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 #include <linux/linkage.h> 14 15 /* 16 * The debug UART is intended for use very early in U-Boot to debug problems 17 * when an ICE or other debug mechanism is not available. 18 * 19 * To use it you should: 20 * - Make sure your UART supports this interface 21 * - Enable CONFIG_DEBUG_UART 22 * - Enable the CONFIG for your UART to tell it to provide this interface 23 * (e.g. CONFIG_DEBUG_UART_NS16550) 24 * - Define the required settings as needed (see below) 25 * - Call debug_uart_init() before use 26 * - Call printch() to output a character 27 * 28 * Depending on your platform it may be possible to use this UART before a 29 * stack is available. 30 * 31 * If your UART does not support this interface you can probably add support 32 * quite easily. Remember that you cannot use driver model and it is preferred 33 * to use no stack. 34 * 35 * You must not use this UART once driver model is working and the serial 36 * drivers are up and running (done in serial_init()). Otherwise the drivers 37 * may conflict and you will get strange output. 38 * 39 * 40 * To enable the debug UART in your serial driver: 41 * 42 * - #include <debug_uart.h> 43 * - Define debug_uart_init(), trying to avoid using the stack 44 * - Define _debug_uart_putc() as static inline (avoiding stack usage) 45 * - Immediately afterwards, add DEBUG_UART_FUNCS to define the rest of the 46 * functionality (printch(), etc.) 47 */ 48 49 /** 50 * debug_uart_init() - Set up the debug UART ready for use 51 * 52 * This sets up the UART with the correct baud rate, etc. 53 * 54 * Available CONFIG is: 55 * 56 * - CONFIG_DEBUG_UART_BASE: Base address of UART 57 * - CONFIG_BAUDRATE: Requested baud rate 58 * - CONFIG_DEBUG_UART_CLOCK: Input clock for UART 59 */ 60 void debug_uart_init(void); 61 62 /** 63 * printch() - Output a character to the debug UART 64 * 65 * @ch: Character to output 66 */ 67 asmlinkage void printch(int ch); 68 69 /** 70 * printascii() - Output an ASCII string to the debug UART 71 * 72 * @str: String to output 73 */ 74 asmlinkage void printascii(const char *str); 75 76 /** 77 * printhex2() - Output a 2-digit hex value 78 * 79 * @value: Value to output 80 */ 81 asmlinkage void printhex2(uint value); 82 83 /** 84 * printhex4() - Output a 4-digit hex value 85 * 86 * @value: Value to output 87 */ 88 asmlinkage void printhex4(uint value); 89 90 /** 91 * printhex8() - Output a 8-digit hex value 92 * 93 * @value: Value to output 94 */ 95 asmlinkage void printhex8(uint value); 96 97 /* 98 * Now define some functions - this should be inserted into the serial driver 99 */ 100 #define DEBUG_UART_FUNCS \ 101 asmlinkage void printch(int ch) \ 102 { \ 103 _debug_uart_putc(ch); \ 104 } \ 105 \ 106 asmlinkage void printascii(const char *str) \ 107 { \ 108 while (*str) \ 109 _debug_uart_putc(*str++); \ 110 } \ 111 \ 112 static inline void printhex1(uint digit) \ 113 { \ 114 digit &= 0xf; \ 115 _debug_uart_putc(digit > 9 ? digit - 10 + 'a' : digit + '0'); \ 116 } \ 117 \ 118 static inline void printhex(uint value, int digits) \ 119 { \ 120 while (digits-- > 0) \ 121 printhex1(value >> (4 * digits)); \ 122 } \ 123 \ 124 asmlinkage void printhex2(uint value) \ 125 { \ 126 printhex(value, 2); \ 127 } \ 128 \ 129 asmlinkage void printhex4(uint value) \ 130 { \ 131 printhex(value, 4); \ 132 } \ 133 \ 134 asmlinkage void printhex8(uint value) \ 135 { \ 136 printhex(value, 8); \ 137 } 138 139 #endif 140