@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LiteUART serial controller (LiteX) Driver
+ *
+ * Copyright (C) 2019 Antmicro Ltd <www.antmicro.com>
+ */
+
+#include <linux/console.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/serial.h>
+#include <linux/serial_core.h>
+#include <linux/timer.h>
+#include <linux/tty_flip.h>
+#include <linux/litex.h>
+
+/* module-related defines */
+#define DRIVER_NAME "liteuart"
+#define DRIVER_MAJOR 0
+#define DRIVER_MINOR 0
+#define DEV_NAME "ttyLXU"
+
+/* base address offsets */
+#define OFF_RXTX 0x00
+#define OFF_TXFULL 0x04
+#define OFF_RXEMPTY 0x08
+#define OFF_EV_STATUS 0x0c
+#define OFF_EV_PENDING 0x10
+#define OFF_EV_ENABLE 0x14
+
+/* events */
+#define EV_TX 0x1
+#define EV_RX 0x2
+
+struct liteuart_port {
+ struct uart_port port;
+ struct timer_list timer;
+};
+
+#define to_liteuart_port(port) container_of(port, struct liteuart_port, port)
+
+static struct liteuart_port liteuart_ports[CONFIG_SERIAL_LITEUART_NR_PORTS];
+
+#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
+static struct console liteuart_console;
+#endif
+
+static struct uart_driver liteuart_driver = {
+ .owner = THIS_MODULE,
+ .driver_name = DRIVER_NAME,
+ .dev_name = DEV_NAME,
+ .major = DRIVER_MAJOR,
+ .minor = DRIVER_MINOR,
+ .nr = CONFIG_SERIAL_LITEUART_NR_PORTS,
+#ifdef CONFIG_SERIAL_LITEUART_CONSOLE
+ .cons = &liteuart_console,
+#endif
+};
+
+static void liteuart_timer(struct timer_list *t)
+{
+ struct liteuart_port *uart = from_timer(uart, t, timer);
+ struct uart_port *port = &uart->port;
+ unsigned char __iomem *membase = port->membase;
+ unsigned int flg = TTY_NORMAL;
+ int ch;
+ unsigned int status;
+
+ while ((status = !LITEX_READ_REG_OFF(membase, OFF_RXEMPTY)) == 1) {
+ ch = LITEX_READ_REG_OFF(membase, OFF_RXTX);
+ port->icount.rx++;
+
+ /* necessary for RXEMPTY to refresh its value */
+ LITEX_WRITE_REG_OFF(EV_TX | EV_RX, membase, OFF_EV_PENDING);
+
+ /* no overflow bits in status */
+ if (!(uart_handle_sysrq_char(port, ch)))
+ uart_insert_char(port, status, 0, ch, flg);
+
+ tty_flip_buffer_push(&port->state->port);
+ }
+
+ mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+}
+
+static void liteuart_putchar(struct uart_port *port, int ch)
+{
+ while (LITEX_READ_REG_OFF(port->membase, OFF_TXFULL))
+ cpu_relax();
+
+ LITEX_WRITE_REG_OFF(ch, port->membase, OFF_RXTX);
+}
+
+static unsigned int liteuart_tx_empty(struct uart_port *port)
+{
+ /* not really tx empty, just checking if tx is not full */
+ if (!LITEX_READ_REG_OFF(port->membase, OFF_TXFULL))
+ return TIOCSER_TEMT;
+
+ return 0;
+}
+
+static void liteuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+ /* modem control register is not present in LiteUART */
+}
+
+static unsigned int liteuart_get_mctrl(struct uart_port *port)
+{
+ return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+}
+
+static void liteuart_stop_tx(struct uart_port *port)
+{
+}
+
+static void liteuart_start_tx(struct uart_port *port)
+{
+ struct circ_buf *xmit = &port->state->xmit;
+ unsigned char ch;
+
+ if (unlikely(port->x_char)) {
+ LITEX_WRITE_REG_OFF(port->x_char, port->membase, OFF_RXTX);
+ port->icount.tx++;
+ port->x_char = 0;
+ } else if (!uart_circ_empty(xmit)) {
+ while (xmit->head != xmit->tail) {
+ ch = xmit->buf[xmit->tail];
+ xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+ port->icount.tx++;
+ liteuart_putchar(port, ch);
+ }
+ }
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(port);
+}
+
+static void liteuart_stop_rx(struct uart_port *port)
+{
+ struct liteuart_port *uart = to_liteuart_port(port);
+
+ /* just delete timer */
+ del_timer(&uart->timer);
+}
+
+static void liteuart_break_ctl(struct uart_port *port, int break_state)
+{
+ /* LiteUART doesn't support sending break signal */
+}
+
+static int liteuart_startup(struct uart_port *port)
+{
+ struct liteuart_port *uart = to_liteuart_port(port);
+
+ /* disable events */
+ LITEX_WRITE_REG_OFF(0, port->membase, OFF_EV_ENABLE);
+
+ /* prepare timer for polling */
+ timer_setup(&uart->timer, liteuart_timer, 0);
+ mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+
+ return 0;
+}
+
+static void liteuart_shutdown(struct uart_port *port)
+{
+}
+
+static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
+ struct ktermios *old)
+{
+ unsigned int baud;
+ unsigned long flags;
+
+ spin_lock_irqsave(&port->lock, flags);
+
+ /* update baudrate */
+ baud = uart_get_baud_rate(port, new, old, 0, 460800);
+ uart_update_timeout(port, new->c_cflag, baud);
+
+ spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static const char *liteuart_type(struct uart_port *port)
+{
+ return (port->type == PORT_LITEUART) ? DRIVER_NAME : NULL;
+}
+
+static void liteuart_release_port(struct uart_port *port)
+{
+}
+
+static int liteuart_request_port(struct uart_port *port)
+{
+ return 0;
+}
+
+static void liteuart_config_port(struct uart_port *port, int flags)
+{
+ if (flags & UART_CONFIG_TYPE)
+ port->type = PORT_LITEUART;
+}
+
+static int liteuart_verify_port(struct uart_port *port,
+ struct serial_struct *ser)
+{
+ if (port->type != PORT_UNKNOWN && ser->type != PORT_LITEUART)
+ return -EINVAL;
+
+ return 0;
+}
+
+static const struct uart_ops liteuart_ops = {
+ .tx_empty = liteuart_tx_empty,
+ .set_mctrl = liteuart_set_mctrl,
+ .get_mctrl = liteuart_get_mctrl,
+ .stop_tx = liteuart_stop_tx,
+ .start_tx = liteuart_start_tx,
+ .stop_rx = liteuart_stop_rx,
+ .break_ctl = liteuart_break_ctl,
+ .startup = liteuart_startup,
+ .shutdown = liteuart_shutdown,
+ .set_termios = liteuart_set_termios,
+ .type = liteuart_type,
+ .release_port = liteuart_release_port,
+ .request_port = liteuart_request_port,
+ .config_port = liteuart_config_port,
+ .verify_port = liteuart_verify_port,
+};
+
+static int liteuart_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct liteuart_port *uart;
+ struct uart_port *port;
+ int dev_id;
+
+ /* no device tree */
+ if (!np)
+ return -ENODEV;
+
+ dev_id = of_alias_get_id(np, "serial");
+ if (dev_id < 0 || dev_id >= CONFIG_SERIAL_LITEUART_NR_PORTS)
+ return -EINVAL;