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/*===========================================================================
//
//      vec_ivsr.S
//
//      SPARClite vectors: interrupt vector service routine
//
//===========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 or (at your option) any later version.
//
// eCos is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License along
// with eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
// License. However the source code for this file must still be made available
// in accordance with section (3) of the GNU General Public License.
//
// This exception does not invalidate any other reasons why a work based on
// this file might be covered by the GNU General Public License.
//
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
// at http://sources.redhat.com/ecos/ecos-license/
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):    hmt
// Contributors: hmt
// Date:         1999-02-20
// Purpose:      SPARClite vector code
// Description:  see vectors.S; this is the default vector service routine
//               for interrupts.
//
//####DESCRIPTIONEND####
//
//=========================================================================*/

!----------------------------------------------------------------------------

//      .file   "vec_ivsr.S"

!----------------------------------------------------------------------------

#include <pkgconf/system.h>
#include <pkgconf/hal.h>

#ifdef CYGPKG_KERNEL
# include <pkgconf/kernel.h>
#else
# undef CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
# undef CYGFUN_HAL_COMMON_KERNEL_SUPPORT
#endif

!------------------------------------------------------------------------

#include <cyg/hal/vectors.h>

#define DELAYS_AFTER_WRPSR_SAME_WINDOW
#define DELAYS_AFTER_WRWIM

! Macro to mark the stack as we descend, for debugging, because it is likely
! that actually running the ISR won~t touch the stack, but the memory needs
! to be there.  Normally blank.
//#define       MARKSTACKUSED st %sp, [ %sp ]
#define MARKSTACKUSED

!------------------------------------------------------------------------

        .text

!---------------------------------------------------------------------------
! default interrupt VSR, which calls the appropriate ISR after scheduler
! lock and interrupt masking, then interrupt_end().  interrupt_end() must be
! called with interrupts enabled, on the original thread stack (no separate
! interrupt stack) or with interrupts masked, on the original stack (when
! separate interrupt stack is supported).

        .global hal_default_interrupt_vsr
hal_default_interrupt_vsr:
        ! here,locals have been set up as follows:
        ! %l0 = psr (with this CWP/window-level in it)
        ! %l1 = pc
        ! %l2 = npc
        ! %l3 = vector number (1-15 for interrupts)
        ! and we are in our own register window, though it is likely that
        ! the next one will need to be saved before we can use it:
        ! ie. this one is the invalid register window.

        ! must establish a safe stack before re-enabling interrupts + traps
        and     %l0, __WINBITS, %l7     ! CWP extracted
        ! no inc/dec here, so no need for special measures for not-8-windows
        mov     1, %l6
        sll     %l6, %l7, %l6           ! 1 << CWP
        rd      %wim, %l5
        cmp     %l5, %l6                ! are they the same?
        bne     1f                      ! No, so the stack is OK as is.

        ! now do by hand an overflow trap, effectively
        mov     %g1, %l7                ! (DELAY SLOT)
        srl     %l5, 1, %l5
        sll     %l6, __WINSIZE-1, %l6
        or      %l6, %l5, %g1           ! new WIM in %g1 so we can get it
                                        ! within the save:
        save                            ! Slip into next window
        mov     %g1, %wim               ! Install the new wim
                                        ! (invalidates current window!)
#ifdef DELAYS_AFTER_WRWIM
        nop
        nop
        nop
#endif

        std     %l0, [%sp + 0 * 4]      ! save L & I registers
        std     %l2, [%sp + 2 * 4]
        std     %l4, [%sp + 4 * 4]
        std     %l6, [%sp + 6 * 4]

        std     %i0, [%sp + 8 * 4]
        std     %i2, [%sp + 10 * 4]
        std     %i4, [%sp + 12 * 4]
        std     %i6, [%sp + 14 * 4]

        restore                         ! Go back to trap window.
        mov     %l7, %g1                ! Restore %g1

1:      ! now save away the regs we must preserve
        sub     %fp, 32 * 4, %sp
#ifdef CYGDBG_HAL_COMMON_INTERRUPTS_SAVE_MINIMUM_CONTEXT
        std     %g0, [%sp + 16 * 4]     ! save G registers
        std     %g2, [%sp + 18 * 4]     ! (set %g0 place to 0 to flag special context)
        std     %g4, [%sp + 20 * 4]
        std     %g6, [%sp + 22 * 4]
#else // not CYGDBG_HAL_COMMON_INTERRUPTS_SAVE_MINIMUM_CONTEXT
        std     %l0, [%sp + 0 * 4]      ! save L & I registers
        std     %l2, [%sp + 2 * 4]
        std     %l4, [%sp + 4 * 4]
        std     %l6, [%sp + 6 * 4]

        std     %i0, [%sp + 8 * 4]
        std     %i2, [%sp + 10 * 4]
        std     %i4, [%sp + 12 * 4]
        std     %i6, [%sp + 14 * 4]

        st      %g1, [%sp + 17 * 4]     ! save G registers
        std     %g2, [%sp + 18 * 4]
        std     %g4, [%sp + 20 * 4]
        std     %g6, [%sp + 22 * 4]

        ! no point whatsoever in saving O registers

        ! and save the CWP in %g0 save place
        st      %l0, [%sp + 16 * 4]
#endif // ! CYGDBG_HAL_COMMON_INTERRUPTS_SAVE_MINIMUM_CONTEXT

        sub     %sp, 24 * 4, %sp        ! fresh frame including
                                        ! arg spill area for callees
        MARKSTACKUSED                   ! kilroy was here

#ifdef CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
        ! we will switch to the interrupt stack unless already running on it

        .extern cyg_interrupt_stack
        .extern cyg_interrupt_stack_base
        set     cyg_interrupt_stack, %g1
        set     cyg_interrupt_stack_base, %g2

        cmp     %sp, %g2                ! below base?
        blu     1f                      ! if so, switch.
        cmp     %sp, %g1                ! below top? (DELAY SLOT)
        blu     2f                      ! if so, DON~T switch.
        nop                             ! (DELAY SLOT)
1:      ! switch to the interrupt stack
        st      %sp, [ %g1 ]            ! there is spare above stack
        sub     %g1, 24 * 4, %sp        ! fresh frame including
                                        ! arg spill area for callees
        MARKSTACKUSED                   ! kilroy was here
2:      
        ! continue as before, already in the interrupt stack.
#endif // CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK

#ifdef CYGFUN_HAL_COMMON_KERNEL_SUPPORT
        ! Lock the scheduler
        .extern SCHED_LOCK_MANGLED_NAME
        sethi   %hi(SCHED_LOCK_MANGLED_NAME), %l7
        ld      [ %l7 + %lo(SCHED_LOCK_MANGLED_NAME) ], %l6
        add     %l6, 1, %l6
        st      %l6, [ %l7 + %lo(SCHED_LOCK_MANGLED_NAME) ]
#endif

        ! HELP_GDB_WITH_BACKTRACE
        mov     %i7, %l5                ! preserve it in l5
        mov     %l1, %i7                ! bogus return link here

        ! and we must preserve the Y register (multiply/divide auxiliary)
        ! over these calls; we will keep it in %l4 which is otherwise unused.
        rd      %y, %l4

        ! Now we can reenable traps and mask off only lower prio interrupts:
        andn    %l0, 0xf00, %l7         ! clear PIL field
        or      %l7, 0x0e0, %l7         ! and ET (+S,PS)
        sll     %l3, 8, %l6             ! trap number (1-15) into PIL bitfield
        wr      %l7, %l6, %psr          ! and enable!
#ifdef DELAYS_AFTER_WRPSR_SAME_WINDOW
        nop
        nop
        nop
#endif
        ! now call the ISR and so on with the appropriate args:
        ! ie.
        ! isr_retcode = (*(hal_interrupt_handlers[ vector ]))
        !                          ( vector, hal_interrupt_data[ vector ] );

        ! from hal_arch.h
        !// ISR tables
        !CYG_ADDRESS    hal_interrupt_handlers[CYGNUM_HAL_ISR_COUNT];
        !CYG_ADDRWORD   hal_interrupt_data[CYGNUM_HAL_ISR_COUNT];
        !CYG_ADDRESS    hal_interrupt_objects[CYGNUM_HAL_ISR_COUNT];        

        mov     %l3, %o0
        sll     %l3, 2, %l3             ! %l3 to a word offset
        sethi   %hi(hal_interrupt_data), %l7
        or      %l7, %lo(hal_interrupt_data), %l7
        ld      [ %l7 + %l3 ], %o1

        sethi   %hi(hal_interrupt_handlers), %l7
        or      %l7, %lo(hal_interrupt_handlers), %l7
        ld      [ %l7 + %l3 ], %l6
        call    %l6
        nop

#ifdef CYGFUN_HAL_COMMON_KERNEL_SUPPORT
        ! We only need to call _interrupt_end() when there is a kernel
        ! present to do any tidying up.

#ifdef CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
        ! now we switch back to the user stack (if we~re at the top
        ! of the interrupt stack).

        or      %l0, 0xfe0, %l7
        wr      %l7, %psr               ! Interrupts all masked, ET
#ifdef DELAYS_AFTER_WRPSR_SAME_WINDOW
        nop
        nop
        nop
#endif
        
        .extern cyg_interrupt_stack
        set     cyg_interrupt_stack - (24 * 4), %g1

        cmp     %sp, %g1                ! is SP less?
        blu     1f                      ! if so, do not change back
        nop
        ! switch to the thread stack
        ld      [ %g1 + (24 * 4) ], %sp         ! there is spare above stack
1:      

#else // CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
        ! First restore the processor interrupt level to that interrupted
        ! (otherwise a task-switch runs at the current PIL) on the assumption
        ! that the ISR dealt with the interrupt source per se, so it is safe
        ! to unmask it, effectively:
        or      %l0, 0x0e0, %l7         ! original PSR and ET (+S,PS)
        wr      %l7, %psr               ! and enable!
#ifdef DELAYS_AFTER_WRPSR_SAME_WINDOW
        nop
        nop
        nop
#endif
#endif // CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK

        ! then call interrupt_end( isr_retcode, &intr_object, &regsave )
        ! to unlock the scheduler and do any rescheduling that~s needed.
        ! argument 0 (isr_retcode) is already in place in %o0
        sethi   %hi(hal_interrupt_objects), %l7
        or      %l7, %lo(hal_interrupt_objects), %l7
        ld      [ %l7 + %l3 ], %o1
        add     %sp, 24 * 4, %o2        ! saved regset (maybe tiny)

        .extern interrupt_end
        call    interrupt_end
        nop
#endif

        ! restore the Y register having done our callouts to C
        wr      %l4, %y

        ! We can reinstall the original CWP here; even if interrupt_end()
        ! performed a reschedule (ie. yield/resume pair) we will be in the
        ! same window.  The window is preserved by reschedule precisely
        ! because it is impossible atomically to disable traps here without
        ! involving a CWP living in a register for a time when other
        ! interrupts may occur.

        ! disable traps (using the saved psr is fastest way)
        wr      %l0, %psr       ! restores flags, disables traps, and old PIL
#ifdef DELAYS_AFTER_WRPSR_SAME_WINDOW
        nop
        nop
        nop
#endif

        ! HELP_GDB_WITH_BACKTRACE
        mov     %l5, %i7        ! restore (unused) return link

        ! and restore other saved regs
        ! (see CYGDBG_HAL_COMMON_INTERRUPTS_SAVE_MINIMUM_CONTEXT)
        add     %sp, 24 * 4, %sp        ! undo fresh frame

        ld      [%sp + 17 * 4], %g1     ! restore G registers
        ldd     [%sp + 18 * 4], %g2
        ldd     [%sp + 20 * 4], %g4
        ldd     [%sp + 22 * 4], %g6

        ! and do NOT restore any other registers L, I or O

        ! Now test for window underflow here and fix up if needs be.
        !
        ! Why?  interrupt_end() might have yielded us, when only
        ! its own frame was restored; its own return to us caused a
        ! window underflow trap, as would our return to interruptee
        ! unless we deal with it now.

        add     %l0, 1, %l7             ! interruptee~s CWP plus noise
        and     %l7, __WINBITS, %l7     ! CWP only
#if 8 == __WINSIZE
        ! it is in range already
#else   // expect 5 or 6 or 7 windows
        cmp     %l7, __WINSIZE
        bge,a   567f                    ! taken: do delay slot, handle overflow
         mov    0, %l7                  ! only if .ge. above
567:    
#endif
        mov     1, %l6
        sll     %l6, %l7, %l6           ! 1 << CWP
        rd      %wim, %l5
        cmp     %l5, %l6                ! are they the same?
        bne     2f                      ! No, so the stack is OK as is.

        ! now do by hand an underflow trap, effectively
        sll     %l5, 1, %l5             ! Rotate wim left
        srl     %l6, __WINSIZE-1, %l6
        wr      %l5, %l6, %wim
#ifdef DELAYS_AFTER_WRWIM
        nop                             ! are these delays needed?
        nop                             ! (following restore uses wim)
        nop
#endif
        restore                         ! Interruptee~s window
        ldd     [%sp + 0 * 4], %l0      ! restore L & I registers
        ldd     [%sp + 2 * 4], %l2
        ldd     [%sp + 4 * 4], %l4
        ldd     [%sp + 6 * 4], %l6

        ldd     [%sp + 8 * 4], %i0
        ldd     [%sp + 10 * 4], %i2
        ldd     [%sp + 12 * 4], %i4
        ldd     [%sp + 14 * 4], %i6
        save                            ! Back to trap window

2:      ! restore the condition codes, PSR and PIL and return from trap.
        wr      %l0, %psr       ! restores flags, disables traps, and old PIL
#ifdef DELAYS_AFTER_WRPSR_SAME_WINDOW
        nop
        nop
        nop
#endif
        jmpl    %l1,  %g0
        rett    %l2

!----------------------------------------------------------------------------

#ifdef CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK

! This routine can only be called from a thread stack, maybe
! with interrupts (but not traps) disabled.
! It switches to the interrupt stack then calls back to the
! kernel to execute DSRs.

        .global hal_interrupt_stack_call_pending_DSRs
hal_interrupt_stack_call_pending_DSRs:
        save    %sp, -24 * 4, %sp

        MARKSTACKUSED                   ! kilroy was here

        ! be atomic
        rd      %psr, %l0
        andn    %l0, 0x20, %l1          ! clear ET to disable traps
        wr      %l1, %psr               ! into the PSR
        nop
        nop
        nop

        mov     %sp, %l7                ! save calling stack location   

        ! now switch stack to the interrupt stack, plus some headroom
        ! for saving a register set if we are interrupted
        .extern cyg_interrupt_stack
        set     cyg_interrupt_stack - 4 * 24, %sp

        MARKSTACKUSED                   ! kilroy was here

        ! and enable interrupts unconditionally to call the DSRs
        or      %l0, 0x0e0, %l2         ! set ET, S, PS
        andn    %l2, 0xf00, %l2         ! PIL to zero
        wr      %l2, %psr               ! into the PSR
        nop
        nop
        nop
                
        .extern cyg_interrupt_call_pending_DSRs
        call    cyg_interrupt_call_pending_DSRs
        nop

        mov     %l7, %sp                ! restore calling stack

        wr      %l0, %psr               ! restore interrupt status
        nop
        nop
        nop

        ret
        restore
#endif // CYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK

!----------------------------------------------------------------------------

! end of vec_ivsr.S