1/* Copyright (c) 2010, 2014 The Linux Foundation. All rights reserved.
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License version 2 and
5 * only version 2 as published by the Free Software Foundation.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
10 * GNU General Public License for more details.
11 */
12
13#include <linux/init.h>
14
15#include <asm/dcc.h>
16#include <asm/processor.h>
17
18#include "hvc_console.h"
19
20/* DCC Status Bits */
21#define DCC_STATUS_RX		(1 << 30)
22#define DCC_STATUS_TX		(1 << 29)
23
24static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
25{
26	int i;
27
28	for (i = 0; i < count; i++) {
29		while (__dcc_getstatus() & DCC_STATUS_TX)
30			cpu_relax();
31
32		__dcc_putchar(buf[i]);
33	}
34
35	return count;
36}
37
38static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
39{
40	int i;
41
42	for (i = 0; i < count; ++i)
43		if (__dcc_getstatus() & DCC_STATUS_RX)
44			buf[i] = __dcc_getchar();
45		else
46			break;
47
48	return i;
49}
50
51static bool hvc_dcc_check(void)
52{
53	unsigned long time = jiffies + (HZ / 10);
54
55	/* Write a test character to check if it is handled */
56	__dcc_putchar('\n');
57
58	while (time_is_after_jiffies(time)) {
59		if (!(__dcc_getstatus() & DCC_STATUS_TX))
60			return true;
61	}
62
63	return false;
64}
65
66static const struct hv_ops hvc_dcc_get_put_ops = {
67	.get_chars = hvc_dcc_get_chars,
68	.put_chars = hvc_dcc_put_chars,
69};
70
71static int __init hvc_dcc_console_init(void)
72{
73	int ret;
74
75	if (!hvc_dcc_check())
76		return -ENODEV;
77
78	/* Returns -1 if error */
79	ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
80
81	return ret < 0 ? -ENODEV : 0;
82}
83console_initcall(hvc_dcc_console_init);
84
85static int __init hvc_dcc_init(void)
86{
87	struct hvc_struct *p;
88
89	if (!hvc_dcc_check())
90		return -ENODEV;
91
92	p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
93
94	return PTR_ERR_OR_ZERO(p);
95}
96device_initcall(hvc_dcc_init);
97