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/*  alt_log_macro.S
 *
 *  Implements the function tx_log_str, called by the assembly macro 
 *  ALT_LOG_PUTS().  The macro will be empty when logging is turned off,
 *  and this function will not be compiled.  When logging is on,
 *  this function is used to print out the strings defined in the beginning
 *  of alt_log_printf.c, using port information taken from system.h and 
 *  alt_log_printf.h.  
 *
 *  This routine only handles strings, and sends a character into the defined
 *  output device's output buffer when the device is ready. It's intended for 
 *  debugging purposes, where messages can be set to print out at certain 
 *  points in the boot code to indicate the progress of the program.
 *
 */

#ifndef __ALT_LOG_MACROS__
#define __ALT_LOG_MACROS__

/* define this flag to skip assembly-incompatible parts
 * of various include files. */
#define ALT_ASM_SRC

#ifdef ALT_LOG_ENABLE // only compile this function if this flag is defined. 
        
        #include "system.h"
        #include "sys/alt_log_printf.h"

        .global tx_log_str
tx_log_str:
        /* load base uart / jtag uart address into r6 */
        movhi r6, %hiadj(ALT_LOG_PORT_BASE)
        addi r6, r6, %lo(ALT_LOG_PORT_BASE)
tx_next_char:
        /* if pointer points to null, return 
         * r4 is the pointer to the str to be printed, set by ALT_LOG_PUTS */
        ldb r7, (r4)
        beq r0, r7, end_tx

        /* check device transmit ready  */
wait_tx_ready_loop:
        ldwio   r5, ALT_LOG_PRINT_REG_OFFSET(r6)
        andi    r5, r5, ALT_LOG_PRINT_MSK
        beq     r5, r0, wait_tx_ready_loop      
        /* write char */
        stwio   r7, ALT_LOG_PRINT_TXDATA_REG_OFFSET (r6)                
        /* advance string pointer */
        addi r4, r4, 1
        br tx_next_char
end_tx: 
        ret
    
#endif

#endif /* __ALT_LOG_MACROS__ */