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 _debug_uart_putc(ch); \ 121 } \ 122 \ 123 void printascii(const char *str) \ 124 { \ 125 while (*str) \ 126 _debug_uart_putc(*str++); \ 127 } \ 128 \ 129 static inline void printhex1(uint digit) \ 130 { \ 131 digit &= 0xf; \ 132 _debug_uart_putc(digit > 9 ? digit - 10 + 'a' : digit + '0'); \ 133 } \ 134 \ 135 static inline void printhex(uint value, int digits) \ 136 { \ 137 while (digits-- > 0) \ 138 printhex1(value >> (4 * digits)); \ 139 } \ 140 \ 141 void printhex2(uint value) \ 142 { \ 143 printhex(value, 2); \ 144 } \ 145 \ 146 void printhex4(uint value) \ 147 { \ 148 printhex(value, 4); \ 149 } \ 150 \ 151 void printhex8(uint value) \ 152 { \ 153 printhex(value, 8); \ 154 } \ 155 \ 156 void debug_uart_init(void) \ 157 { \ 158 board_debug_uart_init(); \ 159 _debug_uart_init(); \ 160 _DEBUG_UART_ANNOUNCE \ 161 } \ 162 163 #endif 164