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
  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