@/***************************************************************************
@ * 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                                                              */
@/**                                                                       */
@/**************************************************************************/
@/**************************************************************************/
@
@#define TX_SOURCE_CODE
@
@
@/* Include necessary system files.  */
@
@#include "tx_api.h"
@#include "tx_thread.h"
@#include "tx_timer.h"
@
@
    .global     _tx_thread_current_ptr
    .global     _tx_timer_time_slice
    .global     _tx_thread_schedule
    .global     _tx_thread_preempt_disable
    .global     _tx_thread_smp_protection
#ifdef TX_ENABLE_EXECUTION_CHANGE_NOTIFY
    .global     _tx_execution_thread_exit
#endif
@
@
    .arm
    .text
    .align 2
@/**************************************************************************/
@/*                                                                        */
@/*  FUNCTION                                               RELEASE        */
@/*                                                                        */
@/*    _tx_thread_system_return                        SMP/Cortex-A7/GNU   */
@/*                                                            6.1         */
@/*  AUTHOR                                                                */
@/*                                                                        */
@/*    William E. Lamie, Microsoft Corporation                             */
@/*                                                                        */
@/*  DESCRIPTION                                                           */
@/*                                                                        */
@/*    This function is target processor specific.  It is used to transfer */
@/*    control from a thread back to the ThreadX system.  Only a           */
@/*    minimal context is saved since the compiler assumes temp registers  */
@/*    are going to get slicked by a function call anyway.                 */
@/*                                                                        */
@/*  INPUT                                                                 */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  OUTPUT                                                                */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  CALLS                                                                 */
@/*                                                                        */
@/*    _tx_thread_schedule                   Thread scheduling loop        */
@/*                                                                        */
@/*  CALLED BY                                                             */
@/*                                                                        */
@/*    ThreadX components                                                  */
@/*                                                                        */
@/**************************************************************************/
@VOID   _tx_thread_system_return(VOID)
@{
    .global _tx_thread_system_return
    .type   _tx_thread_system_return,function
_tx_thread_system_return:
@
@    /* Save minimal context on the stack.  */
@
    STMDB   sp!, {r4-r11, lr}                   @ Save minimal context
@
@    /* Pickup the CPU ID.   */
@
    MRC     p15, 0, r10, c0, c0, 5              @ Read CPU ID register
    AND     r10, r10, #0x03                     @ Mask off, leaving the CPU ID field
    LSL     r12, r10, #2                        @ Build offset to array indexes

    LDR     r3, =_tx_thread_current_ptr         @ Pickup address of current ptr
    ADD     r3, r3, r12                         @ Build index into current ptr array
    LDR     r0, [r3, #0]                        @ Pickup current thread pointer
#ifdef TARGET_FPU_VFP
    LDR     r1, [r0, #160]                      @ Pickup the VFP enabled flag
    CMP     r1, #0                              @ Is the VFP enabled?
    BEQ     _tx_skip_solicited_vfp_save         @ No, skip VFP solicited save
    FMRX    r4, FPSCR                           @ Pickup the FPSCR
    STR     r4, [sp, #-4]!                      @ Save FPSCR
    VSTMDB  sp!, {D16-D31}                      @ Save D16-D31
    VSTMDB  sp!, {D8-D15}                       @ Save D8-D15
_tx_skip_solicited_vfp_save:
#endif
    MOV     r4, #0                              @ Build a solicited stack type
    MRS     r5, CPSR                            @ Pickup the CPSR
    STMDB   sp!, {r4-r5}                        @ Save type and CPSR
@
@   /* Lockout interrupts.  */
@
#ifdef TX_ENABLE_FIQ_SUPPORT
    CPSID   if                                  @ Disable IRQ and FIQ interrupts
#else
    CPSID   i                                   @ Disable IRQ interrupts
#endif

#ifdef TX_ENABLE_EXECUTION_CHANGE_NOTIFY
@
@    /* Call the thread exit function to indicate the thread is no longer executing.  */
@
    MOV     r4, r0                              @ Save r0
    MOV     r5, r3                              @ Save r3
    MOV     r6, r12                             @ Save r12
    BL      _tx_execution_thread_exit           @ Call the thread exit function
    MOV     r3, r5                              @ Recover r3
    MOV     r0, r4                              @ Recover r4
    MOV     r12,r6                              @ Recover r12
#endif
@
    LDR     r2, =_tx_timer_time_slice           @ Pickup address of time slice
    ADD     r2, r2, r12                         @ Build index into time-slice array
    LDR     r1, [r2, #0]                        @ Pickup current time slice
@
@    /* Save current stack and switch to system stack.  */
@    _tx_thread_current_ptr[core] -> tx_thread_stack_ptr =  sp;
@    sp = _tx_thread_system_stack_ptr[core];
@
    STR     sp, [r0, #8]                        @ Save thread stack pointer
@
@    /* Determine if the time-slice is active.  */
@    if (_tx_timer_time_slice[core])
@    {
@
    MOV     r4, #0                              @ Build clear value
    CMP     r1, #0                              @ Is a time-slice active?
    BEQ     __tx_thread_dont_save_ts            @ No, don't save the time-slice
@
@       /* Save time-slice for the thread and clear the current time-slice.  */
@       _tx_thread_current_ptr[core] -> tx_thread_time_slice =  _tx_timer_time_slice[core];
@       _tx_timer_time_slice[core] =  0;
@
    STR     r4, [r2, #0]                        @ Clear time-slice
    STR     r1, [r0, #24]                       @ Save current time-slice
@
@    }
__tx_thread_dont_save_ts:
@
@    /* Clear the current thread pointer.  */
@    _tx_thread_current_ptr[core] =  TX_NULL;
@
    STR     r4, [r3, #0]                        @ Clear current thread pointer
@
@    /* Set ready bit in thread control block.  */
@
    LDR     r2, [r0, #152]                      @ Pickup word with ready bit
    ORR     r2, r2, #0x8000                     @ Build ready bit set
    DMB                                         @ Ensure that accesses to shared resource have completed
    STR     r2, [r0, #152]                      @ Set ready bit
@
@    /* Now clear protection. It is assumed that protection is in force whenever this routine is called.  */
@
    LDR     r3, =_tx_thread_smp_protection      @ Pickup address of protection structure

#ifdef TX_MPCORE_DEBUG_ENABLE
    STR     lr, [r3, #24]                       @ Save last caller
    LDR     r2, [r3, #4]                        @ Pickup owning thread
    CMP     r0, r2                              @ Is it the same as the current thread?
__error_loop:
    BNE     __error_loop                        @ If not, we have a problem!!
#endif

    LDR     r1, =_tx_thread_preempt_disable     @ Build address to preempt disable flag
    MOV     r2, #0                              @ Build clear value
    STR     r2, [r1, #0]                        @ Clear preempt disable flag
    STR     r2, [r3, #12]                       @ Clear protection count
    MOV     r1, #0xFFFFFFFF                     @ Build invalid value
    STR     r1, [r3, #8]                        @ Set core to an invalid value
    DMB                                         @ Ensure that accesses to shared resource have completed
    STR     r2, [r3]                            @ Clear protection
    DSB                                         @ To ensure update of the shared resource occurs before other CPUs awake
    SEV                                         @ Send event to other CPUs, wakes anyone waiting on a mutex (using WFE)

    B       _tx_thread_schedule                 @ Jump to scheduler!
@
@}


