// SPDX-License-Identifier: GPL-2.0
/*
 * uartlite.c: Serial driver for Xilinx uartlite serial controller
 *
 * Copyright (C) 2006 Peter Korsgaard <jacmet@sunsite.dk>
 * Copyright (C) 2007 Secret Lab Technologies Ltd.
 */

#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/console.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/clk.h>
#include <linux/pm_runtime.h>

#define ULITE_NAME              "ttyUL"
#define ULITE_MAJOR             204
#define ULITE_MINOR             187
#define ULITE_NR_UARTS          CONFIG_SERIAL_UARTLITE_NR_UARTS

/* ---------------------------------------------------------------------
 * Register definitions
 *
 * For register details see datasheet:
 * http://www.xilinx.com/support/documentation/ip_documentation/opb_uartlite.pdf
 */

#define ULITE_RX                0x00
#define ULITE_TX                0x04
#define ULITE_STATUS            0x08
#define ULITE_CONTROL           0x0c

#define ULITE_REGION            16

#define ULITE_STATUS_RXVALID    0x01
#define ULITE_STATUS_RXFULL     0x02
#define ULITE_STATUS_TXEMPTY    0x04
#define ULITE_STATUS_TXFULL     0x08
#define ULITE_STATUS_IE         0x10
#define ULITE_STATUS_OVERRUN    0x20
#define ULITE_STATUS_FRAME      0x40
#define ULITE_STATUS_PARITY     0x80

#define ULITE_CONTROL_RST_TX    0x01
#define ULITE_CONTROL_RST_RX    0x02
#define ULITE_CONTROL_IE        0x10
#define UART_AUTOSUSPEND_TIMEOUT        3000

/* Static pointer to console port */
#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
static struct uart_port *console_port;
#endif

struct uartlite_data {
        const struct uartlite_reg_ops *reg_ops;
        struct clk *clk;
        struct uart_driver *ulite_uart_driver;
};

struct uartlite_reg_ops {
        u32 (*in)(void __iomem *addr);
        void (*out)(u32 val, void __iomem *addr);
};

static u32 uartlite_inbe32(void __iomem *addr)
{
        return ioread32be(addr);
}

static void uartlite_outbe32(u32 val, void __iomem *addr)
{
        iowrite32be(val, addr);
}

static const struct uartlite_reg_ops uartlite_be = {
        .in = uartlite_inbe32,
        .out = uartlite_outbe32,
};

static u32 uartlite_inle32(void __iomem *addr)
{
        return ioread32(addr);
}

static void uartlite_outle32(u32 val, void __iomem *addr)
{
        iowrite32(val, addr);
}

static const struct uartlite_reg_ops uartlite_le = {
        .in = uartlite_inle32,
        .out = uartlite_outle32,
};

static inline u32 uart_in32(u32 offset, struct uart_port *port)
{
        struct uartlite_data *pdata = port->private_data;

        return pdata->reg_ops->in(port->membase + offset);
}

static inline void uart_out32(u32 val, u32 offset, struct uart_port *port)
{
        struct uartlite_data *pdata = port->private_data;

        pdata->reg_ops->out(val, port->membase + offset);
}

static struct uart_port ulite_ports[ULITE_NR_UARTS];

/* ---------------------------------------------------------------------
 * Core UART driver operations
 */

static int ulite_receive(struct uart_port *port, int stat)
{
        struct tty_port *tport = &port->state->port;
        unsigned char ch = 0;
        char flag = TTY_NORMAL;

        if ((stat & (ULITE_STATUS_RXVALID | ULITE_STATUS_OVERRUN
                     | ULITE_STATUS_FRAME)) == 0)
                return 0;

        /* stats */
        if (stat & ULITE_STATUS_RXVALID) {
                port->icount.rx++;
                ch = uart_in32(ULITE_RX, port);

                if (stat & ULITE_STATUS_PARITY)
                        port->icount.parity++;
        }

        if (stat & ULITE_STATUS_OVERRUN)
                port->icount.overrun++;

        if (stat & ULITE_STATUS_FRAME)
                port->icount.frame++;


        /* drop byte with parity error if IGNPAR specificed */
        if (stat & port->ignore_status_mask & ULITE_STATUS_PARITY)
                stat &= ~ULITE_STATUS_RXVALID;

        stat &= port->read_status_mask;

        if (stat & ULITE_STATUS_PARITY)
                flag = TTY_PARITY;


        stat &= ~port->ignore_status_mask;

        if (stat & ULITE_STATUS_RXVALID)
                tty_insert_flip_char(tport, ch, flag);

        if (stat & ULITE_STATUS_FRAME)
                tty_insert_flip_char(tport, 0, TTY_FRAME);

        if (stat & ULITE_STATUS_OVERRUN)
                tty_insert_flip_char(tport, 0, TTY_OVERRUN);

        return 1;
}

static int ulite_transmit(struct uart_port *port, int stat)
{
        struct circ_buf *xmit  = &port->state->xmit;

        if (stat & ULITE_STATUS_TXFULL)
                return 0;

        if (port->x_char) {
                uart_out32(port->x_char, ULITE_TX, port);
                port->x_char = 0;
                port->icount.tx++;
                return 1;
        }

        if (uart_circ_empty(xmit) || uart_tx_stopped(port))
                return 0;

        uart_out32(xmit->buf[xmit->tail], ULITE_TX, port);
        xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE-1);
        port->icount.tx++;

        /* wake up */
        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(port);

        return 1;
}

static irqreturn_t ulite_isr(int irq, void *dev_id)
{
        struct uart_port *port = dev_id;
        int stat, busy, n = 0;
        unsigned long flags;

        do {
                spin_lock_irqsave(&port->lock, flags);
                stat = uart_in32(ULITE_STATUS, port);
                busy  = ulite_receive(port, stat);
                busy |= ulite_transmit(port, stat);
                spin_unlock_irqrestore(&port->lock, flags);
                n++;
        } while (busy);

        /* work done? */
        if (n > 1) {
                tty_flip_buffer_push(&port->state->port);
                return IRQ_HANDLED;
        } else {
                return IRQ_NONE;
        }
}

static unsigned int ulite_tx_empty(struct uart_port *port)
{
        unsigned long flags;
        unsigned int ret;

        spin_lock_irqsave(&port->lock, flags);
        ret = uart_in32(ULITE_STATUS, port);
        spin_unlock_irqrestore(&port->lock, flags);

        return ret & ULITE_STATUS_TXEMPTY ? TIOCSER_TEMT : 0;
}

static unsigned int ulite_get_mctrl(struct uart_port *port)
{
        return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
}

static void ulite_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        /* N/A */
}

static void ulite_stop_tx(struct uart_port *port)
{
        /* N/A */
}

static void ulite_start_tx(struct uart_port *port)
{
        ulite_transmit(port, uart_in32(ULITE_STATUS, port));
}

static void ulite_stop_rx(struct uart_port *port)
{
        /* don't forward any more data (like !CREAD) */
        port->ignore_status_mask = ULITE_STATUS_RXVALID | ULITE_STATUS_PARITY
                | ULITE_STATUS_FRAME | ULITE_STATUS_OVERRUN;
}

static void ulite_break_ctl(struct uart_port *port, int ctl)
{
        /* N/A */
}

static int ulite_startup(struct uart_port *port)
{
        struct uartlite_data *pdata = port->private_data;
        int ret;

        ret = clk_enable(pdata->clk);
        if (ret) {
                dev_err(port->dev, "Failed to enable clock\n");
                return ret;
        }

        ret = request_irq(port->irq, ulite_isr, IRQF_SHARED | IRQF_TRIGGER_RISING,
                          "uartlite", port);
        if (ret)
                return ret;

        uart_out32(ULITE_CONTROL_RST_RX | ULITE_CONTROL_RST_TX,
                ULITE_CONTROL, port);
        uart_out32(ULITE_CONTROL_IE, ULITE_CONTROL, port);

        return 0;
}

static void ulite_shutdown(struct uart_port *port)
{
        struct uartlite_data *pdata = port->private_data;

        uart_out32(0, ULITE_CONTROL, port);
        uart_in32(ULITE_CONTROL, port); /* dummy */
        free_irq(port->irq, port);
        clk_disable(pdata->clk);
}

static void ulite_set_termios(struct uart_port *port, struct ktermios *termios,
                              struct ktermios *old)
{
        unsigned long flags;
        unsigned int baud;

        spin_lock_irqsave(&port->lock, flags);

        port->read_status_mask = ULITE_STATUS_RXVALID | ULITE_STATUS_OVERRUN
                | ULITE_STATUS_TXFULL;

        if (termios->c_iflag & INPCK)
                port->read_status_mask |=
                        ULITE_STATUS_PARITY | ULITE_STATUS_FRAME;

        port->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                port->ignore_status_mask |= ULITE_STATUS_PARITY
                        | ULITE_STATUS_FRAME | ULITE_STATUS_OVERRUN;

        /* ignore all characters if CREAD is not set */
        if ((termios->c_cflag & CREAD) == 0)
                port->ignore_status_mask |=
                        ULITE_STATUS_RXVALID | ULITE_STATUS_PARITY
                        | ULITE_STATUS_FRAME | ULITE_STATUS_OVERRUN;

        /* update timeout */
        baud = uart_get_baud_rate(port, termios, old, 0, 460800);
        uart_update_timeout(port, termios->c_cflag, baud);

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

static const char *ulite_type(struct uart_port *port)
{
        return port->type == PORT_UARTLITE ? "uartlite" : NULL;
}

static void ulite_release_port(struct uart_port *port)
{
        release_mem_region(port->mapbase, ULITE_REGION);
        iounmap(port->membase);
        port->membase = NULL;
}

static int ulite_request_port(struct uart_port *port)
{
        struct uartlite_data *pdata = port->private_data;
        int ret;

        pr_debug("ulite console: port=%p; port->mapbase=%llx\n",
                 port, (unsigned long long) port->mapbase);

        if (!request_mem_region(port->mapbase, ULITE_REGION, "uartlite")) {
                dev_err(port->dev, "Memory region busy\n");
                return -EBUSY;
        }

        port->membase = ioremap(port->mapbase, ULITE_REGION);
        if (!port->membase) {
                dev_err(port->dev, "Unable to map registers\n");
                release_mem_region(port->mapbase, ULITE_REGION);
                return -EBUSY;
        }

        pdata->reg_ops = &uartlite_be;
        ret = uart_in32(ULITE_CONTROL, port);
        uart_out32(ULITE_CONTROL_RST_TX, ULITE_CONTROL, port);
        ret = uart_in32(ULITE_STATUS, port);
        /* Endianess detection */
        if ((ret & ULITE_STATUS_TXEMPTY) != ULITE_STATUS_TXEMPTY)
                pdata->reg_ops = &uartlite_le;

        return 0;
}

static void ulite_config_port(struct uart_port *port, int flags)
{
        if (!ulite_request_port(port))
                port->type = PORT_UARTLITE;
}

static int ulite_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        /* we don't want the core code to modify any port params */
        return -EINVAL;
}

static void ulite_pm(struct uart_port *port, unsigned int state,
                     unsigned int oldstate)
{
        if (!state) {
                pm_runtime_get_sync(port->dev);
        } else {
                pm_runtime_mark_last_busy(port->dev);
                pm_runtime_put_autosuspend(port->dev);
        }
}

#ifdef CONFIG_CONSOLE_POLL
static int ulite_get_poll_char(struct uart_port *port)
{
        if (!(uart_in32(ULITE_STATUS, port) & ULITE_STATUS_RXVALID))
                return NO_POLL_CHAR;

        return uart_in32(ULITE_RX, port);
}

static void ulite_put_poll_char(struct uart_port *port, unsigned char ch)
{
        while (uart_in32(ULITE_STATUS, port) & ULITE_STATUS_TXFULL)
                cpu_relax();

        /* write char to device */
        uart_out32(ch, ULITE_TX, port);
}
#endif

static const struct uart_ops ulite_ops = {
        .tx_empty       = ulite_tx_empty,
        .set_mctrl      = ulite_set_mctrl,
        .get_mctrl      = ulite_get_mctrl,
        .stop_tx        = ulite_stop_tx,
        .start_tx       = ulite_start_tx,
        .stop_rx        = ulite_stop_rx,
        .break_ctl      = ulite_break_ctl,
        .startup        = ulite_startup,
        .shutdown       = ulite_shutdown,
        .set_termios    = ulite_set_termios,
        .type           = ulite_type,
        .release_port   = ulite_release_port,
        .request_port   = ulite_request_port,
        .config_port    = ulite_config_port,
        .verify_port    = ulite_verify_port,
        .pm             = ulite_pm,
#ifdef CONFIG_CONSOLE_POLL
        .poll_get_char  = ulite_get_poll_char,
        .poll_put_char  = ulite_put_poll_char,
#endif
};

/* ---------------------------------------------------------------------
 * Console driver operations
 */

#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
static void ulite_console_wait_tx(struct uart_port *port)
{
        u8 val;
        unsigned long timeout;

        /*
         * Spin waiting for TX fifo to have space available.
         * When using the Microblaze Debug Module this can take up to 1s
         */
        timeout = jiffies + msecs_to_jiffies(1000);
        while (1) {
                val = uart_in32(ULITE_STATUS, port);
                if ((val & ULITE_STATUS_TXFULL) == 0)
                        break;
                if (time_after(jiffies, timeout)) {
                        dev_warn(port->dev,
                                 "timeout waiting for TX buffer empty\n");
                        break;
                }
                cpu_relax();
        }
}

static void ulite_console_putchar(struct uart_port *port, int ch)
{
        ulite_console_wait_tx(port);
        uart_out32(ch, ULITE_TX, port);
}

static void ulite_console_write(struct console *co, const char *s,
                                unsigned int count)
{
        struct uart_port *port = console_port;
        unsigned long flags;
        unsigned int ier;
        int locked = 1;

        if (oops_in_progress) {
                locked = spin_trylock_irqsave(&port->lock, flags);
        } else
                spin_lock_irqsave(&port->lock, flags);

        /* save and disable interrupt */
        ier = uart_in32(ULITE_STATUS, port) & ULITE_STATUS_IE;
        uart_out32(0, ULITE_CONTROL, port);

        uart_console_write(port, s, count, ulite_console_putchar);

        ulite_console_wait_tx(port);

        /* restore interrupt state */
        if (ier)
                uart_out32(ULITE_CONTROL_IE, ULITE_CONTROL, port);

        if (locked)
                spin_unlock_irqrestore(&port->lock, flags);
}

static int ulite_console_setup(struct console *co, char *options)
{
        struct uart_port *port;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';


        port = console_port;

        /* Has the device been initialized yet? */
        if (!port->mapbase) {
                pr_debug("console on ttyUL%i not present\n", co->index);
                return -ENODEV;
        }

        /* not initialized yet? */
        if (!port->membase) {
                if (ulite_request_port(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 uart_driver ulite_uart_driver;

static struct console ulite_console = {
        .name   = ULITE_NAME,
        .write  = ulite_console_write,
        .device = uart_console_device,
        .setup  = ulite_console_setup,
        .flags  = CON_PRINTBUFFER,
        .index  = -1, /* Specified on the cmdline (e.g. console=ttyUL0 ) */
        .data   = &ulite_uart_driver,
};

static void early_uartlite_putc(struct uart_port *port, int c)
{
        /*
         * Limit how many times we'll spin waiting for TX FIFO status.
         * This will prevent lockups if the base address is incorrectly
         * set, or any other issue on the UARTLITE.
         * This limit is pretty arbitrary, unless we are at about 10 baud
         * we'll never timeout on a working UART.
         */

        unsigned retries = 1000000;
        /* read status bit - 0x8 offset */
        while (--retries && (readl(port->membase + 8) & (1 << 3)))
                ;

        /* Only attempt the iowrite if we didn't timeout */
        /* write to TX_FIFO - 0x4 offset */
        if (retries)
                writel(c & 0xff, port->membase + 4);
}

static void early_uartlite_write(struct console *console,
                                 const char *s, unsigned n)
{
        struct earlycon_device *device = console->data;
        uart_console_write(&device->port, s, n, early_uartlite_putc);
}

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

        device->con->write = early_uartlite_write;
        return 0;
}
EARLYCON_DECLARE(uartlite, early_uartlite_setup);
OF_EARLYCON_DECLARE(uartlite_b, "xlnx,opb-uartlite-1.00.b", early_uartlite_setup);
OF_EARLYCON_DECLARE(uartlite_a, "xlnx,xps-uartlite-1.00.a", early_uartlite_setup);

#endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */

static struct uart_driver ulite_uart_driver = {
        .owner          = THIS_MODULE,
        .driver_name    = "uartlite",
        .dev_name       = ULITE_NAME,
        .major          = ULITE_MAJOR,
        .minor          = ULITE_MINOR,
        .nr             = ULITE_NR_UARTS,
#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
        .cons           = &ulite_console,
#endif
};

/* ---------------------------------------------------------------------
 * Port assignment functions (mapping devices to uart_port structures)
 */

/** ulite_assign: register a uartlite device with the driver
 *
 * @dev: pointer to device structure
 * @id: requested id number.  Pass -1 for automatic port assignment
 * @base: base address of uartlite registers
 * @irq: irq number for uartlite
 * @pdata: private data for uartlite
 *
 * Returns: 0 on success, <0 otherwise
 */
static int ulite_assign(struct device *dev, int id, u32 base, int irq,
                        struct uartlite_data *pdata)
{
        struct uart_port *port;
        int rc;

        /* if id = -1; then scan for a free id and use that */
        if (id < 0) {
                for (id = 0; id < ULITE_NR_UARTS; id++)
                        if (ulite_ports[id].mapbase == 0)
                                break;
        }
        if (id < 0 || id >= ULITE_NR_UARTS) {
                dev_err(dev, "%s%i too large\n", ULITE_NAME, id);
                return -EINVAL;
        }

        if ((ulite_ports[id].mapbase) && (ulite_ports[id].mapbase != base)) {
                dev_err(dev, "cannot assign to %s%i; it is already in use\n",
                        ULITE_NAME, id);
                return -EBUSY;
        }

        port = &ulite_ports[id];

        spin_lock_init(&port->lock);
        port->fifosize = 16;
        port->regshift = 2;
        port->iotype = UPIO_MEM;
        port->iobase = 1; /* mark port in use */
        port->mapbase = base;
        port->membase = NULL;
        port->ops = &ulite_ops;
        port->irq = irq;
        port->flags = UPF_BOOT_AUTOCONF;
        port->dev = dev;
        port->type = PORT_UNKNOWN;
        port->line = id;
        port->private_data = pdata;

        dev_set_drvdata(dev, port);

#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
        /*
         * If console hasn't been found yet try to assign this port
         * because it is required to be assigned for console setup function.
         * If register_console() don't assign value, then console_port pointer
         * is cleanup.
         */
        if (ulite_uart_driver.cons->index == -1)
                console_port = port;
#endif

        /* Register the port */
        rc = uart_add_one_port(&ulite_uart_driver, port);
        if (rc) {
                dev_err(dev, "uart_add_one_port() failed; err=%i\n", rc);
                port->mapbase = 0;
                dev_set_drvdata(dev, NULL);
                return rc;
        }

#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
        /* This is not port which is used for console that's why clean it up */
        if (ulite_uart_driver.cons->index == -1)
                console_port = NULL;
#endif

        return 0;
}

/** ulite_release: register a uartlite device with the driver
 *
 * @dev: pointer to device structure
 */
static int ulite_release(struct device *dev)
{
        struct uart_port *port = dev_get_drvdata(dev);
        int rc = 0;

        if (port) {
                struct uartlite_data *pdata = port->private_data;

                rc = uart_remove_one_port(pdata->ulite_uart_driver, port);
                dev_set_drvdata(dev, NULL);
                port->mapbase = 0;
        }

        return rc;
}

/**
 * ulite_suspend - Stop the device.
 *
 * @dev: handle to the device structure.
 * Return: 0 always.
 */
static int __maybe_unused ulite_suspend(struct device *dev)
{
        struct uart_port *port = dev_get_drvdata(dev);

        if (port) {
                struct uartlite_data *pdata = port->private_data;

                uart_suspend_port(pdata->ulite_uart_driver, port);
        }

        return 0;
}

/**
 * ulite_resume - Resume the device.
 *
 * @dev: handle to the device structure.
 * Return: 0 on success, errno otherwise.
 */
static int __maybe_unused ulite_resume(struct device *dev)
{
        struct uart_port *port = dev_get_drvdata(dev);

        if (port) {
                struct uartlite_data *pdata = port->private_data;

                uart_resume_port(pdata->ulite_uart_driver, port);
        }

        return 0;
}

static int __maybe_unused ulite_runtime_suspend(struct device *dev)
{
        struct uart_port *port = dev_get_drvdata(dev);
        struct uartlite_data *pdata = port->private_data;

        clk_disable(pdata->clk);
        return 0;
};

static int __maybe_unused ulite_runtime_resume(struct device *dev)
{
        struct uart_port *port = dev_get_drvdata(dev);
        struct uartlite_data *pdata = port->private_data;

        clk_enable(pdata->clk);
        return 0;
}
/* ---------------------------------------------------------------------
 * Platform bus binding
 */

static const struct dev_pm_ops ulite_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(ulite_suspend, ulite_resume)
        SET_RUNTIME_PM_OPS(ulite_runtime_suspend,
                           ulite_runtime_resume, NULL)
};

#if defined(CONFIG_OF)
/* Match table for of_platform binding */
static const struct of_device_id ulite_of_match[] = {
        { .compatible = "xlnx,opb-uartlite-1.00.b", },
        { .compatible = "xlnx,xps-uartlite-1.00.a", },
        {}
};
MODULE_DEVICE_TABLE(of, ulite_of_match);
#endif /* CONFIG_OF */

static int ulite_probe(struct platform_device *pdev)
{
        struct resource *res;
        struct uartlite_data *pdata;
        int irq, ret;
        int id = pdev->id;
#ifdef CONFIG_OF
        const __be32 *prop;

        prop = of_get_property(pdev->dev.of_node, "port-number", NULL);
        if (prop)
                id = be32_to_cpup(prop);
#endif
        if (id < 0) {
                /* Look for a serialN alias */
                id = of_alias_get_id(pdev->dev.of_node, "serial");
                if (id < 0)
                        id = 0;
        }

        if (!ulite_uart_driver.state) {
                dev_dbg(&pdev->dev, "uartlite: calling uart_register_driver()\n");
                ret = uart_register_driver(&ulite_uart_driver);
                if (ret < 0) {
                        dev_err(&pdev->dev, "Failed to register driver\n");
                        return ret;
                }
        }

        pdata = devm_kzalloc(&pdev->dev, sizeof(struct uartlite_data),
                             GFP_KERNEL);
        if (!pdata)
                return -ENOMEM;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

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

        pdata->clk = devm_clk_get(&pdev->dev, "s_axi_aclk");
        if (IS_ERR(pdata->clk)) {
                if (PTR_ERR(pdata->clk) != -ENOENT)
                        return PTR_ERR(pdata->clk);

                /*
                 * Clock framework support is optional, continue on
                 * anyways if we don't find a matching clock.
                 */
                pdata->clk = NULL;
        }

        pdata->ulite_uart_driver = &ulite_uart_driver;
        ret = clk_prepare_enable(pdata->clk);
        if (ret) {
                dev_err(&pdev->dev, "Failed to prepare clock\n");
                return ret;
        }

        pm_runtime_use_autosuspend(&pdev->dev);
        pm_runtime_set_autosuspend_delay(&pdev->dev, UART_AUTOSUSPEND_TIMEOUT);
        pm_runtime_set_active(&pdev->dev);
        pm_runtime_enable(&pdev->dev);

        ret = ulite_assign(&pdev->dev, id, res->start, irq, pdata);

        pm_runtime_mark_last_busy(&pdev->dev);
        pm_runtime_put_autosuspend(&pdev->dev);

        return ret;
}

static int ulite_remove(struct platform_device *pdev)
{
        struct uart_port *port = dev_get_drvdata(&pdev->dev);
        struct uartlite_data *pdata = port->private_data;
        int rc;

        clk_unprepare(pdata->clk);
        rc = ulite_release(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        pm_runtime_set_suspended(&pdev->dev);
        pm_runtime_dont_use_autosuspend(&pdev->dev);
        return rc;
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:uartlite");

static struct platform_driver ulite_platform_driver = {
        .probe = ulite_probe,
        .remove = ulite_remove,
        .driver = {
                .name  = "uartlite",
                .of_match_table = of_match_ptr(ulite_of_match),
                .pm = &ulite_pm_ops,
        },
};

/* ---------------------------------------------------------------------
 * Module setup/teardown
 */

static int __init ulite_init(void)
{

        pr_debug("uartlite: calling platform_driver_register()\n");
        return platform_driver_register(&ulite_platform_driver);
}

static void __exit ulite_exit(void)
{
        platform_driver_unregister(&ulite_platform_driver);
        uart_unregister_driver(&ulite_uart_driver);
}

module_init(ulite_init);
module_exit(ulite_exit);

MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
MODULE_DESCRIPTION("Xilinx uartlite serial driver");
MODULE_LICENSE("GPL");