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
hvc_dcc_put_chars(uint32_t vt,const char * buf,int count)24 static 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
hvc_dcc_get_chars(uint32_t vt,char * buf,int count)38 static 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
hvc_dcc_check(void)51 static 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
66 static 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
hvc_dcc_console_init(void)71 static int __init hvc_dcc_console_init(void)
72 {
73 if (!hvc_dcc_check())
74 return -ENODEV;
75
76 hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
77 return 0;
78 }
79 console_initcall(hvc_dcc_console_init);
80
hvc_dcc_init(void)81 static int __init hvc_dcc_init(void)
82 {
83 if (!hvc_dcc_check())
84 return -ENODEV;
85
86 hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
87 return 0;
88 }
89 device_initcall(hvc_dcc_init);
90