@/**************************************************************************/
@/*                                                                        */
@/*       Copyright (c) Microsoft Corporation. All rights reserved.        */
@/*                                                                        */
@/*       This software is licensed under the Microsoft Software License   */
@/*       Terms for Microsoft Azure RTOS. Full text of the license can be  */
@/*       found in the LICENSE file at https://aka.ms/AzureRTOS_EULA       */
@/*       and in the root directory of this software.                      */
@/*                                                                        */
@/**************************************************************************/
@
@
@/**************************************************************************/
@/**************************************************************************/
@/**                                                                       */
@/** ThreadX Component                                                     */
@/**                                                                       */
@/**   Timer                                                               */
@/**                                                                       */
@/**************************************************************************/
@/**************************************************************************/
@
@#define TX_SOURCE_CODE
@
@
@/* Include necessary system files.  */
@
@#include "tx_api.h"
@#include "tx_timer.h"
@#include "tx_thread.h"
@
@
@Define Assembly language external references...
@
    .global      _tx_timer_time_slice
    .global      _tx_timer_system_clock
    .global      _tx_timer_current_ptr
    .global      _tx_timer_list_start
    .global      _tx_timer_list_end
    .global      _tx_timer_expired_time_slice
    .global      _tx_timer_expired
    .global      _tx_thread_time_slice
    .global      _tx_timer_expiration_process
@
@
    .text
    .align 4
    .syntax unified
@/**************************************************************************/
@/*                                                                        */
@/*  FUNCTION                                               RELEASE        */
@/*                                                                        */
@/*    _tx_timer_interrupt                               Cortex-M3/GNU     */
@/*                                                           6.0          */
@/*  AUTHOR                                                                */
@/*                                                                        */
@/*    William E. Lamie, Microsoft Corporation                             */
@/*                                                                        */
@/*  DESCRIPTION                                                           */
@/*                                                                        */
@/*    This function processes the hardware timer interrupt.  This         */
@/*    processing includes incrementing the system clock and checking for  */
@/*    time slice and/or timer expiration.  If either is found, the        */
@/*    interrupt context save/restore functions are called along with the  */
@/*    expiration functions.                                               */
@/*                                                                        */
@/*  INPUT                                                                 */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  OUTPUT                                                                */
@/*                                                                        */
@/*    None                                                                */
@/*                                                                        */
@/*  CALLS                                                                 */
@/*                                                                        */
@/*    _tx_timer_expiration_process          Timer expiration processing   */
@/*    _tx_thread_time_slice                 Time slice interrupted thread */
@/*                                                                        */
@/*  CALLED BY                                                             */
@/*                                                                        */
@/*    interrupt vector                                                    */
@/*                                                                        */
@/*  RELEASE HISTORY                                                       */
@/*                                                                        */
@/*    DATE              NAME                      DESCRIPTION             */
@/*                                                                        */
@/*  05-19-2020     William E. Lamie         Initial Version 6.0           */
@/*                                                                        */
@/**************************************************************************/
@VOID   _tx_timer_interrupt(VOID)
@{
    .global  _tx_timer_interrupt
    .thumb_func
_tx_timer_interrupt:
@
@    /* Upon entry to this routine, it is assumed that context save has already
@       been called, and therefore the compiler scratch registers are available
@       for use.  */
@
@    /* Increment the system clock.  */
@    _tx_timer_system_clock++;
@
    LDR     r1, =_tx_timer_system_clock             @ Pickup address of system clock
    LDR     r0, [r1, #0]                            @ Pickup system clock
    ADD     r0, r0, #1                              @ Increment system clock
    STR     r0, [r1, #0]                            @ Store new system clock
@
@    /* Test for time-slice expiration.  */
@    if (_tx_timer_time_slice)
@    {
@
    LDR     r3, =_tx_timer_time_slice               @ Pickup address of time-slice 
    LDR     r2, [r3, #0]                            @ Pickup time-slice
    CMP     r2, #0                                  @ Is it non-active?
    BEQ     __tx_timer_no_time_slice                @ Yes, skip time-slice processing
@
@       /* Decrement the time_slice.  */
@       _tx_timer_time_slice--;
@
    SUB     r2, r2, #1                              @ Decrement the time-slice
    STR     r2, [r3, #0]                            @ Store new time-slice value
@
@       /* Check for expiration.  */
@       if (__tx_timer_time_slice == 0)
@
    CMP     r2, #0                                  @ Has it expired?
    BNE     __tx_timer_no_time_slice                @ No, skip expiration processing
@
@       /* Set the time-slice expired flag.  */
@       _tx_timer_expired_time_slice =  TX_TRUE;
@
    LDR     r3, =_tx_timer_expired_time_slice       @ Pickup address of expired flag
    MOV     r0, #1                                  @ Build expired value
    STR     r0, [r3, #0]                            @ Set time-slice expiration flag
@
@    }
@
__tx_timer_no_time_slice:
@
@    /* Test for timer expiration.  */
@    if (*_tx_timer_current_ptr)
@    {
@
    LDR     r1, =_tx_timer_current_ptr              @ Pickup current timer pointer address
    LDR     r0, [r1, #0]                            @ Pickup current timer
    LDR     r2, [r0, #0]                            @ Pickup timer list entry
    CMP     r2, #0                                  @ Is there anything in the list?
    BEQ     __tx_timer_no_timer                     @ No, just increment the timer
@
@        /* Set expiration flag.  */
@        _tx_timer_expired =  TX_TRUE;
@
    LDR     r3, =_tx_timer_expired                  @ Pickup expiration flag address
    MOV     r2, #1                                  @ Build expired value
    STR     r2, [r3, #0]                            @ Set expired flag
    B       __tx_timer_done                         @ Finished timer processing
@
@    }
@    else
@    {
__tx_timer_no_timer:
@
@        /* No timer expired, increment the timer pointer.  */
@        _tx_timer_current_ptr++;
@
    ADD     r0, r0, #4                              @ Move to next timer
@
@        /* Check for wrap-around.  */
@        if (_tx_timer_current_ptr == _tx_timer_list_end)
@
    LDR     r3, =_tx_timer_list_end                 @ Pickup addr of timer list end
    LDR     r2, [r3, #0]                            @ Pickup list end
    CMP     r0, r2                                  @ Are we at list end?
    BNE     __tx_timer_skip_wrap                    @ No, skip wrap-around logic
@
@            /* Wrap to beginning of list.  */
@            _tx_timer_current_ptr =  _tx_timer_list_start;
@
    LDR     r3, =_tx_timer_list_start               @ Pickup addr of timer list start
    LDR     r0, [r3, #0]                            @ Set current pointer to list start
@
__tx_timer_skip_wrap:
@
    STR     r0, [r1, #0]                            @ Store new current timer pointer
@    }
@
__tx_timer_done:
@
@
@    /* See if anything has expired.  */
@    if ((_tx_timer_expired_time_slice) || (_tx_timer_expired))
@    {
@
    LDR     r3, =_tx_timer_expired_time_slice       @ Pickup addr of expired flag
    LDR     r2, [r3, #0]                            @ Pickup time-slice expired flag
    CMP     r2, #0                                  @ Did a time-slice expire?
    BNE     __tx_something_expired                  @ If non-zero, time-slice expired
    LDR     r1, =_tx_timer_expired                  @ Pickup addr of other expired flag
    LDR     r0, [r1, #0]                            @ Pickup timer expired flag
    CMP     r0, #0                                  @ Did a timer expire?
    BEQ     __tx_timer_nothing_expired              @ No, nothing expired
@
__tx_something_expired:
@
@
    STMDB   sp!, {r0, lr}                           @ Save the lr register on the stack
                                                    @   and save r0 just to keep 8-byte alignment
@
@    /* Did a timer expire?  */
@    if (_tx_timer_expired)
@    {
@
    LDR     r1, =_tx_timer_expired                  @ Pickup addr of expired flag
    LDR     r0, [r1, #0]                            @ Pickup timer expired flag
    CMP     r0, #0                                  @ Check for timer expiration
    BEQ     __tx_timer_dont_activate                @ If not set, skip timer activation
@
@        /* Process timer expiration.  */
@        _tx_timer_expiration_process();
@
    BL      _tx_timer_expiration_process            @ Call the timer expiration handling routine
@
@    }
__tx_timer_dont_activate:
@
@    /* Did time slice expire?  */
@    if (_tx_timer_expired_time_slice)
@    {
@
    LDR     r3, =_tx_timer_expired_time_slice       @ Pickup addr of time-slice expired 
    LDR     r2, [r3, #0]                            @ Pickup the actual flag
    CMP     r2, #0                                  @ See if the flag is set
    BEQ     __tx_timer_not_ts_expiration            @ No, skip time-slice processing
@
@        /* Time slice interrupted thread.  */
@        _tx_thread_time_slice(); 
@
    BL      _tx_thread_time_slice                   @ Call time-slice processing
    LDR     r0, =_tx_thread_preempt_disable         @ Build address of preempt disable flag
    LDR     r1, [r0]                                @ Is the preempt disable flag set?
    CBNZ    r1, __tx_timer_skip_time_slice          @ Yes, skip the PendSV logic
    LDR     r0, =_tx_thread_current_ptr             @ Build current thread pointer address
    LDR     r1, [r0]                                @ Pickup the current thread pointer
    LDR     r2, =_tx_thread_execute_ptr             @ Build execute thread pointer address
    LDR     r3, [r2]                                @ Pickup the execute thread pointer
    LDR     r0, =0xE000ED04                         @ Build address of control register
    LDR     r2, =0x10000000                         @ Build value for PendSV bit
    CMP     r1, r3                                  @ Are they the same?
    BEQ     __tx_timer_skip_time_slice              @ If the same, there was no time-slice performed
    STR     r2, [r0]                                @ Not the same, issue the PendSV for preemption
__tx_timer_skip_time_slice:
@
@    }
@
__tx_timer_not_ts_expiration:
@
    LDMIA   sp!, {r0, lr}                           @ Recover lr register (r0 is just there for
                                                    @   the 8-byte stack alignment
@
@    }
@
__tx_timer_nothing_expired:

    DSB                                             @ Complete all memory access
    BX      lr                                      @ Return to caller
@
@}


