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serial: uartlite: Reset RX/TX in init
[u-boot] / drivers / serial / sandbox.c
1 /*
2  * Copyright (c) 2011 The Chromium OS Authors.
3  *
4  * SPDX-License-Identifier:     GPL-2.0+
5  */
6
7 /*
8  * This provide a test serial port. It provides an emulated serial port where
9  * a test program and read out the serial output and inject serial input for
10  * U-Boot.
11  */
12
13 #include <common.h>
14 #include <os.h>
15 #include <serial.h>
16 #include <linux/compiler.h>
17
18 /*
19  *
20  *   serial_buf: A buffer that holds keyboard characters for the
21  *               Sandbox U-boot.
22  *
23  * invariants:
24  *   serial_buf_write            == serial_buf_read -> empty buffer
25  *   (serial_buf_write + 1) % 16 == serial_buf_read -> full buffer
26  */
27 static char serial_buf[16];
28 static unsigned int serial_buf_write;
29 static unsigned int serial_buf_read;
30
31 static int sandbox_serial_init(void)
32 {
33         os_tty_raw(0);
34         return 0;
35 }
36
37 static void sandbox_serial_setbrg(void)
38 {
39 }
40
41 static void sandbox_serial_putc(const char ch)
42 {
43         os_write(1, &ch, 1);
44 }
45
46 static void sandbox_serial_puts(const char *str)
47 {
48         os_write(1, str, strlen(str));
49 }
50
51 static unsigned int increment_buffer_index(unsigned int index)
52 {
53         return (index + 1) % ARRAY_SIZE(serial_buf);
54 }
55
56 static int sandbox_serial_tstc(void)
57 {
58         const unsigned int next_index =
59                 increment_buffer_index(serial_buf_write);
60         ssize_t count;
61
62         os_usleep(100);
63         if (next_index == serial_buf_read)
64                 return 1;       /* buffer full */
65
66         count = os_read_no_block(0, &serial_buf[serial_buf_write], 1);
67         if (count == 1)
68                 serial_buf_write = next_index;
69         return serial_buf_write != serial_buf_read;
70 }
71
72 static int sandbox_serial_getc(void)
73 {
74         int result;
75
76         while (!sandbox_serial_tstc())
77                 ;       /* buffer empty */
78
79         result = serial_buf[serial_buf_read];
80         serial_buf_read = increment_buffer_index(serial_buf_read);
81         return result;
82 }
83
84 static struct serial_device sandbox_serial_drv = {
85         .name   = "sandbox_serial",
86         .start  = sandbox_serial_init,
87         .stop   = NULL,
88         .setbrg = sandbox_serial_setbrg,
89         .putc   = sandbox_serial_putc,
90         .puts   = sandbox_serial_puts,
91         .getc   = sandbox_serial_getc,
92         .tstc   = sandbox_serial_tstc,
93 };
94
95 void sandbox_serial_initialize(void)
96 {
97         serial_register(&sandbox_serial_drv);
98 }
99
100 __weak struct serial_device *default_serial_console(void)
101 {
102         return &sandbox_serial_drv;
103 }