/*
 * Copyright (c) 2020, Texas Instruments Incorporated
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * *  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * *  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * *  Neither the name of Texas Instruments Incorporated nor the names of
 *    its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdint.h>

#include <ti/driverlib/dl_common.h>

void DL_Common_delayCycles(uint32_t cycles)
{
    /* this is a scratch register for the compiler to use */
    uint32_t scratch;

    /* There will be a 2 cycle delay here to fetch & decode instructions
     * if branch and linking to this function */

    /* Subtract 2 net cycles for constant offset: +2 cycles for entry jump,
     * +2 cycles for exit, -1 cycle for a shorter loop cycle on the last loop,
     * -1 for this instruction */

    __asm volatile(
#ifdef __GNUC__
        ".syntax unified\n\t"
#endif
        "SUBS %0, %[numCycles], #2; \n"
        "%=: \n\t"
        "SUBS %0, %0, #4; \n\t"
        "NOP; \n\t"
        "BHS  %=b;" /* branches back to the label defined above if number > 0 */
        /* Return: 2 cycles */
        : "=&r"(scratch)
        : [ numCycles ] "r"(cycles));
}