// SPDX-License-Identifier: GPL-2.0-only
/*
 * amd_axi_w1 - AMD 1Wire programmable logic bus host driver
 *
 * Copyright (C) 2022-2023 Advanced Micro Devices, Inc. All Rights Reserved.
 */

#include <linux/atomic.h>
#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/wait.h>

#include <linux/w1.h>

/* 1-wire AMD IP definition */
#define AXIW1_IPID	0x10ee4453
/* Registers offset */
#define AXIW1_INST_REG	0x0
#define AXIW1_CTRL_REG	0x4
#define AXIW1_IRQE_REG	0x8
#define AXIW1_STAT_REG	0xC
#define AXIW1_DATA_REG	0x10
#define AXIW1_IPVER_REG	0x18
#define AXIW1_IPID_REG	0x1C
/* Instructions */
#define AXIW1_INITPRES	0x0800
#define AXIW1_READBIT	0x0C00
#define AXIW1_WRITEBIT	0x0E00
#define AXIW1_READBYTE	0x0D00
#define AXIW1_WRITEBYTE	0x0F00
/* Status flag masks */
#define AXIW1_DONE	BIT(0)
#define AXIW1_READY	BIT(4)
#define AXIW1_PRESENCE	BIT(31)
#define AXIW1_MAJORVER_MASK	GENMASK(23, 8)
#define AXIW1_MINORVER_MASK	GENMASK(7, 0)
/* Control flag */
#define AXIW1_GO	BIT(0)
#define AXI_CLEAR	0
#define AXI_RESET	BIT(31)
#define AXIW1_READDATA	BIT(0)
/* Interrupt Enable */
#define AXIW1_READY_IRQ_EN	BIT(4)
#define AXIW1_DONE_IRQ_EN	BIT(0)

#define AXIW1_TIMEOUT	msecs_to_jiffies(100)

#define DRIVER_NAME	"amd_axi_w1"

struct amd_axi_w1_local {
	struct device *dev;
	void __iomem *base_addr;
	int irq;
	atomic_t flag;			/* Set on IRQ, cleared once serviced */
	wait_queue_head_t wait_queue;
	struct w1_bus_master bus_host;
};

/**
 * amd_axi_w1_wait_irq_interruptible_timeout() - Wait for IRQ with timeout.
 *
 * @amd_axi_w1_local:	Pointer to device structure
 * @IRQ:		IRQ channel to wait on
 *
 * Return:		%0 - OK, %-EINTR - Interrupted, %-EBUSY - Timed out
 */
static int amd_axi_w1_wait_irq_interruptible_timeout(struct amd_axi_w1_local *amd_axi_w1_local,
						     u32 IRQ)
{
	int ret;

	/* Enable the IRQ requested and wait for flag to indicate it's been triggered */
	iowrite32(IRQ, amd_axi_w1_local->base_addr + AXIW1_IRQE_REG);
	ret = wait_event_interruptible_timeout(amd_axi_w1_local->wait_queue,
					       atomic_read(&amd_axi_w1_local->flag) != 0,
					       AXIW1_TIMEOUT);
	if (ret < 0) {
		dev_err(amd_axi_w1_local->dev, "Wait IRQ Interrupted\n");
		return -EINTR;
	}

	if (!ret) {
		dev_err(amd_axi_w1_local->dev, "Wait IRQ Timeout\n");
		return -EBUSY;
	}

	atomic_set(&amd_axi_w1_local->flag, 0);
	return 0;
}

/**
 * amd_axi_w1_touch_bit() - Performs the touch-bit function - write a 0 or 1 and reads the level.
 *
 * @data:	Pointer to device structure
 * @bit:	The level to write
 *
 * Return:	The level read
 */
static u8 amd_axi_w1_touch_bit(void *data, u8 bit)
{
	struct amd_axi_w1_local *amd_axi_w1_local = data;
	u8 val = 0;
	int rc;

	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_READY) == 0) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local,
							       AXIW1_READY_IRQ_EN);
		if (rc < 0)
			return 1; /* Callee doesn't test for error. Return inactive bus state */
	}

	if (bit)
		/* Read. Write read Bit command in register 0 */
		iowrite32(AXIW1_READBIT, amd_axi_w1_local->base_addr + AXIW1_INST_REG);
	else
		/* Write. Write tx Bit command in instruction register with bit to transmit */
		iowrite32(AXIW1_WRITEBIT + (bit & 0x01),
			  amd_axi_w1_local->base_addr + AXIW1_INST_REG);

	/* Write Go signal and clear control reset signal in control register */
	iowrite32(AXIW1_GO, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	/* Wait for done signal to be 1 */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local, AXIW1_DONE_IRQ_EN);
		if (rc < 0)
			return 1; /* Callee doesn't test for error. Return inactive bus state */
	}

	/* If read, Retrieve data from register */
	if (bit)
		val = (u8)(ioread32(amd_axi_w1_local->base_addr + AXIW1_DATA_REG) & AXIW1_READDATA);

	/* Clear Go signal in register 1 */
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	return val;
}

/**
 * amd_axi_w1_read_byte - Performs the read byte function.
 *
 * @data:	Pointer to device structure
 * Return:	The value read
 */
static u8 amd_axi_w1_read_byte(void *data)
{
	struct amd_axi_w1_local *amd_axi_w1_local = data;
	u8 val = 0;
	int rc;

	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_READY) == 0) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local,
							       AXIW1_READY_IRQ_EN);
		if (rc < 0)
			return 0xFF; /* Return inactive bus state */
	}

	/* Write read Byte command in instruction register*/
	iowrite32(AXIW1_READBYTE, amd_axi_w1_local->base_addr + AXIW1_INST_REG);

	/* Write Go signal and clear control reset signal in control register */
	iowrite32(AXIW1_GO, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	/* Wait for done signal to be 1 */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local, AXIW1_DONE_IRQ_EN);
		if (rc < 0)
			return 0xFF; /* Return inactive bus state */
	}

	/* Retrieve LSB bit in data register to get RX byte */
	val = (u8)(ioread32(amd_axi_w1_local->base_addr + AXIW1_DATA_REG) & 0x000000FF);

	/* Clear Go signal in control register */
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	return val;
}

/**
 * amd_axi_w1_write_byte - Performs the write byte function.
 *
 * @data:	The ds2482 channel pointer
 * @val:	The value to write
 */
static void amd_axi_w1_write_byte(void *data, u8 val)
{
	struct amd_axi_w1_local *amd_axi_w1_local = data;
	int rc;

	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_READY) == 0) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local,
							       AXIW1_READY_IRQ_EN);
		if (rc < 0)
			return;
	}

	/* Write tx Byte command in instruction register with bit to transmit */
	iowrite32(AXIW1_WRITEBYTE + val, amd_axi_w1_local->base_addr + AXIW1_INST_REG);

	/* Write Go signal and clear control reset signal in register 1 */
	iowrite32(AXIW1_GO, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	/* Wait for done signal to be 1 */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local,
							       AXIW1_DONE_IRQ_EN);
		if (rc < 0)
			return;
	}

	/* Clear Go signal in control register */
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);
}

/**
 * amd_axi_w1_reset_bus() - Issues a reset bus sequence.
 *
 * @data:	the bus host data struct
 * Return:	0=Device present, 1=No device present or error
 */
static u8 amd_axi_w1_reset_bus(void *data)
{
	struct amd_axi_w1_local *amd_axi_w1_local = data;
	u8 val = 0;
	int rc;

	/* Reset 1-wire Axi IP */
	iowrite32(AXI_RESET, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	/* Wait for READY signal to be 1 to ensure 1-wire IP is ready */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_READY) == 0) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local,
							       AXIW1_READY_IRQ_EN);
		if (rc < 0)
			return 1; /* Something went wrong with the hardware */
	}
	/* Write Initialization command in instruction register */
	iowrite32(AXIW1_INITPRES, amd_axi_w1_local->base_addr + AXIW1_INST_REG);

	/* Write Go signal and clear control reset signal in register 1 */
	iowrite32(AXIW1_GO, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	/* Wait for done signal to be 1 */
	while ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_DONE) != 1) {
		rc = amd_axi_w1_wait_irq_interruptible_timeout(amd_axi_w1_local, AXIW1_DONE_IRQ_EN);
		if (rc < 0)
			return 1; /* Something went wrong with the hardware */
	}
	/* Retrieve MSB bit in status register to get failure bit */
	if ((ioread32(amd_axi_w1_local->base_addr + AXIW1_STAT_REG) & AXIW1_PRESENCE) != 0)
		val = 1;

	/* Clear Go signal in control register */
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);

	return val;
}

/* Reset the 1-wire AXI IP. Put the IP in reset state and clear registers */
static void amd_axi_w1_reset(struct amd_axi_w1_local *amd_axi_w1_local)
{
	iowrite32(AXI_RESET, amd_axi_w1_local->base_addr + AXIW1_CTRL_REG);
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_INST_REG);
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_IRQE_REG);
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_STAT_REG);
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_DATA_REG);
}

static irqreturn_t amd_axi_w1_irq(int irq, void *lp)
{
	struct amd_axi_w1_local *amd_axi_w1_local = lp;

	/* Reset interrupt trigger */
	iowrite32(AXI_CLEAR, amd_axi_w1_local->base_addr + AXIW1_IRQE_REG);

	atomic_set(&amd_axi_w1_local->flag, 1);
	wake_up_interruptible(&amd_axi_w1_local->wait_queue);

	return IRQ_HANDLED;
}

static int amd_axi_w1_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct amd_axi_w1_local *lp;
	struct clk *clk;
	u32 ver_major, ver_minor;
	int val, rc = 0;

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

	lp->dev = dev;
	lp->base_addr = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(lp->base_addr))
		return PTR_ERR(lp->base_addr);

	lp->irq = platform_get_irq(pdev, 0);
	if (lp->irq < 0)
		return lp->irq;

	rc = devm_request_irq(dev, lp->irq, &amd_axi_w1_irq, IRQF_TRIGGER_HIGH, DRIVER_NAME, lp);
	if (rc)
		return rc;

	/* Initialize wait queue and flag */
	init_waitqueue_head(&lp->wait_queue);

	clk = devm_clk_get_enabled(dev, NULL);
	if (IS_ERR(clk))
		return PTR_ERR(clk);

	/* Verify IP presence in HW */
	if (ioread32(lp->base_addr + AXIW1_IPID_REG) != AXIW1_IPID) {
		dev_err(dev, "AMD 1-wire IP not detected in hardware\n");
		return -ENODEV;
	}

	/*
	 * Allow for future driver expansion supporting new hardware features
	 * This driver currently only supports hardware 1.x, but include logic
	 * to detect if a potentially incompatible future version is used
	 * by reading major version ID. It is highly undesirable for new IP versions
	 * to break the API, but this code will at least allow for graceful failure
	 * should that happen. Future new features can be enabled by hardware
	 * incrementing the minor version and augmenting the driver to detect capability
	 * using the minor version number
	 */
	val = ioread32(lp->base_addr + AXIW1_IPVER_REG);
	ver_major = FIELD_GET(AXIW1_MAJORVER_MASK, val);
	ver_minor = FIELD_GET(AXIW1_MINORVER_MASK, val);

	if (ver_major != 1) {
		dev_err(dev, "AMD AXI W1 host version %u.%u is not supported by this driver",
			ver_major, ver_minor);
		return -ENODEV;
	}

	lp->bus_host.data = lp;
	lp->bus_host.touch_bit = amd_axi_w1_touch_bit;
	lp->bus_host.read_byte = amd_axi_w1_read_byte;
	lp->bus_host.write_byte = amd_axi_w1_write_byte;
	lp->bus_host.reset_bus = amd_axi_w1_reset_bus;

	amd_axi_w1_reset(lp);

	platform_set_drvdata(pdev, lp);
	rc = w1_add_master_device(&lp->bus_host);
	if (rc) {
		dev_err(dev, "Could not add host device\n");
		return rc;
	}

	return 0;
}

static void amd_axi_w1_remove(struct platform_device *pdev)
{
	struct amd_axi_w1_local *lp = platform_get_drvdata(pdev);

	w1_remove_master_device(&lp->bus_host);
}

static const struct of_device_id amd_axi_w1_of_match[] = {
	{ .compatible = "amd,axi-1wire-host" },
	{ /* end of list */ },
};
MODULE_DEVICE_TABLE(of, amd_axi_w1_of_match);

static struct platform_driver amd_axi_w1_driver = {
	.probe = amd_axi_w1_probe,
	.remove = amd_axi_w1_remove,
	.driver = {
		.name = DRIVER_NAME,
		.of_match_table = amd_axi_w1_of_match,
	},
};
module_platform_driver(amd_axi_w1_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kris Chaplin <kris.chaplin@amd.com>");
MODULE_DESCRIPTION("Driver for AMD AXI 1 Wire IP core");