// SPDX-License-Identifier: GPL-2.0 /* * uartlite.c: Serial driver for Xilinx uartlite serial controller * * Copyright (C) 2006 Peter Korsgaard * Copyright (C) 2007 Secret Lab Technologies Ltd. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define ULITE_NAME "ttyUL" #if CONFIG_SERIAL_UARTLITE_NR_UARTS > 4 #define ULITE_MAJOR 0 /* use dynamic node allocation */ #define ULITE_MINOR 0 #else #define ULITE_MAJOR 204 #define ULITE_MINOR 187 #endif #define ULITE_NR_UARTS CONFIG_SERIAL_UARTLITE_NR_UARTS /* --------------------------------------------------------------------- * Register definitions * * For register details see datasheet: * https://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 /* ms */ /* Static pointer to console port */ #ifdef CONFIG_SERIAL_UARTLITE_CONSOLE static struct uart_port *console_port; #endif /** * struct uartlite_data - Driver private data * @reg_ops: Functions to read/write registers * @clk: Our parent clock, if present * @baud: The baud rate configured when this device was synthesized * @cflags: The cflags for parity and data bits */ struct uartlite_data { const struct uartlite_reg_ops *reg_ops; struct clk *clk; unsigned int baud; tcflag_t cflags; }; 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]; static struct uart_driver ulite_uart_driver; /* --------------------------------------------------------------------- * 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 tty_port *tport = &port->state->port; unsigned char ch; 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_tx_stopped(port)) return 0; if (!uart_fifo_get(port, &ch)) return 0; uart_out32(ch, ULITE_TX, port); /* wake up */ if (kfifo_len(&tport->xmit_fifo) < 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 { uart_port_lock_irqsave(port, &flags); stat = uart_in32(ULITE_STATUS, port); busy = ulite_receive(port, stat); busy |= ulite_transmit(port, stat); uart_port_unlock_irqrestore(port, 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; uart_port_lock_irqsave(port, &flags); ret = uart_in32(ULITE_STATUS, port); uart_port_unlock_irqrestore(port, 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, const struct ktermios *old) { unsigned long flags; struct uartlite_data *pdata = port->private_data; /* Set termios to what the hardware supports */ termios->c_iflag &= ~BRKINT; termios->c_cflag &= ~(CSTOPB | PARENB | PARODD | CSIZE); termios->c_cflag |= pdata->cflags & (PARENB | PARODD | CSIZE); tty_termios_encode_baud_rate(termios, pdata->baud, pdata->baud); uart_port_lock_irqsave(port, &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 */ uart_update_timeout(port, termios->c_cflag, pdata->baud); uart_port_unlock_irqrestore(port, 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) { int ret; if (!state) { ret = pm_runtime_get_sync(port->dev); if (ret < 0) dev_err(port->dev, "Failed to enable clocks\n"); } 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; /* * Spin waiting for TX fifo to have space available. * When using the Microblaze Debug Module this can take up to 1s */ if (read_poll_timeout_atomic(uart_in32, val, !(val & ULITE_STATUS_TXFULL), 0, 1000000, false, ULITE_STATUS, port)) dev_warn(port->dev, "timeout waiting for TX buffer empty\n"); } static void ulite_console_putchar(struct uart_port *port, unsigned char 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 = uart_port_trylock_irqsave(port, &flags); } else uart_port_lock_irqsave(port, &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) uart_port_unlock_irqrestore(port, flags); } static int ulite_console_setup(struct console *co, char *options) { struct uart_port *port = NULL; int baud = 9600; int bits = 8; int parity = 'n'; int flow = 'n'; if (co->index >= 0 && co->index < ULITE_NR_UARTS) port = ulite_ports + co->index; /* Has the device been initialized yet? */ if (!port || !port->mapbase) { pr_debug("console on ttyUL%i not present\n", co->index); return -ENODEV; } console_port = port; /* 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 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, unsigned char 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; while (--retries && (readl(port->membase + ULITE_STATUS) & ULITE_STATUS_TXFULL)) ; /* Only attempt the iowrite if we didn't timeout */ if (retries) writel(c & 0xff, port->membase + ULITE_TX); } 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, phys_addr_t 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); /* 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; } return 0; } /** ulite_release: register a uartlite device with the driver * * @dev: pointer to device structure */ static void ulite_release(struct device *dev) { struct uart_port *port = dev_get_drvdata(dev); if (port) { uart_remove_one_port(&ulite_uart_driver, port); dev_set_drvdata(dev, NULL); port->mapbase = 0; } } /** * 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) uart_suspend_port(&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) uart_resume_port(&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; int ret; ret = clk_enable(pdata->clk); if (ret) { dev_err(dev, "Cannot enable clock.\n"); return ret; } 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; pdata = devm_kzalloc(&pdev->dev, sizeof(struct uartlite_data), GFP_KERNEL); if (!pdata) return -ENOMEM; if (IS_ENABLED(CONFIG_OF)) { const char *prop; struct device_node *np = pdev->dev.of_node; u32 val = 0; prop = "port-number"; ret = of_property_read_u32(np, prop, &id); if (ret && ret != -EINVAL) of_err: return dev_err_probe(&pdev->dev, ret, "could not read %s\n", prop); prop = "current-speed"; ret = of_property_read_u32(np, prop, &pdata->baud); if (ret) goto of_err; prop = "xlnx,use-parity"; ret = of_property_read_u32(np, prop, &val); if (ret && ret != -EINVAL) goto of_err; if (val) { prop = "xlnx,odd-parity"; ret = of_property_read_u32(np, prop, &val); if (ret) goto of_err; if (val) pdata->cflags |= PARODD; pdata->cflags |= PARENB; } val = 8; prop = "xlnx,data-bits"; ret = of_property_read_u32(np, prop, &val); if (ret && ret != -EINVAL) goto of_err; switch (val) { case 5: pdata->cflags |= CS5; break; case 6: pdata->cflags |= CS6; break; case 7: pdata->cflags |= CS7; break; case 8: pdata->cflags |= CS8; break; default: return dev_err_probe(&pdev->dev, -EINVAL, "bad data bits %d\n", val); } } else { pdata->baud = 9600; pdata->cflags = CS8; } res = platform_get_resource(pdev, IORESOURCE_MEM, 0); if (!res) return -ENODEV; irq = platform_get_irq(pdev, 0); if (irq < 0) return irq; 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; } 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); 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"); clk_disable_unprepare(pdata->clk); return ret; } } 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 void ulite_remove(struct platform_device *pdev) { struct uart_port *port = dev_get_drvdata(&pdev->dev); struct uartlite_data *pdata = port->private_data; clk_disable_unprepare(pdata->clk); ulite_release(&pdev->dev); pm_runtime_disable(&pdev->dev); pm_runtime_set_suspended(&pdev->dev); pm_runtime_dont_use_autosuspend(&pdev->dev); } /* 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); if (ulite_uart_driver.state) uart_unregister_driver(&ulite_uart_driver); } module_init(ulite_init); module_exit(ulite_exit); MODULE_AUTHOR("Peter Korsgaard "); MODULE_DESCRIPTION("Xilinx uartlite serial driver"); MODULE_LICENSE("GPL");