ports/arm9/gnu/src/tx_thread_fiq_nesting_start.S


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@/***************************************************************************
@ * Copyright (c) 2024 Microsoft Corporation
@ *
@ * This program and the accompanying materials are made available under the
@ * terms of the MIT License which is available at
@ * https://opensource.org/licenses/MIT.
@ *
@ * SPDX-License-Identifier: MIT
@ **************************************************************************/
@
@
@/**************************************************************************/
@/**************************************************************************/
@/**                                                                       */
@/** ThreadX Component                                                     */
@/**                                                                       */
@/**   Thread                                                              */
@/**                                                                       */
@/**************************************************************************/
@/**************************************************************************/
#ifdef TX_INCLUDE_USER_DEFINE_FILE
#include "tx_user.h"
#endif

FIQ_DISABLE     =       0x40                    @ FIQ disable bit
MODE_MASK       =       0x1F                    @ Mode mask
SYS_MODE_BITS   =       0x1F                    @ System mode bits
@
@
@/* No 16-bit Thumb mode veneer code is needed for _tx_thread_fiq_nesting_start
@   since it will never be called 16-bit mode.  */
@
    .arm
    .text
    .align 2
@/**************************************************************************/
@/*                                                                        */
@/*  FUNCTION                                               RELEASE        */
@/*                                                                        */
@/*    _tx_thread_fiq_nesting_start                         ARM9/GNU       */
@/*                                                           6.2.1        */
@/*  AUTHOR                                                                */
@/*                                                                        */
@/*    William E. Lamie, Microsoft Corporation                             */
@/*                                                                        */
@/*  DESCRIPTION                                                           */
@/*                                                                        */
@/*    This function is called by the application from FIQ mode after      */
@/*    _tx_thread_fiq_context_save has been called and switches the FIQ    */
@/*    processing to the system mode so nested FIQ interrupt processing    */
@/*    is possible (system mode has its own "lr" register).  Note that     */
@/*    this function assumes that the system mode stack pointer was setup  */
@/*    during low-level initialization (tx_initialize_low_level.s).        */
@/*                                                                        */
@/*    This function returns with FIQ interrupts enabled.                  */
@/*                                                                        */
@/*  INPUT                                                                 */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  OUTPUT                                                                */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  CALLS                                                                 */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  CALLED BY                                                             */
@/*                                                                        */
@/*    ISRs                                                                */
@/*                                                                        */
@/**************************************************************************/
@VOID   _tx_thread_fiq_nesting_start(VOID)
@{
    .global  _tx_thread_fiq_nesting_start
    .type    _tx_thread_fiq_nesting_start,function
_tx_thread_fiq_nesting_start:
    MOV     r3,lr                               @ Save ISR return address
    MRS     r0, CPSR                            @ Pickup the CPSR
    BIC     r0, r0, #MODE_MASK                  @ Clear the mode bits
    ORR     r0, r0, #SYS_MODE_BITS              @ Build system mode CPSR
    MSR     CPSR_cxsf, r0                       @ Enter system mode
    STMDB   sp!, {r1, lr}                       @ Push the system mode lr on the system mode stack
                                                @   and push r1 just to keep 8-byte alignment
    BIC     r0, r0, #FIQ_DISABLE                @ Build enable FIQ CPSR
    MSR     CPSR_cxsf, r0                       @ Enter system mode
    MOV     pc, r3                              @ Return to caller
@}