[PATCH] ppc64: HVSI driver

This is a console driver for IBM's p5 servers; please consider it for
inclusion.  I've addressed all the comments I've received so far.
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ppc64/kernel/setup.c

@@ -517,10 +517,29 @@ static int __init set_preferred_console(void)
 					return -ENODEV;
 			}
 		}
-	} else if (strcmp(name, "vty") == 0)
-		/* pSeries LPAR virtual console */
-		return add_preferred_console("hvc", 0, NULL);
-	else if (strcmp(name, "ch-a") == 0)
+	} else if (strcmp(name, "vty") == 0) {
+ 		u32 *reg = (u32 *)get_property(prom_stdout, "reg", NULL);
+ 		char *compat = (char *)get_property(prom_stdout, "compatible", NULL);
+
+ 		if (reg && compat && (strcmp(compat, "hvterm-protocol") == 0)) {
+ 			/* Host Virtual Serial Interface */
+ 			int offset;
+ 			switch (reg[0]) {
+ 				case 0x30000000:
+ 					offset = 0;
+ 					break;
+ 				case 0x30000001:
+ 					offset = 1;
+ 					break;
+ 				default:
+ 					return -ENODEV;
+ 			}
+ 			return add_preferred_console("hvsi", offset, NULL);
+ 		} else {
+ 			/* pSeries LPAR virtual console */
+ 			return add_preferred_console("hvc", 0, NULL);
+ 		}
+	} else if (strcmp(name, "ch-a") == 0)
 		offset = 0;
 	else if (strcmp(name, "ch-b") == 0)
 		offset = 1;

drivers/char/Makefile

@@ -39,7 +39,7 @@ obj-$(CONFIG_N_HDLC)		+= n_hdlc.o
 obj-$(CONFIG_AMIGA_BUILTIN_SERIAL) += amiserial.o
 obj-$(CONFIG_SX)		+= sx.o generic_serial.o
 obj-$(CONFIG_RIO)		+= rio/ generic_serial.o
-obj-$(CONFIG_HVC_CONSOLE)	+= hvc_console.o
+obj-$(CONFIG_HVC_CONSOLE)	+= hvc_console.o hvsi.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_VIOCONS) += viocons.o
 obj-$(CONFIG_VIOTAPE)		+= viotape.o

drivers/char/hvsi.c

+/*
+ * Copyright (C) 2004 Hollis Blanchard <hollisb@us.ibm.com>, IBM
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+/* Host Virtual Serial Interface (HVSI) is a protocol between the hosted OS
+ * and the service processor on IBM pSeries servers. On these servers, there
+ * are no serial ports under the OS's control, and sometimes there is no other
+ * console available either. However, the service processor has two standard
+ * serial ports, so this over-complicated protocol allows the OS to control
+ * those ports by proxy.
+ *
+ * Besides data, the procotol supports the reading/writing of the serial
+ * port's DTR line, and the reading of the CD line. This is to allow the OS to
+ * control a modem attached to the service processor's serial port. Note that
+ * the OS cannot change the speed of the port through this protocol.
+ */
+
+/* TODO:
+ * test FSP reset
+ * add udbg support for xmon/kdb
+ */
+
+#undef DEBUG
+
+#include <linux/console.h>
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/major.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/sysrq.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <asm/hvcall.h>
+#include <asm/hvconsole.h>
+#include <asm/prom.h>
+#include <asm/uaccess.h>
+#include <asm/vio.h>
+
+#define HVSI_MAJOR	229
+#define HVSI_MINOR	128
+#define MAX_NR_HVSI_CONSOLES 4
+
+#define HVSI_TIMEOUT (5*HZ)
+#define HVSI_VERSION 1
+#define HVSI_MAX_PACKET 256
+#define HVSI_MAX_READ 16
+#define HVSI_MAX_OUTGOING_DATA 12
+#define N_OUTBUF 12
+
+/*
+ * we pass data via two 8-byte registers, so we would like our char arrays
+ * properly aligned for those loads.
+ */
+#define __ALIGNED__	__attribute__((__aligned__(sizeof(long))))
+
+struct hvsi_struct {
+	struct work_struct writer;
+	wait_queue_head_t emptyq; /* woken when outbuf is emptied */
+	wait_queue_head_t stateq; /* woken when HVSI state changes */
+	spinlock_t lock;
+	int index;
+	struct tty_struct *tty;
+	unsigned int count;
+	uint8_t throttle_buf[128];
+	uint8_t outbuf[N_OUTBUF]; /* to implement write_room and chars_in_buffer */
+	/* inbuf is for packet reassembly. leave a little room for leftovers. */
+	uint8_t inbuf[HVSI_MAX_PACKET + HVSI_MAX_READ];
+	uint8_t *inbuf_end;
+	int n_throttle;
+	int n_outbuf;
+	uint32_t vtermno;
+	uint32_t virq;
+	atomic_t seqno; /* HVSI packet sequence number */
+	uint16_t mctrl;
+	uint8_t state;  /* HVSI protocol state */
+	uint8_t flags;
+#ifdef CONFIG_MAGIC_SYSRQ
+	uint8_t sysrq;
+#endif /* CONFIG_MAGIC_SYSRQ */
+};
+static struct hvsi_struct hvsi_ports[MAX_NR_HVSI_CONSOLES];
+
+static struct tty_driver *hvsi_driver;
+static int hvsi_count;
+static int (*hvsi_wait)(struct hvsi_struct *hp, int state);
+
+enum HVSI_PROTOCOL_STATE {
+	HVSI_CLOSED,
+	HVSI_WAIT_FOR_VER_RESPONSE,
+	HVSI_WAIT_FOR_VER_QUERY,
+	HVSI_OPEN,
+	HVSI_WAIT_FOR_MCTRL_RESPONSE,
+};
+#define HVSI_CONSOLE 0x1
+
+#define VS_DATA_PACKET_HEADER           0xff
+#define VS_CONTROL_PACKET_HEADER        0xfe
+#define VS_QUERY_PACKET_HEADER          0xfd
+#define VS_QUERY_RESPONSE_PACKET_HEADER 0xfc
+
+/* control verbs */
+#define VSV_SET_MODEM_CTL    1 /* to service processor only */
+#define VSV_MODEM_CTL_UPDATE 2 /* from service processor only */
+#define VSV_CLOSE_PROTOCOL   3
+
+/* query verbs */
+#define VSV_SEND_VERSION_NUMBER 1
+#define VSV_SEND_MODEM_CTL_STATUS 2
+
+/* yes, these masks are not consecutive. */
+#define HVSI_TSDTR 0x01
+#define HVSI_TSCD  0x20
+
+struct hvsi_header {
+	uint8_t  type;
+	uint8_t  len;
+	uint16_t seqno;
+} __attribute__((packed));
+
+struct hvsi_data {
+	uint8_t  type;
+	uint8_t  len;
+	uint16_t seqno;
+	uint8_t  data[HVSI_MAX_OUTGOING_DATA];
+} __attribute__((packed));
+
+struct hvsi_control {
+	uint8_t  type;
+	uint8_t  len;
+	uint16_t seqno;
+	uint16_t verb;
+	/* optional depending on verb: */
+	uint32_t word;
+	uint32_t mask;
+} __attribute__((packed));
+
+struct hvsi_query {
+	uint8_t  type;
+	uint8_t  len;
+	uint16_t seqno;
+	uint16_t verb;
+} __attribute__((packed));
+
+struct hvsi_query_response {
+	uint8_t  type;
+	uint8_t  len;
+	uint16_t seqno;
+	uint16_t verb;
+	uint16_t query_seqno;
+	union {
+		uint8_t  version;
+		uint32_t mctrl_word;
+	} u;
+} __attribute__((packed));
+
+static inline int is_open(struct hvsi_struct *hp)
+{
+	/* if we're waiting for an mctrl then we're already open */
+	return (hp->state == HVSI_OPEN)
+			|| (hp->state == HVSI_WAIT_FOR_MCTRL_RESPONSE);
+}
+
+static inline void print_state(struct hvsi_struct *hp)
+{
+#ifdef DEBUG
+	static const char *state_names[] = {
+		"HVSI_CLOSED",
+		"HVSI_WAIT_FOR_VER_RESPONSE",
+		"HVSI_WAIT_FOR_VER_QUERY",
+		"HVSI_OPEN",
+		"HVSI_WAIT_FOR_MCTRL_RESPONSE",
+	};
+	const char *name = state_names[hp->state];
+
+	if (hp->state > (sizeof(state_names)/sizeof(char*)))
+		name = "UNKNOWN";
+
+	pr_debug("hvsi%i: state = %s\n", hp->index, name);
+#endif /* DEBUG */
+}
+
+static inline void __set_state(struct hvsi_struct *hp, int state)
+{
+	hp->state = state;
+	print_state(hp);
+	wake_up_all(&hp->stateq);
+}
+
+static inline void set_state(struct hvsi_struct *hp, int state)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&hp->lock, flags);
+	__set_state(hp, state);
+	spin_unlock_irqrestore(&hp->lock, flags);
+}
+
+static inline int len_packet(const uint8_t *packet)
+{
+	return (int)((struct hvsi_header *)packet)->len;
+}
+
+static inline int is_header(const uint8_t *packet)
+{
+	struct hvsi_header *header = (struct hvsi_header *)packet;
+	return header->type >= VS_QUERY_RESPONSE_PACKET_HEADER;
+}
+
+static inline int got_packet(const struct hvsi_struct *hp, uint8_t *packet)
+{
+	if (hp->inbuf_end < packet + sizeof(struct hvsi_header))
+		return 0; /* don't even have the packet header */
+
+	if (hp->inbuf_end < (packet + len_packet(packet)))
+		return 0; /* don't have the rest of the packet */
+
+	return 1;
+}
+
+/* shift remaining bytes in packetbuf down */
+static void compact_inbuf(struct hvsi_struct *hp, uint8_t *read_to)
+{
+	int remaining = (int)(hp->inbuf_end - read_to);
+
+	pr_debug("%s: %i chars remain\n", __FUNCTION__, remaining);
+
+	if (read_to != hp->inbuf)
+		memmove(hp->inbuf, read_to, remaining);
+
+	hp->inbuf_end = hp->inbuf + remaining;
+}
+
+#ifdef DEBUG
+#define dbg_dump_packet(packet) dump_packet(packet)
+#define dbg_dump_hex(data, len) dump_hex(data, len)
+#else
+#define dbg_dump_packet(packet) do { } while (0)
+#define dbg_dump_hex(data, len) do { } while (0)
+#endif
+
+static void dump_hex(const uint8_t *data, int len)
+{
+	int i;
+
+	printk("    ");
+	for (i=0; i < len; i++)
+		printk("%.2x", data[i]);
+
+	printk("\n    ");
+	for (i=0; i < len; i++) {
+		if (isprint(data[i]))
+			printk("%c", data[i]);
+		else
+			printk(".");
+	}
+	printk("\n");
+}
+
+static void dump_packet(uint8_t *packet)
+{
+	struct hvsi_header *header = (struct hvsi_header *)packet;
+
+	printk("type 0x%x, len %i, seqno %i:\n", header->type, header->len,
+			header->seqno);
+
+	dump_hex(packet, header->len);
+}
+
+/* can't use hvc_get_chars because that strips CRs */
+static int hvsi_read(struct hvsi_struct *hp, char *buf, int count)
+{
+	unsigned long got;
+
+	if (plpar_hcall(H_GET_TERM_CHAR, hp->vtermno, 0, 0, 0, &got,
+			(unsigned long *)buf, (unsigned long *)buf+1) == H_Success)
+		return got;
+	return 0;
+}
+
+/*
+ * we can't call tty_hangup() directly here because we need to call that
+ * outside of our lock
+ */
+static struct tty_struct *hvsi_recv_control(struct hvsi_struct *hp,
+		uint8_t *packet)
+{
+	struct tty_struct *to_hangup = NULL;
+	struct hvsi_control *header = (struct hvsi_control *)packet;
+
+	switch (header->verb) {
+		case VSV_MODEM_CTL_UPDATE:
+			if ((header->word & HVSI_TSCD) == 0) {
+				/* CD went away; no more connection */
+				pr_debug("hvsi%i: CD dropped\n", hp->index);
+				hp->mctrl &= TIOCM_CD;
+				if (!(hp->tty->flags & CLOCAL))
+					to_hangup = hp->tty;
+			}
+			break;
+		case VSV_CLOSE_PROTOCOL:
+			printk(KERN_DEBUG
+				"hvsi%i: service processor closed connection!\n", hp->index);
+			__set_state(hp, HVSI_CLOSED);
+			to_hangup = hp->tty;
+			hp->tty = NULL;
+			break;
+		default:
+			printk(KERN_WARNING "hvsi%i: unknown HVSI control packet: ",
+				hp->index);
+			dump_packet(packet);
+			break;
+	}
+
+	return to_hangup;
+}
+
+static void hvsi_recv_response(struct hvsi_struct *hp, uint8_t *packet)
+{
+	struct hvsi_query_response *resp = (struct hvsi_query_response *)packet;
+
+	switch (hp->state) {
+		case HVSI_WAIT_FOR_VER_RESPONSE:
+			__set_state(hp, HVSI_WAIT_FOR_VER_QUERY);
+			break;
+		case HVSI_WAIT_FOR_MCTRL_RESPONSE:
+			hp->mctrl = 0;
+			if (resp->u.mctrl_word & HVSI_TSDTR)
+				hp->mctrl |= TIOCM_DTR;
+			if (resp->u.mctrl_word & HVSI_TSCD)
+				hp->mctrl |= TIOCM_CD;
+			__set_state(hp, HVSI_OPEN);
+			break;
+		default:
+			printk(KERN_ERR "hvsi%i: unexpected query response: ", hp->index);
+			dump_packet(packet);
+			break;
+	}
+}
+
+/* respond to service processor's version query */
+static int hvsi_version_respond(struct hvsi_struct *hp, uint16_t query_seqno)
+{
+	struct hvsi_query_response packet __ALIGNED__;
+	int wrote;
+
+	packet.type = VS_QUERY_RESPONSE_PACKET_HEADER;
+	packet.len = sizeof(struct hvsi_query_response);
+	packet.seqno = atomic_inc_return(&hp->seqno);
+	packet.verb = VSV_SEND_VERSION_NUMBER;
+	packet.u.version = HVSI_VERSION;
+	packet.query_seqno = query_seqno+1;
+
+	pr_debug("%s: sending %i bytes\n", __FUNCTION__, packet.len);
+	dbg_dump_hex((uint8_t*)&packet, packet.len);
+
+	wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.len);
+	if (wrote != packet.len) {
+		printk(KERN_ERR "hvsi%i: couldn't send query response!\n",
+			hp->index);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static void hvsi_recv_query(struct hvsi_struct *hp, uint8_t *packet)
+{
+	struct hvsi_query *query = (struct hvsi_query *)packet;
+
+	switch (hp->state) {
+		case HVSI_WAIT_FOR_VER_QUERY:
+			__set_state(hp, HVSI_OPEN);
+			hvsi_version_respond(hp, query->seqno);
+			break;
+		default:
+			printk(KERN_ERR "hvsi%i: unexpected query: ", hp->index);
+			dump_packet(packet);
+			break;
+	}
+}
+
+static void hvsi_insert_chars(struct hvsi_struct *hp, const char *buf, int len)
+{
+	int i;
+
+	for (i=0; i < len; i++) {
+		char c = buf[i];
+#ifdef CONFIG_MAGIC_SYSRQ
+		if (c == '\0') {
+			hp->sysrq = 1;
+			continue;
+		} else if (hp->sysrq) {
+			handle_sysrq(c, NULL, hp->tty);
+			hp->sysrq = 0;
+			continue;
+		}
+#endif /* CONFIG_MAGIC_SYSRQ */
+		tty_insert_flip_char(hp->tty, c, 0);
+	}
+}
+
+/*
+ * We could get 252 bytes of data at once here. But the tty layer only
+ * throttles us at TTY_THRESHOLD_THROTTLE (128) bytes, so we could overflow
+ * it. Accordingly we won't send more than 128 bytes at a time to the flip
+ * buffer, which will give the tty buffer a chance to throttle us. Should the
+ * value of TTY_THRESHOLD_THROTTLE change in n_tty.c, this code should be
+ * revisited.
+ */
+#define TTY_THRESHOLD_THROTTLE 128
+static struct tty_struct *hvsi_recv_data(struct hvsi_struct *hp,
+		const uint8_t *packet)
+{
+	const struct hvsi_header *header = (const struct hvsi_header *)packet;
+	const uint8_t *data = packet + sizeof(struct hvsi_header);
+	int datalen = header->len - sizeof(struct hvsi_header);
+	int overflow = datalen - TTY_THRESHOLD_THROTTLE;
+
+	pr_debug("queueing %i chars '%.*s'\n", datalen, datalen, data);
+
+	if (datalen == 0)
+		return NULL;
+
+	if (overflow > 0) {
+		pr_debug("%s: got >TTY_THRESHOLD_THROTTLE bytes\n", __FUNCTION__);
+		datalen = TTY_THRESHOLD_THROTTLE;
+	}
+
+	hvsi_insert_chars(hp, data, datalen);
+
+	if (overflow > 0) {
+		/*
+		 * we still have more data to deliver, so we need to save off the
+		 * overflow and send it later
+		 */
+		pr_debug("%s: deferring overflow\n", __FUNCTION__);
+		memcpy(hp->throttle_buf, data + TTY_THRESHOLD_THROTTLE, overflow);
+		hp->n_throttle = overflow;
+	}
+
+	return hp->tty;
+}
+
+/*
+ * Returns true/false indicating data successfully read from hypervisor.
+ * Used both to get packets for tty connections and to advance the state
+ * machine during console handshaking (in which case tty = NULL and we ignore
+ * incoming data).
+ */
+static int hvsi_load_chunk(struct hvsi_struct *hp, struct tty_struct **flip,
+		struct tty_struct **hangup)
+{
+	uint8_t *packet = hp->inbuf;
+	int chunklen;
+
+	*flip = NULL;
+	*hangup = NULL;
+
+	chunklen = hvsi_read(hp, hp->inbuf_end, HVSI_MAX_READ);
+	if (chunklen == 0)
+		return 0;
+
+	pr_debug("%s: got %i bytes\n", __FUNCTION__, chunklen);
+	dbg_dump_hex(hp->inbuf_end, chunklen);
+
+	hp->inbuf_end += chunklen;
+
+	/* handle all completed packets */
+	while ((packet < hp->inbuf_end) && got_packet(hp, packet)) {
+		struct hvsi_header *header = (struct hvsi_header *)packet;
+
+		if (!is_header(packet)) {
+			printk(KERN_ERR "hvsi%i: got malformed packet\n", hp->index);
+			/* skip bytes until we find a header or run out of data */
+			while ((packet < hp->inbuf_end) && (!is_header(packet)))
+				packet++;
+			continue;
+		}
+
+		pr_debug("%s: handling %i-byte packet\n", __FUNCTION__,
+				len_packet(packet));
+		dbg_dump_packet(packet);
+
+		switch (header->type) {
+			case VS_DATA_PACKET_HEADER:
+				if (!is_open(hp))
+					break;
+				if (hp->tty == NULL)
+					break; /* no tty buffer to put data in */
+				*flip = hvsi_recv_data(hp, packet);
+				break;
+			case VS_CONTROL_PACKET_HEADER:
+				*hangup = hvsi_recv_control(hp, packet);
+				break;
+			case VS_QUERY_RESPONSE_PACKET_HEADER:
+				hvsi_recv_response(hp, packet);
+				break;
+			case VS_QUERY_PACKET_HEADER:
+				hvsi_recv_query(hp, packet);
+				break;
+			default:
+				printk(KERN_ERR "hvsi%i: unknown HVSI packet type 0x%x\n",
+						hp->index, header->type);
+				dump_packet(packet);
+				break;
+		}
+
+		packet += len_packet(packet);
+
+		if (*hangup) {
+			pr_debug("%s: hangup\n", __FUNCTION__);
+			/*
+			 * we need to send the hangup now before receiving any more data.
+			 * If we get "data, hangup, data", we can't deliver the second
+			 * data before the hangup.
+			 */
+			break;
+		}
+	}
+
+	compact_inbuf(hp, packet);
+
+	return 1;
+}
+
+static void hvsi_send_overflow(struct hvsi_struct *hp)
+{
+	pr_debug("%s: delivering %i bytes overflow\n", __FUNCTION__,
+			hp->n_throttle);
+
+	hvsi_insert_chars(hp, hp->throttle_buf, hp->n_throttle);
+	hp->n_throttle = 0;
+}
+
+/*
+ * must get all pending data because we only get an irq on empty->non-empty
+ * transition
+ */
+static irqreturn_t hvsi_interrupt(int irq, void *arg, struct pt_regs *regs)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)arg;
+	struct tty_struct *flip;
+	struct tty_struct *hangup;
+	unsigned long flags;
+	irqreturn_t handled = IRQ_NONE;
+	int again = 1;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	while (again) {
+		spin_lock_irqsave(&hp->lock, flags);
+		again = hvsi_load_chunk(hp, &flip, &hangup);
+		handled = IRQ_HANDLED;
+		spin_unlock_irqrestore(&hp->lock, flags);
+
+		/*
+		 * we have to call tty_flip_buffer_push() and tty_hangup() outside our
+		 * spinlock. But we also have to keep going until we've read all the
+		 * available data.
+		 */
+
+		if (flip) {
+			/* there was data put in the tty flip buffer */
+			tty_flip_buffer_push(flip);
+			flip = NULL;
+		}
+
+		if (hangup) {
+			tty_hangup(hangup);
+		}
+	}
+
+	spin_lock_irqsave(&hp->lock, flags);
+	if (hp->tty && hp->n_throttle
+			&& (!test_bit(TTY_THROTTLED, &hp->tty->flags))) {
+		/* we weren't hung up and we weren't throttled, so we can deliver the
+		 * rest now */
+		flip = hp->tty;
+		hvsi_send_overflow(hp);
+	}
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (flip) {
+		tty_flip_buffer_push(flip);
+	}
+
+	return handled;
+}
+
+/* for boot console, before the irq handler is running */
+static int __init poll_for_state(struct hvsi_struct *hp, int state)
+{
+	unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
+
+	for (;;) {
+		hvsi_interrupt(hp->virq, (void *)hp, NULL); /* get pending data */
+
+		if (hp->state == state)
+			return 0;
+
+		mdelay(5);
+		if (time_after(jiffies, end_jiffies))
+			return -EIO;
+	}
+}
+
+/* wait for irq handler to change our state */
+static int wait_for_state(struct hvsi_struct *hp, int state)
+{
+	unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
+	unsigned long timeout;
+	int ret = 0;
+
+	DECLARE_WAITQUEUE(myself, current);
+	set_current_state(TASK_INTERRUPTIBLE);
+	add_wait_queue(&hp->stateq, &myself);
+
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (hp->state == state)
+			break;
+		timeout = end_jiffies - jiffies;
+		if (time_after(jiffies, end_jiffies)) {
+			ret = -EIO;
+			break;
+		}
+		schedule_timeout(timeout);
+	}
+	remove_wait_queue(&hp->stateq, &myself);
+	set_current_state(TASK_RUNNING);
+
+	return ret;
+}
+
+static int hvsi_query(struct hvsi_struct *hp, uint16_t verb)
+{
+	struct hvsi_query packet __ALIGNED__;
+	int wrote;
+
+	packet.type = VS_QUERY_PACKET_HEADER;
+	packet.len = sizeof(struct hvsi_query);
+	packet.seqno = atomic_inc_return(&hp->seqno);
+	packet.verb = verb;
+
+	pr_debug("%s: sending %i bytes\n", __FUNCTION__, packet.len);
+	dbg_dump_hex((uint8_t*)&packet, packet.len);
+
+	wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.len);
+	if (wrote != packet.len) {
+		printk(KERN_ERR "hvsi%i: couldn't send query (%i)!\n", hp->index,
+			wrote);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int hvsi_get_mctrl(struct hvsi_struct *hp)
+{
+	int ret;
+
+	set_state(hp, HVSI_WAIT_FOR_MCTRL_RESPONSE);
+	hvsi_query(hp, VSV_SEND_MODEM_CTL_STATUS);
+
+	ret = hvsi_wait(hp, HVSI_OPEN);
+	if (ret < 0) {
+		printk(KERN_ERR "hvsi%i: didn't get modem flags\n", hp->index);
+		set_state(hp, HVSI_OPEN);
+		return ret;
+	}
+
+	pr_debug("%s: mctrl 0x%x\n", __FUNCTION__, hp->mctrl);
+
+	return 0;
+}
+
+/* note that we can only set DTR */
+static int hvsi_set_mctrl(struct hvsi_struct *hp, uint16_t mctrl)
+{
+	struct hvsi_control packet __ALIGNED__;
+	int wrote;
+
+	packet.type = VS_CONTROL_PACKET_HEADER,
+	packet.seqno = atomic_inc_return(&hp->seqno);
+	packet.len = sizeof(struct hvsi_control);
+	packet.verb = VSV_SET_MODEM_CTL;
+	packet.mask = HVSI_TSDTR;
+
+	if (mctrl & TIOCM_DTR)
+		packet.word = HVSI_TSDTR;
+
+	pr_debug("%s: sending %i bytes\n", __FUNCTION__, packet.len);
+	dbg_dump_hex((uint8_t*)&packet, packet.len);
+
+	wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.len);
+	if (wrote != packet.len) {
+		printk(KERN_ERR "hvsi%i: couldn't set DTR!\n", hp->index);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static void hvsi_drain_input(struct hvsi_struct *hp)
+{
+	uint8_t buf[HVSI_MAX_READ] __ALIGNED__;
+	unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
+
+	while (time_before(end_jiffies, jiffies))
+		if (0 == hvsi_read(hp, buf, HVSI_MAX_READ))
+			break;
+}
+
+static int hvsi_handshake(struct hvsi_struct *hp)
+{
+	int ret;
+
+	/*
+	 * We could have a CLOSE or other data waiting for us before we even try
+	 * to open; try to throw it all away so we don't get confused. (CLOSE
+	 * is the first message sent up the pipe when the FSP comes online. We
+	 * need to distinguish between "it came up a while ago and we're the first
+	 * user" and "it was just reset before it saw our handshake packet".)
+	 */
+	hvsi_drain_input(hp);
+
+	set_state(hp, HVSI_WAIT_FOR_VER_RESPONSE);
+	ret = hvsi_query(hp, VSV_SEND_VERSION_NUMBER);
+	if (ret < 0) {
+		printk(KERN_ERR "hvsi%i: couldn't send version query\n", hp->index);
+		return ret;
+	}
+
+	ret = hvsi_wait(hp, HVSI_OPEN);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int hvsi_put_chars(struct hvsi_struct *hp, const char *buf, int count)
+{
+	struct hvsi_data packet __ALIGNED__;
+	int ret;
+
+	BUG_ON(count > HVSI_MAX_OUTGOING_DATA);
+
+	packet.type = VS_DATA_PACKET_HEADER;
+	packet.seqno = atomic_inc_return(&hp->seqno);
+	packet.len = count + sizeof(struct hvsi_header);
+	memcpy(&packet.data, buf, count);
+
+	ret = hvc_put_chars(hp->vtermno, (char *)&packet, packet.len);
+	if (ret == packet.len) {
+		/* return the number of chars written, not the packet length */
+		return count;
+	}
+	return ret; /* return any errors */
+}
+
+static void hvsi_close_protocol(struct hvsi_struct *hp)
+{
+	struct hvsi_control packet __ALIGNED__;
+
+	packet.type = VS_CONTROL_PACKET_HEADER;
+	packet.seqno = atomic_inc_return(&hp->seqno);
+	packet.len = 6;
+	packet.verb = VSV_CLOSE_PROTOCOL;
+
+	pr_debug("%s: sending %i bytes\n", __FUNCTION__, packet.len);
+	dbg_dump_hex((uint8_t*)&packet, packet.len);
+
+	hvc_put_chars(hp->vtermno, (char *)&packet, packet.len);
+}
+
+static int hvsi_open(struct tty_struct *tty, struct file *filp)
+{
+	struct hvsi_struct *hp;
+	unsigned long flags;
+	int line = tty->index;
+	int ret;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	if (line < 0 || line >= hvsi_count)
+		return -ENODEV;
+	hp = &hvsi_ports[line];
+
+	tty->driver_data = hp;
+	tty->low_latency = 1; /* avoid throttle/tty_flip_buffer_push race */
+
+	spin_lock_irqsave(&hp->lock, flags);
+	hp->tty = tty;
+	hp->count++;
+	atomic_set(&hp->seqno, 0);
+	h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (hp->flags & HVSI_CONSOLE)
+		return 0; /* this has already been handshaked as the console */
+
+	ret = hvsi_handshake(hp);
+	if (ret < 0) {
+		printk(KERN_ERR "%s: HVSI handshaking failed\n", tty->name);
+		return ret;
+	}
+
+	ret = hvsi_get_mctrl(hp);
+	if (ret < 0) {
+		printk(KERN_ERR "%s: couldn't get initial modem flags\n", tty->name);
+		return ret;
+	}
+
+	ret = hvsi_set_mctrl(hp, hp->mctrl | TIOCM_DTR);
+	if (ret < 0) {
+		printk(KERN_ERR "%s: couldn't set DTR\n", tty->name);
+		return ret;
+	}
+
+	return 0;
+}
+
+/* wait for hvsi_write_worker to empty hp->outbuf */
+static void hvsi_flush_output(struct hvsi_struct *hp)
+{
+	unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
+	unsigned long timeout;
+
+	DECLARE_WAITQUEUE(myself, current);
+	set_current_state(TASK_UNINTERRUPTIBLE);
+	add_wait_queue(&hp->emptyq, &myself);
+
+	for (;;) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (hp->n_outbuf <= 0)
+			break;
+		timeout = end_jiffies - jiffies;
+		if (time_after(jiffies, end_jiffies))
+			break;
+		schedule_timeout(timeout);
+	}
+	remove_wait_queue(&hp->emptyq, &myself);
+	set_current_state(TASK_RUNNING);
+
+	/* 'writer' could still be pending if it didn't see n_outbuf = 0 yet */
+	cancel_delayed_work(&hp->writer);
+	flush_scheduled_work();
+
+	/*
+	 * it's also possible that our timeout expired and hvsi_write_worker
+	 * didn't manage to push outbuf. poof.
+	 */
+	hp->n_outbuf = 0;
+}
+
+static void hvsi_close(struct tty_struct *tty, struct file *filp)
+{
+	struct hvsi_struct *hp = tty->driver_data;
+	unsigned long flags;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	if (tty_hung_up_p(filp))
+		return;
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	if (--hp->count == 0) {
+		hp->tty = NULL;
+		hp->inbuf_end = hp->inbuf; /* discard remaining partial packets */
+
+		/* only close down connection if it is not the console */
+		if (!(hp->flags & HVSI_CONSOLE)) {
+			h_vio_signal(hp->vtermno, VIO_IRQ_DISABLE); /* no more irqs */
+			__set_state(hp, HVSI_CLOSED);
+			/*
+			 * any data delivered to the tty layer after this will be
+			 * discarded (except for XON/XOFF)
+			 */
+			tty->closing = 1;
+
+			spin_unlock_irqrestore(&hp->lock, flags);
+
+			/* let any existing irq handlers finish. no more will start. */
+			synchronize_irq(hp->virq);
+
+			/* hvsi_write_worker will re-schedule until outbuf is empty. */
+			hvsi_flush_output(hp);
+
+			/* tell FSP to stop sending data */
+			hvsi_close_protocol(hp);
+
+			/*
+			 * drain anything FSP is still in the middle of sending, and let
+			 * hvsi_handshake drain the rest on the next open.
+			 */
+			hvsi_drain_input(hp);
+
+			spin_lock_irqsave(&hp->lock, flags);
+		}
+	} else if (hp->count < 0)
+		printk(KERN_ERR "hvsi_close %lu: oops, count is %d\n",
+		       hp - hvsi_ports, hp->count);
+
+	spin_unlock_irqrestore(&hp->lock, flags);
+}
+
+static void hvsi_hangup(struct tty_struct *tty)
+{
+	struct hvsi_struct *hp = tty->driver_data;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	hp->count = 0;
+	hp->tty = NULL;
+}
+
+/* called with hp->lock held */
+static void hvsi_push(struct hvsi_struct *hp)
+{
+	int n;
+
+	if (hp->n_outbuf <= 0)
+		return;
+
+	n = hvsi_put_chars(hp, hp->outbuf, hp->n_outbuf);
+	if (n != 0) {
+		/*
+		 * either all data was sent or there was an error, and we throw away
+		 * data on error.
+		 */
+		hp->n_outbuf = 0;
+	}
+}
+
+/* hvsi_write_worker will keep rescheduling itself until outbuf is empty */
+static void hvsi_write_worker(void *arg)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)arg;
+	unsigned long flags;
+#ifdef DEBUG
+	static long start_j = 0;
+
+	if (start_j == 0)
+		start_j = jiffies;
+#endif /* DEBUG */
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	hvsi_push(hp);
+	if (hp->n_outbuf > 0)
+		schedule_delayed_work(&hp->writer, 10);
+	else {
+#ifdef DEBUG
+		pr_debug("%s: outbuf emptied after %li jiffies\n", __FUNCTION__,
+				jiffies - start_j);
+		start_j = 0;
+#endif /* DEBUG */
+		wake_up_all(&hp->emptyq);
+		if (test_bit(TTY_DO_WRITE_WAKEUP, &hp->tty->flags)
+				&& hp->tty->ldisc.write_wakeup)
+			hp->tty->ldisc.write_wakeup(hp->tty);
+		wake_up_interruptible(&hp->tty->write_wait);
+	}
+
+	spin_unlock_irqrestore(&hp->lock, flags);
+}
+
+static int hvsi_write_room(struct tty_struct *tty)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)tty->driver_data;
+
+	return N_OUTBUF - hp->n_outbuf;
+}
+
+static int hvsi_chars_in_buffer(struct tty_struct *tty)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)tty->driver_data;
+
+	return hp->n_outbuf;
+}
+
+static int hvsi_write(struct tty_struct *tty, int from_user,
+		     const unsigned char *buf, int count)
+{
+	struct hvsi_struct *hp = tty->driver_data;
+	const char *source = buf;
+	char *kbuf;
+	unsigned long flags;
+	int total = 0;
+	int origcount = count;
+
+	if (from_user) {
+		kbuf = kmalloc(count, GFP_KERNEL);
+		if (kbuf == NULL)
+			return -ENOMEM;
+		if (copy_from_user(kbuf, buf, count)) {
+			kfree(kbuf);
+			return -EFAULT;
+		}
+		source = kbuf;
+	}
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	if (!is_open(hp)) {
+		/* we're either closing or not yet open; don't accept data */
+		pr_debug("%s: not open\n", __FUNCTION__);
+		goto out;
+	}
+
+	/*
+	 * when the hypervisor buffer (16K) fills, data will stay in hp->outbuf
+	 * and hvsi_write_worker will be scheduled. subsequent hvsi_write() calls
+	 * will see there is no room in outbuf and return.
+	 */
+	while ((count > 0) && (hvsi_write_room(hp->tty) > 0)) {
+		int chunksize = min(count, hvsi_write_room(hp->tty));
+
+		BUG_ON(hp->n_outbuf < 0);
+		memcpy(hp->outbuf + hp->n_outbuf, source, chunksize);
+		hp->n_outbuf += chunksize;
+
+		total += chunksize;
+		source += chunksize;
+		count -= chunksize;
+		hvsi_push(hp);
+	}
+
+	if (hp->n_outbuf > 0) {
+		/*
+		 * we weren't able to write it all to the hypervisor.
+		 * schedule another push attempt.
+		 */
+		schedule_delayed_work(&hp->writer, 10);
+	}
+
+out:
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (from_user)
+		kfree(kbuf);
+
+	if (total != origcount)
+		pr_debug("%s: wanted %i, only wrote %i\n", __FUNCTION__, origcount,
+			total);
+
+	return total;
+}
+
+/*
+ * I have never seen throttle or unthrottle called, so this little throttle
+ * buffering scheme may or may not work.
+ */
+static void hvsi_throttle(struct tty_struct *tty)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)tty->driver_data;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	h_vio_signal(hp->vtermno, VIO_IRQ_DISABLE);
+}
+
+static void hvsi_unthrottle(struct tty_struct *tty)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)tty->driver_data;
+	unsigned long flags;
+	int shouldflip = 0;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	spin_lock_irqsave(&hp->lock, flags);
+	if (hp->n_throttle) {
+		hvsi_send_overflow(hp);
+		shouldflip = 1;
+	}
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (shouldflip)
+		tty_flip_buffer_push(hp->tty);
+
+	h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
+}
+
+static int hvsi_tiocmget(struct tty_struct *tty, struct file *file)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)tty->driver_data;
+
+	hvsi_get_mctrl(hp);
+	return hp->mctrl;
+}
+
+static int hvsi_tiocmset(struct tty_struct *tty, struct file *file,
+		unsigned int set, unsigned int clear)
+{
+	struct hvsi_struct *hp = (struct hvsi_struct *)tty->driver_data;
+	unsigned long flags;
+	uint16_t new_mctrl;
+
+	/* we can only alter DTR */
+	clear &= TIOCM_DTR;
+	set &= TIOCM_DTR;
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	new_mctrl = (hp->mctrl & ~clear) | set;
+
+	if (hp->mctrl != new_mctrl) {
+		hvsi_set_mctrl(hp, new_mctrl);
+		hp->mctrl = new_mctrl;
+	}
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	return 0;
+}
+
+
+static struct tty_operations hvsi_ops = {
+	.open = hvsi_open,
+	.close = hvsi_close,
+	.write = hvsi_write,
+	.hangup = hvsi_hangup,
+	.write_room = hvsi_write_room,
+	.chars_in_buffer = hvsi_chars_in_buffer,
+	.throttle = hvsi_throttle,
+	.unthrottle = hvsi_unthrottle,
+	.tiocmget = hvsi_tiocmget,
+	.tiocmset = hvsi_tiocmset,
+};
+
+static int __init hvsi_init(void)
+{
+	int i;
+
+	hvsi_driver = alloc_tty_driver(hvsi_count);
+	if (!hvsi_driver)
+		return -ENOMEM;
+
+	hvsi_driver->owner = THIS_MODULE;
+	hvsi_driver->devfs_name = "hvsi/";
+	hvsi_driver->driver_name = "hvsi";
+	hvsi_driver->name = "hvsi";
+	hvsi_driver->major = HVSI_MAJOR;
+	hvsi_driver->minor_start = HVSI_MINOR;
+	hvsi_driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	hvsi_driver->init_termios = tty_std_termios;
+	hvsi_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
+	hvsi_driver->flags = TTY_DRIVER_REAL_RAW;
+	tty_set_operations(hvsi_driver, &hvsi_ops);
+
+	for (i=0; i < hvsi_count; i++) {
+		struct hvsi_struct *hp = &hvsi_ports[i];
+		int ret = 1;
+
+		ret = request_irq(hp->virq, hvsi_interrupt, SA_INTERRUPT, "hvsi", hp);
+		if (ret)
+			printk(KERN_ERR "HVSI: couldn't reserve irq 0x%x (error %i)\n",
+				hp->virq, ret);
+	}
+	hvsi_wait = wait_for_state; /* irqs active now */
+
+	if (tty_register_driver(hvsi_driver))
+		panic("Couldn't register hvsi console driver\n");
+
+	printk(KERN_INFO "HVSI: registered %i devices\n", hvsi_count);
+
+	return 0;
+}
+device_initcall(hvsi_init);
+
+/***** console (not tty) code: *****/
+
+static void hvsi_console_print(struct console *console, const char *buf,
+		unsigned int count)
+{
+	struct hvsi_struct *hp = &hvsi_ports[console->index];
+	char c[HVSI_MAX_OUTGOING_DATA] __ALIGNED__;
+	unsigned int i = 0, n = 0;
+	int ret, donecr = 0;
+
+	mb();
+	if (!is_open(hp))
+		return;
+
+	/*
+	 * ugh, we have to translate LF -> CRLF ourselves, in place.
+	 * copied from hvc_console.c:
+	 */
+	while (count > 0 || i > 0) {
+		if (count > 0 && i < sizeof(c)) {
+			if (buf[n] == '\n' && !donecr) {
+				c[i++] = '\r';
+				donecr = 1;
+			} else {
+				c[i++] = buf[n++];
+				donecr = 0;
+				--count;
+			}
+		} else {
+			ret = hvsi_put_chars(hp, c, i);
+			if (ret < 0)
+				i = 0;
+			i -= ret;
+		}
+	}
+}
+
+static struct tty_driver *hvsi_console_device(struct console *console,
+	int *index)
+{
+	*index = console->index;
+	return hvsi_driver;
+}
+
+static int __init hvsi_console_setup(struct console *console, char *options)
+{
+	struct hvsi_struct *hp = &hvsi_ports[console->index];
+	int ret;
+
+	if (console->index < 0 || console->index >= hvsi_count)
+		return -1;
+
+	/* give the FSP a chance to change the baud rate when we re-open */
+	hvsi_close_protocol(hp);
+
+	ret = hvsi_handshake(hp);
+	if (ret < 0)
+		return ret;
+
+	ret = hvsi_get_mctrl(hp);
+	if (ret < 0)
+		return ret;
+
+	ret = hvsi_set_mctrl(hp, hp->mctrl | TIOCM_DTR);
+	if (ret < 0)
+		return ret;
+
+	hp->flags |= HVSI_CONSOLE;
+
+	return 0;
+}
+
+static struct console hvsi_con_driver = {
+	.name		= "hvsi",
+	.write		= hvsi_console_print,
+	.device		= hvsi_console_device,
+	.setup		= hvsi_console_setup,
+	.flags		= CON_PRINTBUFFER,
+	.index		= -1,
+};
+
+static int __init hvsi_console_init(void)
+{
+	struct device_node *vty;
+
+	hvsi_wait = poll_for_state; /* no irqs yet; must poll */
+
+	/* search device tree for vty nodes */
+	for (vty = of_find_compatible_node(NULL, "serial", "hvterm-protocol");
+			vty != NULL;
+			vty = of_find_compatible_node(vty, "serial", "hvterm-protocol")) {
+		struct hvsi_struct *hp;
+		uint32_t *vtermno;
+		uint32_t *irq;
+
+		vtermno = (uint32_t *)get_property(vty, "reg", NULL);
+		irq = (uint32_t *)get_property(vty, "interrupts", NULL);
+		if (!vtermno || !irq)
+			continue;
+
+		if (hvsi_count >= MAX_NR_HVSI_CONSOLES) {
+			of_node_put(vty);
+			break;
+		}
+
+		hp = &hvsi_ports[hvsi_count];
+		INIT_WORK(&hp->writer, hvsi_write_worker, hp);
+		init_waitqueue_head(&hp->emptyq);
+		init_waitqueue_head(&hp->stateq);
+		hp->lock = SPIN_LOCK_UNLOCKED;
+		hp->index = hvsi_count;
+		hp->inbuf_end = hp->inbuf;
+		hp->state = HVSI_CLOSED;
+		hp->vtermno = *vtermno;
+		hp->virq = virt_irq_create_mapping(irq[0]);
+		if (hp->virq == NO_IRQ) {
+			printk(KERN_ERR "%s: couldn't create irq mapping for 0x%x\n",
+				__FUNCTION__, hp->virq);
+			continue;
+		} else
+			hp->virq = irq_offset_up(hp->virq);
+
+		hvsi_count++;
+	}
+
+	if (hvsi_count)
+		register_console(&hvsi_con_driver);
+	return 0;
+}
+console_initcall(hvsi_console_init);