// SPDX-License-Identifier: GPL-2.0
/*
 * Arcx Anybus-S Controller driver
 *
 * Copyright (C) 2018 Arcx Inc
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/delay.h>
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/regulator/driver.h>
#include <linux/regulator/machine.h>
#include <linux/regmap.h>

/* move to <linux/anybuss-controller.h> when taking this out of staging */
#include "anybuss-controller.h"

#define CPLD_STATUS1		0x80
#define CPLD_CONTROL		0x80
#define CPLD_CONTROL_CRST	0x40
#define CPLD_CONTROL_RST1	0x04
#define CPLD_CONTROL_RST2	0x80
#define CPLD_STATUS1_AB		0x02
#define CPLD_STATUS1_CAN_POWER	0x01
#define CPLD_DESIGN_LO		0x81
#define CPLD_DESIGN_HI		0x82
#define CPLD_CAP		0x83
#define CPLD_CAP_COMPAT		0x01
#define CPLD_CAP_SEP_RESETS	0x02

struct controller_priv {
	struct device *class_dev;
	bool common_reset;
	struct gpio_desc *reset_gpiod;
	void __iomem *cpld_base;
	struct mutex ctrl_lock; /* protects CONTROL register */
	u8 control_reg;
	char version[3];
	u16 design_no;
};

static void do_reset(struct controller_priv *cd, u8 rst_bit, bool reset)
{
	mutex_lock(&cd->ctrl_lock);
	/*
	 * CPLD_CONTROL is write-only, so cache its value in
	 * cd->control_reg
	 */
	if (reset)
		cd->control_reg &= ~rst_bit;
	else
		cd->control_reg |= rst_bit;
	writeb(cd->control_reg, cd->cpld_base + CPLD_CONTROL);
	/*
	 * h/w work-around:
	 * the hardware is 'too fast', so a reset followed by an immediate
	 * not-reset will _not_ change the anybus reset line in any way,
	 * losing the reset. to prevent this from happening, introduce
	 * a minimum reset duration.
	 * Verified minimum safe duration required using a scope
	 * on 14-June-2018: 100 us.
	 */
	if (reset)
		usleep_range(100, 200);
	mutex_unlock(&cd->ctrl_lock);
}

static int anybuss_reset(struct controller_priv *cd,
			 unsigned long id, bool reset)
{
	if (id >= 2)
		return -EINVAL;
	if (cd->common_reset)
		do_reset(cd, CPLD_CONTROL_CRST, reset);
	else
		do_reset(cd, id ? CPLD_CONTROL_RST2 : CPLD_CONTROL_RST1, reset);
	return 0;
}

static void export_reset_0(struct device *dev, bool assert)
{
	struct controller_priv *cd = dev_get_drvdata(dev);

	anybuss_reset(cd, 0, assert);
}

static void export_reset_1(struct device *dev, bool assert)
{
	struct controller_priv *cd = dev_get_drvdata(dev);

	anybuss_reset(cd, 1, assert);
}

/*
 * parallel bus limitation:
 *
 * the anybus is 8-bit wide. we can't assume that the hardware will translate
 * word accesses on the parallel bus to multiple byte-accesses on the anybus.
 *
 * the imx WEIM bus does not provide this type of translation.
 *
 * to be safe, we will limit parallel bus accesses to a single byte
 * at a time for now.
 */

static const struct regmap_config arcx_regmap_cfg = {
	.reg_bits = 16,
	.val_bits = 8,
	.max_register = 0x7ff,
	.use_single_read = true,
	.use_single_write = true,
	/*
	 * single-byte parallel bus accesses are atomic, so don't
	 * require any synchronization.
	 */
	.disable_locking = true,
};

static struct regmap *create_parallel_regmap(struct platform_device *pdev,
					     int idx)
{
	void __iomem *base;
	struct device *dev = &pdev->dev;

	base = devm_platform_ioremap_resource(pdev, idx + 1);
	if (IS_ERR(base))
		return ERR_CAST(base);
	return devm_regmap_init_mmio(dev, base, &arcx_regmap_cfg);
}

static struct anybuss_host *
create_anybus_host(struct platform_device *pdev, int idx)
{
	struct anybuss_ops ops = {};

	switch (idx) {
	case 0:
		ops.reset = export_reset_0;
		break;
	case 1:
		ops.reset = export_reset_1;
		break;
	default:
		return ERR_PTR(-EINVAL);
	}
	ops.host_idx = idx;
	ops.regmap = create_parallel_regmap(pdev, idx);
	if (IS_ERR(ops.regmap))
		return ERR_CAST(ops.regmap);
	ops.irq = platform_get_irq(pdev, idx);
	if (ops.irq < 0)
		return ERR_PTR(ops.irq);
	return devm_anybuss_host_common_probe(&pdev->dev, &ops);
}

static ssize_t version_show(struct device *dev,
			    struct device_attribute *attr, char *buf)
{
	struct controller_priv *cd = dev_get_drvdata(dev);

	return sprintf(buf, "%s\n", cd->version);
}
static DEVICE_ATTR_RO(version);

static ssize_t design_number_show(struct device *dev,
				  struct device_attribute *attr, char *buf)
{
	struct controller_priv *cd = dev_get_drvdata(dev);

	return sprintf(buf, "%d\n", cd->design_no);
}
static DEVICE_ATTR_RO(design_number);

static struct attribute *controller_attributes[] = {
	&dev_attr_version.attr,
	&dev_attr_design_number.attr,
	NULL,
};

static const struct attribute_group controller_attribute_group = {
	.attrs = controller_attributes,
};

static const struct attribute_group *controller_attribute_groups[] = {
	&controller_attribute_group,
	NULL,
};

static void controller_device_release(struct device *dev)
{
	kfree(dev);
}

static int can_power_is_enabled(struct regulator_dev *rdev)
{
	struct controller_priv *cd = rdev_get_drvdata(rdev);

	return !(readb(cd->cpld_base + CPLD_STATUS1) & CPLD_STATUS1_CAN_POWER);
}

static const struct regulator_ops can_power_ops = {
	.is_enabled = can_power_is_enabled,
};

static const struct regulator_desc can_power_desc = {
	.name = "regulator-can-power",
	.id = -1,
	.type = REGULATOR_VOLTAGE,
	.owner = THIS_MODULE,
	.ops = &can_power_ops,
};

static const struct class controller_class = {
	.name = "arcx_anybus_controller",
};

static DEFINE_IDA(controller_index_ida);

static int controller_probe(struct platform_device *pdev)
{
	struct controller_priv *cd;
	struct device *dev = &pdev->dev;
	struct regulator_config config = { };
	struct regulator_dev *regulator;
	int err, id;
	struct anybuss_host *host;
	u8 status1, cap;

	cd = devm_kzalloc(dev, sizeof(*cd), GFP_KERNEL);
	if (!cd)
		return -ENOMEM;
	dev_set_drvdata(dev, cd);
	mutex_init(&cd->ctrl_lock);
	cd->reset_gpiod = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
	if (IS_ERR(cd->reset_gpiod))
		return PTR_ERR(cd->reset_gpiod);

	/* CPLD control memory, sits at index 0 */
	cd->cpld_base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(cd->cpld_base)) {
		dev_err(dev,
			"failed to map cpld base address\n");
		err = PTR_ERR(cd->cpld_base);
		goto out_reset;
	}

	/* identify cpld */
	status1 = readb(cd->cpld_base + CPLD_STATUS1);
	cd->design_no = (readb(cd->cpld_base + CPLD_DESIGN_HI) << 8) |
				readb(cd->cpld_base + CPLD_DESIGN_LO);
	snprintf(cd->version, sizeof(cd->version), "%c%d",
		 'A' + ((status1 >> 5) & 0x7),
		 (status1 >> 2) & 0x7);
	dev_info(dev, "design number %d, revision %s\n",
		 cd->design_no,
		cd->version);
	cap = readb(cd->cpld_base + CPLD_CAP);
	if (!(cap & CPLD_CAP_COMPAT)) {
		dev_err(dev, "unsupported controller [cap=0x%02X]", cap);
		err = -ENODEV;
		goto out_reset;
	}

	if (status1 & CPLD_STATUS1_AB) {
		dev_info(dev, "has anybus-S slot(s)");
		cd->common_reset = !(cap & CPLD_CAP_SEP_RESETS);
		dev_info(dev, "supports %s", cd->common_reset ?
			"a common reset" : "separate resets");
		for (id = 0; id < 2; id++) {
			host = create_anybus_host(pdev, id);
			if (!IS_ERR(host))
				continue;
			err = PTR_ERR(host);
			/* -ENODEV is fine, it just means no card detected */
			if (err != -ENODEV)
				goto out_reset;
		}
	}

	id = ida_simple_get(&controller_index_ida, 0, 0, GFP_KERNEL);
	if (id < 0) {
		err = id;
		goto out_reset;
	}
	/* export can power readout as a regulator */
	config.dev = dev;
	config.driver_data = cd;
	regulator = devm_regulator_register(dev, &can_power_desc, &config);
	if (IS_ERR(regulator)) {
		err = PTR_ERR(regulator);
		goto out_ida;
	}
	/* make controller info visible to userspace */
	cd->class_dev = kzalloc(sizeof(*cd->class_dev), GFP_KERNEL);
	if (!cd->class_dev) {
		err = -ENOMEM;
		goto out_ida;
	}
	cd->class_dev->class = &controller_class;
	cd->class_dev->groups = controller_attribute_groups;
	cd->class_dev->parent = dev;
	cd->class_dev->id = id;
	cd->class_dev->release = controller_device_release;
	dev_set_name(cd->class_dev, "%d", cd->class_dev->id);
	dev_set_drvdata(cd->class_dev, cd);
	err = device_register(cd->class_dev);
	if (err)
		goto out_dev;
	return 0;
out_dev:
	put_device(cd->class_dev);
out_ida:
	ida_simple_remove(&controller_index_ida, id);
out_reset:
	gpiod_set_value_cansleep(cd->reset_gpiod, 1);
	return err;
}

static void controller_remove(struct platform_device *pdev)
{
	struct controller_priv *cd = platform_get_drvdata(pdev);
	int id = cd->class_dev->id;

	device_unregister(cd->class_dev);
	ida_simple_remove(&controller_index_ida, id);
	gpiod_set_value_cansleep(cd->reset_gpiod, 1);
}

static const struct of_device_id controller_of_match[] = {
	{ .compatible = "arcx,anybus-controller" },
	{ }
};

MODULE_DEVICE_TABLE(of, controller_of_match);

static struct platform_driver controller_driver = {
	.probe = controller_probe,
	.remove_new = controller_remove,
	.driver		= {
		.name   = "arcx-anybus-controller",
		.of_match_table	= controller_of_match,
	},
};

static int __init controller_init(void)
{
	int err;

	err = class_register(&controller_class);
	if (err)
		return err;
	err = platform_driver_register(&controller_driver);
	if (err)
		class_unregister(&controller_class);

	return err;
}

static void __exit controller_exit(void)
{
	platform_driver_unregister(&controller_driver);
	class_unregister(&controller_class);
	ida_destroy(&controller_index_ida);
}

module_init(controller_init);
module_exit(controller_exit);

MODULE_DESCRIPTION("Arcx Anybus-S Controller driver");
MODULE_AUTHOR("Sven Van Asbroeck <TheSven73@gmail.com>");
MODULE_LICENSE("GPL v2");