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 47 /** 48 * debug_uart_init() - Set up the debug UART ready for use 49 * 50 * This sets up the UART with the correct baud rate, etc. 51 * 52 * Available CONFIG is: 53 * 54 * - CONFIG_DEBUG_UART_BASE: Base address of UART 55 * - CONFIG_BAUDRATE: Requested baud rate 56 * - CONFIG_DEBUG_UART_CLOCK: Input clock for UART 57 */ 58 void debug_uart_init(void); 59 60 /** 61 * printch() - Output a character to the debug UART 62 * 63 * @ch: Character to output 64 */ 65 void printch(int ch); 66 67 /** 68 * printascii() - Output an ASCII string to the debug UART 69 * 70 * @str: String to output 71 */ 72 void printascii(const char *str); 73 74 /** 75 * printhex2() - Output a 2-digit hex value 76 * 77 * @value: Value to output 78 */ 79 void printhex2(uint value); 80 81 /** 82 * printhex4() - Output a 4-digit hex value 83 * 84 * @value: Value to output 85 */ 86 void printhex4(uint value); 87 88 /** 89 * printhex8() - Output a 8-digit hex value 90 * 91 * @value: Value to output 92 */ 93 void printhex8(uint value); 94 95 /* 96 * Now define some functions - this should be inserted into the serial driver 97 */ 98 #define DEBUG_UART_FUNCS \ 99 void printch(int ch) \ 100 { \ 101 _debug_uart_putc(ch); \ 102 } \ 103 \ 104 void printascii(const char *str) \ 105 { \ 106 while (*str) \ 107 _debug_uart_putc(*str++); \ 108 } \ 109 \ 110 static inline void printhex1(uint digit) \ 111 { \ 112 digit &= 0xf; \ 113 _debug_uart_putc(digit > 9 ? digit - 10 + 'a' : digit + '0'); \ 114 } \ 115 \ 116 static inline void printhex(uint value, int digits) \ 117 { \ 118 while (digits-- > 0) \ 119 printhex1(value >> (4 * digits)); \ 120 } \ 121 \ 122 void printhex2(uint value) \ 123 { \ 124 printhex(value, 2); \ 125 } \ 126 \ 127 void printhex4(uint value) \ 128 { \ 129 printhex(value, 4); \ 130 } \ 131 \ 132 void printhex8(uint value) \ 133 { \ 134 printhex(value, 8); \ 135 } 136 137 #endif 138