drivers/tty/serial/sunsab.c

// SPDX-License-Identifier: GPL-2.0
/* sunsab.c: ASYNC Driver for the SIEMENS SAB82532 DUSCC.
 *
 * Copyright (C) 1997  Eddie C. Dost  (ecd@skynet.be)
 * Copyright (C) 2002, 2006  David S. Miller (davem@davemloft.net)
 *
 * Rewrote buffer handling to use CIRC(Circular Buffer) macros.
 *   Maxim Krasnyanskiy <maxk@qualcomm.com>
 *
 * Fixed to use tty_get_baud_rate, and to allow for arbitrary baud
 * rates to be programmed into the UART.  Also eliminated a lot of
 * duplicated code in the console setup.
 *   Theodore Ts'o <tytso@mit.edu>, 2001-Oct-12
 *
 * Ported to new 2.5.x UART layer.
 *   David S. Miller <davem@davemloft.net>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/circ_buf.h>
#include <linux/serial.h>
#include <linux/sysrq.h>
#include <linux/console.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/of_device.h>

#include <linux/io.h>
#include <asm/irq.h>
#include <asm/prom.h>
#include <asm/setup.h>

#include <linux/serial_core.h>
#include <linux/sunserialcore.h>

#include "sunsab.h"

struct uart_sunsab_port {
	struct uart_port		port;		/* Generic UART port	*/
	union sab82532_async_regs	__iomem *regs;	/* Chip registers	*/
	unsigned long			irqflags;	/* IRQ state flags	*/
	int				dsr;		/* Current DSR state	*/
	unsigned int			cec_timeout;	/* Chip poll timeout... */
	unsigned int			tec_timeout;	/* likewise		*/
	unsigned char			interrupt_mask0;/* ISR0 masking		*/
	unsigned char			interrupt_mask1;/* ISR1 masking		*/
	unsigned char			pvr_dtr_bit;	/* Which PVR bit is DTR */
	unsigned char			pvr_dsr_bit;	/* Which PVR bit is DSR */
	unsigned int			gis_shift;
	int				type;		/* SAB82532 version	*/

	/* Setting configuration bits while the transmitter is active
	 * can cause garbage characters to get emitted by the chip.
	 * Therefore, we cache such writes here and do the real register
	 * write the next time the transmitter becomes idle.
	 */
	unsigned int			cached_ebrg;
	unsigned char			cached_mode;
	unsigned char			cached_pvr;
	unsigned char			cached_dafo;
};

/*
 * This assumes you have a 29.4912 MHz clock for your UART.
 */
#define SAB_BASE_BAUD ( 29491200 / 16 )

static char *sab82532_version[16] = {
	"V1.0", "V2.0", "V3.2", "V(0x03)",
	"V(0x04)", "V(0x05)", "V(0x06)", "V(0x07)",
	"V(0x08)", "V(0x09)", "V(0x0a)", "V(0x0b)",
	"V(0x0c)", "V(0x0d)", "V(0x0e)", "V(0x0f)"
};

#define SAB82532_MAX_TEC_TIMEOUT 200000	/* 1 character time (at 50 baud) */
#define SAB82532_MAX_CEC_TIMEOUT  50000	/* 2.5 TX CLKs (at 50 baud) */

#define SAB82532_RECV_FIFO_SIZE	32      /* Standard async fifo sizes */
#define SAB82532_XMIT_FIFO_SIZE	32

static __inline__ void sunsab_tec_wait(struct uart_sunsab_port *up)
{
	int timeout = up->tec_timeout;

	while ((readb(&up->regs->r.star) & SAB82532_STAR_TEC) && --timeout)
		udelay(1);
}

static __inline__ void sunsab_cec_wait(struct uart_sunsab_port *up)
{
	int timeout = up->cec_timeout;

	while ((readb(&up->regs->r.star) & SAB82532_STAR_CEC) && --timeout)
		udelay(1);
}

static struct tty_port *
receive_chars(struct uart_sunsab_port *up,
	      union sab82532_irq_status *stat)
{
	struct tty_port *port = NULL;
	unsigned char buf[32];
	int saw_console_brk = 0;
	int free_fifo = 0;
	int count = 0;
	int i;

	if (up->port.state != NULL)		/* Unopened serial console */
		port = &up->port.state->port;

	/* Read number of BYTES (Character + Status) available. */
	if (stat->sreg.isr0 & SAB82532_ISR0_RPF) {
		count = SAB82532_RECV_FIFO_SIZE;
		free_fifo++;
	}

	if (stat->sreg.isr0 & SAB82532_ISR0_TCD) {
		count = readb(&up->regs->r.rbcl) & (SAB82532_RECV_FIFO_SIZE - 1);
		free_fifo++;
	}

	/* Issue a FIFO read command in case we where idle. */
	if (stat->sreg.isr0 & SAB82532_ISR0_TIME) {
		sunsab_cec_wait(up);
		writeb(SAB82532_CMDR_RFRD, &up->regs->w.cmdr);
		return port;
	}

	if (stat->sreg.isr0 & SAB82532_ISR0_RFO)
		free_fifo++;

	/* Read the FIFO. */
	for (i = 0; i < count; i++)
		buf[i] = readb(&up->regs->r.rfifo[i]);

	/* Issue Receive Message Complete command. */
	if (free_fifo) {
		sunsab_cec_wait(up);
		writeb(SAB82532_CMDR_RMC, &up->regs->w.cmdr);
	}

	/* Count may be zero for BRK, so we check for it here */
	if ((stat->sreg.isr1 & SAB82532_ISR1_BRK) &&
	    (up->port.line == up->port.cons->index))
		saw_console_brk = 1;

	if (count == 0) {
		if (unlikely(stat->sreg.isr1 & SAB82532_ISR1_BRK)) {
			stat->sreg.isr0 &= ~(SAB82532_ISR0_PERR |
					     SAB82532_ISR0_FERR);
			up->port.icount.brk++;
			uart_handle_break(&up->port);
		}
	}

	for (i = 0; i < count; i++) {
		unsigned char ch = buf[i], flag;

		flag = TTY_NORMAL;
		up->port.icount.rx++;

		if (unlikely(stat->sreg.isr0 & (SAB82532_ISR0_PERR |
						SAB82532_ISR0_FERR |
						SAB82532_ISR0_RFO)) ||
		    unlikely(stat->sreg.isr1 & SAB82532_ISR1_BRK)) {
			/*
			 * For statistics only
			 */
			if (stat->sreg.isr1 & SAB82532_ISR1_BRK) {
				stat->sreg.isr0 &= ~(SAB82532_ISR0_PERR |
						     SAB82532_ISR0_FERR);
				up->port.icount.brk++;
				/*
				 * We do the SysRQ and SAK checking
				 * here because otherwise the break
				 * may get masked by ignore_status_mask
				 * or read_status_mask.
				 */
				if (uart_handle_break(&up->port))
					continue;
			} else if (stat->sreg.isr0 & SAB82532_ISR0_PERR)
				up->port.icount.parity++;
			else if (stat->sreg.isr0 & SAB82532_ISR0_FERR)
				up->port.icount.frame++;
			if (stat->sreg.isr0 & SAB82532_ISR0_RFO)
				up->port.icount.overrun++;

			/*
			 * Mask off conditions which should be ingored.
			 */
			stat->sreg.isr0 &= (up->port.read_status_mask & 0xff);
			stat->sreg.isr1 &= ((up->port.read_status_mask >> 8) & 0xff);

			if (stat->sreg.isr1 & SAB82532_ISR1_BRK) {
				flag = TTY_BREAK;
			} else if (stat->sreg.isr0 & SAB82532_ISR0_PERR)
				flag = TTY_PARITY;
			else if (stat->sreg.isr0 & SAB82532_ISR0_FERR)
				flag = TTY_FRAME;
		}

		if (uart_handle_sysrq_char(&up->port, ch) || !port)
			continue;

		if ((stat->sreg.isr0 & (up->port.ignore_status_mask & 0xff)) == 0 &&
		    (stat->sreg.isr1 & ((up->port.ignore_status_mask >> 8) & 0xff)) == 0)
			tty_insert_flip_char(port, ch, flag);
		if (stat->sreg.isr0 & SAB82532_ISR0_RFO)
			tty_insert_flip_char(port, 0, TTY_OVERRUN);
	}

	if (saw_console_brk)
		sun_do_break();

	return port;
}

static void sunsab_stop_tx(struct uart_port *);
static void sunsab_tx_idle(struct uart_sunsab_port *);

static void transmit_chars(struct uart_sunsab_port *up,
			   union sab82532_irq_status *stat)
{
	struct circ_buf *xmit = &up->port.state->xmit;
	int i;

	if (stat->sreg.isr1 & SAB82532_ISR1_ALLS) {
		up->interrupt_mask1 |= SAB82532_IMR1_ALLS;
		writeb(up->interrupt_mask1, &up->regs->w.imr1);
		set_bit(SAB82532_ALLS, &up->irqflags);
	}

#if 0 /* bde@nwlink.com says this check causes problems */
	if (!(stat->sreg.isr1 & SAB82532_ISR1_XPR))
		return;
#endif

	if (!(readb(&up->regs->r.star) & SAB82532_STAR_XFW))
		return;

	set_bit(SAB82532_XPR, &up->irqflags);
	sunsab_tx_idle(up);

	if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
		up->interrupt_mask1 |= SAB82532_IMR1_XPR;
		writeb(up->interrupt_mask1, &up->regs->w.imr1);
		return;
	}

	up->interrupt_mask1 &= ~(SAB82532_IMR1_ALLS|SAB82532_IMR1_XPR);
	writeb(up->interrupt_mask1, &up->regs->w.imr1);
	clear_bit(SAB82532_ALLS, &up->irqflags);

	/* Stuff 32 bytes into Transmit FIFO. */
	clear_bit(SAB82532_XPR, &up->irqflags);
	for (i = 0; i < up->port.fifosize; i++) {
		writeb(xmit->buf[xmit->tail],
		       &up->regs->w.xfifo[i]);
		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
		up->port.icount.tx++;
		if (uart_circ_empty(xmit))
			break;
	}

	/* Issue a Transmit Frame command. */
	sunsab_cec_wait(up);
	writeb(SAB82532_CMDR_XF, &up->regs->w.cmdr);

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

	if (uart_circ_empty(xmit))
		sunsab_stop_tx(&up->port);
}

static void check_status(struct uart_sunsab_port *up,
			 union sab82532_irq_status *stat)
{
	if (stat->sreg.isr0 & SAB82532_ISR0_CDSC)
		uart_handle_dcd_change(&up->port,
				       !(readb(&up->regs->r.vstr) & SAB82532_VSTR_CD));

	if (stat->sreg.isr1 & SAB82532_ISR1_CSC)
		uart_handle_cts_change(&up->port,
				       (readb(&up->regs->r.star) & SAB82532_STAR_CTS));

	if ((readb(&up->regs->r.pvr) & up->pvr_dsr_bit) ^ up->dsr) {
		up->dsr = (readb(&up->regs->r.pvr) & up->pvr_dsr_bit) ? 0 : 1;
		up->port.icount.dsr++;
	}

	wake_up_interruptible(&up->port.state->port.delta_msr_wait);
}

static irqreturn_t sunsab_interrupt(int irq, void *dev_id)
{
	struct uart_sunsab_port *up = dev_id;
	struct tty_port *port = NULL;
	union sab82532_irq_status status;
	unsigned long flags;
	unsigned char gis;

	spin_lock_irqsave(&up->port.lock, flags);

	status.stat = 0;
	gis = readb(&up->regs->r.gis) >> up->gis_shift;
	if (gis & 1)
		status.sreg.isr0 = readb(&up->regs->r.isr0);
	if (gis & 2)
		status.sreg.isr1 = readb(&up->regs->r.isr1);

	if (status.stat) {
		if ((status.sreg.isr0 & (SAB82532_ISR0_TCD | SAB82532_ISR0_TIME |
					 SAB82532_ISR0_RFO | SAB82532_ISR0_RPF)) ||
		    (status.sreg.isr1 & SAB82532_ISR1_BRK))
			port = receive_chars(up, &status);
		if ((status.sreg.isr0 & SAB82532_ISR0_CDSC) ||
		    (status.sreg.isr1 & SAB82532_ISR1_CSC))
			check_status(up, &status);
		if (status.sreg.isr1 & (SAB82532_ISR1_ALLS | SAB82532_ISR1_XPR))
			transmit_chars(up, &status);
	}

	spin_unlock_irqrestore(&up->port.lock, flags);

	if (port)
		tty_flip_buffer_push(port);

	return IRQ_HANDLED;
}

/* port->lock is not held.  */
static unsigned int sunsab_tx_empty(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	int ret;

	/* Do not need a lock for a state test like this.  */
	if (test_bit(SAB82532_ALLS, &up->irqflags))
		ret = TIOCSER_TEMT;
	else
		ret = 0;

	return ret;
}

/* port->lock held by caller.  */
static void sunsab_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);

	if (mctrl & TIOCM_RTS) {
		up->cached_mode &= ~SAB82532_MODE_FRTS;
		up->cached_mode |= SAB82532_MODE_RTS;
	} else {
		up->cached_mode |= (SAB82532_MODE_FRTS |
				    SAB82532_MODE_RTS);
	}
	if (mctrl & TIOCM_DTR) {
		up->cached_pvr &= ~(up->pvr_dtr_bit);
	} else {
		up->cached_pvr |= up->pvr_dtr_bit;
	}

	set_bit(SAB82532_REGS_PENDING, &up->irqflags);
	if (test_bit(SAB82532_XPR, &up->irqflags))
		sunsab_tx_idle(up);
}

/* port->lock is held by caller and interrupts are disabled.  */
static unsigned int sunsab_get_mctrl(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	unsigned char val;
	unsigned int result;

	result = 0;

	val = readb(&up->regs->r.pvr);
	result |= (val & up->pvr_dsr_bit) ? 0 : TIOCM_DSR;

	val = readb(&up->regs->r.vstr);
	result |= (val & SAB82532_VSTR_CD) ? 0 : TIOCM_CAR;

	val = readb(&up->regs->r.star);
	result |= (val & SAB82532_STAR_CTS) ? TIOCM_CTS : 0;

	return result;
}

/* port->lock held by caller.  */
static void sunsab_stop_tx(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);

	up->interrupt_mask1 |= SAB82532_IMR1_XPR;
	writeb(up->interrupt_mask1, &up->regs->w.imr1);
}

/* port->lock held by caller.  */
static void sunsab_tx_idle(struct uart_sunsab_port *up)
{
	if (test_bit(SAB82532_REGS_PENDING, &up->irqflags)) {
		u8 tmp;

		clear_bit(SAB82532_REGS_PENDING, &up->irqflags);
		writeb(up->cached_mode, &up->regs->rw.mode);
		writeb(up->cached_pvr, &up->regs->rw.pvr);
		writeb(up->cached_dafo, &up->regs->w.dafo);

		writeb(up->cached_ebrg & 0xff, &up->regs->w.bgr);
		tmp = readb(&up->regs->rw.ccr2);
		tmp &= ~0xc0;
		tmp |= (up->cached_ebrg >> 2) & 0xc0;
		writeb(tmp, &up->regs->rw.ccr2);
	}
}

/* port->lock held by caller.  */
static void sunsab_start_tx(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	struct circ_buf *xmit = &up->port.state->xmit;
	int i;

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

	up->interrupt_mask1 &= ~(SAB82532_IMR1_ALLS|SAB82532_IMR1_XPR);
	writeb(up->interrupt_mask1, &up->regs->w.imr1);
	
	if (!test_bit(SAB82532_XPR, &up->irqflags))
		return;

	clear_bit(SAB82532_ALLS, &up->irqflags);
	clear_bit(SAB82532_XPR, &up->irqflags);

	for (i = 0; i < up->port.fifosize; i++) {
		writeb(xmit->buf[xmit->tail],
		       &up->regs->w.xfifo[i]);
		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
		up->port.icount.tx++;
		if (uart_circ_empty(xmit))
			break;
	}

	/* Issue a Transmit Frame command.  */
	sunsab_cec_wait(up);
	writeb(SAB82532_CMDR_XF, &up->regs->w.cmdr);
}

/* port->lock is not held.  */
static void sunsab_send_xchar(struct uart_port *port, char ch)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	unsigned long flags;

	if (ch == __DISABLED_CHAR)
		return;

	spin_lock_irqsave(&up->port.lock, flags);

	sunsab_tec_wait(up);
	writeb(ch, &up->regs->w.tic);

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

/* port->lock held by caller.  */
static void sunsab_stop_rx(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);

	up->interrupt_mask0 |= SAB82532_IMR0_TCD;
	writeb(up->interrupt_mask1, &up->regs->w.imr0);
}

/* port->lock is not held.  */
static void sunsab_break_ctl(struct uart_port *port, int break_state)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	unsigned long flags;
	unsigned char val;

	spin_lock_irqsave(&up->port.lock, flags);

	val = up->cached_dafo;
	if (break_state)
		val |= SAB82532_DAFO_XBRK;
	else
		val &= ~SAB82532_DAFO_XBRK;
	up->cached_dafo = val;

	set_bit(SAB82532_REGS_PENDING, &up->irqflags);
	if (test_bit(SAB82532_XPR, &up->irqflags))
		sunsab_tx_idle(up);

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

/* port->lock is not held.  */
static int sunsab_startup(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	unsigned long flags;
	unsigned char tmp;
	int err = request_irq(up->port.irq, sunsab_interrupt,
			      IRQF_SHARED, "sab", up);
	if (err)
		return err;

	spin_lock_irqsave(&up->port.lock, flags);

	/*
	 * Wait for any commands or immediate characters
	 */
	sunsab_cec_wait(up);
	sunsab_tec_wait(up);

	/*
	 * Clear the FIFO buffers.
	 */
	writeb(SAB82532_CMDR_RRES, &up->regs->w.cmdr);
	sunsab_cec_wait(up);
	writeb(SAB82532_CMDR_XRES, &up->regs->w.cmdr);

	/*
	 * Clear the interrupt registers.
	 */
	(void) readb(&up->regs->r.isr0);
	(void) readb(&up->regs->r.isr1);

	/*
	 * Now, initialize the UART 
	 */
	writeb(0, &up->regs->w.ccr0);				/* power-down */
	writeb(SAB82532_CCR0_MCE | SAB82532_CCR0_SC_NRZ |
	       SAB82532_CCR0_SM_ASYNC, &up->regs->w.ccr0);
	writeb(SAB82532_CCR1_ODS | SAB82532_CCR1_BCR | 7, &up->regs->w.ccr1);
	writeb(SAB82532_CCR2_BDF | SAB82532_CCR2_SSEL |
	       SAB82532_CCR2_TOE, &up->regs->w.ccr2);
	writeb(0, &up->regs->w.ccr3);
	writeb(SAB82532_CCR4_MCK4 | SAB82532_CCR4_EBRG, &up->regs->w.ccr4);
	up->cached_mode = (SAB82532_MODE_RTS | SAB82532_MODE_FCTS |
			   SAB82532_MODE_RAC);
	writeb(up->cached_mode, &up->regs->w.mode);
	writeb(SAB82532_RFC_DPS|SAB82532_RFC_RFTH_32, &up->regs->w.rfc);
	
	tmp = readb(&up->regs->rw.ccr0);
	tmp |= SAB82532_CCR0_PU;	/* power-up */
	writeb(tmp, &up->regs->rw.ccr0);

	/*
	 * Finally, enable interrupts
	 */
	up->interrupt_mask0 = (SAB82532_IMR0_PERR | SAB82532_IMR0_FERR |
			       SAB82532_IMR0_PLLA);
	writeb(up->interrupt_mask0, &up->regs->w.imr0);
	up->interrupt_mask1 = (SAB82532_IMR1_BRKT | SAB82532_IMR1_ALLS |
			       SAB82532_IMR1_XOFF | SAB82532_IMR1_TIN |
			       SAB82532_IMR1_CSC | SAB82532_IMR1_XON |
			       SAB82532_IMR1_XPR);
	writeb(up->interrupt_mask1, &up->regs->w.imr1);
	set_bit(SAB82532_ALLS, &up->irqflags);
	set_bit(SAB82532_XPR, &up->irqflags);

	spin_unlock_irqrestore(&up->port.lock, flags);

	return 0;
}

/* port->lock is not held.  */
static void sunsab_shutdown(struct uart_port *port)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	unsigned long flags;

	spin_lock_irqsave(&up->port.lock, flags);

	/* Disable Interrupts */
	up->interrupt_mask0 = 0xff;
	writeb(up->interrupt_mask0, &up->regs->w.imr0);
	up->interrupt_mask1 = 0xff;
	writeb(up->interrupt_mask1, &up->regs->w.imr1);

	/* Disable break condition */
	up->cached_dafo = readb(&up->regs->rw.dafo);
	up->cached_dafo &= ~SAB82532_DAFO_XBRK;
	writeb(up->cached_dafo, &up->regs->rw.dafo);

	/* Disable Receiver */	
	up->cached_mode &= ~SAB82532_MODE_RAC;
	writeb(up->cached_mode, &up->regs->rw.mode);

	/*
	 * XXX FIXME
	 *
	 * If the chip is powered down here the system hangs/crashes during
	 * reboot or shutdown.  This needs to be investigated further,
	 * similar behaviour occurs in 2.4 when the driver is configured
	 * as a module only.  One hint may be that data is sometimes
	 * transmitted at 9600 baud during shutdown (regardless of the
	 * speed the chip was configured for when the port was open).
	 */
#if 0
	/* Power Down */	
	tmp = readb(&up->regs->rw.ccr0);
	tmp &= ~SAB82532_CCR0_PU;
	writeb(tmp, &up->regs->rw.ccr0);
#endif

	spin_unlock_irqrestore(&up->port.lock, flags);
	free_irq(up->port.irq, up);
}

/*
 * This is used to figure out the divisor speeds.
 *
 * The formula is:    Baud = SAB_BASE_BAUD / ((N + 1) * (1 << M)),
 *
 * with               0 <= N < 64 and 0 <= M < 16
 */

static void calc_ebrg(int baud, int *n_ret, int *m_ret)
{
	int	n, m;

	if (baud == 0) {
		*n_ret = 0;
		*m_ret = 0;
		return;
	}
     
	/*
	 * We scale numbers by 10 so that we get better accuracy
	 * without having to use floating point.  Here we increment m
	 * until n is within the valid range.
	 */
	n = (SAB_BASE_BAUD * 10) / baud;
	m = 0;
	while (n >= 640) {
		n = n / 2;
		m++;
	}
	n = (n+5) / 10;
	/*
	 * We try very hard to avoid speeds with M == 0 since they may
	 * not work correctly for XTAL frequences above 10 MHz.
	 */
	if ((m == 0) && ((n & 1) == 0)) {
		n = n / 2;
		m++;
	}
	*n_ret = n - 1;
	*m_ret = m;
}

/* Internal routine, port->lock is held and local interrupts are disabled.  */
static void sunsab_convert_to_sab(struct uart_sunsab_port *up, unsigned int cflag,
				  unsigned int iflag, unsigned int baud,
				  unsigned int quot)
{
	unsigned char dafo;
	int n, m;

	/* Byte size and parity */
	switch (cflag & CSIZE) {
	      case CS5: dafo = SAB82532_DAFO_CHL5; break;
	      case CS6: dafo = SAB82532_DAFO_CHL6; break;
	      case CS7: dafo = SAB82532_DAFO_CHL7; break;
	      case CS8: dafo = SAB82532_DAFO_CHL8; break;
	      /* Never happens, but GCC is too dumb to figure it out */
	      default:  dafo = SAB82532_DAFO_CHL5; break;
	}

	if (cflag & CSTOPB)
		dafo |= SAB82532_DAFO_STOP;

	if (cflag & PARENB)
		dafo |= SAB82532_DAFO_PARE;

	if (cflag & PARODD) {
		dafo |= SAB82532_DAFO_PAR_ODD;
	} else {
		dafo |= SAB82532_DAFO_PAR_EVEN;
	}
	up->cached_dafo = dafo;

	calc_ebrg(baud, &n, &m);

	up->cached_ebrg = n | (m << 6);

	up->tec_timeout = (10 * 1000000) / baud;
	up->cec_timeout = up->tec_timeout >> 2;

	/* CTS flow control flags */
	/* We encode read_status_mask and ignore_status_mask like so:
	 *
	 * ---------------------
	 * | ... | ISR1 | ISR0 |
	 * ---------------------
	 *  ..    15   8 7    0
	 */

	up->port.read_status_mask = (SAB82532_ISR0_TCD | SAB82532_ISR0_TIME |
				     SAB82532_ISR0_RFO | SAB82532_ISR0_RPF |
				     SAB82532_ISR0_CDSC);
	up->port.read_status_mask |= (SAB82532_ISR1_CSC |
				      SAB82532_ISR1_ALLS |
				      SAB82532_ISR1_XPR) << 8;
	if (iflag & INPCK)
		up->port.read_status_mask |= (SAB82532_ISR0_PERR |
					      SAB82532_ISR0_FERR);
	if (iflag & (IGNBRK | BRKINT | PARMRK))
		up->port.read_status_mask |= (SAB82532_ISR1_BRK << 8);

	/*
	 * Characteres to ignore
	 */
	up->port.ignore_status_mask = 0;
	if (iflag & IGNPAR)
		up->port.ignore_status_mask |= (SAB82532_ISR0_PERR |
						SAB82532_ISR0_FERR);
	if (iflag & IGNBRK) {
		up->port.ignore_status_mask |= (SAB82532_ISR1_BRK << 8);
		/*
		 * If we're ignoring parity and break indicators,
		 * ignore overruns too (for real raw support).
		 */
		if (iflag & IGNPAR)
			up->port.ignore_status_mask |= SAB82532_ISR0_RFO;
	}

	/*
	 * ignore all characters if CREAD is not set
	 */
	if ((cflag & CREAD) == 0)
		up->port.ignore_status_mask |= (SAB82532_ISR0_RPF |
						SAB82532_ISR0_TCD);

	uart_update_timeout(&up->port, cflag,
			    (up->port.uartclk / (16 * quot)));

	/* Now schedule a register update when the chip's
	 * transmitter is idle.
	 */
	up->cached_mode |= SAB82532_MODE_RAC;
	set_bit(SAB82532_REGS_PENDING, &up->irqflags);
	if (test_bit(SAB82532_XPR, &up->irqflags))
		sunsab_tx_idle(up);
}

/* port->lock is not held.  */
static void sunsab_set_termios(struct uart_port *port, struct ktermios *termios,
			       const struct ktermios *old)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);
	unsigned long flags;
	unsigned int baud = uart_get_baud_rate(port, termios, old, 0, 4000000);
	unsigned int quot = uart_get_divisor(port, baud);

	spin_lock_irqsave(&up->port.lock, flags);
	sunsab_convert_to_sab(up, termios->c_cflag, termios->c_iflag, baud, quot);
	spin_unlock_irqrestore(&up->port.lock, flags);
}

static const char *sunsab_type(struct uart_port *port)
{
	struct uart_sunsab_port *up = (void *)port;
	static char buf[36];
	
	sprintf(buf, "SAB82532 %s", sab82532_version[up->type]);
	return buf;
}

static void sunsab_release_port(struct uart_port *port)
{
}

static int sunsab_request_port(struct uart_port *port)
{
	return 0;
}

static void sunsab_config_port(struct uart_port *port, int flags)
{
}

static int sunsab_verify_port(struct uart_port *port, struct serial_struct *ser)
{
	return -EINVAL;
}

static const struct uart_ops sunsab_pops = {
	.tx_empty	= sunsab_tx_empty,
	.set_mctrl	= sunsab_set_mctrl,
	.get_mctrl	= sunsab_get_mctrl,
	.stop_tx	= sunsab_stop_tx,
	.start_tx	= sunsab_start_tx,
	.send_xchar	= sunsab_send_xchar,
	.stop_rx	= sunsab_stop_rx,
	.break_ctl	= sunsab_break_ctl,
	.startup	= sunsab_startup,
	.shutdown	= sunsab_shutdown,
	.set_termios	= sunsab_set_termios,
	.type		= sunsab_type,
	.release_port	= sunsab_release_port,
	.request_port	= sunsab_request_port,
	.config_port	= sunsab_config_port,
	.verify_port	= sunsab_verify_port,
};

static struct uart_driver sunsab_reg = {
	.owner			= THIS_MODULE,
	.driver_name		= "sunsab",
	.dev_name		= "ttyS",
	.major			= TTY_MAJOR,
};

static struct uart_sunsab_port *sunsab_ports;

#ifdef CONFIG_SERIAL_SUNSAB_CONSOLE

static void sunsab_console_putchar(struct uart_port *port, unsigned char c)
{
	struct uart_sunsab_port *up =
		container_of(port, struct uart_sunsab_port, port);

	sunsab_tec_wait(up);
	writeb(c, &up->regs->w.tic);
}

static void sunsab_console_write(struct console *con, const char *s, unsigned n)
{
	struct uart_sunsab_port *up = &sunsab_ports[con->index];
	unsigned long flags;
	int locked = 1;

	if (up->port.sysrq || oops_in_progress)
		locked = spin_trylock_irqsave(&up->port.lock, flags);
	else
		spin_lock_irqsave(&up->port.lock, flags);

	uart_console_write(&up->port, s, n, sunsab_console_putchar);
	sunsab_tec_wait(up);

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

static int sunsab_console_setup(struct console *con, char *options)
{
	struct uart_sunsab_port *up = &sunsab_ports[con->index];
	unsigned long flags;
	unsigned int baud, quot;

	/*
	 * The console framework calls us for each and every port
	 * registered. Defer the console setup until the requested
	 * port has been properly discovered. A bit of a hack,
	 * though...
	 */
	if (up->port.type != PORT_SUNSAB)
		return -EINVAL;

	printk("Console: ttyS%d (SAB82532)\n",
	       (sunsab_reg.minor - 64) + con->index);

	sunserial_console_termios(con, up->port.dev->of_node);

	switch (con->cflag & CBAUD) {
	case B150: baud = 150; break;
	case B300: baud = 300; break;
	case B600: baud = 600; break;
	case B1200: baud = 1200; break;
	case B2400: baud = 2400; break;
	case B4800: baud = 4800; break;
	default: case B9600: baud = 9600; break;
	case B19200: baud = 19200; break;
	case B38400: baud = 38400; break;
	case B57600: baud = 57600; break;
	case B115200: baud = 115200; break;
	case B230400: baud = 230400; break;
	case B460800: baud = 460800; break;
	}

	/*
	 * Temporary fix.
	 */
	spin_lock_init(&up->port.lock);

	/*
	 * Initialize the hardware
	 */
	sunsab_startup(&up->port);

	spin_lock_irqsave(&up->port.lock, flags);

	/*
	 * Finally, enable interrupts
	 */
	up->interrupt_mask0 = SAB82532_IMR0_PERR | SAB82532_IMR0_FERR |
				SAB82532_IMR0_PLLA | SAB82532_IMR0_CDSC;
	writeb(up->interrupt_mask0, &up->regs->w.imr0);
	up->interrupt_mask1 = SAB82532_IMR1_BRKT | SAB82532_IMR1_ALLS |
				SAB82532_IMR1_XOFF | SAB82532_IMR1_TIN |
				SAB82532_IMR1_CSC | SAB82532_IMR1_XON |
				SAB82532_IMR1_XPR;
	writeb(up->interrupt_mask1, &up->regs->w.imr1);

	quot = uart_get_divisor(&up->port, baud);
	sunsab_convert_to_sab(up, con->cflag, 0, baud, quot);
	sunsab_set_mctrl(&up->port, TIOCM_DTR | TIOCM_RTS);

	spin_unlock_irqrestore(&up->port.lock, flags);
	
	return 0;
}

static struct console sunsab_console = {
	.name	=	"ttyS",
	.write	=	sunsab_console_write,
	.device	=	uart_console_device,
	.setup	=	sunsab_console_setup,
	.flags	=	CON_PRINTBUFFER,
	.index	=	-1,
	.data	=	&sunsab_reg,
};

static inline struct console *SUNSAB_CONSOLE(void)
{
	return &sunsab_console;
}
#else
#define SUNSAB_CONSOLE()	(NULL)
#define sunsab_console_init()	do { } while (0)
#endif

static int sunsab_init_one(struct uart_sunsab_port *up,
				     struct platform_device *op,
				     unsigned long offset,
				     int line)
{
	up->port.line = line;
	up->port.dev = &op->dev;

	up->port.mapbase = op->resource[0].start + offset;
	up->port.membase = of_ioremap(&op->resource[0], offset,
				      sizeof(union sab82532_async_regs),
				      "sab");
	if (!up->port.membase)
		return -ENOMEM;
	up->regs = (union sab82532_async_regs __iomem *) up->port.membase;

	up->port.irq = op->archdata.irqs[0];

	up->port.fifosize = SAB82532_XMIT_FIFO_SIZE;
	up->port.iotype = UPIO_MEM;
	up->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_SUNSAB_CONSOLE);

	writeb(SAB82532_IPC_IC_ACT_LOW, &up->regs->w.ipc);

	up->port.ops = &sunsab_pops;
	up->port.type = PORT_SUNSAB;
	up->port.uartclk = SAB_BASE_BAUD;

	up->type = readb(&up->regs->r.vstr) & 0x0f;
	writeb(~((1 << 1) | (1 << 2) | (1 << 4)), &up->regs->w.pcr);
	writeb(0xff, &up->regs->w.pim);
	if ((up->port.line & 0x1) == 0) {
		up->pvr_dsr_bit = (1 << 0);
		up->pvr_dtr_bit = (1 << 1);
		up->gis_shift = 2;
	} else {
		up->pvr_dsr_bit = (1 << 3);
		up->pvr_dtr_bit = (1 << 2);
		up->gis_shift = 0;
	}
	up->cached_pvr = (1 << 1) | (1 << 2) | (1 << 4);
	writeb(up->cached_pvr, &up->regs->w.pvr);
	up->cached_mode = readb(&up->regs->rw.mode);
	up->cached_mode |= SAB82532_MODE_FRTS;
	writeb(up->cached_mode, &up->regs->rw.mode);
	up->cached_mode |= SAB82532_MODE_RTS;
	writeb(up->cached_mode, &up->regs->rw.mode);

	up->tec_timeout = SAB82532_MAX_TEC_TIMEOUT;
	up->cec_timeout = SAB82532_MAX_CEC_TIMEOUT;

	return 0;
}

static int sab_probe(struct platform_device *op)
{
	static int inst;
	struct uart_sunsab_port *up;
	int err;

	up = &sunsab_ports[inst * 2];

	err = sunsab_init_one(&up[0], op,
			      0,
			      (inst * 2) + 0);
	if (err)
		goto out;

	err = sunsab_init_one(&up[1], op,
			      sizeof(union sab82532_async_regs),
			      (inst * 2) + 1);
	if (err)
		goto out1;

	sunserial_console_match(SUNSAB_CONSOLE(), op->dev.of_node,
				&sunsab_reg, up[0].port.line,
				false);

	sunserial_console_match(SUNSAB_CONSOLE(), op->dev.of_node,
				&sunsab_reg, up[1].port.line,
				false);

	err = uart_add_one_port(&sunsab_reg, &up[0].port);
	if (err)
		goto out2;

	err = uart_add_one_port(&sunsab_reg, &up[1].port);
	if (err)
		goto out3;

	platform_set_drvdata(op, &up[0]);

	inst++;

	return 0;

out3:
	uart_remove_one_port(&sunsab_reg, &up[0].port);
out2:
	of_iounmap(&op->resource[0],
		   up[1].port.membase,
		   sizeof(union sab82532_async_regs));
out1:
	of_iounmap(&op->resource[0],
		   up[0].port.membase,
		   sizeof(union sab82532_async_regs));
out:
	return err;
}

static int sab_remove(struct platform_device *op)
{
	struct uart_sunsab_port *up = platform_get_drvdata(op);

	uart_remove_one_port(&sunsab_reg, &up[1].port);
	uart_remove_one_port(&sunsab_reg, &up[0].port);
	of_iounmap(&op->resource[0],
		   up[1].port.membase,
		   sizeof(union sab82532_async_regs));
	of_iounmap(&op->resource[0],
		   up[0].port.membase,
		   sizeof(union sab82532_async_regs));

	return 0;
}

static const struct of_device_id sab_match[] = {
	{
		.name = "se",
	},
	{
		.name = "serial",
		.compatible = "sab82532",
	},
	{},
};
MODULE_DEVICE_TABLE(of, sab_match);

static struct platform_driver sab_driver = {
	.driver = {
		.name = "sab",
		.of_match_table = sab_match,
	},
	.probe		= sab_probe,
	.remove		= sab_remove,
};

static int __init sunsab_init(void)
{
	struct device_node *dp;
	int err;
	int num_channels = 0;

	for_each_node_by_name(dp, "se")
		num_channels += 2;
	for_each_node_by_name(dp, "serial") {
		if (of_device_is_compatible(dp, "sab82532"))
			num_channels += 2;
	}

	if (num_channels) {
		sunsab_ports = kcalloc(num_channels,
				       sizeof(struct uart_sunsab_port),
				       GFP_KERNEL);
		if (!sunsab_ports)
			return -ENOMEM;

		err = sunserial_register_minors(&sunsab_reg, num_channels);
		if (err) {
			kfree(sunsab_ports);
			sunsab_ports = NULL;

			return err;
		}
	}

	return platform_driver_register(&sab_driver);
}

static void __exit sunsab_exit(void)
{
	platform_driver_unregister(&sab_driver);
	if (sunsab_reg.nr) {
		sunserial_unregister_minors(&sunsab_reg, sunsab_reg.nr);
	}

	kfree(sunsab_ports);
	sunsab_ports = NULL;
}

module_init(sunsab_init);
module_exit(sunsab_exit);

MODULE_AUTHOR("Eddie C. Dost and David S. Miller");
MODULE_DESCRIPTION("Sun SAB82532 serial port driver");
MODULE_LICENSE("GPL");