Root/drivers/tty/hvc/hvc_dcc.c

1/* Copyright (c) 2010, Code Aurora Forum. 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 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
15 * 02110-1301, USA.
16 */
17
18#include <linux/console.h>
19#include <linux/delay.h>
20#include <linux/err.h>
21#include <linux/init.h>
22#include <linux/moduleparam.h>
23#include <linux/types.h>
24
25#include <asm/processor.h>
26
27#include "hvc_console.h"
28
29/* DCC Status Bits */
30#define DCC_STATUS_RX (1 << 30)
31#define DCC_STATUS_TX (1 << 29)
32
33static inline u32 __dcc_getstatus(void)
34{
35    u32 __ret;
36    asm volatile("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg"
37        : "=r" (__ret) : : "cc");
38
39    return __ret;
40}
41
42
43static inline char __dcc_getchar(void)
44{
45    char __c;
46
47    asm volatile("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg"
48        : "=r" (__c));
49    isb();
50
51    return __c;
52}
53
54static inline void __dcc_putchar(char c)
55{
56    asm volatile("mcr p14, 0, %0, c0, c5, 0 @ write a char"
57        : /* no output register */
58        : "r" (c));
59    isb();
60}
61
62static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
63{
64    int i;
65
66    for (i = 0; i < count; i++) {
67        while (__dcc_getstatus() & DCC_STATUS_TX)
68            cpu_relax();
69
70        __dcc_putchar(buf[i]);
71    }
72
73    return count;
74}
75
76static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
77{
78    int i;
79
80    for (i = 0; i < count; ++i)
81        if (__dcc_getstatus() & DCC_STATUS_RX)
82            buf[i] = __dcc_getchar();
83        else
84            break;
85
86    return i;
87}
88
89static const struct hv_ops hvc_dcc_get_put_ops = {
90    .get_chars = hvc_dcc_get_chars,
91    .put_chars = hvc_dcc_put_chars,
92};
93
94static int __init hvc_dcc_console_init(void)
95{
96    hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
97    return 0;
98}
99console_initcall(hvc_dcc_console_init);
100
101static int __init hvc_dcc_init(void)
102{
103    hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
104    return 0;
105}
106device_initcall(hvc_dcc_init);
107

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