drivers/tty/hvc/hvc_vio.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * vio driver interface to hvc_console.c
  *
  * This code was moved here to allow the remaining code to be reused as a
  * generic polling mode with semi-reliable transport driver core to the
  * console and tty subsystems.
  *
  *
  * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
  * Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
  * Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
  * Copyright (C) 2004 IBM Corporation
  *
  * Additional Author(s):
  *  Ryan S. Arnold <rsa@us.ibm.com>
  *
  * TODO:
  *
  *   - handle error in sending hvsi protocol packets
  *   - retry nego on subsequent sends ?
  */

 #undef DEBUG

 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/console.h>

 #include <asm/hvconsole.h>
 #include <asm/vio.h>
 #include <asm/prom.h>
 #include <asm/hvsi.h>
 #include <asm/udbg.h>
 #include <asm/machdep.h>

 #include "hvc_console.h"

 static const char hvc_driver_name[] = "hvc_console";

 static const struct vio_device_id hvc_driver_table[] = {
 	{"serial", "hvterm1"},
 #ifndef HVC_OLD_HVSI
 	{"serial", "hvterm-protocol"},
 #endif
 	{ "", "" }
 };

 typedef enum hv_protocol {
 	HV_PROTOCOL_RAW,
 	HV_PROTOCOL_HVSI
 } hv_protocol_t;

 struct hvterm_priv {
 	u32			termno;	/* HV term number */
 	hv_protocol_t		proto;	/* Raw data or HVSI packets */
 	struct hvsi_priv	hvsi;	/* HVSI specific data */
 	spinlock_t		buf_lock;
 	char			buf[SIZE_VIO_GET_CHARS];
 	int			left;
 	int			offset;
 };
 static struct hvterm_priv *hvterm_privs[MAX_NR_HVC_CONSOLES];
 /* For early boot console */
 static struct hvterm_priv hvterm_priv0;

 static int hvterm_raw_get_chars(uint32_t vtermno, char *buf, int count)
 {
 	struct hvterm_priv *pv = hvterm_privs[vtermno];
 	unsigned long i;
 	unsigned long flags;
 	int got;

 	if (WARN_ON(!pv))
 		return 0;

 	spin_lock_irqsave(&pv->buf_lock, flags);

 	if (pv->left == 0) {
 		pv->offset = 0;
 		pv->left = hvc_get_chars(pv->termno, pv->buf, count);

 		/*
 		 * Work around a HV bug where it gives us a null
 		 * after every \r.  -- paulus
 		 */
 		for (i = 1; i < pv->left; ++i) {
 			if (pv->buf[i] == 0 && pv->buf[i-1] == '\r') {
 				--pv->left;
 				if (i < pv->left) {
 					memmove(&pv->buf[i], &pv->buf[i+1],
 						pv->left - i);
 				}
 			}
 		}
 	}

 	got = min(count, pv->left);
 	memcpy(buf, &pv->buf[pv->offset], got);
 	pv->offset += got;
 	pv->left -= got;

 	spin_unlock_irqrestore(&pv->buf_lock, flags);

 	return got;
 }

 /**
  * hvterm_raw_put_chars: send characters to firmware for given vterm adapter
  * @vtermno: The virtual terminal number.
  * @buf: The characters to send. Because of the underlying hypercall in
  *       hvc_put_chars(), this buffer must be at least 16 bytes long, even if
  *       you are sending fewer chars.
  * @count: number of chars to send.
  */
 static int hvterm_raw_put_chars(uint32_t vtermno, const char *buf, int count)
 {
 	struct hvterm_priv *pv = hvterm_privs[vtermno];

 	if (WARN_ON(!pv))
 		return 0;

 	return hvc_put_chars(pv->termno, buf, count);
 }

 static const struct hv_ops hvterm_raw_ops = {
 	.get_chars = hvterm_raw_get_chars,
 	.put_chars = hvterm_raw_put_chars,
 	.notifier_add = notifier_add_irq,
 	.notifier_del = notifier_del_irq,
 	.notifier_hangup = notifier_hangup_irq,
 };

 static int hvterm_hvsi_get_chars(uint32_t vtermno, char *buf, int count)
 {
 	struct hvterm_priv *pv = hvterm_privs[vtermno];

 	if (WARN_ON(!pv))
 		return 0;

 	return hvsilib_get_chars(&pv->hvsi, buf, count);
 }

 static int hvterm_hvsi_put_chars(uint32_t vtermno, const char *buf, int count)
 {
 	struct hvterm_priv *pv = hvterm_privs[vtermno];

 	if (WARN_ON(!pv))
 		return 0;

 	return hvsilib_put_chars(&pv->hvsi, buf, count);
 }

 static int hvterm_hvsi_open(struct hvc_struct *hp, int data)
 {
 	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];
 	int rc;

 	pr_devel("HVSI@%x: open !\n", pv->termno);

 	rc = notifier_add_irq(hp, data);
 	if (rc)
 		return rc;

 	return hvsilib_open(&pv->hvsi, hp);
 }

 static void hvterm_hvsi_close(struct hvc_struct *hp, int data)
 {
 	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

 	pr_devel("HVSI@%x: do close !\n", pv->termno);

 	hvsilib_close(&pv->hvsi, hp);

 	notifier_del_irq(hp, data);
 }

 static void hvterm_hvsi_hangup(struct hvc_struct *hp, int data)
 {
 	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

 	pr_devel("HVSI@%x: do hangup !\n", pv->termno);

 	hvsilib_close(&pv->hvsi, hp);

 	notifier_hangup_irq(hp, data);
 }

 static int hvterm_hvsi_tiocmget(struct hvc_struct *hp)
 {
 	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

 	if (!pv)
 		return -EINVAL;
 	return pv->hvsi.mctrl;
 }

 static int hvterm_hvsi_tiocmset(struct hvc_struct *hp, unsigned int set,
 				unsigned int clear)
 {
 	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

 	pr_devel("HVSI@%x: Set modem control, set=%x,clr=%x\n",
 		 pv->termno, set, clear);

 	if (set & TIOCM_DTR)
 		hvsilib_write_mctrl(&pv->hvsi, 1);
 	else if (clear & TIOCM_DTR)
 		hvsilib_write_mctrl(&pv->hvsi, 0);

 	return 0;
 }

 static const struct hv_ops hvterm_hvsi_ops = {
 	.get_chars = hvterm_hvsi_get_chars,
 	.put_chars = hvterm_hvsi_put_chars,
 	.notifier_add = hvterm_hvsi_open,
 	.notifier_del = hvterm_hvsi_close,
 	.notifier_hangup = hvterm_hvsi_hangup,
 	.tiocmget = hvterm_hvsi_tiocmget,
 	.tiocmset = hvterm_hvsi_tiocmset,
 };

 static void udbg_hvc_putc(char c)
 {
 	int count = -1;
 	unsigned char bounce_buffer[16];

 	if (!hvterm_privs[0])
 		return;

 	if (c == '\n')
 		udbg_hvc_putc('\r');

 	do {
 		switch(hvterm_privs[0]->proto) {
 		case HV_PROTOCOL_RAW:
 			/*
 			 * hvterm_raw_put_chars requires at least a 16-byte
 			 * buffer, so go via the bounce buffer
 			 */
 			bounce_buffer[0] = c;
 			count = hvterm_raw_put_chars(0, bounce_buffer, 1);
 			break;
 		case HV_PROTOCOL_HVSI:
 			count = hvterm_hvsi_put_chars(0, &c, 1);
 			break;
 		}
 	} while(count == 0);
 }

 static int udbg_hvc_getc_poll(void)
 {
 	int rc = 0;
 	char c;

 	if (!hvterm_privs[0])
 		return -1;

 	switch(hvterm_privs[0]->proto) {
 	case HV_PROTOCOL_RAW:
 		rc = hvterm_raw_get_chars(0, &c, 1);
 		break;
 	case HV_PROTOCOL_HVSI:
 		rc = hvterm_hvsi_get_chars(0, &c, 1);
 		break;
 	}
 	if (!rc)
 		return -1;
 	return c;
 }

 static int udbg_hvc_getc(void)
 {
 	int ch;

 	if (!hvterm_privs[0])
 		return -1;

 	for (;;) {
 		ch = udbg_hvc_getc_poll();
 		if (ch == -1) {
 			/* This shouldn't be needed...but... */
 			volatile unsigned long delay;
 			for (delay=0; delay < 2000000; delay++)
 				;
 		} else {
 			return ch;
 		}
 	}
 }

 static int hvc_vio_probe(struct vio_dev *vdev,
 				   const struct vio_device_id *id)
 {
 	const struct hv_ops *ops;
 	struct hvc_struct *hp;
 	struct hvterm_priv *pv;
 	hv_protocol_t proto;
 	int i, termno = -1;

 	/* probed with invalid parameters. */
 	if (!vdev || !id)
 		return -EPERM;

 	if (of_device_is_compatible(vdev->dev.of_node, "hvterm1")) {
 		proto = HV_PROTOCOL_RAW;
 		ops = &hvterm_raw_ops;
 	} else if (of_device_is_compatible(vdev->dev.of_node, "hvterm-protocol")) {
 		proto = HV_PROTOCOL_HVSI;
 		ops = &hvterm_hvsi_ops;
 	} else {
 		pr_err("hvc_vio: Unknown protocol for %pOF\n", vdev->dev.of_node);
 		return -ENXIO;
 	}

 	pr_devel("hvc_vio_probe() device %pOF, using %s protocol\n",
 		 vdev->dev.of_node,
 		 proto == HV_PROTOCOL_RAW ? "raw" : "hvsi");

 	/* Is it our boot one ? */
 	if (hvterm_privs[0] == &hvterm_priv0 &&
 	    vdev->unit_address == hvterm_priv0.termno) {
 		pv = hvterm_privs[0];
 		termno = 0;
 		pr_devel("->boot console, using termno 0\n");
 	}
 	/* nope, allocate a new one */
 	else {
 		for (i = 0; i < MAX_NR_HVC_CONSOLES && termno < 0; i++)
 			if (!hvterm_privs[i])
 				termno = i;
 		pr_devel("->non-boot console, using termno %d\n", termno);
 		if (termno < 0)
 			return -ENODEV;
 		pv = kzalloc(sizeof(struct hvterm_priv), GFP_KERNEL);
 		if (!pv)
 			return -ENOMEM;
 		pv->termno = vdev->unit_address;
 		pv->proto = proto;
 		spin_lock_init(&pv->buf_lock);
 		hvterm_privs[termno] = pv;
 		hvsilib_init(&pv->hvsi, hvc_get_chars, hvc_put_chars,
 			     pv->termno, 0);
 	}

 	hp = hvc_alloc(termno, vdev->irq, ops, MAX_VIO_PUT_CHARS);
 	if (IS_ERR(hp))
 		return PTR_ERR(hp);
 	dev_set_drvdata(&vdev->dev, hp);

 	/* register udbg if it's not there already for console 0 */
 	if (hp->index == 0 && !udbg_putc) {
 		udbg_putc = udbg_hvc_putc;
 		udbg_getc = udbg_hvc_getc;
 		udbg_getc_poll = udbg_hvc_getc_poll;
 	}

 	return 0;
 }

 static struct vio_driver hvc_vio_driver = {
 	.id_table	= hvc_driver_table,
 	.probe		= hvc_vio_probe,
 	.name		= hvc_driver_name,
 	.driver = {
 		.suppress_bind_attrs	= true,
 	},
 };

 static int __init hvc_vio_init(void)
 {
 	int rc;

 	/* Register as a vio device to receive callbacks */
 	rc = vio_register_driver(&hvc_vio_driver);

 	return rc;
 }
 device_initcall(hvc_vio_init); /* after drivers/tty/hvc/hvc_console.c */

 void __init hvc_vio_init_early(void)
 {
 	const __be32 *termno;
 	const struct hv_ops *ops;

 	/* find the boot console from /chosen/stdout */
 	/* Check if it's a virtual terminal */
 	if (!of_node_name_prefix(of_stdout, "vty"))
 		return;
 	termno = of_get_property(of_stdout, "reg", NULL);
 	if (termno == NULL)
 		return;
 	hvterm_priv0.termno = of_read_number(termno, 1);
 	spin_lock_init(&hvterm_priv0.buf_lock);
 	hvterm_privs[0] = &hvterm_priv0;

 	/* Check the protocol */
 	if (of_device_is_compatible(of_stdout, "hvterm1")) {
 		hvterm_priv0.proto = HV_PROTOCOL_RAW;
 		ops = &hvterm_raw_ops;
 	}
 	else if (of_device_is_compatible(of_stdout, "hvterm-protocol")) {
 		hvterm_priv0.proto = HV_PROTOCOL_HVSI;
 		ops = &hvterm_hvsi_ops;
 		hvsilib_init(&hvterm_priv0.hvsi, hvc_get_chars, hvc_put_chars,
 			     hvterm_priv0.termno, 1);
 		/* HVSI, perform the handshake now */
 		hvsilib_establish(&hvterm_priv0.hvsi);
 	} else
 		return;
 	udbg_putc = udbg_hvc_putc;
 	udbg_getc = udbg_hvc_getc;
 	udbg_getc_poll = udbg_hvc_getc_poll;
 #ifdef HVC_OLD_HVSI
 	/* When using the old HVSI driver don't register the HVC
 	 * backend for HVSI, only do udbg
 	 */
 	if (hvterm_priv0.proto == HV_PROTOCOL_HVSI)
 		return;
 #endif
 	/* Check whether the user has requested a different console. */
 	if (!strstr(boot_command_line, "console="))
 		add_preferred_console("hvc", 0, NULL);
 	hvc_instantiate(0, 0, ops);
 }

 /* call this from early_init() for a working debug console on
  * vterm capable LPAR machines
  */
 #ifdef CONFIG_PPC_EARLY_DEBUG_LPAR
 void __init udbg_init_debug_lpar(void)
 {
 	/*
 	 * If we're running as a hypervisor then we definitely can't call the
 	 * hypervisor to print debug output (we *are* the hypervisor), so don't
 	 * register if we detect that MSR_HV=1.
 	 */
 	if (mfmsr() & MSR_HV)
 		return;

 	hvterm_privs[0] = &hvterm_priv0;
 	hvterm_priv0.termno = 0;
 	hvterm_priv0.proto = HV_PROTOCOL_RAW;
 	spin_lock_init(&hvterm_priv0.buf_lock);
 	udbg_putc = udbg_hvc_putc;
 	udbg_getc = udbg_hvc_getc;
 	udbg_getc_poll = udbg_hvc_getc_poll;
 }
 #endif /* CONFIG_PPC_EARLY_DEBUG_LPAR */

 #ifdef CONFIG_PPC_EARLY_DEBUG_LPAR_HVSI
 void __init udbg_init_debug_lpar_hvsi(void)
 {
 	/* See comment above in udbg_init_debug_lpar() */
 	if (mfmsr() & MSR_HV)
 		return;

 	hvterm_privs[0] = &hvterm_priv0;
 	hvterm_priv0.termno = CONFIG_PPC_EARLY_DEBUG_HVSI_VTERMNO;
 	hvterm_priv0.proto = HV_PROTOCOL_HVSI;
 	spin_lock_init(&hvterm_priv0.buf_lock);
 	udbg_putc = udbg_hvc_putc;
 	udbg_getc = udbg_hvc_getc;
 	udbg_getc_poll = udbg_hvc_getc_poll;
 	hvsilib_init(&hvterm_priv0.hvsi, hvc_get_chars, hvc_put_chars,
 		     hvterm_priv0.termno, 1);
 	hvsilib_establish(&hvterm_priv0.hvsi);
 }
 #endif /* CONFIG_PPC_EARLY_DEBUG_LPAR_HVSI */
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* vio driver interface to hvc_console.c
	*
	* This code was moved here to allow the remaining code to be reused as a
	* generic polling mode with semi-reliable transport driver core to the
	* console and tty subsystems.
	*
	*
	* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
	* Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
	* Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
	* Copyright (C) 2004 IBM Corporation
	*
	* Additional Author(s):
	* Ryan S. Arnold <rsa@us.ibm.com>
	*
	* TODO:
	*
	* - handle error in sending hvsi protocol packets
	* - retry nego on subsequent sends ?
	*/

	#undef DEBUG

	#include <linux/types.h>
	#include <linux/init.h>
	#include <linux/delay.h>
	#include <linux/slab.h>
	#include <linux/console.h>

	#include <asm/hvconsole.h>
	#include <asm/vio.h>
	#include <asm/prom.h>
	#include <asm/hvsi.h>
	#include <asm/udbg.h>
	#include <asm/machdep.h>

	#include "hvc_console.h"

	static const char hvc_driver_name[] = "hvc_console";

	static const struct vio_device_id hvc_driver_table[] = {
	{"serial", "hvterm1"},
	#ifndef HVC_OLD_HVSI
	{"serial", "hvterm-protocol"},
	#endif
	{ "", "" }
	};

	typedef enum hv_protocol {
	HV_PROTOCOL_RAW,
	HV_PROTOCOL_HVSI
	} hv_protocol_t;

	struct hvterm_priv {
	u32 termno; /* HV term number */
	hv_protocol_t proto; /* Raw data or HVSI packets */
	struct hvsi_priv hvsi; /* HVSI specific data */
	spinlock_t buf_lock;
	char buf[SIZE_VIO_GET_CHARS];
	int left;
	int offset;
	};
	static struct hvterm_priv *hvterm_privs[MAX_NR_HVC_CONSOLES];
	/* For early boot console */
	static struct hvterm_priv hvterm_priv0;

	static int hvterm_raw_get_chars(uint32_t vtermno, char *buf, int count)
	{
	struct hvterm_priv *pv = hvterm_privs[vtermno];
	unsigned long i;
	unsigned long flags;
	int got;

	if (WARN_ON(!pv))
	return 0;

	spin_lock_irqsave(&pv->buf_lock, flags);

	if (pv->left == 0) {
	pv->offset = 0;
	pv->left = hvc_get_chars(pv->termno, pv->buf, count);

	/*
	* Work around a HV bug where it gives us a null
	* after every \r. -- paulus
	*/
	for (i = 1; i < pv->left; ++i) {
	if (pv->buf[i] == 0 && pv->buf[i-1] == '\r') {
	--pv->left;
	if (i < pv->left) {
	memmove(&pv->buf[i], &pv->buf[i+1],
	pv->left - i);
	}
	}
	}
	}

	got = min(count, pv->left);
	memcpy(buf, &pv->buf[pv->offset], got);
	pv->offset += got;
	pv->left -= got;

	spin_unlock_irqrestore(&pv->buf_lock, flags);

	return got;
	}

	/**
	* hvterm_raw_put_chars: send characters to firmware for given vterm adapter
	* @vtermno: The virtual terminal number.
	* @buf: The characters to send. Because of the underlying hypercall in
	* hvc_put_chars(), this buffer must be at least 16 bytes long, even if
	* you are sending fewer chars.
	* @count: number of chars to send.
	*/
	static int hvterm_raw_put_chars(uint32_t vtermno, const char *buf, int count)
	{
	struct hvterm_priv *pv = hvterm_privs[vtermno];

	if (WARN_ON(!pv))
	return 0;

	return hvc_put_chars(pv->termno, buf, count);
	}

	static const struct hv_ops hvterm_raw_ops = {
	.get_chars = hvterm_raw_get_chars,
	.put_chars = hvterm_raw_put_chars,
	.notifier_add = notifier_add_irq,
	.notifier_del = notifier_del_irq,
	.notifier_hangup = notifier_hangup_irq,
	};

	static int hvterm_hvsi_get_chars(uint32_t vtermno, char *buf, int count)
	{
	struct hvterm_priv *pv = hvterm_privs[vtermno];

	if (WARN_ON(!pv))
	return 0;

	return hvsilib_get_chars(&pv->hvsi, buf, count);
	}

	static int hvterm_hvsi_put_chars(uint32_t vtermno, const char *buf, int count)
	{
	struct hvterm_priv *pv = hvterm_privs[vtermno];

	if (WARN_ON(!pv))
	return 0;

	return hvsilib_put_chars(&pv->hvsi, buf, count);
	}

	static int hvterm_hvsi_open(struct hvc_struct *hp, int data)
	{
	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];
	int rc;

	pr_devel("HVSI@%x: open !\n", pv->termno);

	rc = notifier_add_irq(hp, data);
	if (rc)
	return rc;

	return hvsilib_open(&pv->hvsi, hp);
	}

	static void hvterm_hvsi_close(struct hvc_struct *hp, int data)
	{
	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

	pr_devel("HVSI@%x: do close !\n", pv->termno);

	hvsilib_close(&pv->hvsi, hp);

	notifier_del_irq(hp, data);
	}

	static void hvterm_hvsi_hangup(struct hvc_struct *hp, int data)
	{
	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

	pr_devel("HVSI@%x: do hangup !\n", pv->termno);

	hvsilib_close(&pv->hvsi, hp);

	notifier_hangup_irq(hp, data);
	}

	static int hvterm_hvsi_tiocmget(struct hvc_struct *hp)
	{
	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

	if (!pv)
	return -EINVAL;
	return pv->hvsi.mctrl;
	}

	static int hvterm_hvsi_tiocmset(struct hvc_struct *hp, unsigned int set,
	unsigned int clear)
	{
	struct hvterm_priv *pv = hvterm_privs[hp->vtermno];

	pr_devel("HVSI@%x: Set modem control, set=%x,clr=%x\n",
	pv->termno, set, clear);

	if (set & TIOCM_DTR)
	hvsilib_write_mctrl(&pv->hvsi, 1);
	else if (clear & TIOCM_DTR)
	hvsilib_write_mctrl(&pv->hvsi, 0);

	return 0;
	}

	static const struct hv_ops hvterm_hvsi_ops = {
	.get_chars = hvterm_hvsi_get_chars,
	.put_chars = hvterm_hvsi_put_chars,
	.notifier_add = hvterm_hvsi_open,
	.notifier_del = hvterm_hvsi_close,
	.notifier_hangup = hvterm_hvsi_hangup,
	.tiocmget = hvterm_hvsi_tiocmget,
	.tiocmset = hvterm_hvsi_tiocmset,
	};

	static void udbg_hvc_putc(char c)
	{
	int count = -1;
	unsigned char bounce_buffer[16];

	if (!hvterm_privs[0])
	return;

	if (c == '\n')
	udbg_hvc_putc('\r');

	do {
	switch(hvterm_privs[0]->proto) {
	case HV_PROTOCOL_RAW:
	/*
	* hvterm_raw_put_chars requires at least a 16-byte
	* buffer, so go via the bounce buffer
	*/
	bounce_buffer[0] = c;
	count = hvterm_raw_put_chars(0, bounce_buffer, 1);
	break;
	case HV_PROTOCOL_HVSI:
	count = hvterm_hvsi_put_chars(0, &c, 1);
	break;
	}
	} while(count == 0);
	}

	static int udbg_hvc_getc_poll(void)
	{
	int rc = 0;
	char c;

	if (!hvterm_privs[0])
	return -1;

	switch(hvterm_privs[0]->proto) {
	case HV_PROTOCOL_RAW:
	rc = hvterm_raw_get_chars(0, &c, 1);
	break;
	case HV_PROTOCOL_HVSI:
	rc = hvterm_hvsi_get_chars(0, &c, 1);
	break;
	}
	if (!rc)
	return -1;
	return c;
	}

	static int udbg_hvc_getc(void)
	{
	int ch;

	if (!hvterm_privs[0])
	return -1;

	for (;;) {
	ch = udbg_hvc_getc_poll();
	if (ch == -1) {
	/* This shouldn't be needed...but... */
	volatile unsigned long delay;
	for (delay=0; delay < 2000000; delay++)
	;
	} else {
	return ch;
	}
	}
	}

	static int hvc_vio_probe(struct vio_dev *vdev,
	const struct vio_device_id *id)
	{
	const struct hv_ops *ops;
	struct hvc_struct *hp;
	struct hvterm_priv *pv;
	hv_protocol_t proto;
	int i, termno = -1;

	/* probed with invalid parameters. */
	if (!vdev \|\| !id)
	return -EPERM;

	if (of_device_is_compatible(vdev->dev.of_node, "hvterm1")) {
	proto = HV_PROTOCOL_RAW;
	ops = &hvterm_raw_ops;
	} else if (of_device_is_compatible(vdev->dev.of_node, "hvterm-protocol")) {
	proto = HV_PROTOCOL_HVSI;
	ops = &hvterm_hvsi_ops;
	} else {
	pr_err("hvc_vio: Unknown protocol for %pOF\n", vdev->dev.of_node);
	return -ENXIO;
	}

	pr_devel("hvc_vio_probe() device %pOF, using %s protocol\n",
	vdev->dev.of_node,
	proto == HV_PROTOCOL_RAW ? "raw" : "hvsi");

	/* Is it our boot one ? */
	if (hvterm_privs[0] == &hvterm_priv0 &&
	vdev->unit_address == hvterm_priv0.termno) {
	pv = hvterm_privs[0];
	termno = 0;
	pr_devel("->boot console, using termno 0\n");
	}
	/* nope, allocate a new one */
	else {
	for (i = 0; i < MAX_NR_HVC_CONSOLES && termno < 0; i++)
	if (!hvterm_privs[i])
	termno = i;
	pr_devel("->non-boot console, using termno %d\n", termno);
	if (termno < 0)
	return -ENODEV;
	pv = kzalloc(sizeof(struct hvterm_priv), GFP_KERNEL);
	if (!pv)
	return -ENOMEM;
	pv->termno = vdev->unit_address;
	pv->proto = proto;
	spin_lock_init(&pv->buf_lock);
	hvterm_privs[termno] = pv;
	hvsilib_init(&pv->hvsi, hvc_get_chars, hvc_put_chars,
	pv->termno, 0);
	}

	hp = hvc_alloc(termno, vdev->irq, ops, MAX_VIO_PUT_CHARS);
	if (IS_ERR(hp))
	return PTR_ERR(hp);
	dev_set_drvdata(&vdev->dev, hp);

	/* register udbg if it's not there already for console 0 */
	if (hp->index == 0 && !udbg_putc) {
	udbg_putc = udbg_hvc_putc;
	udbg_getc = udbg_hvc_getc;
	udbg_getc_poll = udbg_hvc_getc_poll;
	}

	return 0;
	}

	static struct vio_driver hvc_vio_driver = {
	.id_table = hvc_driver_table,
	.probe = hvc_vio_probe,
	.name = hvc_driver_name,
	.driver = {
	.suppress_bind_attrs = true,
	},
	};

	static int __init hvc_vio_init(void)
	{
	int rc;

	/* Register as a vio device to receive callbacks */
	rc = vio_register_driver(&hvc_vio_driver);

	return rc;
	}
	device_initcall(hvc_vio_init); /* after drivers/tty/hvc/hvc_console.c */

	void __init hvc_vio_init_early(void)
	{
	const __be32 *termno;
	const struct hv_ops *ops;

	/* find the boot console from /chosen/stdout */
	/* Check if it's a virtual terminal */
	if (!of_node_name_prefix(of_stdout, "vty"))
	return;
	termno = of_get_property(of_stdout, "reg", NULL);
	if (termno == NULL)
	return;
	hvterm_priv0.termno = of_read_number(termno, 1);
	spin_lock_init(&hvterm_priv0.buf_lock);
	hvterm_privs[0] = &hvterm_priv0;

	/* Check the protocol */
	if (of_device_is_compatible(of_stdout, "hvterm1")) {
	hvterm_priv0.proto = HV_PROTOCOL_RAW;
	ops = &hvterm_raw_ops;
	}
	else if (of_device_is_compatible(of_stdout, "hvterm-protocol")) {
	hvterm_priv0.proto = HV_PROTOCOL_HVSI;
	ops = &hvterm_hvsi_ops;
	hvsilib_init(&hvterm_priv0.hvsi, hvc_get_chars, hvc_put_chars,
	hvterm_priv0.termno, 1);
	/* HVSI, perform the handshake now */
	hvsilib_establish(&hvterm_priv0.hvsi);
	} else
	return;
	udbg_putc = udbg_hvc_putc;
	udbg_getc = udbg_hvc_getc;
	udbg_getc_poll = udbg_hvc_getc_poll;
	#ifdef HVC_OLD_HVSI
	/* When using the old HVSI driver don't register the HVC
	* backend for HVSI, only do udbg
	*/
	if (hvterm_priv0.proto == HV_PROTOCOL_HVSI)
	return;
	#endif
	/* Check whether the user has requested a different console. */
	if (!strstr(boot_command_line, "console="))
	add_preferred_console("hvc", 0, NULL);
	hvc_instantiate(0, 0, ops);
	}

	/* call this from early_init() for a working debug console on
	* vterm capable LPAR machines
	*/
	#ifdef CONFIG_PPC_EARLY_DEBUG_LPAR
	void __init udbg_init_debug_lpar(void)
	{
	/*
	* If we're running as a hypervisor then we definitely can't call the
	* hypervisor to print debug output (we are the hypervisor), so don't
	* register if we detect that MSR_HV=1.
	*/
	if (mfmsr() & MSR_HV)
	return;

	hvterm_privs[0] = &hvterm_priv0;
	hvterm_priv0.termno = 0;
	hvterm_priv0.proto = HV_PROTOCOL_RAW;
	spin_lock_init(&hvterm_priv0.buf_lock);
	udbg_putc = udbg_hvc_putc;
	udbg_getc = udbg_hvc_getc;
	udbg_getc_poll = udbg_hvc_getc_poll;
	}
	#endif /* CONFIG_PPC_EARLY_DEBUG_LPAR */

	#ifdef CONFIG_PPC_EARLY_DEBUG_LPAR_HVSI
	void __init udbg_init_debug_lpar_hvsi(void)
	{
	/* See comment above in udbg_init_debug_lpar() */
	if (mfmsr() & MSR_HV)
	return;

	hvterm_privs[0] = &hvterm_priv0;
	hvterm_priv0.termno = CONFIG_PPC_EARLY_DEBUG_HVSI_VTERMNO;
	hvterm_priv0.proto = HV_PROTOCOL_HVSI;
	spin_lock_init(&hvterm_priv0.buf_lock);
	udbg_putc = udbg_hvc_putc;
	udbg_getc = udbg_hvc_getc;
	udbg_getc_poll = udbg_hvc_getc_poll;
	hvsilib_init(&hvterm_priv0.hvsi, hvc_get_chars, hvc_put_chars,
	hvterm_priv0.termno, 1);
	hvsilib_establish(&hvterm_priv0.hvsi);
	}
	#endif /* CONFIG_PPC_EARLY_DEBUG_LPAR_HVSI */