[PATCH v2 0/2] Add RISC-V RPMI device power service support

[PATCH v2 0/2] Add RISC-V RPMI device power service support

[Joshua Yeong]

The RISC-V Platform Management Interface (RPMI) specification defines a
modular and extensible messaging protocol between the supervisor software
and a platform microcontroller (PuC). Among the service groups it defines
is the device power service group (service group ID 0x00009), which allows
the supervisor to enumerate the power domains of platform devices managed
by the PuC, query their attributes, and get/set their power state.

This series adds supervisor-side support for that service group:

 - DT bindings for the power domain controller exposed to the supervisor
   ("riscv,rpmi-device-power") and for the SBI MPXY channel that the SBI
   implementation uses to expose the service group to the supervisor
   ("riscv,rpmi-mpxy-device-power").

 - A generic power domain (genpd) provider driver under
   drivers/pmdomain/riscv/ which talks to the PuC over an SBI MPXY
   mailbox channel. At probe it queries GET_NUM_DOMAINS, then for each
   domain queries GET_ATTRS for the name and transition latency and
   GET_STATE for the initial state, and registers the whole set as a
   onecell genpd provider. Domain power on/off is driven through
   SET_STATE with the generic ON/OFF power state parameters, so devices
   can simply reference a domain through the "power-domains" property.

The series is based on the existing RISC-V RPMI/MPXY infrastructure
already present in the tree (drivers/mailbox/riscv-sbi-mpxy-mbox.c and
include/linux/mailbox/riscv-rpmi-message.h), and only adds the device
power service group definitions on top of it.

Changes in v2:
 - Serialize RPMI transactions on the shared mailbox channel with a
   mutex. The channel is used in non-blocking mode with client signalled
   txdone, so mbox_send_message() only submits a message when the
   channel is idle and silently queues it otherwise, returning the ring
   buffer index. A concurrent caller would therefore see success, return
   with an untouched response buffer, and leave its stack allocated
   struct rpmi_mbox_message referenced by the mailbox ring.
 - Unwind the already initialised power domains with pm_genpd_remove()
   when of_genpd_add_provider_onecell() fails, so that devres does not
   free memory still linked into the global gpd_list.
 - Set .suppress_bind_attrs and drop the .remove() callback. The domains
   are handed out to consumer devices and pm_genpd_remove() cannot fail
   safely from a void remove(), so unbinding is now refused outright.
   Use builtin_platform_driver() to match, since the driver is bool only;
   this also makes a later switch to tristate fail to build rather than
   silently reintroducing the problem. Both match other genpd providers,
   e.g. drivers/pmdomain/starfive/jh71xx-pmu.c.
 - Use __le32 for the RPMI message fields and convert the responses with
   le32_to_cpu(), matching drivers/clk/clk-rpmi.c. The requests were
   already converted with cpu_to_le32() but stored into plain u32.
 - Zero initialise the response structures and reject responses shorter
   than expected with -EPROTO, so a short reply from the PuC can no
   longer leak uninitialised stack into a power domain name. The length
   is checked after the status field so that a legitimate error reply,
   which carries only STATUS, is still reported as the RPMI error.

The v1 review also asked for a sync_state callback, on the grounds that
domains initialised in the ON state would never be powered off. That one
is not addressed, because genpd already handles it: for a provider node
with a bound device, of_genpd_add_provider_onecell() installs its own
genpd_sync_state() through dev_set_drv_sync_state(), which clears
->stay_on and powers off the unclaimed domains once all consumers have
probed. A driver supplied .sync_state would in fact be refused, since
dev_set_drv_sync_state() returns -EBUSY rather than overwriting an
existing callback. This was confirmed under QEMU: domains reported as ON
by the PuC with no consumer do end up powered off, while the domain held
by the RTC stays on.

v1: https://lore.kernel.org/r/20260829205520.1691-1-joshua.yeong@starfivetech.com

Testing
=======

The series was tested under QEMU with the RPMI device power service
implemented in firmware.

Components:

 - OpenSBI: latest master branch
   https://github.com/riscv-software-src/opensbi

 - QEMU: the RPMI-enabled tree at
   https://github.com/yeongjoshua/qemu/tree/rpmi-v11.1.0

Kernel config: enable CONFIG_RISCV_RPMI_DEVICE_POWER (default y on RISC-V
when MAILBOX is enabled) along with the SBI MPXY mailbox driver.

Run with:

  qemu-system-riscv64 \
      -M virt -m 2G -smp 4 \
      -bios fw_dynamic.bin \
      -kernel Image \
      -M rpmi=true \
      -nographic \
      -initrd rootfs-busybox.cpio \
      -append "root=/dev/ram rw console=ttyS0,115200 no_console_suspend mem=2048M earlycon=uart8250,mmio,0x10000000"

The RPMI device power domains advertised by the emulated platform
microcontroller show up as generic power domains and can be inspected
through /sys/kernel/debug/pm_genpd/. The series was additionally booted
with CONFIG_PROVE_LOCKING, CONFIG_DEBUG_MUTEXES and
CONFIG_DEBUG_ATOMIC_SLEEP enabled, with no lockdep reports.

Joshua Yeong (2):
  dt-bindings: power: Add RPMI device power service bindings
  pmdomain: riscv: Add RPMI device power service

 .../power/riscv,rpmi-device-power.yaml        |  65 +++
 .../power/riscv,rpmi-mpxy-device-power.yaml   |  65 +++
 MAINTAINERS                                   |   4 +
 drivers/pmdomain/Kconfig                      |   1 +
 drivers/pmdomain/Makefile                     |   1 +
 drivers/pmdomain/riscv/Kconfig                |  13 +
 drivers/pmdomain/riscv/Makefile               |   3 +
 .../pmdomain/riscv/riscv-rpmi-device-power.c  | 466 ++++++++++++++++++
 include/linux/mailbox/riscv-rpmi-message.h    |  11 +
 9 files changed, 629 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/power/riscv,rpmi-device-power.yaml
 create mode 100644 Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
 create mode 100644 drivers/pmdomain/riscv/Kconfig
 create mode 100644 drivers/pmdomain/riscv/Makefile
 create mode 100644 drivers/pmdomain/riscv/riscv-rpmi-device-power.c


base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
-- 
2.43.0


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[PATCH v2 1/2] dt-bindings: power: Add RPMI device power service bindings

[Joshua Yeong]

Add device tree bindings for the RISC-V Platform Management Interface
(RPMI) device power service group, both for the supervisor-facing power
domain controller and for the SBI MPXY channel which the SBI
implementation uses to expose the service group.

Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
---
 .../power/riscv,rpmi-device-power.yaml        | 65 +++++++++++++++++++
 .../power/riscv,rpmi-mpxy-device-power.yaml   | 65 +++++++++++++++++++
 2 files changed, 130 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/power/riscv,rpmi-device-power.yaml
 create mode 100644 Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml

diff --git a/Documentation/devicetree/bindings/power/riscv,rpmi-device-power.yaml b/Documentation/devicetree/bindings/power/riscv,rpmi-device-power.yaml
new file mode 100644
index 000000000000..5afdc40df7e0
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/riscv,rpmi-device-power.yaml
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/riscv,rpmi-device-power.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V RPMI device power service group based power domain controller
+
+maintainers:
+  - Joshua Yeong <joshua.yeong@starfivetech.com>
+
+description: |
+  The RISC-V Platform Management Interface (RPMI) [1] defines a
+  messaging protocol which is modular and extensible. The supervisor
+  software can send/receive RPMI messages via SBI MPXY extension [2]
+  or some dedicated supervisor-mode RPMI transport.
+
+  The RPMI specification [1] defines device power service group for
+  accessing and controlling the power state of platform devices managed
+  by a platform microcontroller. The supervisor software can access RPMI
+  device power service group via SBI MPXY channel or some dedicated
+  supervisor-mode RPMI transport.
+
+  ===========================================
+  References
+  ===========================================
+
+  [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
+      https://github.com/riscv-non-isa/riscv-rpmi/releases
+
+  [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
+      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
+
+properties:
+  compatible:
+    description:
+      Intended for use by the supervisor software.
+    const: riscv,rpmi-device-power
+
+  mboxes:
+    maxItems: 1
+    description:
+      Mailbox channel of the underlying RPMI transport or SBI message proxy channel.
+
+  "#power-domain-cells":
+    const: 1
+    description:
+      Platform specific DOMAIN_ID as defined by the RISC-V Platform Management
+      Interface (RPMI) specification.
+
+required:
+  - compatible
+  - mboxes
+  - "#power-domain-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    power-controller {
+        compatible = "riscv,rpmi-device-power";
+        mboxes = <&mpxy_mbox 0x1002 0x0>;
+        #power-domain-cells = <1>;
+    };
+...
diff --git a/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
new file mode 100644
index 000000000000..2b7df66ba172
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/riscv,rpmi-mpxy-device-power.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V RPMI device power service group based message proxy
+
+maintainers:
+  - Joshua Yeong <joshua.yeong@starfivetech.com>
+
+description: |
+  The RISC-V Platform Management Interface (RPMI) [1] defines a
+  messaging protocol which is modular and extensible. The supervisor
+  software can send/receive RPMI messages via SBI MPXY extension [2]
+  or some dedicated supervisor-mode RPMI transport.
+
+  The RPMI specification [1] defines device power service group for
+  accessing and controlling the power state of platform devices managed
+  by a platform microcontroller. The SBI implementation (machine mode
+  firmware or hypervisor) can implement an SBI MPXY channel to allow RPMI
+  device power service group access to the supervisor software.
+
+  ===========================================
+  References
+  ===========================================
+
+  [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
+      https://github.com/riscv-non-isa/riscv-rpmi/releases
+
+  [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
+      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
+
+properties:
+  compatible:
+    description:
+      Intended for use by the SBI implementation.
+    const: riscv,rpmi-mpxy-device-power
+
+  mboxes:
+    maxItems: 1
+    description:
+      Mailbox channel of the underlying RPMI transport.
+
+  riscv,sbi-mpxy-channel-id:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      The SBI MPXY channel id to be used for providing RPMI access to
+      the supervisor software.
+
+required:
+  - compatible
+  - mboxes
+  - riscv,sbi-mpxy-channel-id
+
+additionalProperties: false
+
+examples:
+  - |
+    device-power-service {
+        compatible = "riscv,rpmi-mpxy-device-power";
+        mboxes = <&rpmi_shmem_mbox 0x9>;
+        riscv,sbi-mpxy-channel-id = <0x1002>;
+    };
+...
-- 
2.43.0


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[PATCH v2 2/2] pmdomain: riscv: Add RPMI device power service

[Joshua Yeong]

Add a generic power domain provider on top of the RISC-V Platform
Management Interface (RPMI) device power service group, reached through
an SBI MPXY channel.

The driver enumerates the device power domains advertised by the
platform microcontroller, queries their attributes and initial state,
and registers them as an onecell genpd provider so that devices can
reference them through the "power-domains" property.

Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
---
 MAINTAINERS                                   |   4 +
 drivers/pmdomain/Kconfig                      |   1 +
 drivers/pmdomain/Makefile                     |   1 +
 drivers/pmdomain/riscv/Kconfig                |  13 +
 drivers/pmdomain/riscv/Makefile               |   3 +
 .../pmdomain/riscv/riscv-rpmi-device-power.c  | 466 ++++++++++++++++++
 include/linux/mailbox/riscv-rpmi-message.h    |  11 +
 7 files changed, 499 insertions(+)
 create mode 100644 drivers/pmdomain/riscv/Kconfig
 create mode 100644 drivers/pmdomain/riscv/Makefile
 create mode 100644 drivers/pmdomain/riscv/riscv-rpmi-device-power.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 8014b9f8253e..726d4637c074 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23296,6 +23296,7 @@ F:	drivers/perf/riscv_pmu_sbi.c
 RISC-V RPMI AND MPXY DRIVERS
 M:	Rahul Pathak <rahul@summations.net>
 M:	Anup Patel <anup@brainfault.org>
+M:	Joshua Yeong <joshua.yeong@starfivetech.com>
 L:	linux-riscv@lists.infradead.org
 F:	Documentation/devicetree/bindings/clock/riscv,rpmi-clock.yaml
 F:	Documentation/devicetree/bindings/clock/riscv,rpmi-mpxy-clock.yaml
@@ -23303,9 +23304,12 @@ F:	Documentation/devicetree/bindings/interrupt-controller/riscv,rpmi-mpxy-system
 F:	Documentation/devicetree/bindings/interrupt-controller/riscv,rpmi-system-msi.yaml
 F:	Documentation/devicetree/bindings/mailbox/riscv,rpmi-shmem-mbox.yaml
 F:	Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
+F:	Documentation/devicetree/bindings/power/riscv,rpmi-device-power.yaml
+F:	Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
 F:	drivers/clk/clk-rpmi.c
 F:	drivers/irqchip/irq-riscv-rpmi-sysmsi.c
 F:	drivers/mailbox/riscv-sbi-mpxy-mbox.c
+F:	drivers/pmdomain/riscv/
 F:	include/linux/mailbox/riscv-rpmi-message.h
 
 RISC-V SPACEMIT SoC Support
diff --git a/drivers/pmdomain/Kconfig b/drivers/pmdomain/Kconfig
index 23076ae90e66..5341dff669be 100644
--- a/drivers/pmdomain/Kconfig
+++ b/drivers/pmdomain/Kconfig
@@ -11,6 +11,7 @@ source "drivers/pmdomain/marvell/Kconfig"
 source "drivers/pmdomain/mediatek/Kconfig"
 source "drivers/pmdomain/qcom/Kconfig"
 source "drivers/pmdomain/renesas/Kconfig"
+source "drivers/pmdomain/riscv/Kconfig"
 source "drivers/pmdomain/rockchip/Kconfig"
 source "drivers/pmdomain/samsung/Kconfig"
 source "drivers/pmdomain/st/Kconfig"
diff --git a/drivers/pmdomain/Makefile b/drivers/pmdomain/Makefile
index ebc802f13eb9..d7aee13ae571 100644
--- a/drivers/pmdomain/Makefile
+++ b/drivers/pmdomain/Makefile
@@ -9,6 +9,7 @@ obj-y					+= marvell/
 obj-y					+= mediatek/
 obj-y					+= qcom/
 obj-y					+= renesas/
+obj-y					+= riscv/
 obj-y					+= rockchip/
 obj-y					+= samsung/
 obj-y					+= st/
diff --git a/drivers/pmdomain/riscv/Kconfig b/drivers/pmdomain/riscv/Kconfig
new file mode 100644
index 000000000000..5c2ef53218a3
--- /dev/null
+++ b/drivers/pmdomain/riscv/Kconfig
@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config RISCV_RPMI_DEVICE_POWER
+	bool "RISC-V RPMI Based Device Power driver"
+	depends on MAILBOX || COMPILE_TEST
+	default RISCV
+	select PM_GENERIC_DOMAINS if PM
+	help
+	  Support for device power domains based on the device power service
+	  group defined by the RISC-V platform management interface (RPMI)
+	  specification. The power domains advertised by the platform
+	  microcontroller are registered as generic power domains, so that
+	  devices can reference them through the "power-domains" property.
diff --git a/drivers/pmdomain/riscv/Makefile b/drivers/pmdomain/riscv/Makefile
new file mode 100644
index 000000000000..2cb0ee8ad413
--- /dev/null
+++ b/drivers/pmdomain/riscv/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_RISCV_RPMI_DEVICE_POWER)	+= riscv-rpmi-device-power.o
diff --git a/drivers/pmdomain/riscv/riscv-rpmi-device-power.c b/drivers/pmdomain/riscv/riscv-rpmi-device-power.c
new file mode 100644
index 000000000000..6590d622c2a4
--- /dev/null
+++ b/drivers/pmdomain/riscv/riscv-rpmi-device-power.c
@@ -0,0 +1,466 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RISC-V RPMI Based Device Power Driver through SBI MPXY
+ *
+ * Copyright (C) 2026 Shanghai StarFive Technology Co., Ltd.
+ *
+ * Implements a Device Power driver on top of SBI RPMI Message Proxy Extension (MPXY)
+ *
+ * Each SBI MPXY Device Power instance is associated, through the means of a proper DT
+ * entry description, to a specific Transport ID.
+ */
+
+#define pr_fmt(fmt) "riscv-rpmi-device-power: " fmt
+
+#include <linux/bitfield.h>
+#include <linux/mailbox/riscv-rpmi-message.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+
+#define RPMI_PM_DOMAIN_NAME_LEN		16
+
+/* power state for device power domains */
+#define RPMI_POWER_STATE_CONTEXT_MASK		GENMASK(16, 16)
+#define RPMI_POWER_STATE_CONTEXT_PRESERVED	0
+#define RPMI_POWER_STATE_CONTEXT_LOST		1
+#define RPMI_POWER_STATE_VALUE_MASK		GENMASK(15, 0)
+#define RPMI_POWER_STATE_VALUE_ON		0
+#define RPMI_POWER_STATE_VALUE_OFF		3
+
+#define RPMI_POWER_STATE_PARAM(context_type, state_value) \
+	((FIELD_PREP(RPMI_POWER_STATE_CONTEXT_MASK, context_type)) | \
+	(FIELD_PREP(RPMI_POWER_STATE_VALUE_MASK, state_value)))
+
+#define RPMI_POWER_STATE_GENERIC_ON  \
+	RPMI_POWER_STATE_PARAM(RPMI_POWER_STATE_CONTEXT_PRESERVED, \
+				   RPMI_POWER_STATE_VALUE_ON)
+
+#define RPMI_POWER_STATE_GENERIC_OFF  \
+	RPMI_POWER_STATE_PARAM(RPMI_POWER_STATE_CONTEXT_PRESERVED, \
+				   RPMI_POWER_STATE_VALUE_OFF)
+
+/**
+ * struct rpmi_ctx - RPMI transport context shared by all power domains
+ *
+ * @chan: mailbox channel of the underlying SBI MPXY transport
+ * @client: mailbox client bound to @chan
+ * @lock: serialises RPMI transactions on @chan
+ */
+struct rpmi_ctx {
+	struct mbox_chan *chan;
+	struct mbox_client client;
+	/* serialises RPMI transactions on @chan */
+	struct mutex lock;
+};
+
+/**
+ * struct rpmi_device_power_domain - describe one available MPXY Device Power Domain
+ *
+ * @id: the power domain ID as advertised by PuC
+ * @transition_latency: worst case transition latency of power domain from one state
+ *			to another
+ * @dev: device associated with this power domain
+ * @name: device power domain name assigned by PuC
+ */
+struct rpmi_device_power_domain {
+	u32 id;
+	u32 transition_latency;
+	struct device *dev;
+	struct rpmi_ctx *mpxy_ctx;
+	struct generic_pm_domain genpd;
+	char name[RPMI_PM_DOMAIN_NAME_LEN];
+};
+
+#define to_rpmi_pd(gpd) container_of(gpd, struct rpmi_device_power_domain, genpd)
+
+/* Service: ENABLE_NOTIFICATION */
+struct rpmi_pm_enable_notification_tx {
+	__le32 event_id;
+};
+
+struct rpmi_pm_enable_notification_rx {
+	__le32 status;
+};
+
+/* Service: GET_POWER_DOMAINS */
+struct rpmi_pm_get_num_domain_rx {
+	__le32 status;
+	__le32 num_domains;
+};
+
+/* Service: GET_POWER_DOMAIN_ATTRS */
+struct rpmi_pm_get_domain_attrs_tx {
+	__le32 domain_id;
+};
+
+/* pm domain attributes response data */
+struct rpmi_pm_get_domain_attrs_rx {
+	__le32 status;
+	__le32 flags;
+	__le32 transition_latency;
+	char name[RPMI_PM_DOMAIN_NAME_LEN];
+};
+
+/* Service: SET_POWER_DOMAIN_STATE */
+struct rpmi_pm_set_power_state_tx {
+	__le32 domain_id;
+	__le32 power_state;
+};
+
+struct rpmi_pm_set_power_state_rx {
+	__le32 status;
+};
+
+/* Service: GET_POWER_DOMAIN_STATE */
+struct rpmi_pm_get_power_state_tx {
+	__le32 domain_id;
+};
+
+struct rpmi_pm_get_power_state_rx {
+	__le32 status;
+	__le32 power_state;
+};
+
+static int rpmi_pm_send_message(struct rpmi_ctx *mpxy_ctx,
+				struct rpmi_mbox_message *msg)
+{
+	guard(mutex)(&mpxy_ctx->lock);
+
+	return rpmi_mbox_send_message(mpxy_ctx->chan, msg);
+}
+
+static int rpmi_power_state_get(struct rpmi_device_power_domain *mpxy_pm_domain,
+				u32 domain_id, u32 *state)
+{
+	struct rpmi_pm_get_power_state_rx rx = { };
+	struct rpmi_pm_get_power_state_tx tx;
+	struct rpmi_mbox_message msg;
+	int ret;
+
+	tx.domain_id = cpu_to_le32(domain_id);
+
+	rpmi_mbox_init_send_with_response(&msg, RPMI_DP_SRV_GET_STATE,
+					  &tx, sizeof(tx), &rx, sizeof(rx));
+
+	ret = rpmi_pm_send_message(mpxy_pm_domain->mpxy_ctx, &msg);
+	if (ret)
+		return ret;
+
+	if (rx.status)
+		return rpmi_to_linux_error(le32_to_cpu(rx.status));
+
+	if (msg.data.out_response_len < sizeof(rx))
+		return -EPROTO;
+
+	*state = le32_to_cpu(rx.power_state);
+
+	return 0;
+}
+
+static int rpmi_power_state_set(struct rpmi_device_power_domain *mpxy_pm_domain,
+				u32 domain_id, u32 state)
+{
+	struct rpmi_pm_set_power_state_rx rx = { };
+	struct rpmi_pm_set_power_state_tx tx;
+	struct rpmi_mbox_message msg;
+	int ret;
+
+	tx.domain_id = cpu_to_le32(domain_id);
+	tx.power_state = cpu_to_le32(state);
+
+	rpmi_mbox_init_send_with_response(&msg, RPMI_DP_SRV_SET_STATE,
+					  &tx, sizeof(tx), &rx, sizeof(rx));
+	ret = rpmi_pm_send_message(mpxy_pm_domain->mpxy_ctx, &msg);
+	if (ret)
+		return ret;
+
+	if (rx.status)
+		return rpmi_to_linux_error(le32_to_cpu(rx.status));
+
+	if (msg.data.out_response_len < sizeof(rx))
+		return -EPROTO;
+
+	return 0;
+}
+
+static int rpmi_pd_power(struct generic_pm_domain *domain, bool power_on)
+{
+	struct rpmi_device_power_domain *mpxy_pm_domain;
+	u32 state, ret_state, domain_id;
+	int ret;
+
+	if (power_on)
+		state = RPMI_POWER_STATE_GENERIC_ON;
+	else
+		state = RPMI_POWER_STATE_GENERIC_OFF;
+
+	mpxy_pm_domain = to_rpmi_pd(domain);
+	domain_id = mpxy_pm_domain->id;
+
+	ret = rpmi_power_state_set(mpxy_pm_domain, domain_id, state);
+	if (!ret)
+		ret = rpmi_power_state_get(mpxy_pm_domain, domain_id, &ret_state);
+	if (!ret && state != ret_state)
+		return -EIO;
+
+	return ret;
+}
+
+static int rpmi_pd_power_on(struct generic_pm_domain *domain)
+{
+	return rpmi_pd_power(domain, true);
+}
+
+static int rpmi_pd_power_off(struct generic_pm_domain *domain)
+{
+	return rpmi_pd_power(domain, false);
+}
+
+static int rpmi_pm_get_num_domains(struct rpmi_ctx *mpxy_ctx, u32 *domain)
+{
+	struct rpmi_pm_get_num_domain_rx rx = { };
+	struct rpmi_mbox_message msg;
+	int ret;
+
+	rpmi_mbox_init_send_with_response(&msg, RPMI_DP_SRV_GET_NUM_DOMAINS,
+					  NULL, 0, &rx, sizeof(rx));
+	ret = rpmi_pm_send_message(mpxy_ctx, &msg);
+	if (ret)
+		return ret;
+
+	if (rx.status)
+		return rpmi_to_linux_error(le32_to_cpu(rx.status));
+
+	if (msg.data.out_response_len < sizeof(rx))
+		return -EPROTO;
+
+	*domain = le32_to_cpu(rx.num_domains);
+
+	return 0;
+}
+
+/* obtain the MPXY device power domain attributes */
+static int rpmi_device_power_get_attrs(u32 domain_id,
+				       struct rpmi_device_power_domain *mpxy_pm_domain)
+{
+	struct rpmi_pm_get_domain_attrs_rx rx = { };
+	struct rpmi_pm_get_domain_attrs_tx tx;
+	struct rpmi_mbox_message msg;
+	int ret;
+
+	tx.domain_id = cpu_to_le32(domain_id);
+
+	rpmi_mbox_init_send_with_response(&msg, RPMI_DP_SRV_GET_ATTRS,
+					  &tx, sizeof(tx), &rx, sizeof(rx));
+	ret = rpmi_pm_send_message(mpxy_pm_domain->mpxy_ctx, &msg);
+	if (ret)
+		return ret;
+
+	if (rx.status)
+		return rpmi_to_linux_error(le32_to_cpu(rx.status));
+
+	if (msg.data.out_response_len < sizeof(rx))
+		return -EPROTO;
+
+	mpxy_pm_domain->transition_latency = le32_to_cpu(rx.transition_latency);
+	strscpy(mpxy_pm_domain->name, rx.name, sizeof(mpxy_pm_domain->name));
+
+	return 0;
+}
+
+static int rpmi_pm_attr_setup(struct device *dev, struct rpmi_ctx *mpxy_ctx)
+{
+	struct rpmi_mbox_message msg;
+	int ret;
+
+	/* Validate RPMI specification version */
+	rpmi_mbox_init_get_attribute(&msg, RPMI_MBOX_ATTR_SPEC_VERSION);
+	ret = rpmi_pm_send_message(mpxy_ctx, &msg);
+	if (ret) {
+		dev_dbg(dev, "Failed to get spec version\n");
+		return ret;
+	}
+
+	if (msg.attr.value < RPMI_MKVER(1, 0)) {
+		dev_dbg(dev,
+			"msg protocol version mismatch, expected 0x%x, found 0x%x\n",
+			RPMI_MKVER(1, 0), msg.attr.value);
+		return -EINVAL;
+	}
+
+	/* Validate device power service group ID */
+	rpmi_mbox_init_get_attribute(&msg, RPMI_MBOX_ATTR_SERVICEGROUP_ID);
+	ret = rpmi_pm_send_message(mpxy_ctx, &msg);
+	if (ret) {
+		dev_dbg(dev, "Failed to get service group ID\n");
+		return ret;
+	}
+
+	if (msg.attr.value != RPMI_SRVGRP_DEVICE_POWER) {
+		dev_dbg(dev,
+			"service group match failed, expected 0x%x, found 0x%x\n",
+			RPMI_SRVGRP_DEVICE_POWER, msg.attr.value);
+		return -EINVAL;
+	}
+
+	/* Validate device power service group version */
+	rpmi_mbox_init_get_attribute(&msg, RPMI_MBOX_ATTR_SERVICEGROUP_VERSION);
+	ret = rpmi_pm_send_message(mpxy_ctx, &msg);
+	if (ret) {
+		dev_dbg(dev, "Failed to get service group version\n");
+		return ret;
+	}
+
+	if (msg.attr.value < RPMI_MKVER(1, 0)) {
+		dev_dbg(dev,
+			"service group version failed, expected 0x%x, found 0x%x\n",
+			RPMI_MKVER(1, 0), msg.attr.value);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void rpmi_pm_domain_mbox_chan_release(void *data)
+{
+	mbox_free_channel((struct mbox_chan *)data);
+}
+
+static int rpmi_pm_domain_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct rpmi_device_power_domain *mpxy_pd;
+	struct genpd_onecell_data *mpxy_pd_data;
+	struct generic_pm_domain **domains;
+	struct device *dev = &pdev->dev;
+	struct rpmi_ctx *mpxy_ctx;
+	u32 num_domains = 0;
+	int ret;
+	u32 i;
+
+	mpxy_ctx = devm_kzalloc(&pdev->dev, sizeof(*mpxy_ctx), GFP_KERNEL);
+	if (!mpxy_ctx)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(dev, &mpxy_ctx->lock);
+	if (ret)
+		return ret;
+
+	/* Setup mailbox client */
+	mpxy_ctx->client.dev		= dev;
+	mpxy_ctx->client.rx_callback	= NULL;
+	mpxy_ctx->client.tx_block	= false;
+	mpxy_ctx->client.knows_txdone	= true;
+	mpxy_ctx->client.tx_tout	= 0;
+
+	/* Request mailbox channel */
+	mpxy_ctx->chan = mbox_request_channel(&mpxy_ctx->client, 0);
+	if (IS_ERR(mpxy_ctx->chan))
+		return PTR_ERR(mpxy_ctx->chan);
+
+	ret = devm_add_action_or_reset(dev, rpmi_pm_domain_mbox_chan_release,
+				       mpxy_ctx->chan);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to add rpmi mbox channel cleanup\n");
+
+	ret = rpmi_pm_attr_setup(dev, mpxy_ctx);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to verify RPMI attribute\n");
+
+	/* Get number of device power domain */
+	ret = rpmi_pm_get_num_domains(mpxy_ctx, &num_domains);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to get number of pm domains\n");
+
+	if (!num_domains)
+		return dev_err_probe(dev, -EINVAL, "No PM domains found!\n");
+
+	dev_info(&pdev->dev, "%d MPXY PM domains are found\n", num_domains);
+
+	mpxy_pd = devm_kcalloc(&pdev->dev, num_domains, sizeof(*mpxy_pd), GFP_KERNEL);
+	if (!mpxy_pd)
+		return -ENOMEM;
+
+	domains = devm_kcalloc(&pdev->dev, num_domains, sizeof(*domains), GFP_KERNEL);
+	if (!domains)
+		return -ENOMEM;
+
+	mpxy_pd_data = devm_kzalloc(&pdev->dev, sizeof(*mpxy_pd_data), GFP_KERNEL);
+	if (!mpxy_pd_data)
+		return -ENOMEM;
+
+	for (i = 0; i < num_domains; i++, mpxy_pd++) {
+		u32 state;
+
+		mpxy_pd->dev = &pdev->dev;
+		mpxy_pd->mpxy_ctx = mpxy_ctx;
+		mpxy_pd->id = i;
+
+		ret = rpmi_device_power_get_attrs(i, mpxy_pd);
+		if (ret) {
+			dev_warn(mpxy_pd->dev,
+				 "power domain %d initialization failed\n",
+				 mpxy_pd->id);
+			domains[i] = NULL;
+			continue;
+		}
+
+		ret = rpmi_power_state_get(mpxy_pd, i, &state);
+		if (ret || (state != RPMI_POWER_STATE_GENERIC_OFF &&
+			    state != RPMI_POWER_STATE_GENERIC_ON)) {
+			dev_warn(mpxy_pd->dev,
+				 "failed to get state for power domain %d\n",
+				 mpxy_pd->id);
+			domains[i] = NULL;
+			continue;
+		}
+
+		mpxy_pd->genpd.name = mpxy_pd->name;
+		mpxy_pd->genpd.power_off = rpmi_pd_power_off;
+		mpxy_pd->genpd.power_on = rpmi_pd_power_on;
+
+		pm_genpd_init(&mpxy_pd->genpd, NULL,
+			      state == RPMI_POWER_STATE_GENERIC_OFF);
+
+		domains[i] = &mpxy_pd->genpd;
+	}
+
+	mpxy_pd_data->domains = domains;
+	mpxy_pd_data->num_domains = num_domains;
+
+	ret = of_genpd_add_provider_onecell(np, mpxy_pd_data);
+	if (ret) {
+		while (i--) {
+			if (domains[i])
+				pm_genpd_remove(domains[i]);
+		}
+
+		return dev_err_probe(dev, ret, "failed to add genpd provider\n");
+	}
+
+	return 0;
+}
+
+static const struct of_device_id rpmi_pm_domain_of_match[] = {
+	{ .compatible = "riscv,rpmi-device-power" },
+	{},
+};
+
+static struct platform_driver rpmi_pm_domain_platdrv = {
+	.driver = {
+		.name = "riscv-rpmi-device-power",
+		.of_match_table = rpmi_pm_domain_of_match,
+		.suppress_bind_attrs = true,
+	},
+	.probe = rpmi_pm_domain_probe,
+};
+
+builtin_platform_driver(rpmi_pm_domain_platdrv);
+
+MODULE_AUTHOR("Joshua Yeong <joshua.yeong@starfivetech.com>");
+MODULE_DESCRIPTION("Device Power Driver based on RPMI message protocol");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mailbox/riscv-rpmi-message.h b/include/linux/mailbox/riscv-rpmi-message.h
index e135c6564d0c..d5362b5821f9 100644
--- a/include/linux/mailbox/riscv-rpmi-message.h
+++ b/include/linux/mailbox/riscv-rpmi-message.h
@@ -93,6 +93,7 @@ static inline int rpmi_to_linux_error(int rpmi_error)
 /* RPMI service group IDs */
 #define RPMI_SRVGRP_SYSTEM_MSI		0x00002
 #define RPMI_SRVGRP_CLOCK		0x00008
+#define RPMI_SRVGRP_DEVICE_POWER	0x00009
 
 /* RPMI clock service IDs */
 enum rpmi_clock_service_id {
@@ -119,6 +120,16 @@ enum rpmi_sysmsi_service_id {
 	RPMI_SYSMSI_SRV_ID_MAX_COUNT
 };
 
+/* RPMI device power service IDs */
+enum rpmi_device_power_service_id {
+	RPMI_DP_SRV_ENABLE_NOTIFICATION = 0x01,
+	RPMI_DP_SRV_GET_NUM_DOMAINS  = 0x02,
+	RPMI_DP_SRV_GET_ATTRS = 0x03,
+	RPMI_DP_SRV_SET_STATE = 0x04,
+	RPMI_DP_SRV_GET_STATE = 0x05,
+	RPMI_DP_SRV_ID_MAX_COUNT,
+};
+
 /* RPMI Linux mailbox attribute IDs */
 enum rpmi_mbox_attribute_id {
 	RPMI_MBOX_ATTR_SPEC_VERSION,
-- 
2.43.0


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Re: [PATCH v2 1/2] dt-bindings: power: Add RPMI device power service bindings

[Krzysztof Kozlowski]

On Sun, Aug 30, 2026 at 11:28:11PM +0800, Joshua Yeong wrote:
> diff --git a/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
> new file mode 100644
> index 000000000000..2b7df66ba172

A nit, subject: drop second/last, redundant "bindings". The
"dt-bindings" prefix is already stating that these are bindings.
See also:
https://elixir.bootlin.com/linux/v7.1-rc7/source/Documentation/devicetree/bindings/submitting-patches.rst#L23

> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
> @@ -0,0 +1,65 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/power/riscv,rpmi-mpxy-device-power.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V RPMI device power service group based message proxy
> +
> +maintainers:
> +  - Joshua Yeong <joshua.yeong@starfivetech.com>
> +
> +description: |
> +  The RISC-V Platform Management Interface (RPMI) [1] defines a
> +  messaging protocol which is modular and extensible. The supervisor
> +  software can send/receive RPMI messages via SBI MPXY extension [2]
> +  or some dedicated supervisor-mode RPMI transport.
> +
> +  The RPMI specification [1] defines device power service group for
> +  accessing and controlling the power state of platform devices managed
> +  by a platform microcontroller. The SBI implementation (machine mode
> +  firmware or hypervisor) can implement an SBI MPXY channel to allow RPMI
> +  device power service group access to the supervisor software.
> +
> +  ===========================================
> +  References
> +  ===========================================
> +
> +  [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
> +      https://github.com/riscv-non-isa/riscv-rpmi/releases
> +
> +  [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
> +      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
> +
> +properties:
> +  compatible:
> +    description:
> +      Intended for use by the SBI implementation.
> +    const: riscv,rpmi-mpxy-device-power
> +
> +  mboxes:
> +    maxItems: 1
> +    description:
> +      Mailbox channel of the underlying RPMI transport.
> +
> +  riscv,sbi-mpxy-channel-id:
> +    $ref: /schemas/types.yaml#/definitions/uint32

Why isn't this just phandle to mbox? Or even implied by mbox channel? As
your example shows, having same value in two places points that it is
redundant.

> +    description:
> +      The SBI MPXY channel id to be used for providing RPMI access to
> +      the supervisor software.
> +
> +required:
> +  - compatible
> +  - mboxes
> +  - riscv,sbi-mpxy-channel-id
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    device-power-service {
> +        compatible = "riscv,rpmi-mpxy-device-power";
> +        mboxes = <&rpmi_shmem_mbox 0x9>;
> +        riscv,sbi-mpxy-channel-id = <0x1002>;
> +    };
> +...
> -- 
> 2.43.0
> 

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RE: [PATCH v2 1/2] dt-bindings: power: Add RPMI device power service bindings

[Joshua Yeong]

On Mon, Aug 31, 2026 at 11:38:07AM +0200, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> On Sun, Aug 30, 2026 at 11:28:11PM +0800, Joshua Yeong wrote:
> > diff --git a/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
> > new file mode 100644
> > index 000000000000..2b7df66ba172
>
> A nit, subject: drop second/last, redundant "bindings". The
> "dt-bindings" prefix is already stating that these are bindings.
> See also:
> https://elixir.bootlin.com/linux/v7.1-rc7/source/Documentation/devicetree/bindings/submitting-patches.rst#L23
>

Ok, I will drop the redundant "bindings" word in v3.

> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml
> > @@ -0,0 +1,65 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/power/riscv,rpmi-mpxy-device-power.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: RISC-V RPMI device power service group based message proxy
> > +
> > +maintainers:
> > +  - Joshua Yeong <joshua.yeong@starfivetech.com>
> > +
> > +description: |
> > +  The RISC-V Platform Management Interface (RPMI) [1] defines a
> > +  messaging protocol which is modular and extensible. The supervisor
> > +  software can send/receive RPMI messages via SBI MPXY extension [2]
> > +  or some dedicated supervisor-mode RPMI transport.
> > +
> > +  The RPMI specification [1] defines device power service group for
> > +  accessing and controlling the power state of platform devices managed
> > +  by a platform microcontroller. The SBI implementation (machine mode
> > +  firmware or hypervisor) can implement an SBI MPXY channel to allow RPMI
> > +  device power service group access to the supervisor software.
> > +
> > +  ===========================================
> > +  References
> > +  ===========================================
> > +
> > +  [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
> > +      https://github.com/riscv-non-isa/riscv-rpmi/releases
> > +
> > +  [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
> > +      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
> > +
> > +properties:
> > +  compatible:
> > +    description:
> > +      Intended for use by the SBI implementation.
> > +    const: riscv,rpmi-mpxy-device-power
> > +
> > +  mboxes:
> > +    maxItems: 1
> > +    description:
> > +      Mailbox channel of the underlying RPMI transport.
> > +
> > +  riscv,sbi-mpxy-channel-id:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
>
> Why isn't this just phandle to mbox? Or even implied by mbox channel? As
> your example shows, having same value in two places points that it is
> redundant.
>

They look alike but they are in different namespaces, so the two values
are not the same number. In this node "mboxes" points at the RPMI shared
memory transport, whose #mbox-cells is 1 and whose cell is an RPMI
service group ID 0x9 for device power. "riscv,sbi-mpxy-channel-id" is
the SBI MPXY channel number that the SBI implementation then creates for
that service group. The node therefore describes a translation
rather than a duplication, consume RPMI service group 0x9 on the
transport and expose it to the supervisor as MPXY channel 0x1002.

The 0x1002 that does appear twice is spread over two nodes with two
different audiences, sitting under two different mailbox controllers:


    rpmi-shmem@12c10000 {            /* RISC-V machine mode only */
            compatible = "riscv,rpmi-shmem-mbox";
            reg = <...>;
            #mbox-cells = <1>;

            power-domain@9 {         /* read by the SBI implementation */
                    compatible = "riscv,rpmi-mpxy-device-power";
                    mboxes = <&rpmi_shmem 0x9>;
                    riscv,sbi-mpxy-channel-id = <0x1002>;
            };
    };

    sbi-mpxy-mbox {                  /* RISC-V supervisor mode only */
            compatible = "riscv,sbi-mpxy-mbox";
            #mbox-cells = <2>;       /* cells: channel_id, MSG_PROT_ID */
    };

    rpmi-device-power {              /* RISC-V supervisor mode only */
            compatible = "riscv,rpmi-device-power";
            mboxes = <&sbi_mpxy_mbox 0x1002 0x0>;
            #power-domain-cells = <1>;
    };

A phandle from the supervisor node to power-domain@9 would resolve its
"mboxes" to the shared memory transport, which is not something the
supervisor can drive. The windows are owned by machine mode and the
only RPMI mailbox Linux implements is "riscv,sbi-mpxy-mbox". The
supervisor reaches the platform controller through the SBI MPXY extension and
that ABI addresses channels by number, so the channel id has to survive
as a plain integer on both sides of the SBI boundary.

You can have a look at the diagram in RISC-V ratified specifications in
https://github.com/riscv-non-isa/riscv-rpmi/releases/tag/v1.0 -> riscv-rpmi.pdf
in Figure 2 High Level Architecture.

> > +    description:
> > +      The SBI MPXY channel id to be used for providing RPMI access to
> > +      the supervisor software.
> > +
> > +required:
> > +  - compatible
> > +  - mboxes
> > +  - riscv,sbi-mpxy-channel-id
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    device-power-service {
> > +        compatible = "riscv,rpmi-mpxy-device-power";
> > +        mboxes = <&rpmi_shmem_mbox 0x9>;
> > +        riscv,sbi-mpxy-channel-id = <0x1002>;
> > +    };
> > +...
> > -- 
> > 2.43.0
> > 
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