include/debug_uart.h

   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