path: root/drivers/tty/vcc.c

// SPDX-License-Identifier: GPL-2.0
/* vcc.c: sun4v virtual channel concentrator
 *
 * Copyright (C) 2017 Oracle. All rights reserved.
 */

#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <asm/vio.h>
#include <asm/ldc.h>

#define DRV_MODULE_NAME		"vcc"
#define DRV_MODULE_VERSION	"1.1"
#define DRV_MODULE_RELDATE	"July 1, 2017"

static char version[] =
	DRV_MODULE_NAME ".c:v" DRV_MODULE_VERSION " (" DRV_MODULE_RELDATE ")";

MODULE_DESCRIPTION("Sun LDOM virtual console concentrator driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_MODULE_VERSION);

struct vcc_port {
	struct vio_driver_state vio;

	spinlock_t lock;
	char *domain;
	struct tty_struct *tty;	/* only populated while dev is open */
	unsigned long index;	/* index into the vcc_table */

	u64 refcnt;
	bool excl_locked;

	bool removed;

	/* This buffer is required to support the tty write_room interface
	 * and guarantee that any characters that the driver accepts will
	 * be eventually sent, either immediately or later.
	 */
	int chars_in_buffer;
	struct vio_vcc buffer;

	struct timer_list rx_timer;
	struct timer_list tx_timer;
};

/* Microseconds that thread will delay waiting for a vcc port ref */
#define VCC_REF_DELAY		100

#define VCC_MAX_PORTS		1024
#define VCC_MINOR_START		0	/* must be zero */
#define VCC_BUFF_LEN		VIO_VCC_MTU_SIZE

#define VCC_CTL_BREAK		-1
#define VCC_CTL_HUP		-2

static const char vcc_driver_name[] = "vcc";
static const char vcc_device_node[] = "vcc";
static struct tty_driver *vcc_tty_driver;

static struct vcc_port *vcc_table[VCC_MAX_PORTS];
static DEFINE_SPINLOCK(vcc_table_lock);

int vcc_dbg;
int vcc_dbg_ldc;
int vcc_dbg_vio;

module_param(vcc_dbg, uint, 0664);
module_param(vcc_dbg_ldc, uint, 0664);
module_param(vcc_dbg_vio, uint, 0664);

#define VCC_DBG_DRV	0x1
#define VCC_DBG_LDC	0x2
#define VCC_DBG_PKT	0x4

#define vccdbg(f, a...)						\
	do {							\
		if (vcc_dbg & VCC_DBG_DRV)			\
			pr_info(f, ## a);			\
	} while (0)						\

#define vccdbgl(l)						\
	do {							\
		if (vcc_dbg & VCC_DBG_LDC)			\
			ldc_print(l);				\
	} while (0)						\

#define vccdbgp(pkt)						\
	do {							\
		if (vcc_dbg & VCC_DBG_PKT) {			\
			int i;					\
			for (i = 0; i < pkt.tag.stype; i++)	\
				pr_info("[%c]", pkt.data[i]);	\
		}						\
	} while (0)						\

/* Note: Be careful when adding flags to this line discipline.  Don't
 * add anything that will cause echoing or we'll go into recursive
 * loop echoing chars back and forth with the console drivers.
 */
static const struct ktermios vcc_tty_termios = {
	.c_iflag = IGNBRK | IGNPAR,
	.c_oflag = OPOST,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400
};

/**
 * vcc_table_add() - Add VCC port to the VCC table
 * @port: pointer to the VCC port
 *
 * Return: index of the port in the VCC table on success,
 *	   -1 on failure
 */
static int vcc_table_add(struct vcc_port *port)
{
	unsigned long flags;
	int i;

	spin_lock_irqsave(&vcc_table_lock, flags);
	for (i = VCC_MINOR_START; i < VCC_MAX_PORTS; i++) {
		if (!vcc_table[i]) {
			vcc_table[i] = port;
			break;
		}
	}
	spin_unlock_irqrestore(&vcc_table_lock, flags);

	if (i < VCC_MAX_PORTS)
		return i;
	else
		return -1;
}

/**
 * vcc_table_remove() - Removes a VCC port from the VCC table
 * @index: Index into the VCC table
 */
static void vcc_table_remove(unsigned long index)
{
	unsigned long flags;

	if (WARN_ON(index >= VCC_MAX_PORTS))
		return;

	spin_lock_irqsave(&vcc_table_lock, flags);
	vcc_table[index] = NULL;
	spin_unlock_irqrestore(&vcc_table_lock, flags);
}

/**
 * vcc_get() - Gets a reference to VCC port
 * @index: Index into the VCC table
 * @excl: Indicates if an exclusive access is requested
 *
 * Return: reference to the VCC port, if found
 *	   NULL, if port not found
 */
static struct vcc_port *vcc_get(unsigned long index, bool excl)
{
	struct vcc_port *port;
	unsigned long flags;

try_again:
	spin_lock_irqsave(&vcc_table_lock, flags);

	port = vcc_table[index];
	if (!port) {
		spin_unlock_irqrestore(&vcc_table_lock, flags);
		return NULL;
	}

	if (!excl) {
		if (port->excl_locked) {
			spin_unlock_irqrestore(&vcc_table_lock, flags);
			udelay(VCC_REF_DELAY);
			goto try_again;
		}
		port->refcnt++;
		spin_unlock_irqrestore(&vcc_table_lock, flags);
		return port;
	}

	if (port->refcnt) {
		spin_unlock_irqrestore(&vcc_table_lock, flags);
		/* Threads wanting exclusive access will wait half the time,
		 * probably giving them higher priority in the case of
		 * multiple waiters.
		 */
		udelay(VCC_REF_DELAY/2);
		goto try_again;
	}

	port->refcnt++;
	port