// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
 */

#include <linux/clk.h>
#include <linux/console.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>

#include "8250.h"

/*
 * This hardware is similar to 8250, but its register map is a bit different:
 *   - MMIO32 (regshift = 2)
 *   - FCR is not at 2, but 3
 *   - LCR and MCR are not at 3 and 4, they share 4
 *   - No SCR (Instead, CHAR can be used as a scratch register)
 *   - Divisor latch at 9, no divisor latch access bit
 */

#define UNIPHIER_UART_REGSHIFT          2

/* bit[15:8] = CHAR, bit[7:0] = FCR */
#define UNIPHIER_UART_CHAR_FCR          (3 << (UNIPHIER_UART_REGSHIFT))
/* bit[15:8] = LCR, bit[7:0] = MCR */
#define UNIPHIER_UART_LCR_MCR           (4 << (UNIPHIER_UART_REGSHIFT))
/* Divisor Latch Register */
#define UNIPHIER_UART_DLR               (9 << (UNIPHIER_UART_REGSHIFT))

struct uniphier8250_priv {
        int line;
        struct clk *clk;
        spinlock_t atomic_write_lock;
};

#ifdef CONFIG_SERIAL_8250_CONSOLE
static int __init uniphier_early_console_setup(struct earlycon_device *device,
                                               const char *options)
{
        if (!device->port.membase)
                return -ENODEV;

        /* This hardware always expects MMIO32 register interface. */
        device->port.iotype = UPIO_MEM32;
        device->port.regshift = UNIPHIER_UART_REGSHIFT;

        /*
         * Do not touch the divisor register in early_serial8250_setup();
         * we assume it has been initialized by a boot loader.
         */
        device->baud = 0;

        return early_serial8250_setup(device, options);
}
OF_EARLYCON_DECLARE(uniphier, "socionext,uniphier-uart",
                    uniphier_early_console_setup);
#endif

/*
 * The register map is slightly different from that of 8250.
 * IO callbacks must be overridden for correct access to FCR, LCR, MCR and SCR.
 */
static u32 uniphier_serial_in(struct uart_port *p, unsigned int offset)
{
        unsigned int valshift = 0;

        switch (offset) {
        case UART_SCR:
                /* No SCR for this hardware.  Use CHAR as a scratch register */
                valshift = 8;
                offset = UNIPHIER_UART_CHAR_FCR;
                break;
        case UART_LCR:
                valshift = 8;
                fallthrough;
        case UART_MCR:
                offset = UNIPHIER_UART_LCR_MCR;
                break;
        default:
                offset <<= UNIPHIER_UART_REGSHIFT;
                break;
        }

        /*
         * The return value must be masked with 0xff because some registers
         * share the same offset that must be accessed by 32-bit write/read.
         * 8 or 16 bit access to this hardware result in unexpected behavior.
         */
        return (readl(p->membase + offset) >> valshift) & 0xff;
}

static void uniphier_serial_out(struct uart_port *p, unsigned int offset, u32 value)
{
        unsigned int valshift = 0;
        bool normal = false;

        switch (offset) {
        case UART_SCR:
                /* No SCR for this hardware.  Use CHAR as a scratch register */
                valshift = 8;
                fallthrough;
        case UART_FCR:
                offset = UNIPHIER_UART_CHAR_FCR;
                break;
        case UART_LCR:
                valshift = 8;
                /* Divisor latch access bit does not exist. */
                value &= ~UART_LCR_DLAB;
                fallthrough;
        case UART_MCR:
                offset = UNIPHIER_UART_LCR_MCR;
                break;
        default:
                offset <<= UNIPHIER_UART_REGSHIFT;
                normal = true;
                break;
        }

        if (normal) {
                writel(value, p->membase + offset);
        } else {
                /*
                 * Special case: two registers share the same address that
                 * must be 32-bit accessed.  As this is not longer atomic safe,
                 * take a lock just in case.
                 */
                struct uniphier8250_priv *priv = p->private_data;
                unsigned long flags;
                u32 tmp;

                spin_lock_irqsave(&priv->atomic_write_lock, flags);
                tmp = readl(p->membase + offset);
                tmp &= ~(0xff << valshift);
                tmp |= value << valshift;
                writel(tmp, p->membase + offset);
                spin_unlock_irqrestore(&priv->atomic_write_lock, flags);
        }
}

/*
 * This hardware does not have the divisor latch access bit.
 * The divisor latch register exists at different address.
 * Override dl_read/write callbacks.
 */
static u32 uniphier_serial_dl_read(struct uart_8250_port *up)
{
        return readl(up->port.membase + UNIPHIER_UART_DLR);
}

static void uniphier_serial_dl_write(struct uart_8250_port *up, u32 value)
{
        writel(value, up->port.membase + UNIPHIER_UART_DLR);
}

static int uniphier_uart_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct uart_8250_port up;
        struct uniphier8250_priv *priv;
        struct resource *regs;
        void __iomem *membase;
        int ret;

        regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!regs) {
                dev_err(dev, "failed to get memory resource\n");
                return -EINVAL;
        }

        membase = devm_ioremap(dev, regs->start, resource_size(regs));
        if (!membase)
                return -ENOMEM;

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

        memset(&up, 0, sizeof(up));

        priv->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(priv->clk)) {
                dev_err(dev, "failed to get clock\n");
                return PTR_ERR(priv->clk);
        }

        ret = clk_prepare_enable(priv->clk);
        if (ret)
                return ret;

        up.port.uartclk = clk_get_rate(priv->clk);

        spin_lock_init(&priv->atomic_write_lock);

        up.port.dev = dev;
        up.port.private_data = priv;
        up.port.mapbase = regs->start;
        up.port.mapsize = resource_size(regs);
        up.port.membase = membase;

        ret = uart_read_port_properties(&up.port);
        if (ret)
                return ret;

        up.port.type = PORT_16550A;
        up.port.iotype = UPIO_MEM32;
        up.port.fifosize = 64;
        up.port.regshift = UNIPHIER_UART_REGSHIFT;
        up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE;
        up.capabilities = UART_CAP_FIFO;

        if (of_property_read_bool(dev->of_node, "auto-flow-control"))
                up.capabilities |= UART_CAP_AFE;

        up.port.serial_in = uniphier_serial_in;
        up.port.serial_out = uniphier_serial_out;
        up.dl_read = uniphier_serial_dl_read;
        up.dl_write = uniphier_serial_dl_write;

        ret = serial8250_register_8250_port(&up);
        if (ret < 0) {
                dev_err(dev, "failed to register 8250 port\n");
                clk_disable_unprepare(priv->clk);
                return ret;
        }
        priv->line = ret;

        platform_set_drvdata(pdev, priv);

        return 0;
}

static void uniphier_uart_remove(struct platform_device *pdev)
{
        struct uniphier8250_priv *priv = platform_get_drvdata(pdev);

        serial8250_unregister_port(priv->line);
        clk_disable_unprepare(priv->clk);
}

static int __maybe_unused uniphier_uart_suspend(struct device *dev)
{
        struct uniphier8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up = serial8250_get_port(priv->line);

        serial8250_suspend_port(priv->line);

        if (!uart_console(&up->port) || console_suspend_enabled)
                clk_disable_unprepare(priv->clk);

        return 0;
}

static int __maybe_unused uniphier_uart_resume(struct device *dev)
{
        struct uniphier8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up = serial8250_get_port(priv->line);
        int ret;

        if (!uart_console(&up->port) || console_suspend_enabled) {
                ret = clk_prepare_enable(priv->clk);
                if (ret)
                        return ret;
        }

        serial8250_resume_port(priv->line);

        return 0;
}

static const struct dev_pm_ops uniphier_uart_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(uniphier_uart_suspend, uniphier_uart_resume)
};

static const struct of_device_id uniphier_uart_match[] = {
        { .compatible = "socionext,uniphier-uart" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, uniphier_uart_match);

static struct platform_driver uniphier_uart_platform_driver = {
        .probe          = uniphier_uart_probe,
        .remove         = uniphier_uart_remove,
        .driver = {
                .name   = "uniphier-uart",
                .of_match_table = uniphier_uart_match,
                .pm = &uniphier_uart_pm_ops,
        },
};
module_platform_driver(uniphier_uart_platform_driver);

MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
MODULE_DESCRIPTION("UniPhier UART driver");
MODULE_LICENSE("GPL");