// SPDX-License-Identifier: GPL-2.0-or-later
/* Copyright (C) 2019 IBM Corp. */

#include <linux/bitfield.h>
#include <linux/delay.h>
#include <linux/reset.h>
#include <linux/iopoll.h>
#include <linux/mdio.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_mdio.h>
#include <linux/phy.h>
#include <linux/platform_device.h>

#define DRV_NAME "mdio-aspeed"

#define ASPEED_MDIO_CTRL		0x0
#define   ASPEED_MDIO_CTRL_FIRE		BIT(31)
#define   ASPEED_MDIO_CTRL_ST		BIT(28)
#define     ASPEED_MDIO_CTRL_ST_C45	0
#define     ASPEED_MDIO_CTRL_ST_C22	1
#define   ASPEED_MDIO_CTRL_OP		GENMASK(27, 26)
#define     MDIO_C22_OP_WRITE		0b01
#define     MDIO_C22_OP_READ		0b10
#define     MDIO_C45_OP_ADDR		0b00
#define     MDIO_C45_OP_WRITE		0b01
#define     MDIO_C45_OP_PREAD		0b10
#define     MDIO_C45_OP_READ		0b11
#define   ASPEED_MDIO_CTRL_PHYAD	GENMASK(25, 21)
#define   ASPEED_MDIO_CTRL_REGAD	GENMASK(20, 16)
#define   ASPEED_MDIO_CTRL_MIIWDATA	GENMASK(15, 0)

#define ASPEED_MDIO_DATA		0x4
#define   ASPEED_MDIO_DATA_MDC_THRES	GENMASK(31, 24)
#define   ASPEED_MDIO_DATA_MDIO_EDGE	BIT(23)
#define   ASPEED_MDIO_DATA_MDIO_LATCH	GENMASK(22, 20)
#define   ASPEED_MDIO_DATA_IDLE		BIT(16)
#define   ASPEED_MDIO_DATA_MIIRDATA	GENMASK(15, 0)

#define ASPEED_MDIO_INTERVAL_US		100
#define ASPEED_MDIO_TIMEOUT_US		(ASPEED_MDIO_INTERVAL_US * 10)

struct aspeed_mdio {
	void __iomem *base;
	struct reset_control *reset;
};

static int aspeed_mdio_op(struct mii_bus *bus, u8 st, u8 op, u8 phyad, u8 regad,
			  u16 data)
{
	struct aspeed_mdio *ctx = bus->priv;
	u32 ctrl;

	dev_dbg(&bus->dev, "%s: st: %u op: %u, phyad: %u, regad: %u, data: %u\n",
		__func__, st, op, phyad, regad, data);

	ctrl = ASPEED_MDIO_CTRL_FIRE
		| FIELD_PREP(ASPEED_MDIO_CTRL_ST, st)
		| FIELD_PREP(ASPEED_MDIO_CTRL_OP, op)
		| FIELD_PREP(ASPEED_MDIO_CTRL_PHYAD, phyad)
		| FIELD_PREP(ASPEED_MDIO_CTRL_REGAD, regad)
		| FIELD_PREP(ASPEED_MDIO_DATA_MIIRDATA, data);

	iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);

	/* Workaround for read-after-write issue.
	 * The controller may return stale data if a read follows immediately
	 * after a write. A dummy read forces the hardware to update its
	 * internal state, ensuring that the next real read returns correct data.
	 */
	ioread32(ctx->base + ASPEED_MDIO_CTRL);

	return readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl,
				!(ctrl & ASPEED_MDIO_CTRL_FIRE),
				ASPEED_MDIO_INTERVAL_US,
				ASPEED_MDIO_TIMEOUT_US);
}

static int aspeed_mdio_get_data(struct mii_bus *bus)
{
	struct aspeed_mdio *ctx = bus->priv;
	u32 data;
	int rc;

	rc = readl_poll_timeout(ctx->base + ASPEED_MDIO_DATA, data,
				data & ASPEED_MDIO_DATA_IDLE,
				ASPEED_MDIO_INTERVAL_US,
				ASPEED_MDIO_TIMEOUT_US);
	if (rc < 0)
		return rc;

	return FIELD_GET(ASPEED_MDIO_DATA_MIIRDATA, data);
}

static int aspeed_mdio_read_c22(struct mii_bus *bus, int addr, int regnum)
{
	int rc;

	rc = aspeed_mdio_op(bus, ASPEED_MDIO_CTRL_ST_C22, MDIO_C22_OP_READ,
			    addr, regnum, 0);
	if (rc < 0)
		return rc;

	return aspeed_mdio_get_data(bus);
}

static int aspeed_mdio_write_c22(struct mii_bus *bus, int addr, int regnum,
				 u16 val)
{
	return aspeed_mdio_op(bus, ASPEED_MDIO_CTRL_ST_C22, MDIO_C22_OP_WRITE,
			      addr, regnum, val);
}

static int aspeed_mdio_read_c45(struct mii_bus *bus, int addr, int devad,
				int regnum)
{
	int rc;

	rc = aspeed_mdio_op(bus, ASPEED_MDIO_CTRL_ST_C45, MDIO_C45_OP_ADDR,
			    addr, devad, regnum);
	if (rc < 0)
		return rc;

	rc = aspeed_mdio_op(bus, ASPEED_MDIO_CTRL_ST_C45, MDIO_C45_OP_READ,
			    addr, devad, 0);
	if (rc < 0)
		return rc;

	return aspeed_mdio_get_data(bus);
}

static int aspeed_mdio_write_c45(struct mii_bus *bus, int addr, int devad,
				 int regnum, u16 val)
{
	int rc;

	rc = aspeed_mdio_op(bus, ASPEED_MDIO_CTRL_ST_C45, MDIO_C45_OP_ADDR,
			    addr, devad, regnum);
	if (rc < 0)
		return rc;

	return aspeed_mdio_op(bus, ASPEED_MDIO_CTRL_ST_C45, MDIO_C45_OP_WRITE,
			      addr, devad, val);
}

static int aspeed_mdio_probe(struct platform_device *pdev)
{
	struct aspeed_mdio *ctx;
	struct mii_bus *bus;
	int rc;

	bus = devm_mdiobus_alloc_size(&pdev->dev, sizeof(*ctx));
	if (!bus)
		return -ENOMEM;

	ctx = bus->priv;
	ctx->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(ctx->base))
		return PTR_ERR(ctx->base);

	ctx->reset = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
	if (IS_ERR(ctx->reset))
		return PTR_ERR(ctx->reset);

	reset_control_deassert(ctx->reset);

	bus->name = DRV_NAME;
	snprintf(bus->id, MII_BUS_ID_SIZE, "%s%d", pdev->name, pdev->id);
	bus->parent = &pdev->dev;
	bus->read = aspeed_mdio_read_c22;
	bus->write = aspeed_mdio_write_c22;
	bus->read_c45 = aspeed_mdio_read_c45;
	bus->write_c45 = aspeed_mdio_write_c45;

	rc = of_mdiobus_register(bus, pdev->dev.of_node);
	if (rc) {
		dev_err(&pdev->dev, "Cannot register MDIO bus!\n");
		reset_control_assert(ctx->reset);
		return rc;
	}

	platform_set_drvdata(pdev, bus);

	return 0;
}

static void aspeed_mdio_remove(struct platform_device *pdev)
{
	struct mii_bus *bus = (struct mii_bus *)platform_get_drvdata(pdev);
	struct aspeed_mdio *ctx = bus->priv;

	reset_control_assert(ctx->reset);
	mdiobus_unregister(bus);
}

static const struct of_device_id aspeed_mdio_of_match[] = {
	{ .compatible = "aspeed,ast2600-mdio", },
	{ },
};
MODULE_DEVICE_TABLE(of, aspeed_mdio_of_match);

static struct platform_driver aspeed_mdio_driver = {
	.driver = {
		.name = DRV_NAME,
		.of_match_table = aspeed_mdio_of_match,
	},
	.probe = aspeed_mdio_probe,
	.remove_new = aspeed_mdio_remove,
};

module_platform_driver(aspeed_mdio_driver);

MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ASPEED MDIO bus controller");
