xref: /openbmc/u-boot/include/debug_uart.h (revision 70b26cd0)
1 /*
2  * Early debug UART support
3  *
4  * (C) Copyright 2014 Google, Inc
5  * Writte by Simon Glass <sjg@chromium.org>
6  *
7  * SPDX-License-Identifier:	GPL-2.0+
8  */
9 
10 #ifndef _DEBUG_UART_H
11 #define _DEBUG_UART_H
12 
13 /*
14  * The debug UART is intended for use very early in U-Boot to debug problems
15  * when an ICE or other debug mechanism is not available.
16  *
17  * To use it you should:
18  * - Make sure your UART supports this interface
19  * - Enable CONFIG_DEBUG_UART
20  * - Enable the CONFIG for your UART to tell it to provide this interface
21  *       (e.g. CONFIG_DEBUG_UART_NS16550)
22  * - Define the required settings as needed (see below)
23  * - Call debug_uart_init() before use
24  * - Call printch() to output a character
25  *
26  * Depending on your platform it may be possible to use this UART before a
27  * stack is available.
28  *
29  * If your UART does not support this interface you can probably add support
30  * quite easily. Remember that you cannot use driver model and it is preferred
31  * to use no stack.
32  *
33  * You must not use this UART once driver model is working and the serial
34  * drivers are up and running (done in serial_init()). Otherwise the drivers
35  * may conflict and you will get strange output.
36  *
37  *
38  * To enable the debug UART in your serial driver:
39  *
40  * - #include <debug_uart.h>
41  * - Define _debug_uart_init(), trying to avoid using the stack
42  * - Define _debug_uart_putc() as static inline (avoiding stack usage)
43  * - Immediately afterwards, add DEBUG_UART_FUNCS to define the rest of the
44  *     functionality (printch(), etc.)
45  *
46  * If your board needs additional init for the UART to work, enable
47  * CONFIG_DEBUG_UART_BOARD_INIT and write a function called
48  * board_debug_uart_init() to perform that init. When debug_uart_init() is
49  * called, the init will happen automatically.
50  */
51 
52 /**
53  * debug_uart_init() - Set up the debug UART ready for use
54  *
55  * This sets up the UART with the correct baud rate, etc.
56  *
57  * Available CONFIG is:
58  *
59  *    - CONFIG_DEBUG_UART_BASE: Base address of UART
60  *    - CONFIG_BAUDRATE: Requested baud rate
61  *    - CONFIG_DEBUG_UART_CLOCK: Input clock for UART
62  */
63 void debug_uart_init(void);
64 
65 #ifdef CONFIG_DEBUG_UART_BOARD_INIT
66 void board_debug_uart_init(void);
67 #else
68 static inline void board_debug_uart_init(void)
69 {
70 }
71 #endif
72 
73 /**
74  * printch() - Output a character to the debug UART
75  *
76  * @ch:		Character to output
77  */
78 void printch(int ch);
79 
80 /**
81  * printascii() - Output an ASCII string to the debug UART
82  *
83  * @str:	String to output
84  */
85 void printascii(const char *str);
86 
87 /**
88  * printhex2() - Output a 2-digit hex value
89  *
90  * @value:	Value to output
91  */
92 void printhex2(uint value);
93 
94 /**
95  * printhex4() - Output a 4-digit hex value
96  *
97  * @value:	Value to output
98  */
99 void printhex4(uint value);
100 
101 /**
102  * printhex8() - Output a 8-digit hex value
103  *
104  * @value:	Value to output
105  */
106 void printhex8(uint value);
107 
108 #ifdef CONFIG_DEBUG_UART_ANNOUNCE
109 #define _DEBUG_UART_ANNOUNCE	printascii("<debug_uart> ");
110 #else
111 #define _DEBUG_UART_ANNOUNCE
112 #endif
113 
114 /*
115  * Now define some functions - this should be inserted into the serial driver
116  */
117 #define DEBUG_UART_FUNCS \
118 	void printch(int ch) \
119 	{ \
120 		if (ch == '\n') \
121 			_debug_uart_putc('\r'); \
122 		_debug_uart_putc(ch); \
123 	} \
124 \
125 	void printascii(const char *str) \
126 	{ \
127 		while (*str) \
128 			printch(*str++); \
129 	} \
130 \
131 	static inline void printhex1(uint digit) \
132 	{ \
133 		digit &= 0xf; \
134 		_debug_uart_putc(digit > 9 ? digit - 10 + 'a' : digit + '0'); \
135 	} \
136 \
137 	static inline void printhex(uint value, int digits) \
138 	{ \
139 		while (digits-- > 0) \
140 			printhex1(value >> (4 * digits)); \
141 	} \
142 \
143 	void printhex2(uint value) \
144 	{ \
145 		printhex(value, 2); \
146 	} \
147 \
148 	void printhex4(uint value) \
149 	{ \
150 		printhex(value, 4); \
151 	} \
152 \
153 	void printhex8(uint value) \
154 	{ \
155 		printhex(value, 8); \
156 	} \
157 \
158 	void debug_uart_init(void) \
159 	{ \
160 		board_debug_uart_init(); \
161 		_debug_uart_init(); \
162 		_DEBUG_UART_ANNOUNCE \
163 	} \
164 
165 #endif
166