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/*=============================================================================

//

//      context.S

//

//      SPARClite context switch code

//

//=============================================================================

//####ECOSGPLCOPYRIGHTBEGIN####

// -------------------------------------------

// This file is part of eCos, the Embedded Configurable Operating System.

// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

//

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//

// 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

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// at http://sources.redhat.com/ecos/ecos-license/

// -------------------------------------------

//####ECOSGPLCOPYRIGHTEND####

//=============================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):   nickg, gthomas, hmt

// Contributors:        nickg, gthomas, hmt

// Date:        1998-12-15

// Purpose:     SPARClite context switch code

// Description: This file contains implementations of the thread context

//              switch routines. It also contains the longjmp() and setjmp()

//              routines.

//

//####DESCRIPTIONEND####

//

//===========================================================================*/

#include 

#include 

#define DELAYS_AFTER_WRPSR_SAME_WINDOW

#define DELAYS_AFTER_WRWIM

        .text

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

!  hal_thread_switch_context

!  Switch thread contexts

!  %o0 = address of sp of next thread to execute

!  %o1 = address of sp save location of current thread

        .global hal_thread_switch_context

hal_thread_switch_context:

        ! First take the stack down to make room for the saved register

        ! state, including a window save area at the base.  Leave the

        ! current window save area undisturbed.  It is unused within the

        ! save but will become current again when we continue in this

        ! context.  This lets us do this whole piece of work without

        ! diabling interrupts for too long, since, for example, we can

        ! lower the stack atomically with one instruction:

        sub     %sp, SAVE_REGS_SIZE, %sp

        st      %sp, [ %o1 ]            ! return SP for this thread

        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]

#ifdef CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        st      %o7, [%sp + 31 * 4]     ! save only the return address

        ! and no need to preserve %o0 even though it is restored

#else // save a maximal context

        st      %g1, [%sp + 17 * 4]     ! save G & O registers

        std     %g2, [%sp + 18 * 4]

        std     %g4, [%sp + 20 * 4]

        std     %g6, [%sp + 22 * 4]

        std     %o0, [%sp + 24 * 4]

        std     %o2, [%sp + 26 * 4]

        std     %o4, [%sp + 28 * 4]

        std     %o6, [%sp + 30 * 4]

#endif // !CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        ! and save the CWP in %g0 save place

        rd      %psr, %g7

        st      %g7, [%sp + 16 * 4]

        ! Now load the destination thread by dropping through

        ! to hal_thread_load_context

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

!  hal_thread_load_context

!  Load thread context

!  %o0 = address of sp of next thread to execute

!  Note that this function is also the second half of hal_thread_switch_context

!  and is simply dropped into from it.

        .global hal_thread_load_context

hal_thread_load_context:

        ! Here, we are a leaf routine but with slightly odd properties.

        ! The stack is still the callers at this point but the register

        ! set is up for grabs.  So we can use globals:

        ld      [ %o0 ], %g7            ! Get the next saved SP

        ! DISABLE INTERRUPTS *ONLY* NOT TRAPS

        rd      %psr, %g6

        or      %g6, 0xfe0, %g5         ! PIL up to 15 leave traps enabled

        wr      %g5, %psr

        ! force out all our callers register sets onto the stack

        ! if necessary: the system will handily take care of this for

        ! us as follows:

        save    %sp, -16 * 4, %sp       ! need all these to preserve

        save    %sp, -16 * 4, %sp       ! the linked list property...

        save    %sp, -16 * 4, %sp

        save    %sp, -16 * 4, %sp

#if 6 < __WINSIZE

        save    %sp, -16 * 4, %sp

#if 7 < __WINSIZE

        save    %sp, -16 * 4, %sp

#endif

#endif

        ! Fewer saves if fewer register windows.  For 8 register windows,

        ! six of these is correct; a seventh would force out the current

        ! set that was already saved manually above.  Note that minimal

        ! space is allowed on stack for locals and ins in case this

        ! sequence itself gets interrupted and recurses too deep.

        ! now select the new window with traps disabled...

        ! get the new PSR and CWP that we will ultimately restore

        ! from the %g0 save place...

        ld      [%g7 + 16 * 4], %g6     ! %g7 holds the new stack pointer

        andn    %g6, 0x20, %g5          ! clear ET into %g5

        and     %g6, __WINBITS, %g4     ! CWP bits only in %g4

        ! calculate a new WIM...

        add     %g4, 1, %g3             ! required invalid window number

#if 8 == __WINSIZE

        and     %g3, __WINBITS, %g3     ! modulo 8

#else   // expect 5 or 6 or 7 windows

        cmp     %g3, __WINSIZE

        bge,a   567f                    ! taken: do delay slot, handle overflow

         mov    0, %g3                  ! only if .ge. above

567:

#endif

        mov     1, %g2

        sll     %g2, %g3, %g2           ! converted to a mask for the WIM

        ! DISABLE INTERRUPTS (TRAPS)

        wr      %g5, %psr               ! set CWP to new window, disable traps

        wr      %g2, %wim               ! and WIM to new value

        nop

        nop

        nop

        ! Must do this atomically so that the registers match the stack.

        ! After locals and ins are loaded, we are conformant to the PCS

        ! so can re-enable interrupts.

        mov     %g7, %sp                ! target sp in situ (%sp = %o6)

        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

        ! RESTORE INTERRUPTS to saved state

        wr      %g6, %psr               ! set new CWP and old ET and PIL

        nop

        nop

        nop

        ! now load the rest of the context; we can be interrupted here

        ! (if the saved context was a voluntary yield or threadstart)

        ! but that is OK, other state will be preserved in that case...

#ifdef CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        ld      [%sp + 24 * 4], %o0     ! must load the initial argument

#else // restore a maximal context

        ld      [%sp + 17 * 4], %g1

        ldd     [%sp + 18 * 4], %g2

        ldd     [%sp + 20 * 4], %g4

        ldd     [%sp + 22 * 4], %g6

        ldd     [%sp + 24 * 4], %o0

        ldd     [%sp + 26 * 4], %o2

        ldd     [%sp + 28 * 4], %o4

#endif // !CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

                                        ! %o6 = %sp, already set up

        ld      [%sp + 31 * 4], %o7     ! "return" address

        retl

        add     %sp, SAVE_REGS_SIZE, %sp ! and set the stack back

                                        ! to its entrant value

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

!  HAL longjmp, setjmp implementations

!FUNC_START(hal_setjmp)

        .global hal_setjmp

hal_setjmp:

        ! Treat this as a leaf routine, may as well.

        ! %o0 is the address of the buffer.

        std     %l0, [%o0 + 0 * 4]      ! save L & I registers

        std     %l2, [%o0 + 2 * 4]

        std     %l4, [%o0 + 4 * 4]

        std     %l6, [%o0 + 6 * 4]

        std     %i0, [%o0 + 8 * 4]

        std     %i2, [%o0 + 10 * 4]

        std     %i4, [%o0 + 12 * 4]

        std     %i6, [%o0 + 14 * 4]

#ifdef CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        std     %o6, [%o0 + 30 * 4]     ! just save %sp and return address

#else // save a maximal context

        st      %g1, [%o0 + 17 * 4]     ! save G & O registers

        std     %g2, [%o0 + 18 * 4]

        std     %g4, [%o0 + 20 * 4]

        std     %g6, [%o0 + 22 * 4]

        std     %o0, [%o0 + 24 * 4]

        std     %o2, [%o0 + 26 * 4]

        std     %o4, [%o0 + 28 * 4]

        std     %o6, [%o0 + 30 * 4]

#endif // !CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        ! and save the CWP in %g0 save place

        rd      %psr, %g7

        st      %g7, [%o0 + 16 * 4]

        ! DISABLE INTERRUPTS *ONLY* NOT TRAPS

        or      %g7, 0xfe0, %g6         ! PIL up to 15 leave traps enabled

        wr      %g6, %psr

        ! force out all our callers register sets onto the stack

        ! if necessary: the system will handily take care of this for

        ! us as follows:

        save    %sp, -16 * 4, %sp       ! need all these to preserve

        save    %sp, -16 * 4, %sp       ! the linked list property...

        save    %sp, -16 * 4, %sp

        save    %sp, -16 * 4, %sp

#if 6 < __WINSIZE

        save    %sp, -16 * 4, %sp

#if 7 < __WINSIZE

        save    %sp, -16 * 4, %sp

#endif

#endif

        ! Fewer saves if fewer register windows.  For 8 register windows,

        ! six of these is correct; a seventh would force out the current

        ! set that was already saved manually above.  Note that minimal

        ! space is allowed on stack for locals and ins in case this

        ! sequence itself gets interrupted and recurses too deep.

        ! (after all, we are about to call deeper not shallower, otherwise

        !  using setjmp is inappropriate)

        ! ENABLE INTERRUPTS

        wr      %g7, %psr               ! set CWP back to as-was

        nop

        nop

        nop

#ifndef CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        ldd     [%o0 + 22 * 4], %g6     ! preserve %g7 and %g6

#endif

        retl                            ! ret and return zero to indicate

        mov     0, %o0                  ! not longjumped-to

!  hal_longjmp loads state from arg0 and returns arg1

!FUNC_START(hal_longjmp)

        .global hal_longjmp

hal_longjmp:

        ! This is kind of a leaf routine, it returns elsewhere

        ! %o0 is the address of the buffer.

        ! %o1 is the value to return in %o0 (since we are a leaf)

        mov     %o0, %g7                ! keep the pointer handy

        mov     %o1, %g1                ! and the return value

        ! now select the new window with traps disabled...

        rd      %psr, %g6

                                        ! preserve ET, clear CWP

        andn    %g6, __WINBITS_MAXIMAL, %g6

        andn    %g6, 0x20, %g5          ! clear ET also into %g5

        ! get new CWP from %g0 save place...

        ld      [%g7 + 16 * 4], %g4     ! %g7 holds the new stack pointer

        and     %g4, __WINBITS, %g4     ! preserve CWP bits

        ! calculate a new WIM...

        add     %g4, 1, %g3             ! required invalid window number

#if 8 == __WINSIZE

        and     %g3, __WINBITS, %g3     ! modulo 8

#else   // expect 5 or 6 or 7 windows

        cmp     %g3, __WINSIZE

        bge,a   567f                    ! taken: do delay slot, handle overflow

         mov    0, %g3                  ! only if .ge. above

567:

#endif

        mov     1, %g2

        sll     %g2, %g3, %g2           ! converted to a mask for the WIM

        ! DISABLE INTERRUPTS

        wr      %g5, %g4, %psr          ! set CWP to new window, disable traps

        wr      %g2, %wim               ! and WIM to new value

        nop

        nop

        nop

        ! Must do this atomically so that the registers match the stack.

        ! After locals and ins are loaded, we are conformant to the PCS

        ! so can re-enable interrupts.

        ldd     [%g7 + 0 * 4], %l0      ! restore L & I registers

        ldd     [%g7 + 2 * 4], %l2

        ldd     [%g7 + 4 * 4], %l4

        ldd     [%g7 + 6 * 4], %l6

        ldd     [%g7 + 8 * 4], %i0

        ldd     [%g7 + 10 * 4], %i2

        ldd     [%g7 + 12 * 4], %i4

        ldd     [%g7 + 14 * 4], %i6

        ld      [%g7 + 30 * 4], %sp     ! %o6 = %sp, set up now so as to conform

                                        ! to PCS and so be interruptible

        ! ENABLE INTERRUPTS

        wr      %g6, %g4, %psr          ! set new CWP and old ET

        nop

        nop

        nop

        ! now load the rest of the context; we can be interrupted here, but

        ! that is OK, other state will be preserved in that case...

#ifdef CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

        ! we are not preserving globals...

                                        ! %o6 = %sp, already set up

        ld      [%g7 + 31 * 4], %o7     ! "return" address

        retl                            ! %g1 still holds the return value

        mov     %g1, %o0

#else // load a maximal context

        mov     %g7, %o0                ! original pointer was in %o0 anyway

        ldd     [%o0 + 18 * 4], %g2

        ldd     [%o0 + 20 * 4], %g4

        ldd     [%o0 + 22 * 4], %g6

        ld      [%o0 + 25 * 4], %o1     ! %o0 = original pointer

        ldd     [%o0 + 26 * 4], %o2

        ldd     [%o0 + 28 * 4], %o4

                                        ! %o6 = %sp, already set up

        ld      [%o0 + 31 * 4], %o7     ! "return" address

        ! %g1 still holds the return value; want to get this into %o0

        ! and restore %g1 from the saved state;  %o0 is the state pointer:

                                        ! g1 = R,   o0 = P

        xor     %o0, %g1, %g1           ! g1 = R^P, o0 = P

        xor     %o0, %g1, %o0           ! g1 = R^P, o0 = R

        xor     %o0, %g1, %g1           ! g1 = P,   o0 = R all done

        retl

        ld      [%g1 + 17 * 4], %g1     ! and finally restore %g1

#endif // !CYGDBG_HAL_COMMON_CONTEXT_SAVE_MINIMUM

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

! end of context.S