[PATCH v2 0/2] Add support for Marvell MHU on CN9x and CN10x SoC

[PATCH v2 0/2] Add support for Marvell MHU on CN9x and CN10x SoC

[Wojciech Zmuda]

In order to support ARM SCMI for the Marvell CN9x, CN10x SoC, add a
generic platform MHU driver based loosely on arm_mhu.c and pcc.c.

v1->v2:
- Clean up
- Rebase on 6.1
- Remove PCI interrupts

Wojciech Bartczak (1):
  mailbox: mvl-mhu: add OcteonTX2 MHU mailbox driver

Wojciech Zmuda (1):
  Documentation: add Marvell MHU driver bindings

 .../bindings/mailbox/marvell,mvl-mhu.yml      |  65 ++++
 MAINTAINERS                                   |   9 +
 drivers/mailbox/Kconfig                       |  10 +
 drivers/mailbox/Makefile                      |   2 +
 drivers/mailbox/mvl_mhu.c                     | 292 ++++++++++++++++++
 5 files changed, 378 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml
 create mode 100644 drivers/mailbox/mvl_mhu.c

-- 
2.17.1

[PATCH v2 1/2] mailbox: mvl-mhu: add OcteonTX2 MHU mailbox driver

[Wojciech Zmuda]

From: Wojciech Bartczak <wbartczak@marvell.com>

Add driver for Marvell OcteonTX and OcteonTX2 Messaging Handling
Unit mailbox driver. It supports communication with SCP using
SCMI and AVS protocols. The driver supports two channels for
ARM SCMI protocol. Aside SCMI, the AVS events are supported.

SCP is AVS bus master regulating the VRM. In case of an error
detected on AVS bus during the periodic communication from SCP
to VRM, erros are anticipated. SCP now raises an interrupt to
AP in case of any such error detected.

At this moment, interrupts are being raised by SCP to AP in case
of a SCMI work being completed or AVS failure being detected but
the code has been architected in a scalable way to  accommodate
any number of interrupt sources.

Signed-off-by: Sujeet Baranwal <sbaranwal@marvell.com>
Signed-off-by: Wojciech Bartczak <wbartczak@marvell.com>
Signed-off-by: Wojciech Zmuda <wzmuda@marvell.com>
---
 MAINTAINERS               |   8 ++
 drivers/mailbox/Kconfig   |  10 ++
 drivers/mailbox/Makefile  |   2 +
 drivers/mailbox/mvl_mhu.c | 278 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 298 insertions(+)
 create mode 100644 drivers/mailbox/mvl_mhu.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 7af5cd38d7c1..650a198cce24 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11322,6 +11322,14 @@ S:	Supported
 F:	Documentation/devicetree/bindings/mmc/marvell,xenon-sdhci.txt
 F:	drivers/mmc/host/sdhci-xenon*
 
+MARVELL MHU MAILBOX DRIVER
+M:	Sujeet Baranwal <sbaranwal@marvell.com>
+M:	Sunil Goutham <sgoutham@marvell.com>
+M:	Wojciech Bartczak <wbartczak@marvell.com>
+L:	linux-kernel@vger.kernel.org
+S:	Maintained
+F:	drivers/mailbox/mvl_mhu.c
+
 MATROX FRAMEBUFFER DRIVER
 L:	linux-fbdev@vger.kernel.org
 S:	Orphan
diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index c9fc06c7e685..e9aa05d69475 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -160,6 +160,16 @@ config MAILBOX_TEST
 	  Test client to help with testing new Controller driver
 	  implementations.
 
+config MVL_MHU
+	tristate "Marvell MHU Mailbox"
+	depends on OF
+	help
+	  This driver adds support for MARVEL MHU controller.
+	  The MHU mailbox is used by SCMI for OcteonTX and OcteonTX2
+	  to control various aspects of platform operation like cpufreq
+	  or sensors. The controller supports single channel to SCP.
+	  Say Y here to build this module. If unsure say N.
+
 config POLARFIRE_SOC_MAILBOX
 	tristate "PolarFire SoC (MPFS) Mailbox"
 	depends on HAS_IOMEM
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index c2089f04887e..950f78c1806f 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -41,6 +41,8 @@ obj-$(CONFIG_BCM_PDC_MBOX)	+= bcm-pdc-mailbox.o
 
 obj-$(CONFIG_BCM_FLEXRM_MBOX)	+= bcm-flexrm-mailbox.o
 
+obj-$(CONFIG_MVL_MHU)	+= mvl_mhu.o
+
 obj-$(CONFIG_POLARFIRE_SOC_MAILBOX)	+= mailbox-mpfs.o
 
 obj-$(CONFIG_QCOM_APCS_IPC)	+= qcom-apcs-ipc-mailbox.o
diff --git a/drivers/mailbox/mvl_mhu.c b/drivers/mailbox/mvl_mhu.c
new file mode 100644
index 000000000000..07052b43a624
--- /dev/null
+++ b/drivers/mailbox/mvl_mhu.c
@@ -0,0 +1,278 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Marvell Message Handling Unit driver
+ *
+ * Copyright (c) 2023 Marvell
+ *
+ * https://spdx.org/licenses/GPL-2.0-only.html
+ */
+
+#define pr_fmt(fmt)	"mvl-mhu: " fmt
+
+#include <linux/pci.h>
+#include <linux/acpi.h>
+#include <linux/mailbox_controller.h>
+
+#define BAR0		0
+#define SCP_INDEX	0x0
+#define DEV_AP0		0x2
+#define SCP_TO_AP_INTERRUPT	2
+#define INT_VECS_MIN	0
+#define INT_VECS_MAX	3
+
+#define XCPX_DEVY_XCP_MBOX_LINT_OFFSET	0x000E1C00
+#define XCP_TO_DEV_XCP_MBOX_LINT(xcp_core, device_id)  \
+	(XCPX_DEVY_XCP_MBOX_LINT_OFFSET | \
+	((uint64_t)(xcp_core) << 36) | \
+	((uint64_t)(device_id) << 4))
+
+#define AP0_TO_SCP_MBOX_LINT    XCP_TO_DEV_XCP_MBOX_LINT(SCP_INDEX, DEV_AP0)
+
+/*
+ * Doorbell-Register: XCP(0..1)_DEV(0..7)_XCP_MBOX
+ * Communication data from devices to XCP. When written, sets
+ * XCP(0..1)_DEV(0..7)_XCP_MBOX.
+ * PS: it doesn't matter what is written into this register,
+ * Attempting to writing 'anything' would cause an interrupt
+ * to the target!
+ */
+
+#define XCPX_DEVY_XCP_MBOX_OFFSET	0x000E1000
+#define XCP_TO_DEV_XCP_MBOX(xcp_core, device_id) \
+	(XCPX_DEVY_XCP_MBOX_OFFSET | \
+	((uint64_t)(xcp_core) << 36) | \
+	((uint64_t)(device_id) << 4))
+
+/* AP0-to-SCP doorbell */
+#define AP0_TO_SCP_MBOX         XCP_TO_DEV_XCP_MBOX(SCP_INDEX, DEV_AP0)
+
+/*  Register offset: Enable interrupt from SCP to AP */
+#define XCP0_XCP_DEV0_MBOX_RINT_ENA_W1S	0x000D1C40
+#define XCP0_XCP_DEV1_MBOX_RINT_ENA_W1S	0x000D1C50
+#define XCP0_XCP_DEV2_MBOX_RINT_ENA_W1S	0x000D1C60
+#define XCP0_XCP_DEV3_MBOX_RINT_ENA_W1S	0x000D1C70
+
+/* Rx interrupt from SCP to Non-secure AP (linux kernel) */
+#define XCPX_XCP_DEVY_MBOX_RINT_OFFSET 0x000D1C00
+#define XCPX_XCP_DEVY_MBOX_RINT(xcp_core, device_id) \
+	(XCPX_XCP_DEVY_MBOX_RINT_OFFSET | \
+	((uint64_t)(xcp_core) << 36) | \
+	((uint64_t)(device_id) << 4))
+
+/* The interrupt status register */
+#define SCP_TO_AP0_MBOX_RINT  XCPX_XCP_DEVY_MBOX_RINT(SCP_INDEX, DEV_AP0)
+
+#define XCPX_XCP_DEVY_MBOX_RINT_OFFSET	0x000D1C00
+#define XCPX_XCP_DEVY_MBOX_RINT(xcp_core, device_id) \
+	(XCPX_XCP_DEVY_MBOX_RINT_OFFSET | \
+	((uint64_t)(xcp_core) << 36) | \
+	((uint64_t)(device_id) << 4))
+
+#define SCP_TO_AP0_MBOX_RINT  XCPX_XCP_DEVY_MBOX_RINT(SCP_INDEX, DEV_AP0)
+#define SCP_TO_DEV0 XCPX_XCP_DEVY_MBOX_RINT(0, 0)
+#define SCP_TO_DEV1 XCPX_XCP_DEVY_MBOX_RINT(0, 1)
+#define SCP_TO_DEV2 XCPX_XCP_DEVY_MBOX_RINT(0, 2)
+#define SCP_TO_DEV3 XCPX_XCP_DEVY_MBOX_RINT(0, 3)
+
+struct mhu {
+	struct device *dev;
+
+	/* SCP link information */
+	void __iomem *base; /* tx_reg, rx_reg */
+	struct mbox_chan *chan;
+};
+
+static irqreturn_t mhu_rx_interrupt(int irq, void *p)
+{
+	struct mhu *mhu = (struct mhu *)p;
+	u64 val;
+
+	/* Read interrupt status register */
+	val = readq_relaxed(mhu->base + SCP_TO_AP0_MBOX_RINT);
+	if (val) {
+		/* Clear the interrupt : Write on clear */
+		writeq_relaxed(1ul, mhu->base + SCP_TO_AP0_MBOX_RINT);
+		/* Poke mbox */
+		mbox_chan_received_data(mhu->chan, (void *)&val);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int mhu_send_data(struct mbox_chan *chan, void *data)
+{
+	const u64 doorbell = 0xff;  /* Arbitrary value, SCP requires a value */
+	struct mhu *mhu = chan->con_priv;
+
+	/* signal SCP */
+	iowrite64(doorbell, mhu->base + AP0_TO_SCP_MBOX);
+
+	return 0;
+}
+
+static bool mhu_last_tx_done(struct mbox_chan *chan)
+{
+	struct mhu *mhu = chan->con_priv;
+	u64 status;
+
+	status = ioread64(mhu->base + XCPX_XCP_DEVY_MBOX_RINT(0, 2));
+
+	return status != 0;
+}
+
+static int mhu_startup(struct mbox_chan *chan)
+{
+	struct mhu *mhu = chan->con_priv;
+
+	/* Enable interrupts only if there is client for data */
+	writeq_relaxed(1ul, mhu->base + XCP0_XCP_DEV2_MBOX_RINT_ENA_W1S);
+
+	return 0;
+}
+
+/* Define operations related to mbox */
+static const struct mbox_chan_ops mhu_chan_ops = {
+	.startup = mhu_startup,
+	.send_data = mhu_send_data,
+	.last_tx_done = mhu_last_tx_done,
+};
+
+static struct mbox_chan mhu_chan = {};
+
+static struct mbox_controller mhu_mbox_ctrl = {
+	.chans = &mhu_chan,
+	.num_chans = 1,
+	.txdone_irq = false,
+	.txdone_poll = true,
+	.txpoll_period = 100,
+	.ops = &mhu_chan_ops,
+};
+
+static int mhu_setup_mbox(struct device *dev)
+{
+	struct mhu *mhu;
+	struct mbox_chan *chan;
+
+	mhu = dev_get_drvdata(dev);
+
+	chan = &mhu_mbox_ctrl.chans[0];
+	chan->con_priv = mhu;
+	mhu->chan = chan;
+	mhu_mbox_ctrl.dev = dev;
+
+	return mbox_controller_register(&mhu_mbox_ctrl);
+}
+
+static int mhu_setup_irq(struct pci_dev *pdev)
+{
+	struct device *dev;
+	struct mhu *mhu;
+	int irq, ret, nvec;
+
+	mhu = pci_get_drvdata(pdev);
+	dev = &pdev->dev;
+
+	nvec = pci_alloc_irq_vectors(pdev, INT_VECS_MIN, INT_VECS_MAX, PCI_IRQ_MSIX);
+	if (nvec < 0)
+		return nvec;
+
+	irq = pci_irq_vector(pdev, SCP_TO_AP_INTERRUPT);
+	if (irq < 0) {
+		ret = irq;
+		goto irq_err;
+	}
+
+	ret = devm_request_irq(dev, irq, mhu_rx_interrupt, 0, "mvl-mhu", mhu);
+	if (ret)
+		goto irq_err;
+
+	return 0;
+
+irq_err:
+	pci_free_irq_vectors(pdev);
+
+	return ret;
+}
+
+static int mhu_probe(struct pci_dev *pdev, const struct pci_device_id *id)
+{
+	struct mhu *mhu;
+	struct device *dev;
+	int ret;
+
+	/* This driver doesn't support ACPI */
+	if (!acpi_disabled)
+		return -ENODEV;
+
+	dev = &pdev->dev;
+	/* Enable only configured instances */
+	if (!dev->of_node)
+		return -ENODEV;
+
+	mhu = devm_kzalloc(dev, sizeof(*mhu), GFP_KERNEL);
+	if (!mhu)
+		return -ENOMEM;
+
+	/* Enable PCI device */
+	pci_set_drvdata(pdev, mhu);
+	ret = pcim_enable_device(pdev);
+	if (ret)
+		return ret;
+
+	ret = pci_request_region(pdev, BAR0, "mvl-mhu");
+	if (ret)
+		return ret;
+
+	mhu->base = pcim_iomap(pdev, BAR0, pci_resource_len(pdev, BAR0));
+	if (!mhu->base)
+		return -EINVAL;
+
+	/* Configure IRQ from SCP to AP */
+	ret = mhu_setup_irq(pdev);
+	if (ret)
+		goto irq_err;
+	/* Configure mbox controller */
+	ret = mhu_setup_mbox(dev);
+	if (!ret) /* Success */
+		return 0;
+
+	/* In case of error, release the resources */
+	pci_free_irq_vectors(pdev);
+irq_err:
+	pci_release_region(pdev, BAR0);
+
+	return ret;
+}
+
+static void mhu_remove(struct pci_dev *pdev)
+{
+	struct mhu *mhu;
+
+	mhu = pci_get_drvdata(pdev);
+	mbox_controller_unregister(&mhu_mbox_ctrl);
+
+	pci_free_irq_vectors(pdev);
+	pcim_iounmap(pdev, mhu->base);
+	pci_release_region(pdev, BAR0);
+}
+
+static const struct pci_device_id mhu_ids[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_CAVIUM, 0xA067) },
+	{ 0 },
+};
+MODULE_DEVICE_TABLE(pci, mhu_ids);
+
+static struct pci_driver mhu_driver = {
+	.name = "mvl-mhu",
+	.id_table = mhu_ids,
+	.probe = mhu_probe,
+	.remove = mhu_remove,
+};
+
+module_pci_driver(mhu_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Marvell MHU Driver");
+MODULE_AUTHOR("Sujeet Baranwal <sbaranwal@marvell.com>");
+MODULE_AUTHOR("Wojciech Bartczak <wbartczak@marvell.com>");
-- 
2.17.1

[PATCH v2 2/2] Documentation: add Marvell MHU driver bindings

[Wojciech Zmuda]

From: Wojciech Bartczak <wbartczak@marvell.com>

Marvell Message Handling Unit is a mailbox controller present in
Marvell OcteonTx and OcteonTX2 SoC family.

Signed-off-by: Wojciech Bartczak <wbartczak@marvell.com>
Signed-off-by: Wojciech Zmuda <wzmuda@marvell.com>
---
 .../bindings/mailbox/marvell,mvl-mhu.yml      | 67 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 68 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml

diff --git a/Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml b/Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml
new file mode 100644
index 000000000000..e06a17eab0f9
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/marvell,mvl-mhu.yml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Marvell Message Handling Unit driver
+
+maintainers:
+  - Sujeet Baranwal <sbaranwal@marvell.com>
+  - Sunil Goutham <sgoutham@marvell.com>
+  - Wojciech Bartczak <wbartczak@marvell.com>
+
+description:
+  The Control-Processors Cluster (CPC) provides Arm-platform specification
+  entities for managing the system. On of the CPC processors is the System
+  Control Processor (SCP). The SCP is responsible, among others, for booting
+  the chip, clock and power initialization, controlling power consumption
+  through DVFS, monitoring temperature sensors and controlling AVS. The SCP,
+  as each XCP, contains mailboxes for software-to-software communications.
+  Mailbox writes cause an interrupt to the local XCP core or to the AP.
+  This driver exposes AP-SCP Message Handling Unit to the system, providing
+  the mailbox communication mechanism to the system, with the intention
+  of plugging into the SCMI framework. It is designed to work with Marvell
+  OcteonTX and OcteonTX2-based platforms.
+  Mailbox has no other usage than SCMI communication. In case of
+  configurations running without SCMI support it should be disabled.
+
+properties:
+  compatible:
+    items:
+      - const: marvell,mbox
+
+  reg:
+    maxItems: 1
+
+  "#mbox-cells":
+    description: Index of the channel
+    const: 1
+
+required:
+  - "#mbox-cells"
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+		/ {
+			mailbox: mailbox@28,0 {
+				compatible = "marvell,mbox";
+				#mbox-cells = <1>;
+				reg = <0xE000 0 0 0 0>;/*  DEVFN = 0xE0 (1C:0) */
+			};
+
+			/* ... */
+
+			firmware {
+				scmi {
+					compatible = "arm,scmi";
+					mboxes = <&mailbox 0>;
+					mbox-names = "scp_ap";
+					/* ... */
+				};
+			};
+		};
+
diff --git a/MAINTAINERS b/MAINTAINERS
index 650a198cce24..e53f001a15c3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11328,6 +11328,7 @@ M:	Sunil Goutham <sgoutham@marvell.com>
 M:	Wojciech Bartczak <wbartczak@marvell.com>
 L:	linux-kernel@vger.kernel.org
 S:	Maintained
+F:	Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml
 F:	drivers/mailbox/mvl_mhu.c
 
 MATROX FRAMEBUFFER DRIVER
-- 
2.17.1

Re: [PATCH v2 0/2] Add support for Marvell MHU on CN9x and CN10x SoC

[Krzysztof Kozlowski]

On 03/01/2023 16:56, Wojciech Zmuda wrote:
> In order to support ARM SCMI for the Marvell CN9x, CN10x SoC, add a
> generic platform MHU driver based loosely on arm_mhu.c and pcc.c.
> 
> v1->v2:
> - Clean up
> - Rebase on 6.1
> - Remove PCI interrupts

Where is the v1?

https://lore.kernel.org/all/?q=%22mailbox%3A+mvl-mhu%3A+add+OcteonTX2+MHU+mailbox+driver%22

Best regards,
Krzysztof

Re: [PATCH v2 2/2] Documentation: add Marvell MHU driver bindings

[Krzysztof Kozlowski]

On 03/01/2023 16:56, Wojciech Zmuda wrote:
> From: Wojciech Bartczak <wbartczak@marvell.com>
> 
> Marvell Message Handling Unit is a mailbox controller present in
> Marvell OcteonTx and OcteonTX2 SoC family.

1. Use subject prefixes matching the subsystem (which you can get for
example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
your patch is touching).

2. Subject: drop second, redundant "bindings".

3. Subject: drop "driver", unless your piece of hardware is called driver?


> 
> Signed-off-by: Wojciech Bartczak <wbartczak@marvell.com>
> Signed-off-by: Wojciech Zmuda <wzmuda@marvell.com>
> ---
>  .../bindings/mailbox/marvell,mvl-mhu.yml      | 67 +++++++++++++++++++
>  MAINTAINERS                                   |  1 +
>  2 files changed, 68 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml b/Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml
> new file mode 100644
> index 000000000000..e06a17eab0f9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/marvell,mvl-mhu.yml

Filenames should be based on compatibles, e.g. be the same.

> @@ -0,0 +1,67 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mailbox/marvell,mvl-mhu.yml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Marvell Message Handling Unit driver

Drop driver

> +
> +maintainers:
> +  - Sujeet Baranwal <sbaranwal@marvell.com>
> +  - Sunil Goutham <sgoutham@marvell.com>
> +  - Wojciech Bartczak <wbartczak@marvell.com>
> +
> +description:
> +  The Control-Processors Cluster (CPC) provides Arm-platform specification
> +  entities for managing the system. On of the CPC processors is the System

On->One?

> +  Control Processor (SCP). The SCP is responsible, among others, for booting
> +  the chip, clock and power initialization, controlling power consumption
> +  through DVFS, monitoring temperature sensors and controlling AVS. The SCP,
> +  as each XCP, contains mailboxes for software-to-software communications.
> +  Mailbox writes cause an interrupt to the local XCP core or to the AP.
> +  This driver exposes AP-SCP Message Handling Unit to the system, providing
> +  the mailbox communication mechanism to the system, with the intention
> +  of plugging into the SCMI framework. It is designed to work with Marvell
> +  OcteonTX and OcteonTX2-based platforms.
> +  Mailbox has no other usage than SCMI communication. In case of
> +  configurations running without SCMI support it should be disabled.
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: marvell,mbox

This is too generic. Are you sure that all Marvel mailboxes - past,
current and future - will be exactly same as this one. No differences
for next 100 years? IOW, compatible has to be specific to hardware (SoC,
device etc).

> +
> +  reg:
> +    maxItems: 1
> +
> +  "#mbox-cells":
> +    description: Index of the channel
> +    const: 1

No interrupts?

> +
> +required:
> +  - "#mbox-cells"
> +  - reg
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +		/ {

Use 4 spaces for example indentation.

> +			mailbox: mailbox@28,0 {
> +				compatible = "marvell,mbox";
> +				#mbox-cells = <1>;
> +				reg = <0xE000 0 0 0 0>;/*  DEVFN = 0xE0 (1C:0) */

1. reg is a second property, after compatible.
2. unit address is wrong.
3. lowercase hex.
4. Two spaces after /* but missing space before.

> +			};
> +
> +			/* ... */
> +
> +			firmware {
> +				scmi {
> +					compatible = "arm,scmi";
> +					mboxes = <&mailbox 0>;

Drop entire firmware example, unrelated.

> +					mbox-names = "scp_ap";
> +					/* ... */

Best regards,
Krzysztof