1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2010, 2014 The Linux Foundation. All rights reserved. */
3
4 #include <linux/console.h>
5 #include <linux/init.h>
6 #include <linux/serial.h>
7 #include <linux/serial_core.h>
8
9 #include <asm/dcc.h>
10 #include <asm/processor.h>
11
12 #include "hvc_console.h"
13
14 /* DCC Status Bits */
15 #define DCC_STATUS_RX (1 << 30)
16 #define DCC_STATUS_TX (1 << 29)
17
dcc_uart_console_putchar(struct uart_port * port,int ch)18 static void dcc_uart_console_putchar(struct uart_port *port, int ch)
19 {
20 while (__dcc_getstatus() & DCC_STATUS_TX)
21 cpu_relax();
22
23 __dcc_putchar(ch);
24 }
25
dcc_early_write(struct console * con,const char * s,unsigned n)26 static void dcc_early_write(struct console *con, const char *s, unsigned n)
27 {
28 struct earlycon_device *dev = con->data;
29
30 uart_console_write(&dev->port, s, n, dcc_uart_console_putchar);
31 }
32
dcc_early_console_setup(struct earlycon_device * device,const char * opt)33 static int __init dcc_early_console_setup(struct earlycon_device *device,
34 const char *opt)
35 {
36 device->con->write = dcc_early_write;
37
38 return 0;
39 }
40
41 EARLYCON_DECLARE(dcc, dcc_early_console_setup);
42
hvc_dcc_put_chars(uint32_t vt,const char * buf,int count)43 static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
44 {
45 int i;
46
47 for (i = 0; i < count; i++) {
48 while (__dcc_getstatus() & DCC_STATUS_TX)
49 cpu_relax();
50
51 __dcc_putchar(buf[i]);
52 }
53
54 return count;
55 }
56
hvc_dcc_get_chars(uint32_t vt,char * buf,int count)57 static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
58 {
59 int i;
60
61 for (i = 0; i < count; ++i)
62 if (__dcc_getstatus() & DCC_STATUS_RX)
63 buf[i] = __dcc_getchar();
64 else
65 break;
66
67 return i;
68 }
69
hvc_dcc_check(void)70 static bool hvc_dcc_check(void)
71 {
72 unsigned long time = jiffies + (HZ / 10);
73
74 /* Write a test character to check if it is handled */
75 __dcc_putchar('\n');
76
77 while (time_is_after_jiffies(time)) {
78 if (!(__dcc_getstatus() & DCC_STATUS_TX))
79 return true;
80 }
81
82 return false;
83 }
84
85 static const struct hv_ops hvc_dcc_get_put_ops = {
86 .get_chars = hvc_dcc_get_chars,
87 .put_chars = hvc_dcc_put_chars,
88 };
89
hvc_dcc_console_init(void)90 static int __init hvc_dcc_console_init(void)
91 {
92 int ret;
93
94 if (!hvc_dcc_check())
95 return -ENODEV;
96
97 /* Returns -1 if error */
98 ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
99
100 return ret < 0 ? -ENODEV : 0;
101 }
102 console_initcall(hvc_dcc_console_init);
103
hvc_dcc_init(void)104 static int __init hvc_dcc_init(void)
105 {
106 struct hvc_struct *p;
107
108 if (!hvc_dcc_check())
109 return -ENODEV;
110
111 p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
112
113 return PTR_ERR_OR_ZERO(p);
114 }
115 device_initcall(hvc_dcc_init);
116