diff mbox series

[v7,02/10] hw/fsi: Introduce IBM's scratchpad

Message ID 20231026164741.1184058-3-ninad@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series Introduce model for IBM's FSI | expand

Commit Message

Ninad Palsule Oct. 26, 2023, 4:47 p.m. UTC 
This is a part of patchset where scratchpad is introduced.

The scratchpad provides a set of non-functional registers. The firmware
is free to use them, hardware does not support any special management
support. The scratchpad registers can be read or written from LBUS
slave.

In this model, The LBUS device is parent for the scratchpad.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
---
v2:
- Incorporated Joel's review comments.
v5:
- Incorporated review comments by Cedric.
v6:
- Incorporated review comments by Daniel.
v7:
- Incorporated review comments by Philippe.
- Cleaned up unused bits.
---
 meson.build                        |  1 +
 hw/fsi/trace.h                     |  1 +
 include/hw/fsi/engine-scratchpad.h | 27 +++++++++
 include/hw/fsi/fsi.h               | 16 +++++
 hw/fsi/engine-scratchpad.c         | 93 ++++++++++++++++++++++++++++++
 hw/fsi/Kconfig                     |  4 ++
 hw/fsi/meson.build                 |  1 +
 hw/fsi/trace-events                |  2 +
 8 files changed, 145 insertions(+)
 create mode 100644 hw/fsi/trace.h
 create mode 100644 include/hw/fsi/engine-scratchpad.h
 create mode 100644 include/hw/fsi/fsi.h
 create mode 100644 hw/fsi/engine-scratchpad.c
 create mode 100644 hw/fsi/trace-events

Comments

Cédric Le Goater Nov. 27, 2023, 4:09 p.m. UTC | #1 
On 10/26/23 18:47, Ninad Palsule wrote:
> This is a part of patchset where scratchpad is introduced.
> 
> The scratchpad provides a set of non-functional registers. The firmware
> is free to use them, hardware does not support any special management
> support. The scratchpad registers can be read or written from LBUS
> slave.
> 
> In this model, The LBUS device is parent for the scratchpad.
> 
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
> ---
> v2:
> - Incorporated Joel's review comments.
> v5:
> - Incorporated review comments by Cedric.
> v6:
> - Incorporated review comments by Daniel.
> v7:
> - Incorporated review comments by Philippe.
> - Cleaned up unused bits.
> ---
>   meson.build                        |  1 +
>   hw/fsi/trace.h                     |  1 +
>   include/hw/fsi/engine-scratchpad.h | 27 +++++++++
>   include/hw/fsi/fsi.h               | 16 +++++
>   hw/fsi/engine-scratchpad.c         | 93 ++++++++++++++++++++++++++++++
>   hw/fsi/Kconfig                     |  4 ++
>   hw/fsi/meson.build                 |  1 +
>   hw/fsi/trace-events                |  2 +
>   8 files changed, 145 insertions(+)
>   create mode 100644 hw/fsi/trace.h
>   create mode 100644 include/hw/fsi/engine-scratchpad.h
>   create mode 100644 include/hw/fsi/fsi.h
>   create mode 100644 hw/fsi/engine-scratchpad.c
>   create mode 100644 hw/fsi/trace-events
> 
> diff --git a/meson.build b/meson.build
> index dcef8b1e79..793c7c1f20 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -3257,6 +3257,7 @@ if have_system
>       'hw/char',
>       'hw/display',
>       'hw/dma',
> +    'hw/fsi',

This should be introduced in the first patch.

>       'hw/hyperv',
>       'hw/i2c',
>       'hw/i386',
> diff --git a/hw/fsi/trace.h b/hw/fsi/trace.h
> new file mode 100644
> index 0000000000..ee67c7fb04
> --- /dev/null
> +++ b/hw/fsi/trace.h
> @@ -0,0 +1 @@
> +#include "trace/trace-hw_fsi.h"
> diff --git a/include/hw/fsi/engine-scratchpad.h b/include/hw/fsi/engine-scratchpad.h
> new file mode 100644
> index 0000000000..4ffa871965
> --- /dev/null
> +++ b/include/hw/fsi/engine-scratchpad.h

This model is introduced to early please drop from this patch.

> @@ -0,0 +1,27 @@
> +/*
> + * 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 "hw/fsi/lbus.h"
> +#include "hw/fsi/fsi.h"
> +
> +#define ENGINE_CONFIG_NEXT            BE_BIT(0)
> +#define ENGINE_CONFIG_TYPE_PEEK       (0x02 << 4)
> +#define ENGINE_CONFIG_TYPE_FSI        (0x03 << 4)
> +#define ENGINE_CONFIG_TYPE_SCRATCHPAD (0x06 << 4)
> +
> +#define TYPE_FSI_SCRATCHPAD "fsi.scratchpad"
> +#define SCRATCHPAD(obj) OBJECT_CHECK(FSIScratchPad, (obj), TYPE_FSI_SCRATCHPAD)
> +
> +typedef struct FSIScratchPad {
> +        FSILBusDevice parent;
> +
> +        uint32_t reg;
> +} FSIScratchPad;
> +
> +#endif /* FSI_ENGINE_SCRATCHPAD_H */
> diff --git a/include/hw/fsi/fsi.h b/include/hw/fsi/fsi.h
> new file mode 100644
> index 0000000000..b08b97f62b
> --- /dev/null
> +++ b/include/hw/fsi/fsi.h
> @@ -0,0 +1,16 @@
> +/*
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + * Copyright (C) 2023 IBM Corp.
> + *
> + * IBM Flexible Service Interface
> + */
> +#ifndef FSI_FSI_H
> +#define FSI_FSI_H
> +
> +#include "qemu/bitops.h"
> +
> +/* Bitwise operations at the word level. */
> +#define BE_BIT(x)           BIT(31 - (x))

31 ? BITS_PER_LONG would be better I think.

> +#define BE_GENMASK(hb, lb)  MAKE_64BIT_MASK((lb), ((hb) - (lb) + 1))
> +
> +#endif
> diff --git a/hw/fsi/engine-scratchpad.c b/hw/fsi/engine-scratchpad.c
> new file mode 100644
> index 0000000000..a8887cd613
> --- /dev/null
> +++ b/hw/fsi/engine-scratchpad.c

DRop FSIScratchPad from this patch. It should be introduced later.

However, TYPE_FSI_BUS should be introcuded now because the following
patch needs it.


> @@ -0,0 +1,93 @@
> +/*
> + * 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 "trace.h"
> +
> +#include "hw/fsi/engine-scratchpad.h"
> +
> +static uint64_t fsi_scratchpad_read(void *opaque, hwaddr addr, unsigned size)
> +{
> +    FSIScratchPad *s = SCRATCHPAD(opaque);
> +
> +    trace_fsi_scratchpad_read(addr, size);
> +
> +    if (addr) {
> +        return 0;
> +    }
> +
> +    return s->reg;
> +}
> +
> +static void fsi_scratchpad_write(void *opaque, hwaddr addr, uint64_t data,
> +                                 unsigned size)
> +{
> +    FSIScratchPad *s = SCRATCHPAD(opaque);
> +
> +    trace_fsi_scratchpad_write(addr, size, data);
> +
> +    if (addr) {
> +        return;
> +    }
> +
> +    s->reg = data;
> +}
> +
> +static const struct MemoryRegionOps scratchpad_ops = {
> +    .read = fsi_scratchpad_read,
> +    .write = fsi_scratchpad_write,
> +    .endianness = DEVICE_BIG_ENDIAN,
> +};
> +
> +static void fsi_scratchpad_realize(DeviceState *dev, Error **errp)
> +{
> +    FSILBusDevice *ldev = FSI_LBUS_DEVICE(dev);
> +
> +    memory_region_init_io(&ldev->iomem, OBJECT(ldev), &scratchpad_ops,
> +                          ldev, TYPE_FSI_SCRATCHPAD, 0x400);
> +}
> +
> +static void fsi_scratchpad_reset(DeviceState *dev)
> +{
> +    FSIScratchPad *s = SCRATCHPAD(dev);
> +
> +    s->reg = 0;
> +}
> +
> +static void fsi_scratchpad_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    FSILBusDeviceClass *ldc = FSI_LBUS_DEVICE_CLASS(klass);
> +
> +    dc->realize = fsi_scratchpad_realize;
> +    dc->reset = fsi_scratchpad_reset;
> +
> +    ldc->config =
> +          ENGINE_CONFIG_NEXT            | /* valid */
> +          0x00010000                    | /* slots */
> +          0x00001000                    | /* version */
> +          ENGINE_CONFIG_TYPE_SCRATCHPAD | /* type */
> +          0x00000007;                     /* crc */
> +}
> +
> +static const TypeInfo fsi_scratchpad_info = {
> +    .name = TYPE_FSI_SCRATCHPAD,
> +    .parent = TYPE_FSI_LBUS_DEVICE,
> +    .instance_size = sizeof(FSIScratchPad),
> +    .class_init = fsi_scratchpad_class_init,
> +    .class_size = sizeof(FSILBusDeviceClass),
> +};
> +
> +static void fsi_scratchpad_register_types(void)
> +{
> +    type_register_static(&fsi_scratchpad_info);
> +}
> +
> +type_init(fsi_scratchpad_register_types);
> diff --git a/hw/fsi/Kconfig b/hw/fsi/Kconfig
> index e650c660f0..f7c7fd1b28 100644
> --- a/hw/fsi/Kconfig
> +++ b/hw/fsi/Kconfig
> @@ -1,2 +1,6 @@
> +config FSI_SCRATCHPAD
> +    bool
> +    select FSI_LBUS
> +
>   config FSI_LBUS
>       bool


I am not sure we need all this config option. We will see that at the end
when the models are ready.


Thanks,

C.



> diff --git a/hw/fsi/meson.build b/hw/fsi/meson.build
> index 4074d3a7d2..d45a98c223 100644
> --- a/hw/fsi/meson.build
> +++ b/hw/fsi/meson.build
> @@ -1 +1,2 @@
>   system_ss.add(when: 'CONFIG_FSI_LBUS', if_true: files('lbus.c'))
> +system_ss.add(when: 'CONFIG_FSI_SCRATCHPAD', if_true: files('engine-scratchpad.c'))
> diff --git a/hw/fsi/trace-events b/hw/fsi/trace-events
> new file mode 100644
> index 0000000000..c5753e2791
> --- /dev/null
> +++ b/hw/fsi/trace-events
> @@ -0,0 +1,2 @@
> +fsi_scratchpad_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " size=%d"
> +fsi_scratchpad_write(uint64_t addr, uint32_t size, uint64_t data) "@0x%" PRIx64 " size=%d value=0x%"PRIx64
Ninad Palsule Nov. 28, 2023, 10:30 p.m. UTC | #2 
Hello Cedric,

On 11/27/23 10:09, Cédric Le Goater wrote:
> On 10/26/23 18:47, Ninad Palsule wrote:
>> This is a part of patchset where scratchpad is introduced.
>>
>> The scratchpad provides a set of non-functional registers. The firmware
>> is free to use them, hardware does not support any special management
>> support. The scratchpad registers can be read or written from LBUS
>> slave.
>>
>> In this model, The LBUS device is parent for the scratchpad.
>>
>> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
>> Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
>> ---
>> v2:
>> - Incorporated Joel's review comments.
>> v5:
>> - Incorporated review comments by Cedric.
>> v6:
>> - Incorporated review comments by Daniel.
>> v7:
>> - Incorporated review comments by Philippe.
>> - Cleaned up unused bits.
>> ---
>>   meson.build                        |  1 +
>>   hw/fsi/trace.h                     |  1 +
>>   include/hw/fsi/engine-scratchpad.h | 27 +++++++++
>>   include/hw/fsi/fsi.h               | 16 +++++
>>   hw/fsi/engine-scratchpad.c         | 93 ++++++++++++++++++++++++++++++
>>   hw/fsi/Kconfig                     |  4 ++
>>   hw/fsi/meson.build                 |  1 +
>>   hw/fsi/trace-events                |  2 +
>>   8 files changed, 145 insertions(+)
>>   create mode 100644 hw/fsi/trace.h
>>   create mode 100644 include/hw/fsi/engine-scratchpad.h
>>   create mode 100644 include/hw/fsi/fsi.h
>>   create mode 100644 hw/fsi/engine-scratchpad.c
>>   create mode 100644 hw/fsi/trace-events
>>
>> diff --git a/meson.build b/meson.build
>> index dcef8b1e79..793c7c1f20 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -3257,6 +3257,7 @@ if have_system
>>       'hw/char',
>>       'hw/display',
>>       'hw/dma',
>> +    'hw/fsi',
>
> This should be introduced in the first patch.
ok, Thanks for fixing it.
>
>>       'hw/hyperv',
>>       'hw/i2c',
>>       'hw/i386',
>> diff --git a/hw/fsi/trace.h b/hw/fsi/trace.h
>> new file mode 100644
>> index 0000000000..ee67c7fb04
>> --- /dev/null
>> +++ b/hw/fsi/trace.h
>> @@ -0,0 +1 @@
>> +#include "trace/trace-hw_fsi.h"
>> diff --git a/include/hw/fsi/engine-scratchpad.h 
>> b/include/hw/fsi/engine-scratchpad.h
>> new file mode 100644
>> index 0000000000..4ffa871965
>> --- /dev/null
>> +++ b/include/hw/fsi/engine-scratchpad.h
>
> This model is introduced to early please drop from this patch.
ok, Thanks for fixing it. We should update the commit message. I will 
send it.
>
>> @@ -0,0 +1,27 @@
>> +/*
>> + * 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 "hw/fsi/lbus.h"
>> +#include "hw/fsi/fsi.h"
>> +
>> +#define ENGINE_CONFIG_NEXT            BE_BIT(0)
>> +#define ENGINE_CONFIG_TYPE_PEEK       (0x02 << 4)
>> +#define ENGINE_CONFIG_TYPE_FSI        (0x03 << 4)
>> +#define ENGINE_CONFIG_TYPE_SCRATCHPAD (0x06 << 4)
>> +
>> +#define TYPE_FSI_SCRATCHPAD "fsi.scratchpad"
>> +#define SCRATCHPAD(obj) OBJECT_CHECK(FSIScratchPad, (obj), 
>> TYPE_FSI_SCRATCHPAD)
>> +
>> +typedef struct FSIScratchPad {
>> +        FSILBusDevice parent;
>> +
>> +        uint32_t reg;
>> +} FSIScratchPad;
>> +
>> +#endif /* FSI_ENGINE_SCRATCHPAD_H */
>> diff --git a/include/hw/fsi/fsi.h b/include/hw/fsi/fsi.h
>> new file mode 100644
>> index 0000000000..b08b97f62b
>> --- /dev/null
>> +++ b/include/hw/fsi/fsi.h
>> @@ -0,0 +1,16 @@
>> +/*
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + * Copyright (C) 2023 IBM Corp.
>> + *
>> + * IBM Flexible Service Interface
>> + */
>> +#ifndef FSI_FSI_H
>> +#define FSI_FSI_H
>> +
>> +#include "qemu/bitops.h"
>> +
>> +/* Bitwise operations at the word level. */
>> +#define BE_BIT(x)           BIT(31 - (x))
>
> 31 ? BITS_PER_LONG would be better I think.
>
>> +#define BE_GENMASK(hb, lb) MAKE_64BIT_MASK((lb), ((hb) - (lb) + 1))
>> +
>> +#endif
>> diff --git a/hw/fsi/engine-scratchpad.c b/hw/fsi/engine-scratchpad.c
>> new file mode 100644
>> index 0000000000..a8887cd613
>> --- /dev/null
>> +++ b/hw/fsi/engine-scratchpad.c
>
> DRop FSIScratchPad from this patch. It should be introduced later.
>
> However, TYPE_FSI_BUS should be introcuded now because the following
> patch needs it.
ok, The scratpad is a engine/device which is attached to the LBUS hence 
it was introduced early. But I am fine with the change. Thanks for the 
change.
>
>
>> @@ -0,0 +1,93 @@
>> +/*
>> + * 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 "trace.h"
>> +
>> +#include "hw/fsi/engine-scratchpad.h"
>> +
>> +static uint64_t fsi_scratchpad_read(void *opaque, hwaddr addr, 
>> unsigned size)
>> +{
>> +    FSIScratchPad *s = SCRATCHPAD(opaque);
>> +
>> +    trace_fsi_scratchpad_read(addr, size);
>> +
>> +    if (addr) {
>> +        return 0;
>> +    }
>> +
>> +    return s->reg;
>> +}
>> +
>> +static void fsi_scratchpad_write(void *opaque, hwaddr addr, uint64_t 
>> data,
>> +                                 unsigned size)
>> +{
>> +    FSIScratchPad *s = SCRATCHPAD(opaque);
>> +
>> +    trace_fsi_scratchpad_write(addr, size, data);
>> +
>> +    if (addr) {
>> +        return;
>> +    }
>> +
>> +    s->reg = data;
>> +}
>> +
>> +static const struct MemoryRegionOps scratchpad_ops = {
>> +    .read = fsi_scratchpad_read,
>> +    .write = fsi_scratchpad_write,
>> +    .endianness = DEVICE_BIG_ENDIAN,
>> +};
>> +
>> +static void fsi_scratchpad_realize(DeviceState *dev, Error **errp)
>> +{
>> +    FSILBusDevice *ldev = FSI_LBUS_DEVICE(dev);
>> +
>> +    memory_region_init_io(&ldev->iomem, OBJECT(ldev), &scratchpad_ops,
>> +                          ldev, TYPE_FSI_SCRATCHPAD, 0x400);
>> +}
>> +
>> +static void fsi_scratchpad_reset(DeviceState *dev)
>> +{
>> +    FSIScratchPad *s = SCRATCHPAD(dev);
>> +
>> +    s->reg = 0;
>> +}
>> +
>> +static void fsi_scratchpad_class_init(ObjectClass *klass, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +    FSILBusDeviceClass *ldc = FSI_LBUS_DEVICE_CLASS(klass);
>> +
>> +    dc->realize = fsi_scratchpad_realize;
>> +    dc->reset = fsi_scratchpad_reset;
>> +
>> +    ldc->config =
>> +          ENGINE_CONFIG_NEXT            | /* valid */
>> +          0x00010000                    | /* slots */
>> +          0x00001000                    | /* version */
>> +          ENGINE_CONFIG_TYPE_SCRATCHPAD | /* type */
>> +          0x00000007;                     /* crc */
>> +}
>> +
>> +static const TypeInfo fsi_scratchpad_info = {
>> +    .name = TYPE_FSI_SCRATCHPAD,
>> +    .parent = TYPE_FSI_LBUS_DEVICE,
>> +    .instance_size = sizeof(FSIScratchPad),
>> +    .class_init = fsi_scratchpad_class_init,
>> +    .class_size = sizeof(FSILBusDeviceClass),
>> +};
>> +
>> +static void fsi_scratchpad_register_types(void)
>> +{
>> +    type_register_static(&fsi_scratchpad_info);
>> +}
>> +
>> +type_init(fsi_scratchpad_register_types);
>> diff --git a/hw/fsi/Kconfig b/hw/fsi/Kconfig
>> index e650c660f0..f7c7fd1b28 100644
>> --- a/hw/fsi/Kconfig
>> +++ b/hw/fsi/Kconfig
>> @@ -1,2 +1,6 @@
>> +config FSI_SCRATCHPAD
>> +    bool
>> +    select FSI_LBUS
>> +
>>   config FSI_LBUS
>>       bool
>
>
> I am not sure we need all this config option. We will see that at the end
> when the models are ready.

OK

Thanks for the review.

Regards,

Ninad

>
>
> Thanks,
>
> C.
>
>
>
>> diff --git a/hw/fsi/meson.build b/hw/fsi/meson.build
>> index 4074d3a7d2..d45a98c223 100644
>> --- a/hw/fsi/meson.build
>> +++ b/hw/fsi/meson.build
>> @@ -1 +1,2 @@
>>   system_ss.add(when: 'CONFIG_FSI_LBUS', if_true: files('lbus.c'))
>> +system_ss.add(when: 'CONFIG_FSI_SCRATCHPAD', if_true: 
>> files('engine-scratchpad.c'))
>> diff --git a/hw/fsi/trace-events b/hw/fsi/trace-events
>> new file mode 100644
>> index 0000000000..c5753e2791
>> --- /dev/null
>> +++ b/hw/fsi/trace-events
>> @@ -0,0 +1,2 @@
>> +fsi_scratchpad_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " 
>> size=%d"
>> +fsi_scratchpad_write(uint64_t addr, uint32_t size, uint64_t data) 
>> "@0x%" PRIx64 " size=%d value=0x%"PRIx64
>
diff mbox series

Patch

diff --git a/meson.build b/meson.build
index dcef8b1e79..793c7c1f20 100644
--- a/meson.build
+++ b/meson.build
@@ -3257,6 +3257,7 @@  if have_system
     'hw/char',
     'hw/display',
     'hw/dma',
+    'hw/fsi',
     'hw/hyperv',
     'hw/i2c',
     'hw/i386',
diff --git a/hw/fsi/trace.h b/hw/fsi/trace.h
new file mode 100644
index 0000000000..ee67c7fb04
--- /dev/null
+++ b/hw/fsi/trace.h
@@ -0,0 +1 @@ 
+#include "trace/trace-hw_fsi.h"
diff --git a/include/hw/fsi/engine-scratchpad.h b/include/hw/fsi/engine-scratchpad.h
new file mode 100644
index 0000000000..4ffa871965
--- /dev/null
+++ b/include/hw/fsi/engine-scratchpad.h
@@ -0,0 +1,27 @@ 
+/*
+ * 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 "hw/fsi/lbus.h"
+#include "hw/fsi/fsi.h"
+
+#define ENGINE_CONFIG_NEXT            BE_BIT(0)
+#define ENGINE_CONFIG_TYPE_PEEK       (0x02 << 4)
+#define ENGINE_CONFIG_TYPE_FSI        (0x03 << 4)
+#define ENGINE_CONFIG_TYPE_SCRATCHPAD (0x06 << 4)
+
+#define TYPE_FSI_SCRATCHPAD "fsi.scratchpad"
+#define SCRATCHPAD(obj) OBJECT_CHECK(FSIScratchPad, (obj), TYPE_FSI_SCRATCHPAD)
+
+typedef struct FSIScratchPad {
+        FSILBusDevice parent;
+
+        uint32_t reg;
+} FSIScratchPad;
+
+#endif /* FSI_ENGINE_SCRATCHPAD_H */
diff --git a/include/hw/fsi/fsi.h b/include/hw/fsi/fsi.h
new file mode 100644
index 0000000000..b08b97f62b
--- /dev/null
+++ b/include/hw/fsi/fsi.h
@@ -0,0 +1,16 @@ 
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM Flexible Service Interface
+ */
+#ifndef FSI_FSI_H
+#define FSI_FSI_H
+
+#include "qemu/bitops.h"
+
+/* Bitwise operations at the word level. */
+#define BE_BIT(x)           BIT(31 - (x))
+#define BE_GENMASK(hb, lb)  MAKE_64BIT_MASK((lb), ((hb) - (lb) + 1))
+
+#endif
diff --git a/hw/fsi/engine-scratchpad.c b/hw/fsi/engine-scratchpad.c
new file mode 100644
index 0000000000..a8887cd613
--- /dev/null
+++ b/hw/fsi/engine-scratchpad.c
@@ -0,0 +1,93 @@ 
+/*
+ * 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 "trace.h"
+
+#include "hw/fsi/engine-scratchpad.h"
+
+static uint64_t fsi_scratchpad_read(void *opaque, hwaddr addr, unsigned size)
+{
+    FSIScratchPad *s = SCRATCHPAD(opaque);
+
+    trace_fsi_scratchpad_read(addr, size);
+
+    if (addr) {
+        return 0;
+    }
+
+    return s->reg;
+}
+
+static void fsi_scratchpad_write(void *opaque, hwaddr addr, uint64_t data,
+                                 unsigned size)
+{
+    FSIScratchPad *s = SCRATCHPAD(opaque);
+
+    trace_fsi_scratchpad_write(addr, size, data);
+
+    if (addr) {
+        return;
+    }
+
+    s->reg = data;
+}
+
+static const struct MemoryRegionOps scratchpad_ops = {
+    .read = fsi_scratchpad_read,
+    .write = fsi_scratchpad_write,
+    .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static void fsi_scratchpad_realize(DeviceState *dev, Error **errp)
+{
+    FSILBusDevice *ldev = FSI_LBUS_DEVICE(dev);
+
+    memory_region_init_io(&ldev->iomem, OBJECT(ldev), &scratchpad_ops,
+                          ldev, TYPE_FSI_SCRATCHPAD, 0x400);
+}
+
+static void fsi_scratchpad_reset(DeviceState *dev)
+{
+    FSIScratchPad *s = SCRATCHPAD(dev);
+
+    s->reg = 0;
+}
+
+static void fsi_scratchpad_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    FSILBusDeviceClass *ldc = FSI_LBUS_DEVICE_CLASS(klass);
+
+    dc->realize = fsi_scratchpad_realize;
+    dc->reset = fsi_scratchpad_reset;
+
+    ldc->config =
+          ENGINE_CONFIG_NEXT            | /* valid */
+          0x00010000                    | /* slots */
+          0x00001000                    | /* version */
+          ENGINE_CONFIG_TYPE_SCRATCHPAD | /* type */
+          0x00000007;                     /* crc */
+}
+
+static const TypeInfo fsi_scratchpad_info = {
+    .name = TYPE_FSI_SCRATCHPAD,
+    .parent = TYPE_FSI_LBUS_DEVICE,
+    .instance_size = sizeof(FSIScratchPad),
+    .class_init = fsi_scratchpad_class_init,
+    .class_size = sizeof(FSILBusDeviceClass),
+};
+
+static void fsi_scratchpad_register_types(void)
+{
+    type_register_static(&fsi_scratchpad_info);
+}
+
+type_init(fsi_scratchpad_register_types);
diff --git a/hw/fsi/Kconfig b/hw/fsi/Kconfig
index e650c660f0..f7c7fd1b28 100644
--- a/hw/fsi/Kconfig
+++ b/hw/fsi/Kconfig
@@ -1,2 +1,6 @@ 
+config FSI_SCRATCHPAD
+    bool
+    select FSI_LBUS
+
 config FSI_LBUS
     bool
diff --git a/hw/fsi/meson.build b/hw/fsi/meson.build
index 4074d3a7d2..d45a98c223 100644
--- a/hw/fsi/meson.build
+++ b/hw/fsi/meson.build
@@ -1 +1,2 @@ 
 system_ss.add(when: 'CONFIG_FSI_LBUS', if_true: files('lbus.c'))
+system_ss.add(when: 'CONFIG_FSI_SCRATCHPAD', if_true: files('engine-scratchpad.c'))
diff --git a/hw/fsi/trace-events b/hw/fsi/trace-events
new file mode 100644
index 0000000000..c5753e2791
--- /dev/null
+++ b/hw/fsi/trace-events
@@ -0,0 +1,2 @@ 
+fsi_scratchpad_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " size=%d"
+fsi_scratchpad_write(uint64_t addr, uint32_t size, uint64_t data) "@0x%" PRIx64 " size=%d value=0x%"PRIx64