// SPDX-License-Identifier: GPL-2.0+
/*
 * Mediatek 8250 driver.
 *
 * Copyright (c) 2014 MundoReader S.L.
 * Author: Matthias Brugger <matthias.bgg@gmail.com>
 */
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/serial_8250.h>
#include <linux/serial_reg.h>
#include <linux/console.h>
#include <linux/dma-mapping.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>

#include "8250.h"

#define MTK_UART_HIGHS          0x09    /* Highspeed register */
#define MTK_UART_SAMPLE_COUNT   0x0a    /* Sample count register */
#define MTK_UART_SAMPLE_POINT   0x0b    /* Sample point register */
#define MTK_UART_RATE_FIX       0x0d    /* UART Rate Fix Register */
#define MTK_UART_ESCAPE_DAT     0x10    /* Escape Character register */
#define MTK_UART_ESCAPE_EN      0x11    /* Escape Enable register */
#define MTK_UART_DMA_EN         0x13    /* DMA Enable register */
#define MTK_UART_RXTRI_AD       0x14    /* RX Trigger address */
#define MTK_UART_FRACDIV_L      0x15    /* Fractional divider LSB address */
#define MTK_UART_FRACDIV_M      0x16    /* Fractional divider MSB address */
#define MTK_UART_DEBUG0 0x18
#define MTK_UART_IER_XOFFI      0x20    /* Enable XOFF character interrupt */
#define MTK_UART_IER_RTSI       0x40    /* Enable RTS Modem status interrupt */
#define MTK_UART_IER_CTSI       0x80    /* Enable CTS Modem status interrupt */

#define MTK_UART_EFR_EN         0x10    /* Enable enhancement feature */
#define MTK_UART_EFR_RTS        0x40    /* Enable hardware rx flow control */
#define MTK_UART_EFR_CTS        0x80    /* Enable hardware tx flow control */
#define MTK_UART_EFR_NO_SW_FC   0x0     /* no sw flow control */
#define MTK_UART_EFR_XON1_XOFF1 0xa     /* XON1/XOFF1 as sw flow control */
#define MTK_UART_EFR_XON2_XOFF2 0x5     /* XON2/XOFF2 as sw flow control */
#define MTK_UART_EFR_SW_FC_MASK 0xf     /* Enable CTS Modem status interrupt */
#define MTK_UART_EFR_HW_FC      (MTK_UART_EFR_RTS | MTK_UART_EFR_CTS)
#define MTK_UART_DMA_EN_TX      0x2
#define MTK_UART_DMA_EN_RX      0x5

#define MTK_UART_ESCAPE_CHAR    0x77    /* Escape char added under sw fc */
#define MTK_UART_RX_SIZE        0x8000
#define MTK_UART_TX_TRIGGER     1
#define MTK_UART_RX_TRIGGER     MTK_UART_RX_SIZE

#ifdef CONFIG_SERIAL_8250_DMA
enum dma_rx_status {
        DMA_RX_START = 0,
        DMA_RX_RUNNING = 1,
        DMA_RX_SHUTDOWN = 2,
};
#endif

struct mtk8250_data {
        int                     line;
        unsigned int            rx_pos;
        unsigned int            clk_count;
        struct clk              *uart_clk;
        struct clk              *bus_clk;
        struct uart_8250_dma    *dma;
#ifdef CONFIG_SERIAL_8250_DMA
        enum dma_rx_status      rx_status;
#endif
        int                     rx_wakeup_irq;
};

/* flow control mode */
enum {
        MTK_UART_FC_NONE,
        MTK_UART_FC_SW,
        MTK_UART_FC_HW,
};

#ifdef CONFIG_SERIAL_8250_DMA
static void mtk8250_rx_dma(struct uart_8250_port *up);

static void mtk8250_dma_rx_complete(void *param)
{
        struct uart_8250_port *up = param;
        struct uart_8250_dma *dma = up->dma;
        struct mtk8250_data *data = up->port.private_data;
        struct tty_port *tty_port = &up->port.state->port;
        struct dma_tx_state state;
        int copied, total, cnt;
        unsigned char *ptr;
        unsigned long flags;

        if (data->rx_status == DMA_RX_SHUTDOWN)
                return;

        spin_lock_irqsave(&up->port.lock, flags);

        dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
        total = dma->rx_size - state.residue;
        cnt = total;

        if ((data->rx_pos + cnt) > dma->rx_size)
                cnt = dma->rx_size - data->rx_pos;

        ptr = (unsigned char *)(data->rx_pos + dma->rx_buf);
        copied = tty_insert_flip_string(tty_port, ptr, cnt);
        data->rx_pos += cnt;

        if (total > cnt) {
                ptr = (unsigned char *)(dma->rx_buf);
                cnt = total - cnt;
                copied += tty_insert_flip_string(tty_port, ptr, cnt);
                data->rx_pos = cnt;
        }

        up->port.icount.rx += copied;

        tty_flip_buffer_push(tty_port);

        mtk8250_rx_dma(up);

        spin_unlock_irqrestore(&up->port.lock, flags);
}

static void mtk8250_rx_dma(struct uart_8250_port *up)
{
        struct uart_8250_dma *dma = up->dma;
        struct dma_async_tx_descriptor  *desc;

        desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
                                           dma->rx_size, DMA_DEV_TO_MEM,
                                           DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                pr_err("failed to prepare rx slave single\n");
                return;
        }

        desc->callback = mtk8250_dma_rx_complete;
        desc->callback_param = up;

        dma->rx_cookie = dmaengine_submit(desc);

        dma_async_issue_pending(dma->rxchan);
}

static void mtk8250_dma_enable(struct uart_8250_port *up)
{
        struct uart_8250_dma *dma = up->dma;
        struct mtk8250_data *data = up->port.private_data;
        int lcr = serial_in(up, UART_LCR);

        if (data->rx_status != DMA_RX_START)
                return;

        dma->rxconf.src_port_window_size        = dma->rx_size;
        dma->rxconf.src_addr                            = dma->rx_addr;

        dma->txconf.dst_port_window_size        = UART_XMIT_SIZE;
        dma->txconf.dst_addr                            = dma->tx_addr;

        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR |
                UART_FCR_CLEAR_XMIT);
        serial_out(up, MTK_UART_DMA_EN,
                   MTK_UART_DMA_EN_RX | MTK_UART_DMA_EN_TX);

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_out(up, UART_EFR, UART_EFR_ECB);
        serial_out(up, UART_LCR, lcr);

        if (dmaengine_slave_config(dma->rxchan, &dma->rxconf) != 0)
                pr_err("failed to configure rx dma channel\n");
        if (dmaengine_slave_config(dma->txchan, &dma->txconf) != 0)
                pr_err("failed to configure tx dma channel\n");

        data->rx_status = DMA_RX_RUNNING;
        data->rx_pos = 0;
        mtk8250_rx_dma(up);
}
#endif

static int mtk8250_startup(struct uart_port *port)
{
#ifdef CONFIG_SERIAL_8250_DMA
        struct uart_8250_port *up = up_to_u8250p(port);
        struct mtk8250_data *data = port->private_data;

        /* disable DMA for console */
        if (uart_console(port))
                up->dma = NULL;

        if (up->dma) {
                data->rx_status = DMA_RX_START;
                uart_circ_clear(&port->state->xmit);
        }
#endif
        memset(&port->icount, 0, sizeof(port->icount));

        return serial8250_do_startup(port);
}

static void mtk8250_shutdown(struct uart_port *port)
{
#ifdef CONFIG_SERIAL_8250_DMA
        struct uart_8250_port *up = up_to_u8250p(port);
        struct mtk8250_data *data = port->private_data;

        if (up->dma)
                data->rx_status = DMA_RX_SHUTDOWN;
#endif

        return serial8250_do_shutdown(port);
}

static void mtk8250_disable_intrs(struct uart_8250_port *up, int mask)
{
        serial_out(up, UART_IER, serial_in(up, UART_IER) & (~mask));
}

static void mtk8250_enable_intrs(struct uart_8250_port *up, int mask)
{
        serial_out(up, UART_IER, serial_in(up, UART_IER) | mask);
}

static void mtk8250_set_flow_ctrl(struct uart_8250_port *up, int mode)
{
        struct uart_port *port = &up->port;
        int lcr = serial_in(up, UART_LCR);

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_out(up, UART_EFR, UART_EFR_ECB);
        serial_out(up, UART_LCR, lcr);
        lcr = serial_in(up, UART_LCR);

        switch (mode) {
        case MTK_UART_FC_NONE:
                serial_out(up, MTK_UART_ESCAPE_DAT, MTK_UART_ESCAPE_CHAR);
                serial_out(up, MTK_UART_ESCAPE_EN, 0x00);
                serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
                serial_out(up, UART_EFR, serial_in(up, UART_EFR) &
                        (~(MTK_UART_EFR_HW_FC | MTK_UART_EFR_SW_FC_MASK)));
                serial_out(up, UART_LCR, lcr);
                mtk8250_disable_intrs(up, MTK_UART_IER_XOFFI |
                        MTK_UART_IER_RTSI | MTK_UART_IER_CTSI);
                break;

        case MTK_UART_FC_HW:
                serial_out(up, MTK_UART_ESCAPE_DAT, MTK_UART_ESCAPE_CHAR);
                serial_out(up, MTK_UART_ESCAPE_EN, 0x00);
                serial_out(up, UART_MCR, UART_MCR_RTS);
                serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);

                /*enable hw flow control*/
                serial_out(up, UART_EFR, MTK_UART_EFR_HW_FC |
                        (serial_in(up, UART_EFR) &
                        (~(MTK_UART_EFR_HW_FC | MTK_UART_EFR_SW_FC_MASK))));

                serial_out(up, UART_LCR, lcr);
                mtk8250_disable_intrs(up, MTK_UART_IER_XOFFI);
                mtk8250_enable_intrs(up, MTK_UART_IER_CTSI | MTK_UART_IER_RTSI);
                break;

        case MTK_UART_FC_SW:    /*MTK software flow control */
                serial_out(up, MTK_UART_ESCAPE_DAT, MTK_UART_ESCAPE_CHAR);
                serial_out(up, MTK_UART_ESCAPE_EN, 0x01);
                serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);

                /*enable sw flow control */
                serial_out(up, UART_EFR, MTK_UART_EFR_XON1_XOFF1 |
                        (serial_in(up, UART_EFR) &
                        (~(MTK_UART_EFR_HW_FC | MTK_UART_EFR_SW_FC_MASK))));

                serial_out(up, UART_XON1, START_CHAR(port->state->port.tty));
                serial_out(up, UART_XOFF1, STOP_CHAR(port->state->port.tty));
                serial_out(up, UART_LCR, lcr);
                mtk8250_disable_intrs(up, MTK_UART_IER_CTSI|MTK_UART_IER_RTSI);
                mtk8250_enable_intrs(up, MTK_UART_IER_XOFFI);
                break;
        default:
                break;
        }
}

static void
mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
                        struct ktermios *old)
{
        unsigned short fraction_L_mapping[] = {
                0, 1, 0x5, 0x15, 0x55, 0x57, 0x57, 0x77, 0x7F, 0xFF, 0xFF
        };
        unsigned short fraction_M_mapping[] = {
                0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3
        };
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned int baud, quot, fraction;
        unsigned long flags;
        int mode;

#ifdef CONFIG_SERIAL_8250_DMA
        if (up->dma) {
                if (uart_console(port)) {
                        devm_kfree(up->port.dev, up->dma);
                        up->dma = NULL;
                } else {
                        mtk8250_dma_enable(up);
                }
        }
#endif

        /*
         * Store the requested baud rate before calling the generic 8250
         * set_termios method. Standard 8250 port expects bauds to be
         * no higher than (uartclk / 16) so the baud will be clamped if it
         * gets out of that bound. Mediatek 8250 port supports speed
         * higher than that, therefore we'll get original baud rate back
         * after calling the generic set_termios method and recalculate
         * the speed later in this method.
         */
        baud = tty_termios_baud_rate(termios);

        serial8250_do_set_termios(port, termios, NULL);

        tty_termios_encode_baud_rate(termios, baud, baud);

        /*
         * Mediatek UARTs use an extra highspeed register (MTK_UART_HIGHS)
         *
         * We need to recalcualte the quot register, as the claculation depends
         * on the vaule in the highspeed register.
         *
         * Some baudrates are not supported by the chip, so we use the next
         * lower rate supported and update termios c_flag.
         *
         * If highspeed register is set to 3, we need to specify sample count
         * and sample point to increase accuracy. If not, we reset the
         * registers to their default values.
         */
        baud = uart_get_baud_rate(port, termios, old,
                                  port->uartclk / 16 / UART_DIV_MAX,
                                  port->uartclk);

        if (baud < 115200) {
                serial_port_out(port, MTK_UART_HIGHS, 0x0);
                quot = uart_get_divisor(port, baud);
        } else {
                serial_port_out(port, MTK_UART_HIGHS, 0x3);
                quot = DIV_ROUND_UP(port->uartclk, 256 * baud);
        }

        /*
         * Ok, we're now changing the port state.  Do it with
         * interrupts disabled.
         */
        spin_lock_irqsave(&port->lock, flags);

        /*
         * Update the per-port timeout.
         */
        uart_update_timeout(port, termios->c_cflag, baud);

        /* set DLAB we have cval saved in up->lcr from the call to the core */
        serial_port_out(port, UART_LCR, up->lcr | UART_LCR_DLAB);
        serial_dl_write(up, quot);

        /* reset DLAB */
        serial_port_out(port, UART_LCR, up->lcr);

        if (baud >= 115200) {
                unsigned int tmp;

                tmp = (port->uartclk / (baud *  quot)) - 1;
                serial_port_out(port, MTK_UART_SAMPLE_COUNT, tmp);
                serial_port_out(port, MTK_UART_SAMPLE_POINT,
                                        (tmp >> 1) - 1);

                /*count fraction to set fractoin register */
                fraction = ((port->uartclk  * 100) / baud / quot) % 100;
                fraction = DIV_ROUND_CLOSEST(fraction, 10);
                serial_port_out(port, MTK_UART_FRACDIV_L,
                                                fraction_L_mapping[fraction]);
                serial_port_out(port, MTK_UART_FRACDIV_M,
                                                fraction_M_mapping[fraction]);
        } else {
                serial_port_out(port, MTK_UART_SAMPLE_COUNT, 0x00);
                serial_port_out(port, MTK_UART_SAMPLE_POINT, 0xff);
                serial_port_out(port, MTK_UART_FRACDIV_L, 0x00);
                serial_port_out(port, MTK_UART_FRACDIV_M, 0x00);
        }

        if ((termios->c_cflag & CRTSCTS) && (!(termios->c_iflag & CRTSCTS)))
                mode = MTK_UART_FC_HW;
        else if (termios->c_iflag & CRTSCTS)
                mode = MTK_UART_FC_SW;
        else
                mode = MTK_UART_FC_NONE;

        mtk8250_set_flow_ctrl(up, mode);

        if (uart_console(port))
                up->port.cons->cflag = termios->c_cflag;

        spin_unlock_irqrestore(&port->lock, flags);
        /* Don't rewrite B0 */
        if (tty_termios_baud_rate(termios))
                tty_termios_encode_baud_rate(termios, baud, baud);
}

static int __maybe_unused mtk8250_runtime_suspend(struct device *dev)
{
        struct mtk8250_data *data = dev_get_drvdata(dev);
        struct uart_8250_port *up = serial8250_get_port(data->line);

        /* wait until UART in idle status */
        while
                (serial_in(up, MTK_UART_DEBUG0));

        if (data->clk_count == 0U) {
                dev_dbg(dev, "%s clock count is 0\n", __func__);
        } else {
                clk_disable_unprepare(data->bus_clk);
                data->clk_count--;
        }

        return 0;
}

static int __maybe_unused mtk8250_runtime_resume(struct device *dev)
{
        struct mtk8250_data *data = dev_get_drvdata(dev);
        int err;

        if (data->clk_count > 0U) {
                dev_dbg(dev, "%s clock count is %d\n", __func__,
                        data->clk_count);
        } else {
                err = clk_prepare_enable(data->bus_clk);
                if (err) {
                        dev_warn(dev, "Can't enable bus clock\n");
                        return err;
                }
                data->clk_count++;
        }

        return 0;
}

static void
mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
{
        if (!state)
                if (!mtk8250_runtime_resume(port->dev))
                        pm_runtime_get_sync(port->dev);

        serial8250_do_pm(port, state, old);

        if (state)
                if (!pm_runtime_put_sync_suspend(port->dev))
                        mtk8250_runtime_suspend(port->dev);
}

#ifdef CONFIG_SERIAL_8250_DMA
static bool mtk8250_dma_filter(struct dma_chan *chan, void *param)
{
        return false;
}
#endif

static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
                           struct mtk8250_data *data)
{
#ifdef CONFIG_SERIAL_8250_DMA
        int dmacnt;
#endif

        data->uart_clk = devm_clk_get(&pdev->dev, "baud");
        if (IS_ERR(data->uart_clk)) {
                /*
                 * For compatibility with older device trees try unnamed
                 * clk when no baud clk can be found.
                 */
                data->uart_clk = devm_clk_get(&pdev->dev, NULL);
                if (IS_ERR(data->uart_clk)) {
                        dev_warn(&pdev->dev, "Can't get uart clock\n");
                        return PTR_ERR(data->uart_clk);
                }

                return 0;
        }

        data->bus_clk = devm_clk_get(&pdev->dev, "bus");
        if (IS_ERR(data->bus_clk))
                return PTR_ERR(data->bus_clk);

        data->dma = NULL;
#ifdef CONFIG_SERIAL_8250_DMA
        dmacnt = of_property_count_strings(pdev->dev.of_node, "dma-names");
        if (dmacnt == 2) {
                data->dma = devm_kzalloc(&pdev->dev, sizeof(*data->dma),
                                         GFP_KERNEL);
                if (!data->dma)
                        return -ENOMEM;

                data->dma->fn = mtk8250_dma_filter;
                data->dma->rx_size = MTK_UART_RX_SIZE;
                data->dma->rxconf.src_maxburst = MTK_UART_RX_TRIGGER;
                data->dma->txconf.dst_maxburst = MTK_UART_TX_TRIGGER;
        }
#endif

        return 0;
}

static int mtk8250_probe(struct platform_device *pdev)
{
        struct uart_8250_port uart = {};
        struct mtk8250_data *data;
        struct resource *regs;
        int irq, err;

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

        regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!regs) {
                dev_err(&pdev->dev, "no registers defined\n");
                return -EINVAL;
        }

        uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
                                         resource_size(regs));
        if (!uart.port.membase)
                return -ENOMEM;

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

        data->clk_count = 0;

        if (pdev->dev.of_node) {
                err = mtk8250_probe_of(pdev, &uart.port, data);
                if (err)
                        return err;
        } else
                return -ENODEV;

        spin_lock_init(&uart.port.lock);
        uart.port.mapbase = regs->start;
        uart.port.irq = irq;
        uart.port.pm = mtk8250_do_pm;
        uart.port.type = PORT_16550;
        uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
        uart.port.dev = &pdev->dev;
        uart.port.iotype = UPIO_MEM32;
        uart.port.regshift = 2;
        uart.port.private_data = data;
        uart.port.shutdown = mtk8250_shutdown;
        uart.port.startup = mtk8250_startup;
        uart.port.set_termios = mtk8250_set_termios;
        uart.port.uartclk = clk_get_rate(data->uart_clk);
#ifdef CONFIG_SERIAL_8250_DMA
        if (data->dma)
                uart.dma = data->dma;
#endif

        /* Disable Rate Fix function */
        writel(0x0, uart.port.membase +
                        (MTK_UART_RATE_FIX << uart.port.regshift));

        platform_set_drvdata(pdev, data);

        pm_runtime_enable(&pdev->dev);
        err = mtk8250_runtime_resume(&pdev->dev);
        if (err)
                goto err_pm_disable;

        data->line = serial8250_register_8250_port(&uart);
        if (data->line < 0) {
                err = data->line;
                goto err_pm_disable;
        }

        data->rx_wakeup_irq = platform_get_irq_optional(pdev, 1);

        return 0;

err_pm_disable:
        pm_runtime_disable(&pdev->dev);

        return err;
}

static int mtk8250_remove(struct platform_device *pdev)
{
        struct mtk8250_data *data = platform_get_drvdata(pdev);

        pm_runtime_get_sync(&pdev->dev);

        serial8250_unregister_port(data->line);

        pm_runtime_disable(&pdev->dev);
        pm_runtime_put_noidle(&pdev->dev);

        if (!pm_runtime_status_suspended(&pdev->dev))
                mtk8250_runtime_suspend(&pdev->dev);

        return 0;
}

static int __maybe_unused mtk8250_suspend(struct device *dev)
{
        struct mtk8250_data *data = dev_get_drvdata(dev);
        int irq = data->rx_wakeup_irq;
        int err;

        serial8250_suspend_port(data->line);

        pinctrl_pm_select_sleep_state(dev);
        if (irq >= 0) {
                err = enable_irq_wake(irq);
                if (err) {
                        dev_err(dev,
                                "failed to enable irq wake on IRQ %d: %d\n",
                                irq, err);
                        pinctrl_pm_select_default_state(dev);
                        serial8250_resume_port(data->line);
                        return err;
                }
        }

        return 0;
}

static int __maybe_unused mtk8250_resume(struct device *dev)
{
        struct mtk8250_data *data = dev_get_drvdata(dev);
        int irq = data->rx_wakeup_irq;

        if (irq >= 0)
                disable_irq_wake(irq);
        pinctrl_pm_select_default_state(dev);

        serial8250_resume_port(data->line);

        return 0;
}

static const struct dev_pm_ops mtk8250_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(mtk8250_suspend, mtk8250_resume)
        SET_RUNTIME_PM_OPS(mtk8250_runtime_suspend, mtk8250_runtime_resume,
                                NULL)
};

static const struct of_device_id mtk8250_of_match[] = {
        { .compatible = "mediatek,mt6577-uart" },
        { /* Sentinel */ }
};
MODULE_DEVICE_TABLE(of, mtk8250_of_match);

static struct platform_driver mtk8250_platform_driver = {
        .driver = {
                .name           = "mt6577-uart",
                .pm             = &mtk8250_pm_ops,
                .of_match_table = mtk8250_of_match,
        },
        .probe                  = mtk8250_probe,
        .remove                 = mtk8250_remove,
};
module_platform_driver(mtk8250_platform_driver);

#ifdef CONFIG_SERIAL_8250_CONSOLE
static int __init early_mtk8250_setup(struct earlycon_device *device,
                                        const char *options)
{
        if (!device->port.membase)
                return -ENODEV;

        device->port.iotype = UPIO_MEM32;
        device->port.regshift = 2;

        return early_serial8250_setup(device, NULL);
}

OF_EARLYCON_DECLARE(mtk8250, "mediatek,mt6577-uart", early_mtk8250_setup);
#endif

MODULE_AUTHOR("Matthias Brugger");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Mediatek 8250 serial port driver");