text: /*
   *  Driver for Conexant Digicolor serial ports (USART)
   *
   * Author: Baruch Siach <baruch@tkos.co.il>
   *
   * Copyright (C) 2014 Paradox Innovation Ltd.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  
  #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;
  
  	spin_lock_irqsave(&port->lock, flags);
  
  	while (1) {
  		u8 status, ch;
  		unsigned int 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);
  	}
  
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	tty_flip_buffer_push(&port->state->port);
  }
  
  static void digicolor_uart_tx(struct uart_port *port)
  {
  	struct circ_buf *xmit = &port->state->xmit;
  	unsigned long flags;
  
  	if (digicolor_uart_tx_full(port))
  		return;
  
  	spin_lock_irqsave(&port->lock, 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 (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
  		digicolor_uart_stop_tx(port);
  		goto out;
  	}
  
  	while (!uart_circ_empty(xmit)) {
  		writeb(xmit->buf[xmit->tail], port->membase + UA_EMI_REC);
  		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
  		port->icount.tx++;
  
  		if (digicolor_uart_tx_full(port))
  			break;
  	}
  
  	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
  		uart_write_wakeup(port);
  
  out:
  	spin_unlock_irqrestore(&port->lock, 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,
  				       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;
  		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;
  
  	spin_lock_irqsave(&port->lock, 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);
  
  	spin_unlock_irqrestore(&port->lock, 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, int 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 = spin_trylock_irqsave(&port->lock, flags);
  	else
  		spin_lock_irqsave(&port->lock, flags);
  
  	uart_console_write(port, c, n, digicolor_uart_console_putchar);
  
  	if (locked)
  		spin_unlock_irqrestore(&port->lock, 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 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);
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	dp->port.mapbase = res->start;
  	dp->port.membase = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(dp->port.membase))
  		return PTR_ERR(dp->port.membase);
  
  	dp->port.irq = platform_get_irq(pdev, 0);
  	if (IS_ERR_VALUE(dp->port.irq))
  		return dp->port.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 int digicolor_uart_remove(struct platform_device *pdev)
  {
  	struct uart_port *port = platform_get_drvdata(pdev);
  
  	uart_remove_one_port(&digicolor_uart, port);
  
  	return 0;
  }
  
  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;
  
  	return platform_driver_register(&digicolor_uart_platform);
  }
  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");
  