source: rtems/cpukit/score/cpu/arm/cpu_asm.S @ fbda4a8

/**
 * @file
 *
 * @ingroup ScoreCPU
 *
 * @brief ARM architecture support implementation.
 */

/*
 *  This file contains all assembly code for the ARM implementation
 *  of RTEMS.
 *
 *  Copyright (c) 2007 by Ray Xu, <Rayx.cn@gmail.com>
 *          Thumb support added.
 *
 *  Copyright (c) 2002 by Advent Networks, Inc.
 *          Jay Monkman <jmonkman@adventnetworks.com>
 *
 *  COPYRIGHT (c) 2000 Canon Research Centre France SA.
 *  Emmanuel Raguet, mailto:raguet@crf.canon.fr
 *
 *  Copyright (c) 2013-2014 embedded brains GmbH
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/asm.h>

#ifdef ARM_MULTILIB_ARCH_V4

        .text

/*
 *  void _CPU_Context_switch( run_context, heir_context )
 *  void _CPU_Context_restore( run_context, heir_context )
 *
 *  This routine performs a normal non-FP context.
 *
 *  R0 = run_context    R1 = heir_context
 *
 *  This function copies the current registers to where r0 points, then
 *  restores the ones from where r1 points.
 *
 *  Using the ldm/stm opcodes save 2-3 us on 100 MHz ARM9TDMI with
 *  a 16 bit data bus.
 *
 */

DEFINE_FUNCTION_ARM(_CPU_Context_switch)
/* Start saving context */
        mrs     r2, CPSR
        stmia   r0,  {r2, r4, r5, r6, r7, r8, r9, r10, r11, r13, r14}

#ifdef ARM_MULTILIB_VFP_D32
        add     r3, r0, #ARM_CONTEXT_CONTROL_D8_OFFSET
        vstm    r3, {d8-d15}
#endif

#ifdef ARM_MULTILIB_HAS_THREAD_ID_REGISTER
        mrc     p15, 0, r3, c13, c0, 3
        str     r3, [r0, #ARM_CONTEXT_CONTROL_THREAD_ID_OFFSET]
#endif

#ifdef RTEMS_SMP
        /* The executing context no longer executes on this processor */
        dmb
        mov     r3, #0
        strb    r3, [r0, #ARM_CONTEXT_CONTROL_IS_EXECUTING_OFFSET]

.L_check_is_executing:

        /* Check the is executing indicator of the heir context */
        add     r3, r1, #ARM_CONTEXT_CONTROL_IS_EXECUTING_OFFSET
        ldrexb  r4, [r3]
        cmp     r4, #0
        bne     .L_check_thread_dispatch_necessary

        /* Try to update the is executing indicator of the heir context */
        mov     r4, #1
        strexb  r5, r4, [r3]
        cmp     r5, #0
        bne     .L_check_thread_dispatch_necessary
        dmb
#endif

/* Start restoring context */
.L_restore:
#if !defined(RTEMS_SMP) && defined(ARM_MULTILIB_HAS_LOAD_STORE_EXCLUSIVE)
        clrex
#endif

#ifdef ARM_MULTILIB_HAS_THREAD_ID_REGISTER
        ldr     r3, [r1, #ARM_CONTEXT_CONTROL_THREAD_ID_OFFSET]
        mcr     p15, 0, r3, c13, c0, 3
#endif

#ifdef ARM_MULTILIB_VFP_D32
        add     r3, r1, #ARM_CONTEXT_CONTROL_D8_OFFSET
        vldm    r3, {d8-d15}
#endif

        ldmia   r1,  {r2, r4, r5, r6, r7, r8, r9, r10, r11, r13, r14}
        msr     CPSR_fsxc, r2
#ifdef __thumb__
        bx      lr
        nop
#else
        mov     pc, lr
#endif
/*
 *  void _CPU_Context_restore( new_context )
 *
 *  This function copies the restores the registers from where r0 points.
 *  It must match _CPU_Context_switch()
 *
 */
DEFINE_FUNCTION_ARM(_CPU_Context_restore)
        mov     r1, r0
        b       .L_restore

#ifdef RTEMS_SMP
.L_check_thread_dispatch_necessary:

        GET_SELF_CPU_CONTROL    r2, r3

        /* Check if a thread dispatch is necessary */
        ldrb    r4, [r2, #PER_CPU_DISPATCH_NEEDED]
        cmp     r4, #0
        beq     .L_check_is_executing

        /* We have a new heir */

        /* Clear the thread dispatch necessary flag */
        mov     r4, #0
        strb    r4, [r2, #PER_CPU_DISPATCH_NEEDED]
        dmb

        /* Read the executing and heir */
        ldr     r4, [r2, #PER_CPU_OFFSET_EXECUTING]
        ldr     r5, [r2, #PER_CPU_OFFSET_HEIR]

        /* Calculate the heir context pointer */
        sub     r4, r1, r4
        add     r1, r5, r4

        /* Update the executing */
        str     r5, [r2, #PER_CPU_OFFSET_EXECUTING]

        b       .L_check_is_executing
#endif

#endif /* ARM_MULTILIB_ARCH_V4 */