debug_uart.h
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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