[PATCH v4 0/3] Apple Mailbox Controller support

[PATCH v4 0/3] Apple Mailbox Controller support

[Sven Peter]

Hi,

This is the fourth version of my series which adds support for the mailbox
controllers found on the Apple M1.

v1: https://lore.kernel.org/lkml/20210907145501.69161-1-sven@svenpeter.dev/
v2: https://lore.kernel.org/lkml/20210916154911.3168-1-sven@svenpeter.dev/
v3: https://lore.kernel.org/lkml/20211017114054.67737-1-sven@svenpeter.dev/

Changes from v3 to v4:
 - dropped minItems: 4 from the bindings
 - added back of_xlate since the mailbox core only supports #mbox-cells = <1>
   but this mailbox uses #mbox-cells = <0>
 - Split of the MAINTAINERS changes to a separate file since we have quite a few
   changes in flight and there will likely be conflicts once the pull requests
   from various subsystems are sent to Linus

Changes from v2 to v3:
 - removed dma barriers since the mbox client will take care of these
 - moved the of_device_id table and related code to the bottom of the file
 - removed of_xlate
 - dropped clock handling from the code and the binding since we now understand
   that these are actually power domains

Changes from v1 to v2:
 - switched to txdone_irq instead of introducing a new mode
 - switched to a threaded interrupt handler for receiving messages
 - added co-processor examples to the device tree binding
 - reformatted the register defines and clarified multiple comments

Best,

Sven

Sven Peter (3):
  MAINTAINERS: Add Apple mailbox files
  dt-bindings: mailbox: Add Apple mailbox bindings
  mailbox: apple: Add driver for Apple mailboxes

 .../bindings/mailbox/apple,mailbox.yaml       |  77 ++++
 MAINTAINERS                                   |   3 +
 drivers/mailbox/Kconfig                       |  12 +
 drivers/mailbox/Makefile                      |   2 +
 drivers/mailbox/apple-mailbox.c               | 384 ++++++++++++++++++
 include/linux/apple-mailbox.h                 |  19 +
 6 files changed, 497 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml
 create mode 100644 drivers/mailbox/apple-mailbox.c
 create mode 100644 include/linux/apple-mailbox.h

-- 
2.25.1

[PATCH v4 1/3] MAINTAINERS: Add Apple mailbox files

[Sven Peter]

Add Apple mailbox files under the ARM/APPLE MACHINE SUPPORT entry.

Signed-off-by: Sven Peter <sven@svenpeter.dev>
---
As mentioned in the cover letter, there are very likely going to be
conflicts in MAINTAINERS when the various patches that are in-flight
in different subsystems will be merged.

 MAINTAINERS | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index a4a0c2baaf27..e149f7d7258a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1723,11 +1723,14 @@ C:	irc://irc.oftc.net/asahi-dev
 T:	git https://github.com/AsahiLinux/linux.git
 F:	Documentation/devicetree/bindings/arm/apple.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml
+F:	Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml
 F:	Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
 F:	arch/arm64/boot/dts/apple/
 F:	drivers/irqchip/irq-apple-aic.c
+F:	drivers/mailbox/apple-mailbox.c
 F:	include/dt-bindings/interrupt-controller/apple-aic.h
 F:	include/dt-bindings/pinctrl/apple.h
+F:	include/linux/apple-mailbox.h
 
 ARM/ARTPEC MACHINE SUPPORT
 M:	Jesper Nilsson <jesper.nilsson@axis.com>
-- 
2.25.1

[PATCH v4 2/3] dt-bindings: mailbox: Add Apple mailbox bindings

[Sven Peter]

Apple mailbox controller are found on the M1 and are used for
communication with various co-processors.

Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
---
 .../bindings/mailbox/apple,mailbox.yaml       | 77 +++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml

diff --git a/Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml b/Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml
new file mode 100644
index 000000000000..2c1704b34e7a
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml
@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/apple,mailbox.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple Mailbox Controller
+
+maintainers:
+  - Hector Martin <marcan@marcan.st>
+  - Sven Peter <sven@svenpeter.dev>
+
+description:
+  The Apple mailbox consists of two FIFOs used to exchange 64+32 bit
+  messages between the main CPU and a co-processor. Multiple instances
+  of this mailbox can be found on Apple SoCs.
+  One of the two FIFOs is used to send data to a co-processor while the other
+  FIFO is used for the other direction.
+  Various clients implement different IPC protocols based on these simple
+  messages and shared memory buffers.
+
+properties:
+  compatible:
+    oneOf:
+      - description:
+          ASC mailboxes are the most common variant found on the M1 used
+          for example for the display controller, the system management
+          controller and the NVMe coprocessor.
+        items:
+          - const: apple,t8103-asc-mailbox
+
+      - description:
+          M3 mailboxes are an older variant with a slightly different MMIO
+          interface still found on the M1. It is used for the Thunderbolt
+          co-processors.
+        items:
+          - const: apple,t8103-m3-mailbox
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: send fifo is empty interrupt
+      - description: send fifo is not empty interrupt
+      - description: receive fifo is empty interrupt
+      - description: receive fifo is not empty interrupt
+
+  interrupt-names:
+    items:
+      - const: send-empty
+      - const: send-not-empty
+      - const: recv-empty
+      - const: recv-not-empty
+
+  "#mbox-cells":
+    const: 0
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-names
+  - "#mbox-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+        mailbox@77408000 {
+                compatible = "apple,t8103-asc-mailbox";
+                reg = <0x77408000 0x4000>;
+                interrupts = <1 583 4>, <1 584 4>, <1 585 4>, <1 586 4>;
+                interrupt-names = "send-empty", "send-not-empty",
+                 "recv-empty", "recv-not-empty";
+                #mbox-cells = <0>;
+        };
-- 
2.25.1

[PATCH v4 3/3] mailbox: apple: Add driver for Apple mailboxes

[Sven Peter]

Apple SoCs such as the M1 come with various co-processors. Mailboxes
are used to communicate with those. This driver adds support for
two variants of those mailboxes.

Signed-off-by: Sven Peter <sven@svenpeter.dev>
---
 drivers/mailbox/Kconfig         |  12 +
 drivers/mailbox/Makefile        |   2 +
 drivers/mailbox/apple-mailbox.c | 384 ++++++++++++++++++++++++++++++++
 include/linux/apple-mailbox.h   |  19 ++
 4 files changed, 417 insertions(+)
 create mode 100644 drivers/mailbox/apple-mailbox.c
 create mode 100644 include/linux/apple-mailbox.h

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index c9fc06c7e685..d9cd3606040e 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -8,6 +8,18 @@ menuconfig MAILBOX
 
 if MAILBOX
 
+config APPLE_MAILBOX
+	tristate "Apple Mailbox driver"
+	depends on ARCH_APPLE || (ARM64 && COMPILE_TEST)
+	default ARCH_APPLE
+	help
+	  Apple SoCs have various co-processors required for certain
+	  peripherals to work (NVMe, display controller, etc.). This
+	  driver adds support for the mailbox controller used to
+	  communicate with those.
+
+	  Say Y here if you have a Apple SoC.
+
 config ARM_MHU
 	tristate "ARM MHU Mailbox"
 	depends on ARM_AMBA
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index c2089f04887e..338cc05e5431 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -58,3 +58,5 @@ obj-$(CONFIG_SUN6I_MSGBOX)	+= sun6i-msgbox.o
 obj-$(CONFIG_SPRD_MBOX)		+= sprd-mailbox.o
 
 obj-$(CONFIG_QCOM_IPCC)		+= qcom-ipcc.o
+
+obj-$(CONFIG_APPLE_MAILBOX)	+= apple-mailbox.o
diff --git a/drivers/mailbox/apple-mailbox.c b/drivers/mailbox/apple-mailbox.c
new file mode 100644
index 000000000000..72942002a54a
--- /dev/null
+++ b/drivers/mailbox/apple-mailbox.c
@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple mailbox driver
+ *
+ * Copyright (C) 2021 The Asahi Linux Contributors
+ *
+ * This driver adds support for two mailbox variants (called ASC and M3 by
+ * Apple) found in Apple SoCs such as the M1. It consists of two FIFOs used to
+ * exchange 64+32 bit messages between the main CPU and a co-processor.
+ * Various coprocessors implement different IPC protocols based on these simple
+ * messages and shared memory buffers.
+ *
+ * Both the main CPU and the co-processor see the same set of registers but
+ * the first FIFO (A2I) is always used to transfer messages from the application
+ * processor (us) to the I/O processor and the second one (I2A) for the
+ * other direction.
+ */
+
+#include <linux/apple-mailbox.h>
+#include <linux/device.h>
+#include <linux/gfp.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#define APPLE_ASC_MBOX_CONTROL_FULL  BIT(16)
+#define APPLE_ASC_MBOX_CONTROL_EMPTY BIT(17)
+
+#define APPLE_ASC_MBOX_A2I_CONTROL 0x110
+#define APPLE_ASC_MBOX_A2I_SEND0   0x800
+#define APPLE_ASC_MBOX_A2I_SEND1   0x808
+#define APPLE_ASC_MBOX_A2I_RECV0   0x810
+#define APPLE_ASC_MBOX_A2I_RECV1   0x818
+
+#define APPLE_ASC_MBOX_I2A_CONTROL 0x114
+#define APPLE_ASC_MBOX_I2A_SEND0   0x820
+#define APPLE_ASC_MBOX_I2A_SEND1   0x828
+#define APPLE_ASC_MBOX_I2A_RECV0   0x830
+#define APPLE_ASC_MBOX_I2A_RECV1   0x838
+
+#define APPLE_M3_MBOX_CONTROL_FULL  BIT(16)
+#define APPLE_M3_MBOX_CONTROL_EMPTY BIT(17)
+
+#define APPLE_M3_MBOX_A2I_CONTROL 0x50
+#define APPLE_M3_MBOX_A2I_SEND0	  0x60
+#define APPLE_M3_MBOX_A2I_SEND1	  0x68
+#define APPLE_M3_MBOX_A2I_RECV0	  0x70
+#define APPLE_M3_MBOX_A2I_RECV1	  0x78
+
+#define APPLE_M3_MBOX_I2A_CONTROL 0x80
+#define APPLE_M3_MBOX_I2A_SEND0	  0x90
+#define APPLE_M3_MBOX_I2A_SEND1	  0x98
+#define APPLE_M3_MBOX_I2A_RECV0	  0xa0
+#define APPLE_M3_MBOX_I2A_RECV1	  0xa8
+
+#define APPLE_M3_MBOX_IRQ_ENABLE	0x48
+#define APPLE_M3_MBOX_IRQ_ACK		0x4c
+#define APPLE_M3_MBOX_IRQ_A2I_EMPTY	BIT(0)
+#define APPLE_M3_MBOX_IRQ_A2I_NOT_EMPTY BIT(1)
+#define APPLE_M3_MBOX_IRQ_I2A_EMPTY	BIT(2)
+#define APPLE_M3_MBOX_IRQ_I2A_NOT_EMPTY BIT(3)
+
+#define APPLE_MBOX_MSG1_OUTCNT GENMASK(56, 52)
+#define APPLE_MBOX_MSG1_INCNT  GENMASK(51, 48)
+#define APPLE_MBOX_MSG1_OUTPTR GENMASK(47, 44)
+#define APPLE_MBOX_MSG1_INPTR  GENMASK(43, 40)
+#define APPLE_MBOX_MSG1_MSG    GENMASK(31, 0)
+
+struct apple_mbox_hw {
+	unsigned int control_full;
+	unsigned int control_empty;
+
+	unsigned int a2i_control;
+	unsigned int a2i_send0;
+	unsigned int a2i_send1;
+
+	unsigned int i2a_control;
+	unsigned int i2a_recv0;
+	unsigned int i2a_recv1;
+
+	bool has_irq_controls;
+	unsigned int irq_enable;
+	unsigned int irq_ack;
+	unsigned int irq_bit_recv_not_empty;
+	unsigned int irq_bit_send_empty;
+};
+
+struct apple_mbox {
+	void __iomem *regs;
+	const struct apple_mbox_hw *hw;
+
+	int irq_recv_not_empty;
+	int irq_send_empty;
+
+	struct mbox_chan chan;
+
+	struct device *dev;
+	struct mbox_controller controller;
+};
+
+static const struct of_device_id apple_mbox_of_match[];
+
+static bool apple_mbox_hw_can_send(struct apple_mbox *apple_mbox)
+{
+	u32 mbox_ctrl =
+		readl_relaxed(apple_mbox->regs + apple_mbox->hw->a2i_control);
+
+	return !(mbox_ctrl & apple_mbox->hw->control_full);
+}
+
+static int apple_mbox_hw_send(struct apple_mbox *apple_mbox,
+			      struct apple_mbox_msg *msg)
+{
+	if (!apple_mbox_hw_can_send(apple_mbox))
+		return -EBUSY;
+
+	dev_dbg(apple_mbox->dev, "> TX %016llx %08x\n", msg->msg0, msg->msg1);
+
+	writeq_relaxed(msg->msg0, apple_mbox->regs + apple_mbox->hw->a2i_send0);
+	writeq_relaxed(FIELD_PREP(APPLE_MBOX_MSG1_MSG, msg->msg1),
+		       apple_mbox->regs + apple_mbox->hw->a2i_send1);
+
+	return 0;
+}
+
+static bool apple_mbox_hw_can_recv(struct apple_mbox *apple_mbox)
+{
+	u32 mbox_ctrl =
+		readl_relaxed(apple_mbox->regs + apple_mbox->hw->i2a_control);
+
+	return !(mbox_ctrl & apple_mbox->hw->control_empty);
+}
+
+static int apple_mbox_hw_recv(struct apple_mbox *apple_mbox,
+			      struct apple_mbox_msg *msg)
+{
+	if (!apple_mbox_hw_can_recv(apple_mbox))
+		return -ENOMSG;
+
+	msg->msg0 = readq_relaxed(apple_mbox->regs + apple_mbox->hw->i2a_recv0);
+	msg->msg1 = FIELD_GET(
+		APPLE_MBOX_MSG1_MSG,
+		readq_relaxed(apple_mbox->regs + apple_mbox->hw->i2a_recv1));
+
+	dev_dbg(apple_mbox->dev, "< RX %016llx %08x\n", msg->msg0, msg->msg1);
+
+	return 0;
+}
+
+static int apple_mbox_chan_send_data(struct mbox_chan *chan, void *data)
+{
+	struct apple_mbox *apple_mbox = chan->con_priv;
+	struct apple_mbox_msg *msg = data;
+	int ret;
+
+	ret = apple_mbox_hw_send(apple_mbox, msg);
+	if (ret)
+		return ret;
+
+	/*
+	 * The interrupt is level triggered and will keep firing as long as the
+	 * FIFO is empty. It will also keep firing if the FIFO was empty
+	 * at any point in the past until it has been acknowledged at the
+	 * mailbox level. By acknowledging it here we can ensure that we will
+	 * only get the interrupt once the FIFO has been cleared again.
+	 * If the FIFO is already empty before the ack it will fire again
+	 * immediately after the ack.
+	 */
+	if (apple_mbox->hw->has_irq_controls) {
+		writel_relaxed(apple_mbox->hw->irq_bit_send_empty,
+			       apple_mbox->regs + apple_mbox->hw->irq_ack);
+	}
+	enable_irq(apple_mbox->irq_send_empty);
+
+	return 0;
+}
+
+static irqreturn_t apple_mbox_send_empty_irq(int irq, void *data)
+{
+	struct apple_mbox *apple_mbox = data;
+
+	/*
+	 * We don't need to acknowledge the interrupt at the mailbox level
+	 * here even if supported by the hardware. It will keep firing but that
+	 * doesn't matter since it's disabled at the main interrupt controller.
+	 * apple_mbox_chan_send_data will acknowledge it before enabling
+	 * it at the main controller again.
+	 */
+	disable_irq_nosync(apple_mbox->irq_send_empty);
+	mbox_chan_txdone(&apple_mbox->chan, 0);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t apple_mbox_recv_irq(int irq, void *data)
+{
+	struct apple_mbox *apple_mbox = data;
+	struct apple_mbox_msg msg;
+
+	while (apple_mbox_hw_recv(apple_mbox, &msg) == 0)
+		mbox_chan_received_data(&apple_mbox->chan, (void *)&msg);
+
+	/*
+	 * The interrupt will keep firing even if there are no more messages
+	 * unless we also acknowledge it at the mailbox level here.
+	 * There's no race if a message comes in between the check in the while
+	 * loop above and the ack below: If a new messages arrives inbetween
+	 * those two the interrupt will just fire again immediately after the
+	 * ack since it's level triggered.
+	 */
+	if (apple_mbox->hw->has_irq_controls) {
+		writel_relaxed(apple_mbox->hw->irq_bit_recv_not_empty,
+			       apple_mbox->regs + apple_mbox->hw->irq_ack);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int apple_mbox_chan_startup(struct mbox_chan *chan)
+{
+	struct apple_mbox *apple_mbox = chan->con_priv;
+
+	/*
+	 * Only some variants of this mailbox HW provide interrupt control
+	 * at the mailbox level. We therefore need to handle enabling/disabling
+	 * interrupts at the main interrupt controller anyway for hardware that
+	 * doesn't. Just always keep the interrupts we care about enabled at
+	 * the mailbox level so that both hardware revisions behave almost
+	 * the same.
+	 */
+	if (apple_mbox->hw->has_irq_controls) {
+		writel_relaxed(apple_mbox->hw->irq_bit_recv_not_empty |
+				       apple_mbox->hw->irq_bit_send_empty,
+			       apple_mbox->regs + apple_mbox->hw->irq_enable);
+	}
+
+	enable_irq(apple_mbox->irq_recv_not_empty);
+	return 0;
+}
+
+static void apple_mbox_chan_shutdown(struct mbox_chan *chan)
+{
+	struct apple_mbox *apple_mbox = chan->con_priv;
+
+	disable_irq(apple_mbox->irq_recv_not_empty);
+}
+
+static const struct mbox_chan_ops apple_mbox_ops = {
+	.send_data = apple_mbox_chan_send_data,
+	.startup = apple_mbox_chan_startup,
+	.shutdown = apple_mbox_chan_shutdown,
+};
+
+static struct mbox_chan *apple_mbox_of_xlate(struct mbox_controller *mbox,
+					     const struct of_phandle_args *args)
+{
+	if (args->args_count != 0)
+		return ERR_PTR(-EINVAL);
+
+	return &mbox->chans[0];
+}
+
+static int apple_mbox_probe(struct platform_device *pdev)
+{
+	int ret;
+	const struct of_device_id *match;
+	char *irqname;
+	struct apple_mbox *mbox;
+	struct device *dev = &pdev->dev;
+
+	match = of_match_node(apple_mbox_of_match, pdev->dev.of_node);
+	if (!match)
+		return -EINVAL;
+	if (!match->data)
+		return -EINVAL;
+
+	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
+	if (!mbox)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, mbox);
+
+	mbox->dev = dev;
+	mbox->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(mbox->regs))
+		return PTR_ERR(mbox->regs);
+
+	mbox->hw = match->data;
+	mbox->irq_recv_not_empty =
+		platform_get_irq_byname(pdev, "recv-not-empty");
+	if (mbox->irq_recv_not_empty < 0)
+		return -ENODEV;
+
+	mbox->irq_send_empty = platform_get_irq_byname(pdev, "send-empty");
+	if (mbox->irq_send_empty < 0)
+		return -ENODEV;
+
+	mbox->controller.dev = mbox->dev;
+	mbox->controller.num_chans = 1;
+	mbox->controller.chans = &mbox->chan;
+	mbox->controller.ops = &apple_mbox_ops;
+	mbox->controller.txdone_irq = true;
+	mbox->controller.of_xlate = apple_mbox_of_xlate;
+	mbox->chan.con_priv = mbox;
+
+	irqname = devm_kasprintf(dev, GFP_KERNEL, "%s-recv", dev_name(dev));
+	if (!irqname)
+		return -ENOMEM;
+
+	ret = devm_request_threaded_irq(dev, mbox->irq_recv_not_empty, NULL,
+					apple_mbox_recv_irq,
+					IRQF_NO_AUTOEN | IRQF_ONESHOT, irqname,
+					mbox);
+	if (ret)
+		return ret;
+
+	irqname = devm_kasprintf(dev, GFP_KERNEL, "%s-send", dev_name(dev));
+	if (!irqname)
+		return -ENOMEM;
+
+	ret = devm_request_irq(dev, mbox->irq_send_empty,
+			       apple_mbox_send_empty_irq, IRQF_NO_AUTOEN,
+			       irqname, mbox);
+	if (ret)
+		return ret;
+
+	return devm_mbox_controller_register(dev, &mbox->controller);
+}
+
+static const struct apple_mbox_hw apple_mbox_asc_hw = {
+	.control_full = APPLE_ASC_MBOX_CONTROL_FULL,
+	.control_empty = APPLE_ASC_MBOX_CONTROL_EMPTY,
+
+	.a2i_control = APPLE_ASC_MBOX_A2I_CONTROL,
+	.a2i_send0 = APPLE_ASC_MBOX_A2I_SEND0,
+	.a2i_send1 = APPLE_ASC_MBOX_A2I_SEND1,
+
+	.i2a_control = APPLE_ASC_MBOX_I2A_CONTROL,
+	.i2a_recv0 = APPLE_ASC_MBOX_I2A_RECV0,
+	.i2a_recv1 = APPLE_ASC_MBOX_I2A_RECV1,
+
+	.has_irq_controls = false,
+};
+
+static const struct apple_mbox_hw apple_mbox_m3_hw = {
+	.control_full = APPLE_M3_MBOX_CONTROL_FULL,
+	.control_empty = APPLE_M3_MBOX_CONTROL_EMPTY,
+
+	.a2i_control = APPLE_M3_MBOX_A2I_CONTROL,
+	.a2i_send0 = APPLE_M3_MBOX_A2I_SEND0,
+	.a2i_send1 = APPLE_M3_MBOX_A2I_SEND1,
+
+	.i2a_control = APPLE_M3_MBOX_I2A_CONTROL,
+	.i2a_recv0 = APPLE_M3_MBOX_I2A_RECV0,
+	.i2a_recv1 = APPLE_M3_MBOX_I2A_RECV1,
+
+	.has_irq_controls = true,
+	.irq_enable = APPLE_M3_MBOX_IRQ_ENABLE,
+	.irq_ack = APPLE_M3_MBOX_IRQ_ACK,
+	.irq_bit_recv_not_empty = APPLE_M3_MBOX_IRQ_I2A_NOT_EMPTY,
+	.irq_bit_send_empty = APPLE_M3_MBOX_IRQ_A2I_EMPTY,
+};
+
+static const struct of_device_id apple_mbox_of_match[] = {
+	{ .compatible = "apple,t8103-asc-mailbox", .data = &apple_mbox_asc_hw },
+	{ .compatible = "apple,t8103-m3-mailbox", .data = &apple_mbox_m3_hw },
+	{}
+};
+MODULE_DEVICE_TABLE(of, apple_mbox_of_match);
+
+static struct platform_driver apple_mbox_driver = {
+	.driver = {
+		.name = "apple-mailbox",
+		.of_match_table = apple_mbox_of_match,
+	},
+	.probe = apple_mbox_probe,
+};
+module_platform_driver(apple_mbox_driver);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
+MODULE_DESCRIPTION("Apple Mailbox driver");
diff --git a/include/linux/apple-mailbox.h b/include/linux/apple-mailbox.h
new file mode 100644
index 000000000000..720fbb70294a
--- /dev/null
+++ b/include/linux/apple-mailbox.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+/*
+ * Apple mailbox message format
+ *
+ * Copyright (C) 2021 The Asahi Linux Contributors
+ */
+
+#ifndef _LINUX_APPLE_MAILBOX_H_
+#define _LINUX_APPLE_MAILBOX_H_
+
+#include <linux/types.h>
+
+/* encodes a single 96bit message sent over the single channel */
+struct apple_mbox_msg {
+	u64 msg0;
+	u32 msg1;
+};
+
+#endif
-- 
2.25.1