// SPDX-License-Identifier: GPL-2.0+
/*
 *  Driver for Conexant Digicolor serial ports (USART)
 *
 * Author: Baruch Siach <baruch@tkos.co.il>
 *
 * Copyright (C) 2014 Paradox Innovation Ltd.
 */

#include <linux/module.h>
#include <linux/console.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/workqueue.h>

#define UA_ENABLE                       0x00
#define UA_ENABLE_ENABLE                BIT(0)

#define UA_CONTROL                      0x01
#define UA_CONTROL_RX_ENABLE            BIT(0)
#define UA_CONTROL_TX_ENABLE            BIT(1)
#define UA_CONTROL_SOFT_RESET           BIT(2)

#define UA_STATUS                       0x02
#define UA_STATUS_PARITY_ERR            BIT(0)
#define UA_STATUS_FRAME_ERR             BIT(1)
#define UA_STATUS_OVERRUN_ERR           BIT(2)
#define UA_STATUS_TX_READY              BIT(6)

#define UA_CONFIG                       0x03
#define UA_CONFIG_CHAR_LEN              BIT(0)
#define UA_CONFIG_STOP_BITS             BIT(1)
#define UA_CONFIG_PARITY                BIT(2)
#define UA_CONFIG_ODD_PARITY            BIT(4)

#define UA_EMI_REC                      0x04

#define UA_HBAUD_LO                     0x08
#define UA_HBAUD_HI                     0x09

#define UA_STATUS_FIFO                  0x0a
#define UA_STATUS_FIFO_RX_EMPTY         BIT(2)
#define UA_STATUS_FIFO_RX_INT_ALMOST    BIT(3)
#define UA_STATUS_FIFO_TX_FULL          BIT(4)
#define UA_STATUS_FIFO_TX_INT_ALMOST    BIT(7)

#define UA_CONFIG_FIFO                  0x0b
#define UA_CONFIG_FIFO_RX_THRESH        7
#define UA_CONFIG_FIFO_RX_FIFO_MODE     BIT(3)
#define UA_CONFIG_FIFO_TX_FIFO_MODE     BIT(7)

#define UA_INTFLAG_CLEAR                0x1c
#define UA_INTFLAG_SET                  0x1d
#define UA_INT_ENABLE                   0x1e
#define UA_INT_STATUS                   0x1f

#define UA_INT_TX                       BIT(0)
#define UA_INT_RX                       BIT(1)

#define DIGICOLOR_USART_NR              3

/*
 * We use the 16 bytes hardware FIFO to buffer Rx traffic. Rx interrupt is
 * only produced when the FIFO is filled more than a certain configurable
 * threshold. Unfortunately, there is no way to set this threshold below half
 * FIFO. This means that we must periodically poll the FIFO status register to
 * see whether there are waiting Rx bytes.
 */

struct digicolor_port {
        struct uart_port port;
        struct delayed_work rx_poll_work;
};

static struct uart_port *digicolor_ports[DIGICOLOR_USART_NR];

static bool digicolor_uart_tx_full(struct uart_port *port)
{
        return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
                  UA_STATUS_FIFO_TX_FULL);
}

static bool digicolor_uart_rx_empty(struct uart_port *port)
{
        return !!(readb_relaxed(port->membase + UA_STATUS_FIFO) &
                  UA_STATUS_FIFO_RX_EMPTY);
}

static void digicolor_uart_stop_tx(struct uart_port *port)
{
        u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);

        int_enable &= ~UA_INT_TX;
        writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
}

static void digicolor_uart_start_tx(struct uart_port *port)
{
        u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);

        int_enable |= UA_INT_TX;
        writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
}

static void digicolor_uart_stop_rx(struct uart_port *port)
{
        u8 int_enable = readb_relaxed(port->membase + UA_INT_ENABLE);

        int_enable &= ~UA_INT_RX;
        writeb_relaxed(int_enable, port->membase + UA_INT_ENABLE);
}

static void digicolor_rx_poll(struct work_struct *work)
{
        struct digicolor_port *dp =
                container_of(to_delayed_work(work),
                             struct digicolor_port, rx_poll_work);

        if (!digicolor_uart_rx_empty(&dp->port))
                /* force RX interrupt */
                writeb_relaxed(UA_INT_RX, dp->port.membase + UA_INTFLAG_SET);

        schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));
}

static void digicolor_uart_rx(struct uart_port *port)
{
        unsigned long flags;

        uart_port_lock_irqsave(port, &flags);

        while (1) {
                u8 status, ch, ch_flag;

                if (digicolor_uart_rx_empty(port))
                        break;

                ch = readb_relaxed(port->membase + UA_EMI_REC);
                status = readb_relaxed(port->membase + UA_STATUS);

                port->icount.rx++;
                ch_flag = TTY_NORMAL;

                if (status) {
                        if (status & UA_STATUS_PARITY_ERR)
                                port->icount.parity++;
                        else if (status & UA_STATUS_FRAME_ERR)
                                port->icount.frame++;
                        else if (status & UA_STATUS_OVERRUN_ERR)
                                port->icount.overrun++;

                        status &= port->read_status_mask;

                        if (status & UA_STATUS_PARITY_ERR)
                                ch_flag = TTY_PARITY;
                        else if (status & UA_STATUS_FRAME_ERR)
                                ch_flag = TTY_FRAME;
                        else if (status & UA_STATUS_OVERRUN_ERR)
                                ch_flag = TTY_OVERRUN;
                }

                if (status & port->ignore_status_mask)
                        continue;

                uart_insert_char(port, status, UA_STATUS_OVERRUN_ERR, ch,
                                 ch_flag);
        }

        uart_port_unlock_irqrestore(port, flags);

        tty_flip_buffer_push(&port->state->port);
}

static void digicolor_uart_tx(struct uart_port *port)
{
        struct tty_port *tport = &port->state->port;
        unsigned long flags;
        unsigned char c;

        if (digicolor_uart_tx_full(port))
                return;

        uart_port_lock_irqsave(port, &flags);

        if (port->x_char) {
                writeb_relaxed(port->x_char, port->membase + UA_EMI_REC);
                port->icount.tx++;
                port->x_char = 0;
                goto out;
        }

        if (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port)) {
                digicolor_uart_stop_tx(port);
                goto out;
        }

        while (uart_fifo_get(port, &c)) {
                writeb(c, port->membase + UA_EMI_REC);

                if (digicolor_uart_tx_full(port))
                        break;
        }

        if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
                uart_write_wakeup(port);

out:
        uart_port_unlock_irqrestore(port, flags);
}

static irqreturn_t digicolor_uart_int(int irq, void *dev_id)
{
        struct uart_port *port = dev_id;
        u8 int_status = readb_relaxed(port->membase + UA_INT_STATUS);

        writeb_relaxed(UA_INT_RX | UA_INT_TX,
                       port->membase + UA_INTFLAG_CLEAR);

        if (int_status & UA_INT_RX)
                digicolor_uart_rx(port);
        if (int_status & UA_INT_TX)
                digicolor_uart_tx(port);

        return IRQ_HANDLED;
}

static unsigned int digicolor_uart_tx_empty(struct uart_port *port)
{
        u8 status = readb_relaxed(port->membase + UA_STATUS);

        return (status & UA_STATUS_TX_READY) ? TIOCSER_TEMT : 0;
}

static unsigned int digicolor_uart_get_mctrl(struct uart_port *port)
{
        return TIOCM_CTS;
}

static void digicolor_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}

static void digicolor_uart_break_ctl(struct uart_port *port, int state)
{
}

static int digicolor_uart_startup(struct uart_port *port)
{
        struct digicolor_port *dp =
                container_of(port, struct digicolor_port, port);

        writeb_relaxed(UA_ENABLE_ENABLE, port->membase + UA_ENABLE);
        writeb_relaxed(UA_CONTROL_SOFT_RESET, port->membase + UA_CONTROL);
        writeb_relaxed(0, port->membase + UA_CONTROL);

        writeb_relaxed(UA_CONFIG_FIFO_RX_FIFO_MODE
                       | UA_CONFIG_FIFO_TX_FIFO_MODE | UA_CONFIG_FIFO_RX_THRESH,
                       port->membase + UA_CONFIG_FIFO);
        writeb_relaxed(UA_STATUS_FIFO_RX_INT_ALMOST,
                       port->membase + UA_STATUS_FIFO);
        writeb_relaxed(UA_CONTROL_RX_ENABLE | UA_CONTROL_TX_ENABLE,
                       port->membase + UA_CONTROL);
        writeb_relaxed(UA_INT_TX | UA_INT_RX,
                       port->membase + UA_INT_ENABLE);

        schedule_delayed_work(&dp->rx_poll_work, msecs_to_jiffies(100));

        return 0;
}

static void digicolor_uart_shutdown(struct uart_port *port)
{
        struct digicolor_port *dp =
                container_of(port, struct digicolor_port, port);

        writeb_relaxed(0, port->membase + UA_ENABLE);
        cancel_delayed_work_sync(&dp->rx_poll_work);
}

static void digicolor_uart_set_termios(struct uart_port *port,
                                       struct ktermios *termios,
                                       const struct ktermios *old)
{
        unsigned int baud, divisor;
        u8 config = 0;
        unsigned long flags;

        /* Mask termios capabilities we don't support */
        termios->c_cflag &= ~CMSPAR;
        termios->c_iflag &= ~(BRKINT | IGNBRK);

        /* Limit baud rates so that we don't need the fractional divider */
        baud = uart_get_baud_rate(port, termios, old,
                                  port->uartclk / (0x10000*16),
                                  port->uartclk / 256);
        divisor = uart_get_divisor(port, baud) - 1;

        switch (termios->c_cflag & CSIZE) {
        case CS7:
                break;
        case CS8:
        default:
                config |= UA_CONFIG_CHAR_LEN;
                termios->c_cflag &= ~CSIZE;
                termios->c_cflag |= CS8;
                break;
        }

        if (termios->c_cflag & CSTOPB)
                config |= UA_CONFIG_STOP_BITS;

        if (termios->c_cflag & PARENB) {
                config |= UA_CONFIG_PARITY;
                if (termios->c_cflag & PARODD)
                        config |= UA_CONFIG_ODD_PARITY;
        }

        /* Set read status mask */
        port->read_status_mask = UA_STATUS_OVERRUN_ERR;
        if (termios->c_iflag & INPCK)
                port->read_status_mask |= UA_STATUS_PARITY_ERR
                        | UA_STATUS_FRAME_ERR;

        /* Set status ignore mask */
        port->ignore_status_mask = 0;
        if (!(termios->c_cflag & CREAD))
                port->ignore_status_mask |= UA_STATUS_OVERRUN_ERR
                        | UA_STATUS_PARITY_ERR | UA_STATUS_FRAME_ERR;

        uart_port_lock_irqsave(port, &flags);

        uart_update_timeout(port, termios->c_cflag, baud);

        writeb_relaxed(config, port->membase + UA_CONFIG);
        writeb_relaxed(divisor & 0xff, port->membase + UA_HBAUD_LO);
        writeb_relaxed(divisor >> 8, port->membase + UA_HBAUD_HI);

        uart_port_unlock_irqrestore(port, flags);
}

static const char *digicolor_uart_type(struct uart_port *port)
{
        return (port->type == PORT_DIGICOLOR) ? "DIGICOLOR USART" : NULL;
}

static void digicolor_uart_config_port(struct uart_port *port, int flags)
{
        if (flags & UART_CONFIG_TYPE)
                port->type = PORT_DIGICOLOR;
}

static void digicolor_uart_release_port(struct uart_port *port)
{
}

static int digicolor_uart_request_port(struct uart_port *port)
{
        return 0;
}

static const struct uart_ops digicolor_uart_ops = {
        .tx_empty       = digicolor_uart_tx_empty,
        .set_mctrl      = digicolor_uart_set_mctrl,
        .get_mctrl      = digicolor_uart_get_mctrl,
        .stop_tx        = digicolor_uart_stop_tx,
        .start_tx       = digicolor_uart_start_tx,
        .stop_rx        = digicolor_uart_stop_rx,
        .break_ctl      = digicolor_uart_break_ctl,
        .startup        = digicolor_uart_startup,
        .shutdown       = digicolor_uart_shutdown,
        .set_termios    = digicolor_uart_set_termios,
        .type           = digicolor_uart_type,
        .config_port    = digicolor_uart_config_port,
        .release_port   = digicolor_uart_release_port,
        .request_port   = digicolor_uart_request_port,
};

static void digicolor_uart_console_putchar(struct uart_port *port, unsigned char ch)
{
        while (digicolor_uart_tx_full(port))
                cpu_relax();

        writeb_relaxed(ch, port->membase + UA_EMI_REC);
}

static void digicolor_uart_console_write(struct console *co, const char *c,
                                         unsigned n)
{
        struct uart_port *port = digicolor_ports[co->index];
        u8 status;
        unsigned long flags;
        int locked = 1;

        if (oops_in_progress)
                locked = uart_port_trylock_irqsave(port, &flags);
        else
                uart_port_lock_irqsave(port, &flags);

        uart_console_write(port, c, n, digicolor_uart_console_putchar);

        if (locked)
                uart_port_unlock_irqrestore(port, flags);

        /* Wait for transmitter to become empty */
        do {
                status = readb_relaxed(port->membase + UA_STATUS);
        } while ((status & UA_STATUS_TX_READY) == 0);
}

static int digicolor_uart_console_setup(struct console *co, char *options)
{
        int baud = 115200, bits = 8, parity = 'n', flow = 'n';
        struct uart_port *port;

        if (co->index < 0 || co->index >= DIGICOLOR_USART_NR)
                return -EINVAL;

        port = digicolor_ports[co->index];
        if (!port)
                return -ENODEV;

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);

        return uart_set_options(port, co, baud, parity, bits, flow);
}

static struct console digicolor_console = {
        .name   = "ttyS",
        .device = uart_console_device,
        .write  = digicolor_uart_console_write,
        .setup  = digicolor_uart_console_setup,
        .flags  = CON_PRINTBUFFER,
        .index  = -1,
};

static struct uart_driver digicolor_uart = {
        .driver_name    = "digicolor-usart",
        .dev_name       = "ttyS",
        .nr             = DIGICOLOR_USART_NR,
};

static int digicolor_uart_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        int irq, ret, index;
        struct digicolor_port *dp;
        struct resource *res;
        struct clk *uart_clk;

        if (!np) {
                dev_err(&pdev->dev, "Missing device tree node\n");
                return -ENXIO;
        }

        index = of_alias_get_id(np, "serial");
        if (index < 0 || index >= DIGICOLOR_USART_NR)
                return -EINVAL;

        dp = devm_kzalloc(&pdev->dev, sizeof(*dp), GFP_KERNEL);
        if (!dp)
                return -ENOMEM;

        uart_clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(uart_clk))
                return PTR_ERR(uart_clk);

        dp->port.membase = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(dp->port.membase))
                return PTR_ERR(dp->port.membase);
        dp->port.mapbase = res->start;

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;
        dp->port.irq = irq;

        dp->port.iotype = UPIO_MEM;
        dp->port.uartclk = clk_get_rate(uart_clk);
        dp->port.fifosize = 16;
        dp->port.dev = &pdev->dev;
        dp->port.ops = &digicolor_uart_ops;
        dp->port.line = index;
        dp->port.type = PORT_DIGICOLOR;
        spin_lock_init(&dp->port.lock);

        digicolor_ports[index] = &dp->port;
        platform_set_drvdata(pdev, &dp->port);

        INIT_DELAYED_WORK(&dp->rx_poll_work, digicolor_rx_poll);

        ret = devm_request_irq(&pdev->dev, dp->port.irq, digicolor_uart_int, 0,
                               dev_name(&pdev->dev), &dp->port);
        if (ret)
                return ret;

        return uart_add_one_port(&digicolor_uart, &dp->port);
}

static void digicolor_uart_remove(struct platform_device *pdev)
{
        struct uart_port *port = platform_get_drvdata(pdev);

        uart_remove_one_port(&digicolor_uart, port);
}

static const struct of_device_id digicolor_uart_dt_ids[] = {
        { .compatible = "cnxt,cx92755-usart", },
        { }
};
MODULE_DEVICE_TABLE(of, digicolor_uart_dt_ids);

static struct platform_driver digicolor_uart_platform = {
        .driver = {
                .name           = "digicolor-usart",
                .of_match_table = of_match_ptr(digicolor_uart_dt_ids),
        },
        .probe  = digicolor_uart_probe,
        .remove = digicolor_uart_remove,
};

static int __init digicolor_uart_init(void)
{
        int ret;

        if (IS_ENABLED(CONFIG_SERIAL_CONEXANT_DIGICOLOR_CONSOLE)) {
                digicolor_uart.cons = &digicolor_console;
                digicolor_console.data = &digicolor_uart;
        }

        ret = uart_register_driver(&digicolor_uart);
        if (ret)
                return ret;

        ret = platform_driver_register(&digicolor_uart_platform);
        if (ret)
                uart_unregister_driver(&digicolor_uart);

        return ret;
}
module_init(digicolor_uart_init);

static void __exit digicolor_uart_exit(void)
{
        platform_driver_unregister(&digicolor_uart_platform);
        uart_unregister_driver(&digicolor_uart);
}
module_exit(digicolor_uart_exit);

MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
MODULE_DESCRIPTION("Conexant Digicolor USART serial driver");
MODULE_LICENSE("GPL");