[PATCH] Altix console driver

From: Patrick Gefre <pfg@sgi.com>

Add ia64 Altix serial console driver.

MAINTAINERS

@@ -1753,6 +1753,12 @@ L: 	selinux@tycho.nsa.gov (general discussion)
 W:	http://www.nsa.gov/selinux
 S:	Supported
 
+SGI SN-IA64 (Altix) SERIAL CONSOLE DRIVER
+P:	Pat Gefre
+M:	pfg@sgi.com
+L:	linux-ia64@vger.kernel.org
+S:	Supported
+
 SGI VISUAL WORKSTATION 320 AND 540
 P:	Andrey Panin
 M:	pazke@donpac.ru

drivers/char/Kconfig

@@ -373,6 +373,22 @@ config AU1000_UART
 	  If you have an Alchemy AU1000 processor (MIPS based) and you want
 	  to use serial ports, say Y.  Otherwise, say N.
 
+config SGI_L1_SERIAL
+	bool "SGI Altix L1 serial support"
+	depends on SERIAL_NONSTANDARD && IA64
+	help
+	  If you have an SGI Altix and you want to use the serial port
+	  connected to the system controller (you want this!), say Y.
+	  Otherwise, say N.
+
+config SGI_L1_SERIAL_CONSOLE
+	bool "SGI Altix L1 serial console support"
+	depends on SGI_L1_SERIAL
+	help
+	  If you have an SGI Altix and you would like to use the system
+	  controller serial port as your console (you want this!),
+	  say Y.  Otherwise, say N.
+
 config AU1000_SERIAL_CONSOLE
 	bool "Enable Au1000 serial console"
 	depends on AU1000_UART

drivers/char/Makefile

@@ -42,6 +42,7 @@ obj-$(CONFIG_RIO)		+= rio/ generic_serial.o
 obj-$(CONFIG_SH_SCI)		+= sh-sci.o generic_serial.o
 obj-$(CONFIG_HVC_CONSOLE)	+= hvc_console.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
+obj-$(CONFIG_SGI_L1_SERIAL)	+= sn_serial.o
 
 obj-$(CONFIG_PRINTER) += lp.o
 obj-$(CONFIG_TIPAR) += tipar.o

drivers/char/sn_serial.c

+/*
+ * C-Brick Serial Port (and console) driver for SGI Altix machines.
+ *
+ * This driver is NOT suitable for talking to the l1-controller for
+ * anything other than 'console activities' --- please use the l1
+ * driver for that.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2003 Silicon Graphics, Inc. All rights reserved.
+ */
+
+#include <linux/config.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/serial.h>
+#include <linux/console.h>
+#include <linux/module.h>
+#include <linux/sysrq.h>
+#include <linux/circ_buf.h>
+#include <linux/serial_reg.h>
+#include <asm/sn/sn_sal.h>
+#include <asm/sn/pci/pciio.h>		/* this is needed for get_console_nasid */
+#include <asm/sn/simulator.h>
+#include <asm/sn/sn2/sn_private.h>
+
+#if defined(CONFIG_SGI_L1_SERIAL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+static char sysrq_serial_str[] = "\eSYS";
+static char *sysrq_serial_ptr = sysrq_serial_str;
+static unsigned long sysrq_requested;
+#endif /* CONFIG_SGI_L1_SERIAL_CONSOLE && CONFIG_MAGIC_SYSRQ */
+
+/* minor device number */
+#define SN_SAL_MINOR 64
+
+/* number of characters left in xmit buffer before we ask for more */
+#define WAKEUP_CHARS 128
+
+/* number of characters we can transmit to the SAL console at a time */
+#define SN_SAL_MAX_CHARS 120
+
+#define SN_SAL_EVENT_WRITE_WAKEUP 0
+
+/* 64K, when we're asynch, it must be at least printk's LOG_BUF_LEN to
+ * avoid losing chars, (always has to be a power of 2) */
+#define SN_SAL_BUFFER_SIZE (64 * (1 << 10))
+
+#define SN_SAL_UART_FIFO_DEPTH 16
+#define SN_SAL_UART_FIFO_SPEED_CPS 9600/10
+
+/* we don't kmalloc/get_free_page these as we want them available
+ * before either of those are initialized */
+static char sn_xmit_buff_mem[SN_SAL_BUFFER_SIZE];
+
+struct volatile_circ_buf {
+	char *cb_buf;
+	int cb_head;
+	int cb_tail;
+};
+
+static struct volatile_circ_buf xmit = { .cb_buf = sn_xmit_buff_mem };
+static char sn_tmp_buffer[SN_SAL_BUFFER_SIZE];
+
+static struct tty_struct *sn_sal_tty;
+
+static struct timer_list sn_sal_timer;
+static int sn_sal_event; /* event type for task queue */
+
+static int sn_sal_is_asynch;
+static int sn_sal_irq;
+static spinlock_t sn_sal_lock = SPIN_LOCK_UNLOCKED;
+static int sn_total_tx_count;
+static int sn_total_rx_count;
+
+static void sn_sal_tasklet_action(unsigned long data);
+static DECLARE_TASKLET(sn_sal_tasklet, sn_sal_tasklet_action, 0);
+
+static unsigned long sn_interrupt_timeout;
+
+extern u64 master_node_bedrock_address;
+
+static int sn_debug_printf(const char *fmt, ...);
+
+#undef DEBUG
+#ifdef DEBUG
+#define DPRINTF(x...) sn_debug_printf(x)
+#else
+#define DPRINTF(x...) do { } while (0)
+#endif
+
+struct sn_sal_ops {
+	int (*sal_puts)(const char *s, int len);
+	int (*sal_getc)(void);
+	int (*sal_input_pending)(void);
+	void (*sal_wakeup_transmit)(void);
+};
+
+/* This is the pointer used. It is assigned to point to one of
+ * the tables below.
+ */
+static struct sn_sal_ops *sn_func;
+
+/* Prototypes */
+static void __init sn_sal_serial_console_init(void);
+static int snt_hw_puts(const char *, int);
+static int snt_poll_getc(void);
+static int snt_poll_input_pending(void);
+static int snt_sim_puts(const char *, int);
+static int snt_sim_getc(void);
+static int snt_sim_input_pending(void);
+static int snt_intr_getc(void);
+static int snt_intr_input_pending(void);
+static void sn_intr_transmit_chars(void);
+
+/* A table for polling */
+static struct sn_sal_ops poll_ops = {
+	.sal_puts		= snt_hw_puts,
+	.sal_getc		= snt_poll_getc,
+	.sal_input_pending	= snt_poll_input_pending
+};
+
+/* A table for the simulator */
+static struct sn_sal_ops sim_ops = {
+	.sal_puts		= snt_sim_puts,
+	.sal_getc		= snt_sim_getc,
+	.sal_input_pending	= snt_sim_input_pending
+};
+
+/* A table for interrupts enabled */
+static struct sn_sal_ops intr_ops = {
+	.sal_puts		= snt_hw_puts,
+	.sal_getc		= snt_intr_getc,
+	.sal_input_pending	= snt_intr_input_pending,
+	.sal_wakeup_transmit	= sn_intr_transmit_chars
+};
+
+
+/* the console does output in two distinctly different ways:
+ * synchronous and asynchronous (buffered).  initally, early_printk
+ * does synchronous output.  any data written goes directly to the SAL
+ * to be output (incidentally, it is internally buffered by the SAL)
+ * after interrupts and timers are initialized and available for use,
+ * the console init code switches to asynchronous output.  this is
+ * also the earliest opportunity to begin polling for console input.
+ * after console initialization, console output and tty (serial port)
+ * output is buffered and sent to the SAL asynchronously (either by
+ * timer callback or by UART interrupt) */
+
+
+/* routines for running the console in polling mode */
+
+static int
+snt_hw_puts(const char *s, int len)
+{
+	/* looking at the PROM source code, putb calls the flush
+	 * routine, so if we send characters in FIFO sized chunks, it
+	 * should go out by the next time the timer gets called */
+	return ia64_sn_console_putb(s, len);
+}
+
+static int
+snt_poll_getc(void)
+{
+	int ch;
+	ia64_sn_console_getc(&ch);
+	return ch;
+}
+
+static int
+snt_poll_input_pending(void)
+{
+	int status, input;
+
+	status = ia64_sn_console_check(&input);
+	return !status && input;
+}
+
+
+/* routines for running the console on the simulator */
+
+static int
+snt_sim_puts(const char *str, int count)
+{
+	int counter = count;
+
+#ifdef FLAG_DIRECT_CONSOLE_WRITES
+	/* This is an easy way to pre-pend the output to know whether the output
+	 * was done via sal or directly */
+	writeb('[', master_node_bedrock_address + (UART_TX << 3));
+	writeb('+', master_node_bedrock_address + (UART_TX << 3));
+	writeb(']', master_node_bedrock_address + (UART_TX << 3));
+	writeb(' ', master_node_bedrock_address + (UART_TX << 3));
+#endif /* FLAG_DIRECT_CONSOLE_WRITES */
+	while (counter > 0) {
+		writeb(*str, master_node_bedrock_address + (UART_TX << 3));
+		counter--;
+		str++;
+	}
+
+	return count;
+}
+
+static int
+snt_sim_getc(void)
+{
+	return readb(master_node_bedrock_address + (UART_RX << 3));
+}
+
+static int
+snt_sim_input_pending(void)
+{
+	return readb(master_node_bedrock_address + (UART_LSR << 3)) & UART_LSR_DR;
+}
+
+
+/* routines for an interrupt driven console (normal) */
+
+static int
+snt_intr_getc(void)
+{
+	return ia64_sn_console_readc();
+}
+
+static int
+snt_intr_input_pending(void)
+{
+	return ia64_sn_console_intr_status() & SAL_CONSOLE_INTR_RECV;
+}
+
+/* The early printk (possible setup) and function call */
+
+void
+early_printk_sn_sal(const char *s, unsigned count)
+{
+	extern void early_sn_setup(void);
+
+	if (!sn_func) {
+		if (IS_RUNNING_ON_SIMULATOR())
+			sn_func = &sim_ops;
+		else
+			sn_func = &poll_ops;
+
+		early_sn_setup();
+	}
+	sn_func->sal_puts(s, count);
+}
+
+/* this is as "close to the metal" as we can get, used when the driver
+ * itself may be broken */
+static int
+sn_debug_printf(const char *fmt, ...)
+{
+	static char printk_buf[1024];
+	int printed_len;
+	va_list args;
+
+	va_start(args, fmt);
+	printed_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args);
+	early_printk_sn_sal(printk_buf, printed_len);
+	va_end(args);
+	return printed_len;
+}
+
+/*
+ * Interrupt handling routines.
+ */
+
+static void
+sn_sal_sched_event(int event)
+{
+	sn_sal_event |= (1 << event);
+	tasklet_schedule(&sn_sal_tasklet);
+}
+
+/* sn_receive_chars can be called before sn_sal_tty is initialized.  in
+ * that case, its only use is to trigger sysrq and kdb */
+static void
+sn_receive_chars(struct pt_regs *regs, unsigned long *flags)
+{
+	int ch;
+
+	while (sn_func->sal_input_pending()) {
+		ch = sn_func->sal_getc();
+		if (ch < 0) {
+			printk(KERN_ERR "sn_serial: An error occured while "
+			       "obtaining data from the console (0x%0x)\n", ch);
+			break;
+		}
+#if defined(CONFIG_SGI_L1_SERIAL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+		if (sysrq_requested) {
+			unsigned long sysrq_timeout = sysrq_requested + HZ*5;
+
+			sysrq_requested = 0;
+			if (ch && time_before(jiffies, sysrq_timeout)) {
+				spin_unlock_irqrestore(&sn_sal_lock, *flags);
+				handle_sysrq(ch, regs, NULL);
+				spin_lock_irqsave(&sn_sal_lock, *flags);
+				/* don't record this char */
+				continue;
+			}
+		}
+		if (ch == *sysrq_serial_ptr) {
+			if (!(*++sysrq_serial_ptr)) {
+				sysrq_requested = jiffies;
+				sysrq_serial_ptr = sysrq_serial_str;
+			}
+		}
+		else
+			sysrq_serial_ptr = sysrq_serial_str;
+#endif /* CONFIG_SGI_L1_SERIAL_CONSOLE && CONFIG_MAGIC_SYSRQ */
+
+		/* record the character to pass up to the tty layer */
+		if (sn_sal_tty) {
+			*sn_sal_tty->flip.char_buf_ptr = ch;
+			sn_sal_tty->flip.char_buf_ptr++;
+			sn_sal_tty->flip.count++;
+			if (sn_sal_tty->flip.count == TTY_FLIPBUF_SIZE)
+				break;
+		}
+		sn_total_rx_count++;
+	}
+
+	if (sn_sal_tty)
+		tty_flip_buffer_push((struct tty_struct *)sn_sal_tty);
+}
+
+
+/* synch_flush_xmit must be called with sn_sal_lock */
+static void
+synch_flush_xmit(void)
+{
+	int xmit_count, tail, head, loops, ii;
+	int result;
+	char *start;
+
+	if (xmit.cb_head == xmit.cb_tail)
+		return; /* Nothing to do. */
+
+	head = xmit.cb_head;
+	tail = xmit.cb_tail;
+	start = &xmit.cb_buf[tail];
+
+	/* twice around gets the tail to the end of the buffer and
+	 * then to the head, if needed */
+	loops = (head < tail) ? 2 : 1;
+
+	for (ii = 0; ii < loops; ii++) {
+		xmit_count = (head < tail) ?  (SN_SAL_BUFFER_SIZE - tail) : (head - tail);
+
+		if (xmit_count > 0) {
+			result = sn_func->sal_puts((char *)start, xmit_count);
+			if (!result)
+				sn_debug_printf("\n*** synch_flush_xmit failed to flush\n");
+			if (result > 0) {
+				xmit_count -= result;
+				sn_total_tx_count += result;
+				tail += result;
+				tail &= SN_SAL_BUFFER_SIZE - 1;
+				xmit.cb_tail = tail;
+				start = (char *)&xmit.cb_buf[tail];
+			}
+		}
+	}
+}
+
+/* must be called with a lock protecting the circular buffer and
+ * sn_sal_tty */
+static void
+sn_poll_transmit_chars(void)
+{
+	int xmit_count, tail, head;
+	int result;
+	char *start;
+
+	BUG_ON(!sn_sal_is_asynch);
+
+	if (xmit.cb_head == xmit.cb_tail ||
+	    (sn_sal_tty && (sn_sal_tty->stopped || sn_sal_tty->hw_stopped))) {
+		/* Nothing to do. */
+		return;
+	}
+
+	head = xmit.cb_head;
+	tail = xmit.cb_tail;
+	start = &xmit.cb_buf[tail];
+
+	xmit_count = (head < tail) ?  (SN_SAL_BUFFER_SIZE - tail) : (head - tail);
+
+	if (xmit_count == 0)
+		sn_debug_printf("\n*** empty xmit_count\n");
+
+	/* use the ops, as we could be on the simulator */
+	result = sn_func->sal_puts((char *)start, xmit_count);
+	if (!result)
+		sn_debug_printf("\n*** error in synchronous sal_puts\n");
+	/* XXX chadt clean this up */
+	if (result > 0) {
+		xmit_count -= result;
+		sn_total_tx_count += result;
+		tail += result;
+		tail &= SN_SAL_BUFFER_SIZE - 1;
+		xmit.cb_tail = tail;
+		start = &xmit.cb_buf[tail];
+	}
+
+	/* if there's few enough characters left in the xmit buffer
+	 * that we could stand for the upper layer to send us some
+	 * more, ask for it. */
+	if (sn_sal_tty)
+		if (CIRC_CNT(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE) < WAKEUP_CHARS)
+			sn_sal_sched_event(SN_SAL_EVENT_WRITE_WAKEUP);
+}
+
+
+/* must be called with a lock protecting the circular buffer and
+ * sn_sal_tty */
+static void
+sn_intr_transmit_chars(void)
+{
+	int xmit_count, tail, head, loops, ii;
+	int result;
+	char *start;
+
+	BUG_ON(!sn_sal_is_asynch);
+
+	if (xmit.cb_head == xmit.cb_tail ||
+	    (sn_sal_tty && (sn_sal_tty->stopped || sn_sal_tty->hw_stopped))) {
+		/* Nothing to do. */
+		return;
+	}
+
+	head = xmit.cb_head;
+	tail = xmit.cb_tail;
+	start = &xmit.cb_buf[tail];
+
+	/* twice around gets the tail to the end of the buffer and
+	 * then to the head, if needed */
+	loops = (head < tail) ? 2 : 1;
+
+	for (ii = 0; ii < loops; ii++) {
+		xmit_count = (head < tail) ?
+			(SN_SAL_BUFFER_SIZE - tail) : (head - tail);
+
+		if (xmit_count > 0) {
+			result = ia64_sn_console_xmit_chars((char *)start, xmit_count);
+#ifdef DEBUG
+			if (!result)
+				sn_debug_printf("`");
+#endif
+			if (result > 0) {
+				xmit_count -= result;
+				sn_total_tx_count += result;
+				tail += result;
+				tail &= SN_SAL_BUFFER_SIZE - 1;
+				xmit.cb_tail = tail;
+				start = &xmit.cb_buf[tail];
+			}
+		}
+	}
+
+	/* if there's few enough characters left in the xmit buffer
+	 * that we could stand for the upper layer to send us some
+	 * more, ask for it. */
+	if (sn_sal_tty)
+		if (CIRC_CNT(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE) < WAKEUP_CHARS)
+			sn_sal_sched_event(SN_SAL_EVENT_WRITE_WAKEUP);
+}
+
+
+static irqreturn_t
+sn_sal_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	/* this call is necessary to pass the interrupt back to the
+	 * SAL, since it doesn't intercept the UART interrupts
+	 * itself */
+	int status = ia64_sn_console_intr_status();
+	unsigned long flags;
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	if (status & SAL_CONSOLE_INTR_RECV)
+		sn_receive_chars(regs, &flags);
+	if (status & SAL_CONSOLE_INTR_XMIT)
+		sn_intr_transmit_chars();
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+	return IRQ_HANDLED;
+}
+
+
+/* returns the console irq if interrupt is successfully registered,
+ * else 0 */
+static int
+sn_sal_connect_interrupt(void)
+{
+	cpuid_t intr_cpuid;
+	unsigned int intr_cpuloc;
+	nasid_t console_nasid;
+	unsigned int console_irq;
+	int result;
+
+	console_nasid = ia64_sn_get_console_nasid();
+	intr_cpuid = NODEPDA(NASID_TO_COMPACT_NODEID(console_nasid))->node_first_cpu;
+	intr_cpuloc = cpu_physical_id(intr_cpuid);
+	console_irq = CPU_VECTOR_TO_IRQ(intr_cpuloc, SGI_UART_VECTOR);
+
+	result = intr_connect_level(intr_cpuid, SGI_UART_VECTOR);
+	BUG_ON(result != SGI_UART_VECTOR);
+
+	result = request_irq(console_irq, sn_sal_interrupt, SA_INTERRUPT,  "SAL console driver", &sn_sal_tty);
+	if (result >= 0)
+		return console_irq;
+
+	printk(KERN_INFO "sn_serial: console proceeding in polled mode\n");
+	return 0;
+}
+
+static void
+sn_sal_tasklet_action(unsigned long data)
+{
+	unsigned long flags;
+
+	if (sn_sal_tty) {
+		spin_lock_irqsave(&sn_sal_lock, flags);
+		if (sn_sal_tty) {
+			if (test_and_clear_bit(SN_SAL_EVENT_WRITE_WAKEUP, &sn_sal_event)) {
+				if ((sn_sal_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) && sn_sal_tty->ldisc.write_wakeup)
+					(sn_sal_tty->ldisc.write_wakeup)((struct tty_struct *)sn_sal_tty);
+				wake_up_interruptible((wait_queue_head_t *)&sn_sal_tty->write_wait);
+			}
+		}
+		spin_unlock_irqrestore(&sn_sal_lock, flags);
+	}
+}
+
+
+/*
+ * This function handles polled mode.
+ */
+static void
+sn_sal_timer_poll(unsigned long dummy)
+{
+	unsigned long flags;
+
+	if (!sn_sal_irq) {
+		spin_lock_irqsave(&sn_sal_lock, flags);
+		sn_receive_chars(NULL, &flags);
+		sn_poll_transmit_chars();
+		spin_unlock_irqrestore(&sn_sal_lock, flags);
+		mod_timer(&sn_sal_timer, jiffies + sn_interrupt_timeout);
+	}
+}
+
+
+/*
+ * User-level console routines
+ */
+
+static int
+sn_sal_open(struct tty_struct *tty, struct file *filp)
+{
+	unsigned long flags;
+
+	DPRINTF("sn_sal_open: sn_sal_tty = %p, tty = %p, filp = %p\n",
+		sn_sal_tty, tty, filp);
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	if (!sn_sal_tty)
+		sn_sal_tty = tty;
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+
+	return 0;
+}
+
+
+/* We're keeping all our resources.  We're keeping interrupts turned
+ * on.  Maybe just let the tty layer finish its stuff...? GMSH
+ */
+static void
+sn_sal_close(struct tty_struct *tty, struct file * filp)
+{
+	if (tty->count == 1) {
+		unsigned long flags;
+		tty->closing = 1;
+		if (tty->driver->flush_buffer)
+			tty->driver->flush_buffer(tty);
+		if (tty->ldisc.flush_buffer)
+			tty->ldisc.flush_buffer(tty);
+		tty->closing = 0;
+		spin_lock_irqsave(&sn_sal_lock, flags);
+		sn_sal_tty = NULL;
+		spin_unlock_irqrestore(&sn_sal_lock, flags);
+	}
+}
+
+
+static int
+sn_sal_write(struct tty_struct *tty, int from_user,
+	     const unsigned char *buf, int count)
+{
+	int c, ret = 0;
+	unsigned long flags;
+
+	if (from_user) {
+		while (1) {
+			int c1;
+			c = CIRC_SPACE_TO_END(xmit.cb_head, xmit.cb_tail,
+					      SN_SAL_BUFFER_SIZE);
+
+			if (count < c)
+				c = count;
+			if (c <= 0)
+				break;
+
+			c -= copy_from_user(sn_tmp_buffer, buf, c);
+			if (!c) {
+				if (!ret)
+					ret = -EFAULT;
+				break;
+			}
+
+			/* Turn off interrupts and see if the xmit buffer has
+			 * moved since the last time we looked.
+			 */
+			spin_lock_irqsave(&sn_sal_lock, flags);
+			c1 = CIRC_SPACE_TO_END(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE);
+
+			if (c1 < c)
+				c = c1;
+
+			memcpy(xmit.cb_buf + xmit.cb_head, sn_tmp_buffer, c);
+			xmit.cb_head = ((xmit.cb_head + c) & (SN_SAL_BUFFER_SIZE - 1));
+			spin_unlock_irqrestore(&sn_sal_lock, flags);
+
+			buf += c;
+			count -= c;
+			ret += c;
+		}
+	}
+	else {
+		/* The buffer passed in isn't coming from userland,
+		 * so cut out the middleman (sn_tmp_buffer).
+		 */
+		spin_lock_irqsave(&sn_sal_lock, flags);
+		while (1) {
+			c = CIRC_SPACE_TO_END(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE);
+
+			if (count < c)
+				c = count;
+			if (c <= 0) {
+				break;
+			}
+			memcpy(xmit.cb_buf + xmit.cb_head, buf, c);
+			xmit.cb_head = ((xmit.cb_head + c) & (SN_SAL_BUFFER_SIZE - 1));
+			buf += c;
+			count -= c;
+			ret += c;
+		}
+		spin_unlock_irqrestore(&sn_sal_lock, flags);
+	}
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	if (xmit.cb_head != xmit.cb_tail && !(tty && (tty->stopped || tty->hw_stopped)))
+		if (sn_func->sal_wakeup_transmit)
+			sn_func->sal_wakeup_transmit();
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+
+	return ret;
+}
+
+
+static void
+sn_sal_put_char(struct tty_struct *tty, unsigned char ch)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	if (CIRC_SPACE(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE) != 0) {
+		xmit.cb_buf[xmit.cb_head] = ch;
+		xmit.cb_head = (xmit.cb_head + 1) & (SN_SAL_BUFFER_SIZE-1);
+		if ( sn_func->sal_wakeup_transmit )
+			sn_func->sal_wakeup_transmit();
+	}
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+}
+
+
+static void
+sn_sal_flush_chars(struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	if (CIRC_CNT(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE))
+		if (sn_func->sal_wakeup_transmit)
+			sn_func->sal_wakeup_transmit();
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+}
+
+
+static int
+sn_sal_write_room(struct tty_struct *tty)
+{
+	unsigned long flags;
+	int space;
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	space = CIRC_SPACE(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE);
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+	return space;
+}
+
+
+static int
+sn_sal_chars_in_buffer(struct tty_struct *tty)
+{
+	unsigned long flags;
+	int space;
+
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	space = CIRC_CNT(xmit.cb_head, xmit.cb_tail, SN_SAL_BUFFER_SIZE);
+	DPRINTF("<%d>", space);
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+	return space;
+}
+
+
+static void
+sn_sal_flush_buffer(struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	/* drop everything */
+	spin_lock_irqsave(&sn_sal_lock, flags);
+	xmit.cb_head = xmit.cb_tail = 0;
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+
+	/* wake up tty level */
+	wake_up_interruptible(&tty->write_wait);
+	if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) && tty->ldisc.write_wakeup)
+		(tty->ldisc.write_wakeup)(tty);
+}
+
+
+static void
+sn_sal_hangup(struct tty_struct *tty)
+{
+	sn_sal_flush_buffer(tty);
+}
+
+
+static void
+sn_sal_wait_until_sent(struct tty_struct *tty, int timeout)
+{
+	/* this is SAL's problem */
+	DPRINTF("<sn_serial: should wait until sent>");
+}
+
+
+/*
+ * sn_sal_read_proc
+ *
+ * Console /proc interface
+ */
+
+static int
+sn_sal_read_proc(char *page, char **start, off_t off, int count,
+		   int *eof, void *data)
+{
+	int len = 0;
+	off_t	begin = 0;
+
+	len += sprintf(page, "sn_serial: nasid:%d irq:%d tx:%d rx:%d\n",
+		       get_console_nasid(), sn_sal_irq,
+		       sn_total_tx_count, sn_total_rx_count);
+	*eof = 1;
+
+	if (off >= len+begin)
+		return 0;
+	*start = page + (off-begin);
+
+	return count < begin+len-off ? count : begin+len-off;
+}
+
+
+static struct tty_operations sn_sal_driver_ops = {
+	.open		 = sn_sal_open,
+	.close		 = sn_sal_close,
+	.write		 = sn_sal_write,
+	.put_char	 = sn_sal_put_char,
+	.flush_chars	 = sn_sal_flush_chars,
+	.write_room	 = sn_sal_write_room,
+	.chars_in_buffer = sn_sal_chars_in_buffer,
+	.hangup		 = sn_sal_hangup,
+	.wait_until_sent = sn_sal_wait_until_sent,
+	.read_proc	 = sn_sal_read_proc,
+};
+static struct tty_driver *sn_sal_driver;
+
+/* sn_sal_init wishlist:
+ * - allocate sn_tmp_buffer
+ * - fix up the tty_driver struct
+ * - turn on receive interrupts
+ * - do any termios twiddling once and for all
+ */
+
+/*
+ * Boot-time initialization code
+ */
+
+static void __init
+sn_sal_switch_to_asynch(void)
+{
+	unsigned long flags;
+
+	sn_debug_printf("sn_serial: about to switch to asynchronous console\n");
+
+	/* without early_printk, we may be invoked late enough to race
+	 * with other cpus doing console IO at this point, however
+	 * console interrupts will never be enabled */
+	spin_lock_irqsave(&sn_sal_lock, flags);
+
+	/* early_printk invocation may have done this for us */
+	if (!sn_func) {
+		if (IS_RUNNING_ON_SIMULATOR())
+			sn_func = &sim_ops;
+		else
+			sn_func = &poll_ops;
+	}
+
+	/* we can't turn on the console interrupt (as request_irq
+	 * calls kmalloc, which isn't set up yet), so we rely on a
+	 * timer to poll for input and push data from the console
+	 * buffer.
+	 */
+	init_timer(&sn_sal_timer);
+	sn_sal_timer.function = sn_sal_timer_poll;
+
+	if (IS_RUNNING_ON_SIMULATOR())
+		sn_interrupt_timeout = 6;
+	else {
+		/* 960cps / 16 char FIFO = 60HZ
+		 * HZ / (SN_SAL_FIFO_SPEED_CPS / SN_SAL_FIFO_DEPTH) */
+		sn_interrupt_timeout = HZ * SN_SAL_UART_FIFO_DEPTH / SN_SAL_UART_FIFO_SPEED_CPS;
+	}
+	mod_timer(&sn_sal_timer, jiffies + sn_interrupt_timeout);
+
+	sn_sal_is_asynch = 1;
+	spin_unlock_irqrestore(&sn_sal_lock, flags);
+}
+
+static void __init
+sn_sal_switch_to_interrupts(void)
+{
+	int irq;
+
+	sn_debug_printf("sn_serial: switching to interrupt driven console\n");
+
+	irq = sn_sal_connect_interrupt();
+	if (irq) {
+		unsigned long flags;
+		spin_lock_irqsave(&sn_sal_lock, flags);
+
+		/* sn_sal_irq is a global variable.  When it's set to
+		 * a non-zero value, we stop polling for input (since
+		 * interrupts should now be enabled). */
+		sn_sal_irq = irq;
+		sn_func = &intr_ops;
+
+		/* turn on receive interrupts */
+		ia64_sn_console_intr_enable(SAL_CONSOLE_INTR_RECV);
+		spin_unlock_irqrestore(&sn_sal_lock, flags);
+	}
+}
+
+static int __init
+sn_sal_module_init(void)
+{
+	int retval;
+
+	printk("sn_serial: sn_sal_module_init\n");
+
+	if (!ia64_platform_is("sn2"))
+		return -ENODEV;
+
+	sn_sal_driver = alloc_tty_driver(1);
+	if ( !sn_sal_driver )
+		return -ENOMEM;
+
+	sn_sal_driver->owner = THIS_MODULE;
+	sn_sal_driver->driver_name = "sn_serial";
+	sn_sal_driver->name = "ttyS";
+	sn_sal_driver->major = TTY_MAJOR;
+	sn_sal_driver->minor_start = SN_SAL_MINOR;
+	sn_sal_driver->type = TTY_DRIVER_TYPE_SERIAL;
+	sn_sal_driver->subtype = SERIAL_TYPE_NORMAL;
+	sn_sal_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_NO_DEVFS;
+
+	tty_set_operations(sn_sal_driver, &sn_sal_driver_ops);
+
+	/* when this driver is compiled in, the console initialization
+	 * will have already switched us into asynchronous operation
+	 * before we get here through the module initcalls */
+	if (!sn_sal_is_asynch)
+		sn_sal_switch_to_asynch();
+
+	/* at this point (module_init) we can try to turn on interrupts */
+	if (!IS_RUNNING_ON_SIMULATOR())
+	    sn_sal_switch_to_interrupts();
+
+	sn_sal_driver->init_termios = tty_std_termios;
+	sn_sal_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
+
+	if ((retval = tty_register_driver(sn_sal_driver))) {
+		printk(KERN_ERR "sn_serial: Unable to register tty driver\n");
+		return retval;
+	}
+#ifdef CONFIG_SGI_L1_SERIAL_CONSOLE
+	sn_sal_serial_console_init();
+#endif	/* CONFIG_SGI_L1_SERIAL_CONSOLE */
+	return 0;
+}
+
+
+static void __exit
+sn_sal_module_exit(void)
+{
+	del_timer_sync(&sn_sal_timer);
+	tty_unregister_driver(sn_sal_driver);
+	put_tty_driver(sn_sal_driver);
+}
+
+module_init(sn_sal_module_init);
+module_exit(sn_sal_module_exit);
+
+/*
+ * Kernel console definitions
+ */
+
+#ifdef CONFIG_SGI_L1_SERIAL_CONSOLE
+/*
+ * Print a string to the SAL console.  The console_lock must be held
+ * when we get here.
+ */
+static void
+sn_sal_console_write(struct console *co, const char *s, unsigned count)
+{
+	unsigned long flags;
+
+	BUG_ON(!sn_sal_is_asynch);
+
+	/* somebody really wants this output, might be an
+	 * oops, kdb, panic, etc.  make sure they get it. */
+	if (spin_is_locked(&sn_sal_lock)) {
+		synch_flush_xmit();
+		sn_func->sal_puts(s, count);
+	}
+	else if (in_interrupt()) {
+		spin_lock_irqsave(&sn_sal_lock, flags);
+		synch_flush_xmit();
+		spin_unlock_irqrestore(&sn_sal_lock, flags);
+		sn_func->sal_puts(s, count);
+	}
+	else
+		sn_sal_write(NULL, 0, s, count);
+}
+
+static struct tty_driver *
+sn_sal_console_device(struct console *c, int *index)
+{
+	*index = c->index;
+	return sn_sal_driver;
+}
+
+static int __init
+sn_sal_console_setup(struct console *co, char *options)
+{
+	return 0;
+}
+
+
+static struct console sal_console = {
+	.name = "ttyS",
+	.write = sn_sal_console_write,
+	.device = sn_sal_console_device,
+	.setup = sn_sal_console_setup,
+	.index = -1
+};
+
+static void __init
+sn_sal_serial_console_init(void)
+{
+	if (ia64_platform_is("sn2")) {
+		sn_sal_switch_to_asynch();
+		sn_debug_printf("sn_sal_serial_console_init : register console\n");
+		register_console(&sal_console);
+	}
+}
+
+#endif /* CONFIG_SGI_L1_SERIAL_CONSOLE */