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bootloader/u-boot_2015_04/include/debug_uart.h 3.25 KB
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  /*
   * Early debug UART support
   *
   * (C) Copyright 2014 Google, Inc
   * Writte by Simon Glass <sjg@chromium.org>
   *
   * SPDX-License-Identifier:	GPL-2.0+
   */
  
  #ifndef _DEBUG_UART_H
  #define _DEBUG_UART_H
  
  #include <linux/linkage.h>
  
  /*
   * The debug UART is intended for use very early in U-Boot to debug problems
   * when an ICE or other debug mechanism is not available.
   *
   * To use it you should:
   * - Make sure your UART supports this interface
   * - Enable CONFIG_DEBUG_UART
   * - Enable the CONFIG for your UART to tell it to provide this interface
   *       (e.g. CONFIG_DEBUG_UART_NS16550)
   * - Define the required settings as needed (see below)
   * - Call debug_uart_init() before use
   * - Call printch() to output a character
   *
   * Depending on your platform it may be possible to use this UART before a
   * stack is available.
   *
   * If your UART does not support this interface you can probably add support
   * quite easily. Remember that you cannot use driver model and it is preferred
   * to use no stack.
   *
   * You must not use this UART once driver model is working and the serial
   * drivers are up and running (done in serial_init()). Otherwise the drivers
   * may conflict and you will get strange output.
   *
   *
   * To enable the debug UART in your serial driver:
   *
   * - #include <debug_uart.h>
   * - Define debug_uart_init(), trying to avoid using the stack
   * - Define _debug_uart_putc() as static inline (avoiding stack usage)
   * - Immediately afterwards, add DEBUG_UART_FUNCS to define the rest of the
   *     functionality (printch(), etc.)
   */
  
  /**
   * debug_uart_init() - Set up the debug UART ready for use
   *
   * This sets up the UART with the correct baud rate, etc.
   *
   * Available CONFIG is:
   *
   *    - CONFIG_DEBUG_UART_BASE: Base address of UART
   *    - CONFIG_BAUDRATE: Requested baud rate
   *    - CONFIG_DEBUG_UART_CLOCK: Input clock for UART
   */
  void debug_uart_init(void);
  
  /**
   * printch() - Output a character to the debug UART
   *
   * @ch:		Character to output
   */
  asmlinkage void printch(int ch);
  
  /**
   * printascii() - Output an ASCII string to the debug UART
   *
   * @str:	String to output
   */
  asmlinkage void printascii(const char *str);
  
  /**
   * printhex2() - Output a 2-digit hex value
   *
   * @value:	Value to output
   */
  asmlinkage void printhex2(uint value);
  
  /**
   * printhex4() - Output a 4-digit hex value
   *
   * @value:	Value to output
   */
  asmlinkage void printhex4(uint value);
  
  /**
   * printhex8() - Output a 8-digit hex value
   *
   * @value:	Value to output
   */
  asmlinkage void printhex8(uint value);
  
  /*
   * Now define some functions - this should be inserted into the serial driver
   */
  #define DEBUG_UART_FUNCS \
  	asmlinkage void printch(int ch) \
  	{ \
  		_debug_uart_putc(ch); \
  	} \
  \
  	asmlinkage void printascii(const char *str) \
  	{ \
  		while (*str) \
  			_debug_uart_putc(*str++); \
  	} \
  \
  	static inline void printhex1(uint digit) \
  	{ \
  		digit &= 0xf; \
  		_debug_uart_putc(digit > 9 ? digit - 10 + 'a' : digit + '0'); \
  	} \
  \
  	static inline void printhex(uint value, int digits) \
  	{ \
  		while (digits-- > 0) \
  			printhex1(value >> (4 * digits)); \
  	} \
  \
  	asmlinkage void printhex2(uint value) \
  	{ \
  		printhex(value, 2); \
  	} \
  \
  	asmlinkage void printhex4(uint value) \
  	{ \
  		printhex(value, 4); \
  	} \
  \
  	asmlinkage void printhex8(uint value) \
  	{ \
  		printhex(value, 8); \
  	}
  
  #endif