pnx8xxx_uart.c

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/*
 * UART driver for PNX8XXX SoCs
 *
 * Author: Per Hallsmark [e-mail]
 * Ported to 2.6 kernel by EmbeddedAlley
 * Reworked by Vitaly Wool <[e-mail]>
 *
 * Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 * Copyright (C) 2000 Deep Blue Solutions Ltd.
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2. This program is licensed "as is" without any warranty of
 * any kind, whether express or implied.
 *
 */

#if defined(CONFIG_SERIAL_PNX8XXX_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/serial_pnx8xxx.h>

#include <asm/io.h>
#include <asm/irq.h>

/* We'll be using StrongARM sa1100 serial port major/minor */
#define SERIAL_PNX8XXX_MAJOR	204
#define MINOR_START		5

#define NR_PORTS		2

#define PNX8XXX_ISR_PASS_LIMIT	256

/*
 * Convert from ignore_status_mask or read_status_mask to FIFO
 * and interrupt status bits
 */
#define SM_TO_FIFO(x)	((x) >> 10)
#define SM_TO_ISTAT(x)	((x) & 0x000001ff)
#define FIFO_TO_SM(x)	((x) << 10)
#define ISTAT_TO_SM(x)	((x) & 0x000001ff)

/*
 * This is the size of our serial port register set.
 */
#define UART_PORT_SIZE	0x1000

/*
 * This determines how often we check the modem status signals
 * for any change.  They generally aren't connected to an IRQ
 * so we have to poll them.  We also check immediately before
 * filling the TX fifo incase CTS has been dropped.
 */
#define MCTRL_TIMEOUT	(250*HZ/1000)

extern struct pnx8xxx_port pnx8xxx_ports[];

static inline int serial_in(struct pnx8xxx_port *sport, int offset)
{
	return (__raw_readl(sport->port.membase + offset));
}

static inline void serial_out(struct pnx8xxx_port *sport, int offset, int value)
{
	__raw_writel(value, sport->port.membase + offset);
}

/*
 * Handle any change of modem status signal since we were last called.
 */
static void pnx8xxx_mctrl_check(struct pnx8xxx_port *sport)
{
	unsigned int status, changed;

	status = sport->port.ops->get_mctrl(&sport->port);
	changed = status ^ sport->old_status;

	if (changed == 0)
		return;

	sport->old_status = status;

	if (changed & TIOCM_RI)
		sport->port.icount.rng++;
	if (changed & TIOCM_DSR)
		sport->port.icount.dsr++;
	if (changed & TIOCM_CAR)
		uart_handle_dcd_change(&sport->port, status & TIOCM_CAR);
	if (changed & TIOCM_CTS)
		uart_handle_cts_change(&sport->port, status & TIOCM_CTS);

	wake_up_interruptible(&sport->port.info->delta_msr_wait);
}

/*
 * This is our per-port timeout handler, for checking the
 * modem status signals.
 */
static void pnx8xxx_timeout(unsigned long data)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)data;
	unsigned long flags;

	if (sport->port.info) {
		spin_lock_irqsave(&sport->port.lock, flags);
		pnx8xxx_mctrl_check(sport);
		spin_unlock_irqrestore(&sport->port.lock, flags);

		mod_timer(&sport->timer, jiffies + MCTRL_TIMEOUT);
	}
}

/*
 * interrupts disabled on entry
 */
static void pnx8xxx_stop_tx(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	u32 ien;

	/* Disable TX intr */
	ien = serial_in(sport, PNX8XXX_IEN);
	serial_out(sport, PNX8XXX_IEN, ien & ~PNX8XXX_UART_INT_ALLTX);

	/* Clear all pending TX intr */
	serial_out(sport, PNX8XXX_ICLR, PNX8XXX_UART_INT_ALLTX);
}

/*
 * interrupts may not be disabled on entry
 */
static void pnx8xxx_start_tx(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	u32 ien;

	/* Clear all pending TX intr */
	serial_out(sport, PNX8XXX_ICLR, PNX8XXX_UART_INT_ALLTX);

	/* Enable TX intr */
	ien = serial_in(sport, PNX8XXX_IEN);
	serial_out(sport, PNX8XXX_IEN, ien | PNX8XXX_UART_INT_ALLTX);
}

/*
 * Interrupts enabled
 */
static void pnx8xxx_stop_rx(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	u32 ien;

	/* Disable RX intr */
	ien = serial_in(sport, PNX8XXX_IEN);
	serial_out(sport, PNX8XXX_IEN, ien & ~PNX8XXX_UART_INT_ALLRX);

	/* Clear all pending RX intr */
	serial_out(sport, PNX8XXX_ICLR, PNX8XXX_UART_INT_ALLRX);
}

/*
 * Set the modem control timer to fire immediately.
 */
static void pnx8xxx_enable_ms(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;

	mod_timer(&sport->timer, jiffies);
}

static void pnx8xxx_rx_chars(struct pnx8xxx_port *sport)
{
	struct tty_struct *tty = sport->port.info->tty;
	unsigned int status, ch, flg;

	status = FIFO_TO_SM(serial_in(sport, PNX8XXX_FIFO)) |
		 ISTAT_TO_SM(serial_in(sport, PNX8XXX_ISTAT));
	while (status & FIFO_TO_SM(PNX8XXX_UART_FIFO_RXFIFO)) {
		ch = serial_in(sport, PNX8XXX_FIFO);

		sport->port.icount.rx++;

		flg = TTY_NORMAL;

		/*
		 * note that the error handling code is
		 * out of the main execution path
		 */
		if (status & (FIFO_TO_SM(PNX8XXX_UART_FIFO_RXFE |
					PNX8XXX_UART_FIFO_RXPAR) |
			      ISTAT_TO_SM(PNX8XXX_UART_INT_RXOVRN))) {
			if (status & FIFO_TO_SM(PNX8XXX_UART_FIFO_RXPAR))
				sport->port.icount.parity++;
			else if (status & FIFO_TO_SM(PNX8XXX_UART_FIFO_RXFE))
				sport->port.icount.frame++;
			if (status & ISTAT_TO_SM(PNX8XXX_UART_INT_RXOVRN))
				sport->port.icount.overrun++;

			status &= sport->port.read_status_mask;

			if (status & FIFO_TO_SM(PNX8XXX_UART_FIFO_RXPAR))
				flg = TTY_PARITY;
			else if (status & FIFO_TO_SM(PNX8XXX_UART_FIFO_RXFE))
				flg = TTY_FRAME;

#ifdef SUPPORT_SYSRQ
			sport->port.sysrq = 0;
#endif
		}

		if (uart_handle_sysrq_char(&sport->port, ch))
			goto ignore_char;

		uart_insert_char(&sport->port, status,
				ISTAT_TO_SM(PNX8XXX_UART_INT_RXOVRN), ch, flg);

	ignore_char:
		serial_out(sport, PNX8XXX_LCR, serial_in(sport, PNX8XXX_LCR) |
				PNX8XXX_UART_LCR_RX_NEXT);
		status = FIFO_TO_SM(serial_in(sport, PNX8XXX_FIFO)) |
			 ISTAT_TO_SM(serial_in(sport, PNX8XXX_ISTAT));
	}
	tty_flip_buffer_push(tty);
}

static void pnx8xxx_tx_chars(struct pnx8xxx_port *sport)
{
	struct circ_buf *xmit = &sport->port.info->xmit;

	if (sport->port.x_char) {
		serial_out(sport, PNX8XXX_FIFO, sport->port.x_char);
		sport->port.icount.tx++;
		sport->port.x_char = 0;
		return;
	}

	/*
	 * Check the modem control lines before
	 * transmitting anything.
	 */
	pnx8xxx_mctrl_check(sport);

	if (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port)) {
		pnx8xxx_stop_tx(&sport->port);
		return;
	}

	/*
	 * TX while bytes available
	 */
	while (((serial_in(sport, PNX8XXX_FIFO) &
					PNX8XXX_UART_FIFO_TXFIFO) >> 16) < 16) {
		serial_out(sport, PNX8XXX_FIFO, xmit->buf[xmit->tail]);
		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
		sport->port.icount.tx++;
		if (uart_circ_empty(xmit))
			break;
	}

	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
		uart_write_wakeup(&sport->port);

	if (uart_circ_empty(xmit))
		pnx8xxx_stop_tx(&sport->port);
}

static irqreturn_t pnx8xxx_int(int irq, void *dev_id)
{
	struct pnx8xxx_port *sport = dev_id;
	unsigned int status;

	spin_lock(&sport->port.lock);
	/* Get the interrupts */
	status  = serial_in(sport, PNX8XXX_ISTAT) & serial_in(sport, PNX8XXX_IEN);

	/* Break signal received */
	if (status & PNX8XXX_UART_INT_BREAK) {
		sport->port.icount.brk++;
		uart_handle_break(&sport->port);
	}

	/* Byte received */
	if (status & PNX8XXX_UART_INT_RX)
		pnx8xxx_rx_chars(sport);

	/* TX holding register empty - transmit a byte */
	if (status & PNX8XXX_UART_INT_TX)
		pnx8xxx_tx_chars(sport);

	/* Clear the ISTAT register */
	serial_out(sport, PNX8XXX_ICLR, status);

	spin_unlock(&sport->port.lock);
	return IRQ_HANDLED;
}

/*
 * Return TIOCSER_TEMT when transmitter is not busy.
 */
static unsigned int pnx8xxx_tx_empty(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;

	return serial_in(sport, PNX8XXX_FIFO) & PNX8XXX_UART_FIFO_TXFIFO_STA ? 0 : TIOCSER_TEMT;
}

static unsigned int pnx8xxx_get_mctrl(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	unsigned int mctrl = TIOCM_DSR;
	unsigned int msr;

	/* REVISIT */

	msr = serial_in(sport, PNX8XXX_MCR);

	mctrl |= msr & PNX8XXX_UART_MCR_CTS ? TIOCM_CTS : 0;
	mctrl |= msr & PNX8XXX_UART_MCR_DCD ? TIOCM_CAR : 0;

	return mctrl;
}

static void pnx8xxx_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
#if	0	/* FIXME */
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	unsigned int msr;
#endif
}

/*
 * Interrupts always disabled.
 */
static void pnx8xxx_break_ctl(struct uart_port *port, int break_state)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	unsigned long flags;
	unsigned int lcr;

	spin_lock_irqsave(&sport->port.lock, flags);
	lcr = serial_in(sport, PNX8XXX_LCR);
	if (break_state == -1)
		lcr |= PNX8XXX_UART_LCR_TXBREAK;
	else
		lcr &= ~PNX8XXX_UART_LCR_TXBREAK;
	serial_out(sport, PNX8XXX_LCR, lcr);
	spin_unlock_irqrestore(&sport->port.lock, flags);
}

static int pnx8xxx_startup(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	int retval;

	/*
	 * Allocate the IRQ
	 */
	retval = request_irq(sport->port.irq, pnx8xxx_int, 0,
			     "pnx8xxx-uart", sport);
	if (retval)
		return retval;

	/*
	 * Finally, clear and enable interrupts
	 */

	serial_out(sport, PNX8XXX_ICLR, PNX8XXX_UART_INT_ALLRX |
			     PNX8XXX_UART_INT_ALLTX);

	serial_out(sport, PNX8XXX_IEN, serial_in(sport, PNX8XXX_IEN) |
			    PNX8XXX_UART_INT_ALLRX |
			    PNX8XXX_UART_INT_ALLTX);

	/*
	 * Enable modem status interrupts
	 */
	spin_lock_irq(&sport->port.lock);
	pnx8xxx_enable_ms(&sport->port);
	spin_unlock_irq(&sport->port.lock);

	return 0;
}

static void pnx8xxx_shutdown(struct uart_port *port)
{
	struct pnx8xxx_port *sport = (struct pnx8xxx_port *)port;
	int lcr;

	/*
	 * Stop our timer.
	 */
	del_timer_sync(&sport->timer);

	/*
	 * Disable all interrupts
	 */
	serial_out(sport, PNX8XXX_IEN, 0);

	/*
	 * Reset the Tx and Rx FIFOS, disable the break condition
	 */
	lcr = serial_in(sport, PNX8XXX_LCR);
	lcr &= ~PNX8XXX_UART_LCR_TXBREAK;
	lcr |= PNX8XXX_UART_LCR_TX_RST | PNX8XXX_UART_LCR_RX_RST;
	serial_out(sport, PNX8XXX_LCR, lcr);

	/*
	 * Clear all interrupts
	 */
	serial_out(sport, PNX8XXX_ICLR, PNX8XXX_UART_INT_ALLRX |
			     PNX8XXX_UART_INT_ALLTX);

	/*
	 * Free the interrupt
	 */
	free_irq(sport->port.irq, sport);