drivers/soc/apple/mailbox.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only OR MIT
 /*
  * Apple mailbox driver
  *
  * Copyright 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/bitfield.h>
 #include <linux/bits.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
 #include "mailbox.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)

 #define APPLE_MBOX_TX_TIMEOUT 500

 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;
 };

 int apple_mbox_send(struct apple_mbox *mbox, const struct apple_mbox_msg msg,
 		    bool atomic)
 {
 	unsigned long flags;
 	int ret;
 	u32 mbox_ctrl;
 	long t;

 	spin_lock_irqsave(&mbox->tx_lock, flags);
 	mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->a2i_control);

 	while (mbox_ctrl & mbox->hw->control_full) {
 		if (atomic) {
 			ret = readl_poll_timeout_atomic(
 				mbox->regs + mbox->hw->a2i_control, mbox_ctrl,
 				!(mbox_ctrl & mbox->hw->control_full), 100,
 				APPLE_MBOX_TX_TIMEOUT * 1000);

 			if (ret) {
 				spin_unlock_irqrestore(&mbox->tx_lock, flags);
 				return ret;
 			}

 			break;
 		}
 		/*
 		 * 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 (mbox->hw->has_irq_controls) {
 			writel_relaxed(mbox->hw->irq_bit_send_empty,
 				       mbox->regs + mbox->hw->irq_ack);
 		}
 		enable_irq(mbox->irq_send_empty);
 		reinit_completion(&mbox->tx_empty);
 		spin_unlock_irqrestore(&mbox->tx_lock, flags);

 		t = wait_for_completion_interruptible_timeout(
 			&mbox->tx_empty,
 			msecs_to_jiffies(APPLE_MBOX_TX_TIMEOUT));
 		if (t < 0)
 			return t;
 		else if (t == 0)
 			return -ETIMEDOUT;

 		spin_lock_irqsave(&mbox->tx_lock, flags);
 		mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->a2i_control);
 	}

 	writeq_relaxed(msg.msg0, mbox->regs + mbox->hw->a2i_send0);
 	writeq_relaxed(FIELD_PREP(APPLE_MBOX_MSG1_MSG, msg.msg1),
 		       mbox->regs + mbox->hw->a2i_send1);

 	spin_unlock_irqrestore(&mbox->tx_lock, flags);

 	return 0;
 }
 EXPORT_SYMBOL(apple_mbox_send);

 static irqreturn_t apple_mbox_send_empty_irq(int irq, void *data)
 {
 	struct apple_mbox *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_send will acknowledge it before enabling
 	 * it at the main controller again.
 	 */
 	spin_lock(&mbox->tx_lock);
 	disable_irq_nosync(mbox->irq_send_empty);
 	complete(&mbox->tx_empty);
 	spin_unlock(&mbox->tx_lock);

 	return IRQ_HANDLED;
 }

 static int apple_mbox_poll_locked(struct apple_mbox *mbox)
 {
 	struct apple_mbox_msg msg;
 	int ret = 0;

 	u32 mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->i2a_control);

 	while (!(mbox_ctrl & mbox->hw->control_empty)) {
 		msg.msg0 = readq_relaxed(mbox->regs + mbox->hw->i2a_recv0);
 		msg.msg1 = FIELD_GET(
 			APPLE_MBOX_MSG1_MSG,
 			readq_relaxed(mbox->regs + mbox->hw->i2a_recv1));

 		mbox->rx(mbox, msg, mbox->cookie);
 		ret++;
 		mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->i2a_control);
 	}

 	/*
 	 * 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 (mbox->hw->has_irq_controls) {
 		writel_relaxed(mbox->hw->irq_bit_recv_not_empty,
 			       mbox->regs + mbox->hw->irq_ack);
 	}

 	return ret;
 }

 static irqreturn_t apple_mbox_recv_irq(int irq, void *data)
 {
 	struct apple_mbox *mbox = data;

 	spin_lock(&mbox->rx_lock);
 	apple_mbox_poll_locked(mbox);
 	spin_unlock(&mbox->rx_lock);

 	return IRQ_HANDLED;
 }

 int apple_mbox_poll(struct apple_mbox *mbox)
 {
 	unsigned long flags;
 	int ret;

 	spin_lock_irqsave(&mbox->rx_lock, flags);
 	ret = apple_mbox_poll_locked(mbox);
 	spin_unlock_irqrestore(&mbox->rx_lock, flags);

 	return ret;
 }
 EXPORT_SYMBOL(apple_mbox_poll);

 int apple_mbox_start(struct apple_mbox *mbox)
 {
 	int ret;

 	if (mbox->active)
 		return 0;

 	ret = pm_runtime_resume_and_get(mbox->dev);
 	if (ret)
 		return ret;

 	/*
 	 * 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 (mbox->hw->has_irq_controls) {
 		writel_relaxed(mbox->hw->irq_bit_recv_not_empty |
 				       mbox->hw->irq_bit_send_empty,
 			       mbox->regs + mbox->hw->irq_enable);
 	}

 	enable_irq(mbox->irq_recv_not_empty);
 	mbox->active = true;
 	return 0;
 }
 EXPORT_SYMBOL(apple_mbox_start);

 void apple_mbox_stop(struct apple_mbox *mbox)
 {
 	if (!mbox->active)
 		return;

 	mbox->active = false;
 	disable_irq(mbox->irq_recv_not_empty);
 	pm_runtime_mark_last_busy(mbox->dev);
 	pm_runtime_put_autosuspend(mbox->dev);
 }
 EXPORT_SYMBOL(apple_mbox_stop);

 struct apple_mbox *apple_mbox_get(struct device *dev, int index)
 {
 	struct of_phandle_args args;
 	struct platform_device *pdev;
 	struct apple_mbox *mbox;
 	int ret;

 	ret = of_parse_phandle_with_args(dev->of_node, "mboxes", "#mbox-cells",
 					 index, &args);
 	if (ret || !args.np)
 		return ERR_PTR(ret);

 	pdev = of_find_device_by_node(args.np);
 	of_node_put(args.np);

 	if (!pdev)
 		return ERR_PTR(-EPROBE_DEFER);

 	mbox = platform_get_drvdata(pdev);
 	if (!mbox)
 		return ERR_PTR(-EPROBE_DEFER);

 	if (!device_link_add(dev, &pdev->dev, DL_FLAG_AUTOREMOVE_CONSUMER))
 		return ERR_PTR(-ENODEV);

 	return mbox;
 }
 EXPORT_SYMBOL(apple_mbox_get);

 struct apple_mbox *apple_mbox_get_byname(struct device *dev, const char *name)
 {
 	int index;

 	index = of_property_match_string(dev->of_node, "mbox-names", name);
 	if (index < 0)
 		return ERR_PTR(index);

 	return apple_mbox_get(dev, index);
 }
 EXPORT_SYMBOL(apple_mbox_get_byname);

 static int apple_mbox_probe(struct platform_device *pdev)
 {
 	int ret;
 	char *irqname;
 	struct apple_mbox *mbox;
 	struct device *dev = &pdev->dev;

 	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
 	if (!mbox)
 		return -ENOMEM;

 	mbox->dev = &pdev->dev;
 	mbox->hw = of_device_get_match_data(dev);
 	if (!mbox->hw)
 		return -EINVAL;

 	mbox->regs = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(mbox->regs))
 		return PTR_ERR(mbox->regs);

 	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;

 	spin_lock_init(&mbox->rx_lock);
 	spin_lock_init(&mbox->tx_lock);
 	init_completion(&mbox->tx_empty);

 	irqname = devm_kasprintf(dev, GFP_KERNEL, "%s-recv", dev_name(dev));
 	if (!irqname)
 		return -ENOMEM;

 	ret = devm_request_irq(dev, mbox->irq_recv_not_empty,
 			       apple_mbox_recv_irq,
 			       IRQF_NO_AUTOEN | IRQF_NO_SUSPEND, 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 | IRQF_NO_SUSPEND, irqname, mbox);
 	if (ret)
 		return ret;

 	ret = devm_pm_runtime_enable(dev);
 	if (ret)
 		return ret;

 	platform_set_drvdata(pdev, mbox);
 	return 0;
 }

 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,asc-mailbox-v4", .data = &apple_mbox_asc_hw },
 	{ .compatible = "apple,m3-mailbox-v2", .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");
	// SPDX-License-Identifier: GPL-2.0-only OR MIT
	/*
	* Apple mailbox driver
	*
	* Copyright 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/bitfield.h>
	#include <linux/bits.h>
	#include <linux/delay.h>
	#include <linux/device.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/iopoll.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_platform.h>
	#include <linux/platform_device.h>
	#include <linux/pm_runtime.h>
	#include <linux/spinlock.h>
	#include <linux/types.h>
	#include "mailbox.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)

	#define APPLE_MBOX_TX_TIMEOUT 500

	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;
	};

	int apple_mbox_send(struct apple_mbox *mbox, const struct apple_mbox_msg msg,
	bool atomic)
	{
	unsigned long flags;
	int ret;
	u32 mbox_ctrl;
	long t;

	spin_lock_irqsave(&mbox->tx_lock, flags);
	mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->a2i_control);

	while (mbox_ctrl & mbox->hw->control_full) {
	if (atomic) {
	ret = readl_poll_timeout_atomic(
	mbox->regs + mbox->hw->a2i_control, mbox_ctrl,
	!(mbox_ctrl & mbox->hw->control_full), 100,
	APPLE_MBOX_TX_TIMEOUT * 1000);

	if (ret) {
	spin_unlock_irqrestore(&mbox->tx_lock, flags);
	return ret;
	}

	break;
	}
	/*
	* 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 (mbox->hw->has_irq_controls) {
	writel_relaxed(mbox->hw->irq_bit_send_empty,
	mbox->regs + mbox->hw->irq_ack);
	}
	enable_irq(mbox->irq_send_empty);
	reinit_completion(&mbox->tx_empty);
	spin_unlock_irqrestore(&mbox->tx_lock, flags);

	t = wait_for_completion_interruptible_timeout(
	&mbox->tx_empty,
	msecs_to_jiffies(APPLE_MBOX_TX_TIMEOUT));
	if (t < 0)
	return t;
	else if (t == 0)
	return -ETIMEDOUT;

	spin_lock_irqsave(&mbox->tx_lock, flags);
	mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->a2i_control);
	}

	writeq_relaxed(msg.msg0, mbox->regs + mbox->hw->a2i_send0);
	writeq_relaxed(FIELD_PREP(APPLE_MBOX_MSG1_MSG, msg.msg1),
	mbox->regs + mbox->hw->a2i_send1);

	spin_unlock_irqrestore(&mbox->tx_lock, flags);

	return 0;
	}
	EXPORT_SYMBOL(apple_mbox_send);

	static irqreturn_t apple_mbox_send_empty_irq(int irq, void *data)
	{
	struct apple_mbox *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_send will acknowledge it before enabling
	* it at the main controller again.
	*/
	spin_lock(&mbox->tx_lock);
	disable_irq_nosync(mbox->irq_send_empty);
	complete(&mbox->tx_empty);
	spin_unlock(&mbox->tx_lock);

	return IRQ_HANDLED;
	}

	static int apple_mbox_poll_locked(struct apple_mbox *mbox)
	{
	struct apple_mbox_msg msg;
	int ret = 0;

	u32 mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->i2a_control);

	while (!(mbox_ctrl & mbox->hw->control_empty)) {
	msg.msg0 = readq_relaxed(mbox->regs + mbox->hw->i2a_recv0);
	msg.msg1 = FIELD_GET(
	APPLE_MBOX_MSG1_MSG,
	readq_relaxed(mbox->regs + mbox->hw->i2a_recv1));

	mbox->rx(mbox, msg, mbox->cookie);
	ret++;
	mbox_ctrl = readl_relaxed(mbox->regs + mbox->hw->i2a_control);
	}

	/*
	* 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 (mbox->hw->has_irq_controls) {
	writel_relaxed(mbox->hw->irq_bit_recv_not_empty,
	mbox->regs + mbox->hw->irq_ack);
	}

	return ret;
	}

	static irqreturn_t apple_mbox_recv_irq(int irq, void *data)
	{
	struct apple_mbox *mbox = data;

	spin_lock(&mbox->rx_lock);
	apple_mbox_poll_locked(mbox);
	spin_unlock(&mbox->rx_lock);

	return IRQ_HANDLED;
	}

	int apple_mbox_poll(struct apple_mbox *mbox)
	{
	unsigned long flags;
	int ret;

	spin_lock_irqsave(&mbox->rx_lock, flags);
	ret = apple_mbox_poll_locked(mbox);
	spin_unlock_irqrestore(&mbox->rx_lock, flags);

	return ret;
	}
	EXPORT_SYMBOL(apple_mbox_poll);

	int apple_mbox_start(struct apple_mbox *mbox)
	{
	int ret;

	if (mbox->active)
	return 0;

	ret = pm_runtime_resume_and_get(mbox->dev);
	if (ret)
	return ret;

	/*
	* 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 (mbox->hw->has_irq_controls) {
	writel_relaxed(mbox->hw->irq_bit_recv_not_empty \|
	mbox->hw->irq_bit_send_empty,
	mbox->regs + mbox->hw->irq_enable);
	}

	enable_irq(mbox->irq_recv_not_empty);
	mbox->active = true;
	return 0;
	}
	EXPORT_SYMBOL(apple_mbox_start);

	void apple_mbox_stop(struct apple_mbox *mbox)
	{
	if (!mbox->active)
	return;

	mbox->active = false;
	disable_irq(mbox->irq_recv_not_empty);
	pm_runtime_mark_last_busy(mbox->dev);
	pm_runtime_put_autosuspend(mbox->dev);
	}
	EXPORT_SYMBOL(apple_mbox_stop);

	struct apple_mbox apple_mbox_get(struct device dev, int index)
	{
	struct of_phandle_args args;
	struct platform_device *pdev;
	struct apple_mbox *mbox;
	int ret;

	ret = of_parse_phandle_with_args(dev->of_node, "mboxes", "#mbox-cells",
	index, &args);
	if (ret \|\| !args.np)
	return ERR_PTR(ret);

	pdev = of_find_device_by_node(args.np);
	of_node_put(args.np);

	if (!pdev)
	return ERR_PTR(-EPROBE_DEFER);

	mbox = platform_get_drvdata(pdev);
	if (!mbox)
	return ERR_PTR(-EPROBE_DEFER);

	if (!device_link_add(dev, &pdev->dev, DL_FLAG_AUTOREMOVE_CONSUMER))
	return ERR_PTR(-ENODEV);

	return mbox;
	}
	EXPORT_SYMBOL(apple_mbox_get);

	struct apple_mbox apple_mbox_get_byname(struct device dev, const char *name)
	{
	int index;

	index = of_property_match_string(dev->of_node, "mbox-names", name);
	if (index < 0)
	return ERR_PTR(index);

	return apple_mbox_get(dev, index);
	}
	EXPORT_SYMBOL(apple_mbox_get_byname);

	static int apple_mbox_probe(struct platform_device *pdev)
	{
	int ret;
	char *irqname;
	struct apple_mbox *mbox;
	struct device *dev = &pdev->dev;

	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
	if (!mbox)
	return -ENOMEM;

	mbox->dev = &pdev->dev;
	mbox->hw = of_device_get_match_data(dev);
	if (!mbox->hw)
	return -EINVAL;

	mbox->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(mbox->regs))
	return PTR_ERR(mbox->regs);

	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;

	spin_lock_init(&mbox->rx_lock);
	spin_lock_init(&mbox->tx_lock);
	init_completion(&mbox->tx_empty);

	irqname = devm_kasprintf(dev, GFP_KERNEL, "%s-recv", dev_name(dev));
	if (!irqname)
	return -ENOMEM;

	ret = devm_request_irq(dev, mbox->irq_recv_not_empty,
	apple_mbox_recv_irq,
	IRQF_NO_AUTOEN \| IRQF_NO_SUSPEND, 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 \| IRQF_NO_SUSPEND, irqname, mbox);
	if (ret)
	return ret;

	ret = devm_pm_runtime_enable(dev);
	if (ret)
	return ret;

	platform_set_drvdata(pdev, mbox);
	return 0;
	}

	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,asc-mailbox-v4", .data = &apple_mbox_asc_hw },
	{ .compatible = "apple,m3-mailbox-v2", .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");