_SLOTS             BE_GENMASK(8, 15)
+#define ENGINE_CONFIG_VERSION           BE_GENMASK(16, 19)
+#define ENGINE_CONFIG_TYPE              BE_GENMASK(20, 27)
+#define   ENGINE_CONFIG_TYPE_PEEK       (0x02 << 4)
+#define   ENGINE_CONFIG_TYPE_FSI        (0x03 << 4)
+#define   ENGINE_CONFIG_TYPE_SCRATCHPAD (0x06 << 4)
+#define ENGINE_CONFIG_CRC              BE_GENMASK(28, 31)
+
+#define TYPE_SCRATCHPAD "scratchpad"
+#define SCRATCHPAD(obj) OBJECT_CHECK(ScratchPad, (obj), TYPE_SCRATCHPAD)
+
+typedef struct ScratchPad {
+        LBusDevice parent;
+
+        uint32_t reg;
+} ScratchPad;
+
+#endif /* FSI_ENGINE_SCRATCHPAD_H */
-- 
2.39.2