/*
 * Copyright (c) 2016 Cadence Design Systems, Inc.
 * SPDX-License-Identifier: Apache-2.0
 */

/* XTENSA VECTORS AND LOW LEVEL HANDLERS FOR AN RTOS
 *
 * FIXME: A lot of this is not applicable to Zephyr, remove. In particular,
 * we do not support installing interrupt or exception handlers at runtime.
 *
 * Xtensa low level exception and interrupt vectors and handlers for an RTOS.
 *
 * Interrupt handlers and user exception handlers support interaction with the
 * RTOS by calling XT_RTOS_INT_ENTER and XT_RTOS_INT_EXIT before and after
 * user's specific interrupt handlers. These macros are defined in
 * xtensa_<rtos>.h to call suitable functions in a specific RTOS.
 *
 * Users can install application-specific interrupt handlers for low and medium
 * level interrupts, by calling _xt_set_interrupt_handler(). These handlers can
 * be written in C, and must obey C calling convention. The handler table is
 * indexed by the interrupt number. Each handler may be provided with an
 * argument.
 *
 * Note that the system timer interrupt is handled specially, and is dispatched
 * to the RTOS-specific handler. This timer cannot be hooked  by application
 * code.
 *
 * Optional hooks are also provided to install a handler per level at run-time,
 * made available by compiling this source file with '-DXT_INTEXC_HOOKS'
 * (useful for automated testing).
 *
 * NOTE: This file is a template that usually needs to be modified to handle
 * application specific interrupts. Search USER_EDIT for helpful comments on
 * where to insert handlers and how to write them.
 *
 * Users can also install application-specific exception handlers in the same
 * way, by calling _xt_set_exception_handler(). One handler slot is provided
 * for each exception type. Note that some exceptions are handled by the
 * porting layer itself, and cannot be taken over by application code in this
 * manner. These are the alloca, syscall, and coprocessor exceptions.
 *
 * The exception handlers can be written in C, and must follow C calling
 * convention. Each handler is passed a pointer to an exception frame as its
 * single argument. The exception frame is created on the stack, and holds the
 * saved context of the thread that took the exception. If the handler returns,
 * the context will be restored and the instruction that caused the exception
 * will be retried. If the handler makes any changes to the saved state in the
 * exception frame, the changes will be applied when restoring the context.
 *
 * Because Xtensa is a configurable architecture, this port supports all user
 * generated configurations (except restrictions stated in the release notes).
 * This is accomplished by conditional compilation using macros and functions
 * defined in the Xtensa HAL (hardware adaptation layer) for your
 * configuration. Only the relevant parts of this file will be included in your
 * RTOS build. For example, this file provides interrupt vector templates for
 * all types and all priority levels, but only the ones in your configuration
 * are built.
 *
 * NOTES on the use of 'call0' for long jumps instead of 'j':
 *
 * 1. This file should be assembled with the -mlongcalls option to xt-xcc.
 *
 * 2. The -mlongcalls compiler option causes 'call0 dest' to be expanded to
 *    a sequence 'l32r a0, dest' 'callx0 a0' which works regardless of the
 *    distance from the call to the destination. The linker then relaxes
 *    it back to 'call0 dest' if it determines that dest is within range.
 *    This allows more flexibility in locating code without the performance
 *    overhead of the 'l32r' literal data load in cases where the destination
 *    is in range of 'call0'. There is an additional benefit in that 'call0'
 *    has a longer range than 'j' due to the target being word-aligned, so
 *    the 'l32r' sequence is less likely needed.
 *
 * 3. The use of 'call0' with -mlongcalls requires that register a0 not be
 *    live at the time of the call, which is always the case for a function
 *    call but needs to be ensured if 'call0' is used as a jump in lieu of 'j'.
 *
 * 4. This use of 'call0' is independent of the C function call ABI.
 */

#include <offsets_short.h>
#include "xtensa_rtos.h"

#define GEN_MED_INTERRUPT(l)                                            \
    (XCHAL_NUM_INTLEVELS >= (l) &&                                      \
     XCHAL_DEBUGLEVEL != (l) &&                                         \
     XCHAL_EXCM_LEVEL >= (l))

#define GEN_HIGH_INTERRUPT(l)                                           \
    (XCHAL_NUM_INTLEVELS >= (l) &&                                      \
     XCHAL_DEBUGLEVEL != (l) &&                                         \
     (XCHAL_EXCM_LEVEL < (l) && !defined(CONFIG_XTENSA_OMIT_HIGH_INTERRUPTS)))

/*
 * Defines used to access _xtos_interrupt_table.
 */
/**
 * Zephyr has its own SW interrupt service routines table.
 * Xtensa's table is made an alias of it.
 **/
#define _xt_interrupt_table _sw_isr_table
#define XIE_ARG         0
#define XIE_HANDLER     4
#define XIE_SIZE        8

/* Macro extract_msb - return the input with only the highest bit set.
 *
 * Input  : "ain"  - Input value, clobbered.
 * Output : "aout" - Output value, has only one bit set, MSB of "ain".
 *
 * The two arguments must be different AR registers.
 */

    .macro  extract_msb     aout ain
1:
    addi    \aout, \ain, -1         /* aout = ain - 1        */
    and     \ain, \ain, \aout       /* ain  = ain & aout     */
    bnez    \ain, 1b                /* repeat until ain == 0 */
    addi    \aout, \aout, 1         /* return aout + 1       */
    .endm

/* Macro dispatch_c_isr - dispatch interrupts to user ISRs.
 * This will dispatch to user handlers (if any) that are registered in the
 * XTOS dispatch table (_xtos_interrupt_table). These handlers would have
 * been registered by calling _xtos_set_interrupt_handler(). There is one
 * exception - the timer interrupt used by the OS will not be dispatched
 * to a user handler - this must be handled by the caller of this macro.
 *
 * Level triggered and software interrupts are automatically deasserted by
 * this code.
 *
 * ASSUMPTIONS:
 * -- PS.INTLEVEL is set to "level" at entry
 * -- PS.EXCM = 0, C calling enabled
 *
 * NOTE: For CALL0 ABI, a12-a15 have not yet been saved.
 *
 * NOTE: This macro will use registers a0 and a2-a6. The arguments are:
 * level -- interrupt level
 * mask  -- interrupt bitmask for this level
 */
    .extern _kernel
    .extern _sys_power_save_idle_exit

    .macro  dispatch_c_isr    level  mask

    /* Get mask of pending, enabled interrupts at this level into a2. */

.L_xt_user_int_&level&:
    rsr     a2, INTENABLE
    rsr     a3, INTERRUPT
    movi    a4, \mask
    and     a2, a2, a3
    and     a2, a2, a4
    beqz    a2, 9f                          /* nothing to do */

    /* This bit of code provides a nice debug backtrace in the debugger.
       It does take a few more instructions, so undef XT_DEBUG_BACKTRACE
       if you want to save the cycles.
    */
    #if XT_DEBUG_BACKTRACE
    #ifndef __XTENSA_CALL0_ABI__
    rsr     a0, EPC_1 + \level - 1	/* return address */
    movi    a4, 0xC0000000  /* constant with top 2 bits set (call size) */
    or      a0, a0, a4      /* set top 2 bits */
    addx2   a0, a4, a0      /* clear top bit -- simulating call4 size   */
    #endif
    #endif

#ifdef CONFIG_TRACING
    /*
     * Register the interrupt.
     * We just saved all registers.
     */
#ifdef __XTENSA_CALL0_ABI__
    call0 z_sys_trace_isr_enter
#else
    call4 z_sys_trace_isr_enter
#endif
#endif

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a4, _xt_intexc_hooks
    l32i    a4, a4, \level << 2
    beqz    a4, 2f
    #ifdef __XTENSA_CALL0_ABI__
    callx0  a4
    beqz    a2, 9f
    #else
    mov     a6, a2
    callx4  a4
    beqz    a6, 9f
    mov     a2, a6
    #endif
2:
    #endif

#ifdef CONFIG_SYS_POWER_MANAGEMENT
    movi    a3, _kernel
#ifdef __XTENSA_CALL0_ABI__
    mov     a12, a2
    l32i    a2, a3, _kernel_offset_to_idle
    beqz    a2, 10f
    xor     a4, a2, a2
    s32i    a4, a3, _kernel_offset_to_idle
    call0   _sys_power_save_idle_exit
    mov     a2, a12
#else
    l32i    a6, a3, _kernel_offset_to_idle
    beqz    a6, 10f
    xor     a4, a6, a6
    s32i    a4, a3, _kernel_offset_to_idle
    call4   _sys_power_save_idle_exit
#endif /* __XTENSA_CALL0_ABI__ */
10:
#endif /* CONFIG_SYS_POWER_MANAGEMENT */

    /* Now look up in the dispatch table and call user ISR if any. */
    /* If multiple bits are set then MSB has highest priority.     */

    extract_msb  a4, a2                     /* a4 = MSB of a2, a2 trashed */

    #ifdef XT_USE_SWPRI
    /* Enable all interrupts at this level that are numerically highe
     * than the one we just selected, since they are treated as higher
     * priority.
     * */
    movi    a3, \mask       /* a3 = all interrupts at this level */
    add     a2, a4, a4      /* a2 = a4 << 1 */
    addi    a2, a2, -1      /* a2 = mask of 1's <= a4 bit */
    and     a2, a2, a3      /* a2 = mask of all bits <= a4 at this level */
    movi    a3, _xt_intdata
    l32i    a6, a3, 4       /* a6 = _xt_vpri_mask */
    neg     a2, a2
    addi    a2, a2, -1      /* a2 = mask to apply */
    and     a5, a6, a2      /* mask off all bits <= a4 bit */
    s32i    a5, a3, 4       /* update _xt_vpri_mask */
    rsr     a3, INTENABLE
    and     a3, a3, a2      /* mask off all bits <= a4 bit */
    wsr     a3, INTENABLE
    rsil    a3, \level - 1  /* lower interrupt level by 1 */
    #endif

    movi    a3, XT_TIMER_INTEN  /* a3 = timer interrupt bit */
    wsr     a4, INTCLEAR        /* clear sw or edge-triggered interrupt */
    beq     a3, a4, 7f          /* if timer interrupt then skip table */

    find_ms_setbit a3, a4, a3, 0	/* a3 = interrupt number */

    movi    a4, _xt_interrupt_table
    addx8   a3, a3, a4          /* a3 = address of interrupt table entry */
    l32i    a4, a3, XIE_HANDLER             /* a4 = handler address */
    #ifdef __XTENSA_CALL0_ABI__
    mov     a12, a6                         /* save in callee-saved reg */
    l32i    a2, a3, XIE_ARG                 /* a2 = handler arg */
    callx0  a4                              /* call handler */
    mov     a2, a12
    #else
    mov     a2, a6                          /* save in windowed reg */
    l32i    a6, a3, XIE_ARG                 /* a6 = handler arg */
    callx4  a4                              /* call handler */
    #endif

    #ifdef XT_USE_SWPRI
    j       8f
    #else
    j       .L_xt_user_int_&level&          /* check for more interrupts */
    #endif

7:

    .ifeq XT_TIMER_INTPRI - \level
.L_xt_user_int_timer_&level&:
    /*
     * Interrupt handler for the RTOS tick timer if at this level.
     * We'll be reading the interrupt state again after this call
     * so no need to preserve any registers except a6 (vpri_mask).
     */

    #ifdef __XTENSA_CALL0_ABI__
    mov     a12, a6
    call0   XT_RTOS_TIMER_INT
    mov     a2, a12
    #else
    mov     a2, a6
    call4   XT_RTOS_TIMER_INT
    #endif
    .endif

    #ifdef XT_USE_SWPRI
    j       8f
    #else
    j       .L_xt_user_int_&level&          /* check for more interrupts */
    #endif

    #ifdef XT_USE_SWPRI
8:
    /* Restore old value of _xt_vpri_mask from a2. Also update INTENABLE
     * from virtual _xt_intenable which _could_ have changed during
     * interrupt processing.
     */
    movi    a3, _xt_intdata
    l32i    a4, a3, 0                       /* a4 = _xt_intenable    */
    s32i    a2, a3, 4                       /* update _xt_vpri_mask  */
    and     a4, a4, a2                      /* a4 = masked intenable */
    wsr     a4, INTENABLE                   /* update INTENABLE      */
    #endif

9:
    /* done */

    .endm


/* Panic handler.
 *
 * Should be reached by call0 (preferable) or jump only. If call0, a0 says
 * where from. If on simulator, display panic message and abort, else loop
 * indefinitely.
 */

    .text
    .global     _xt_panic
    .type       _xt_panic,@function
    .align      4

_xt_panic:
    #ifdef XT_SIMULATOR
    addi    a4, a0, -3              /* point to call0 */
    movi    a3, _xt_panic_message
    movi    a2, SYS_log_msg
    simcall
    movi    a2, SYS_gdb_abort
    simcall
    #else
    rsil    a2, XCHAL_EXCM_LEVEL    /* disable all low & med ints */
1:  j       1b                          /* loop infinitely */
    #endif

    .section    .rodata, "a"
    .align      4

_xt_panic_message:
    .string "\n*** _xt_panic() was called from 0x%08x or jumped to. ***\n"


/* Hooks to dynamically install handlers for exceptions and interrupts. Allows
 * automated regression frameworks to install handlers per test.  Consists of
 * an array of function pointers indexed by interrupt level, with index 0
 * containing the entry for user exceptions.  Initialized with all 0s, meaning
 * no handler is installed at each level.  See comment in xtensa_rtos.h for
 * more details.
 */

    #ifdef XT_INTEXC_HOOKS
    .data
    .global     _xt_intexc_hooks
    .type       _xt_intexc_hooks,@object
    .align      4

_xt_intexc_hooks:
    .fill       XT_INTEXC_HOOK_NUM, 4, 0
    #endif


/* EXCEPTION AND LEVEL 1 INTERRUPT VECTORS AND LOW LEVEL HANDLERS (except
 * window exception vectors).
 *
 * Each vector goes at a predetermined location according to the Xtensa
 * hardware configuration, which is ensured by its placement in a special
 * section known to the Xtensa linker support package (LSP). It performs the
 * minimum necessary before jumping to the handler in the .text section.
 *
 * The corresponding handler goes in the normal .text section. It sets up the
 * appropriate stack frame, saves a few vector-specific registers and calls
 * XT_RTOS_INT_ENTER to save the rest of the interrupted context and enter the
 * RTOS, then sets up a C environment. It then calls the user's interrupt
 * handler code (which may be coded in C) and finally calls XT_RTOS_INT_EXIT to
 * transfer control to the RTOS for scheduling.
 *
 * While XT_RTOS_INT_EXIT does not return directly to the interruptee,
 * eventually the RTOS scheduler will want to dispatch the interrupted task or
 * handler. The scheduler will return to the exit point that was saved in the
 * interrupt stack frame at XT_STK_EXIT.
 */

/*
 * Debug Exception.
 */

#if XCHAL_HAVE_DEBUG

    .begin      literal_prefix .DebugExceptionVector
    .section    .DebugExceptionVector.text, "ax"
    .global     _DebugExceptionVector
    .align      4

_DebugExceptionVector:

    #ifdef XT_SIMULATOR
    /* In the simulator, let the debugger (if any) handle the debug
     * exception, or simply stop the simulation:
     */
    wsr     a2, EXCSAVE+XCHAL_DEBUGLEVEL /* save a2 where sim expects it */
    movi    a2, SYS_gdb_enter_sktloop
    simcall                              /* have ISS handle debug exc. */
    #elif 0 /* change condition to 1 to use the HAL minimal debug handler */
    wsr     a3, EXCSAVE+XCHAL_DEBUGLEVEL
    movi    a3, xthal_debugexc_defhndlr_nw  /* use default debug handler */
    jx      a3
    #else
    wsr     a0, EXCSAVE+XCHAL_DEBUGLEVEL    /* save original a0 somewhere */
    call0   _xt_panic                       /* does not return */
    rfi     XCHAL_DEBUGLEVEL        /* make a0 point here not later */
    #endif

    .end        literal_prefix

#endif

/* Double Exception.
 *
 * Double exceptions are not a normal occurrence. They indicate a bug of some
 * kind.
 */

#ifdef XCHAL_DOUBLEEXC_VECTOR_VADDR

    .begin      literal_prefix .DoubleExceptionVector
    .section    .DoubleExceptionVector.text, "ax"
    .global     _DoubleExceptionVector
    .align      4

_DoubleExceptionVector:

    #if XCHAL_HAVE_DEBUG
    break   1, 4                    /* unhandled double exception */
    #endif
    call0   _xt_panic               /* does not return */
    rfde                            /* make a0 point here not later */

    .end        literal_prefix

#endif /* XCHAL_DOUBLEEXC_VECTOR_VADDR */

/*
 * Kernel Exception (including Level 1 Interrupt from kernel mode).
 */

    .begin      literal_prefix .KernelExceptionVector
    .section    .KernelExceptionVector.text, "ax"
    .global     _KernelExceptionVector
    .align      4

_KernelExceptionVector:

    wsr     a0, EXCSAVE_1           /* preserve a0 */
    call0   _xt_kernel_exc          /* kernel exception handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .align      4

_xt_kernel_exc:
    #if XCHAL_HAVE_DEBUG
    break   1, 0                    /* unhandled kernel exception */
    #endif
    call0   _xt_panic               /* does not return */
    rfe                             /* make a0 point here not there */


/* User Exception (including Level 1 Interrupt from user mode). */

    .begin      literal_prefix .UserExceptionVector
    .section    .UserExceptionVector.text, "ax"
    .global     _UserExceptionVector
    .type       _UserExceptionVector,@function
    .align      4

_UserExceptionVector:

    wsr     a0, EXCSAVE_1                   /* preserve a0 */
    call0   _xt_user_exc                    /* user exception handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

/* Insert some waypoints for jumping beyond the signed 8-bit range of
 * conditional branch instructions, so the conditional branchces to specific
 * exception handlers are not taken in the mainline. Saves some cycles in the
 * mainline.
 */
    .text

    #if XCHAL_HAVE_WINDOWED
    .align      4
_xt_to_alloca_exc:
    call0   _xt_alloca_exc                  /* in window vectors section */
    /* never returns here - call0 is used as a jump (see note at top) */
    #endif

    .align      4
_xt_to_syscall_exc:
    call0   _xt_syscall_exc
    /* never returns here - call0 is used as a jump (see note at top) */

    #if XCHAL_CP_NUM > 0
    .align      4
_xt_to_coproc_exc:
    call0   _xt_coproc_exc
    /* never returns here - call0 is used as a jump (see note at top) */
    #endif


/*
 * User exception handler.
 */

    .type       _xt_user_exc,@function
    .align      4

_xt_user_exc:

    /* If level 1 interrupt then jump to the dispatcher */
    rsr     a0, EXCCAUSE
    beqi    a0, EXCCAUSE_LEVEL1INTERRUPT, _xt_lowint1

    /* Handle any coprocessor exceptions. Rely on the fact that exception
     * numbers above EXCCAUSE_CP0_DISABLED all relate to the coprocessors.
     */
    #if XCHAL_CP_NUM > 0
    bgeui   a0, EXCCAUSE_CP0_DISABLED, _xt_to_coproc_exc
    #endif

    /* Handle alloca and syscall exceptions */
    #if XCHAL_HAVE_WINDOWED
    beqi    a0, EXCCAUSE_ALLOCA,  _xt_to_alloca_exc
    #endif
    beqi    a0, EXCCAUSE_SYSCALL, _xt_to_syscall_exc

    /* Handle all other exceptions. All can have user-defined handlers. */
    /* NOTE: we'll stay on the user stack for exception handling.       */

    /* Allocate exception frame and save minimal context. */
    mov     a0, sp
    addi    sp, sp, -XT_STK_FRMSZ
    s32i    a0, sp, XT_STK_a1
    #if XCHAL_HAVE_WINDOWED
    s32e    a0, sp, -12             /* for debug backtrace */
    #endif
    rsr     a0, PS                  /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_1               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_1           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    #if XCHAL_HAVE_WINDOWED
    s32e    a0, sp, -16             /* for debug backtrace */
    #endif
    s32i    a12, sp, XT_STK_a12     /* _xt_context_save requires A12- */
    s32i    a13, sp, XT_STK_a13     /* A13 to have already been saved */
    call0   _xt_context_save

    /* Save exc cause and vaddr into exception frame */
    rsr     a0, EXCCAUSE
    s32i    a0, sp, XT_STK_exccause
    rsr     a0, EXCVADDR
    s32i    a0, sp, XT_STK_excvaddr

    /* Set up PS for C, reenable hi-pri interrupts, and clear EXCM. */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(XCHAL_EXCM_LEVEL) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS

    #ifdef XT_DEBUG_BACKTRACE
    #ifndef __XTENSA_CALL0_ABI__
    rsr     a0, EPC_1           /* return address for debug backtrace */
    /* constant with top 2 bits set (call size) */
    movi    a5, 0xC0000000
    rsync                       /* wait for WSR.PS to complete */
    or      a0, a0, a5          /* set top 2 bits */
    addx2   a0, a5, a0          /* clear top bit, simulating call4 size */
    #else
    rsync                       /* wait for WSR.PS to complete */
    #endif
    #endif

    rsr     a2, EXCCAUSE        /* recover exc cause */

    #ifdef XT_INTEXC_HOOKS
    /* Call exception hook to pre-handle exceptions (if installed).
     * Pass EXCCAUSE in a2, and check result in a2 (if -1, skip default
     * handling).
     */
    movi    a4, _xt_intexc_hooks
    l32i    a4, a4, 0	    /* user exception hook index 0 */
    beqz    a4, 1f
.Ln_xt_user_exc_call_hook:
    #ifdef __XTENSA_CALL0_ABI__
    callx0  a4
    beqi    a2, -1, .L_xt_user_done
    #else
    mov     a6, a2
    callx4  a4
    beqi    a6, -1, .L_xt_user_done
    mov     a2, a6
    #endif
1:
    #endif

    rsr     a2, EXCCAUSE        /* recover exc cause */
    movi    a3, _xt_exception_table
    addx4   a4, a2, a3          /* a4 = address of exception table entry */
    l32i    a4, a4, 0           /* a4 = handler address */
    #ifdef __XTENSA_CALL0_ABI__
    mov     a2, sp              /* a2 = pointer to exc frame */
    callx0  a4                  /* call handler */
    #else
    mov     a6, sp              /* a6 = pointer to exc frame */
    callx4  a4                  /* call handler */
    #endif

.L_xt_user_done:

    /* Restore context and return */
    call0   _xt_context_restore
    l32i    a0, sp, XT_STK_ps               /* retrieve interruptee's PS */
    wsr     a0, PS
    l32i    a0, sp, XT_STK_pc               /* retrieve interruptee's PC */
    wsr     a0, EPC_1
    l32i    a0, sp, XT_STK_a0               /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1               /* remove exception frame */
    rsync                                   /* ensure PS and EPC written */
    rfe                                     /* PS.EXCM is cleared */


/*
 * Exit point for dispatch. Saved in interrupt stack frame at XT_STK_EXIT
 * on entry and used to return to a thread or interrupted interrupt handler.
 */

    .global     _xt_user_exit
    .type       _xt_user_exit,@function
    .align      4
_xt_user_exit:
    l32i    a0, sp, XT_STK_ps       /* retrieve interruptee's PS */
    wsr     a0, PS
    l32i    a0, sp, XT_STK_pc       /* retrieve interruptee's PC */
    wsr     a0, EPC_1
    l32i    a0, sp, XT_STK_a0       /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1       /* remove interrupt stack frame */
    rsync                           /* ensure PS and EPC written */
    rfe                             /* PS.EXCM is cleared */


/* Syscall Exception Handler (jumped to from User Exception Handler).
 *
 * Syscall 0 is required to spill the register windows (no-op in Call 0 ABI).
 * Only syscall 0 is handled here. Other syscalls return -1 to caller in a2.
 */

    .text
    .type       _xt_syscall_exc,@function
    .align      4
_xt_syscall_exc:
    #ifdef __XTENSA_CALL0_ABI__
    /* Save minimal regs for scratch. Syscall 0 does nothing in Call0 ABI.
     * Use a minimal stack frame (16B) to save A2 & A3 for scratch.
     * PS.EXCM could be cleared here, but unlikely to improve worst-case
     * latency.
     */
    addi    sp, sp, -16
    s32i    a2, sp, 8
    s32i    a3, sp, 12
    #else   /* Windowed ABI */
    /* Save necessary context and spill the register windows. PS.EXCM is
     * still set and must remain set until after the spill. Reuse context
     * save function though it saves more than necessary. For this reason,
     * a full interrupt stack frame is allocated.
     */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a12, sp, XT_STK_a12     /* _xt_context_save requires A12- */
    s32i    a13, sp, XT_STK_a13     /* A13 to have already been saved */
    call0   _xt_context_save
    #endif

    /* Grab the interruptee's PC and skip over the 'syscall' instruction.
     * If it's at the end of a zero-overhead loop and it's not on the last
     * iteration, decrement loop counter and skip to beginning of loop.
     */
    rsr     a2, EPC_1               /* a2 = PC of 'syscall' */
    addi    a3, a2, 3               /* ++PC                 */
    #if XCHAL_HAVE_LOOPS
    rsr     a0, LEND                /* if (PC == LEND       */
    bne     a3, a0, 1f
    rsr     a0, LCOUNT              /*     && LCOUNT != 0)  */
    beqz    a0, 1f                  /* {                    */
    addi    a0, a0, -1              /*   --LCOUNT           */
    rsr     a3, LBEG                /*   PC = LBEG          */
    wsr     a0, LCOUNT              /* }                    */
    #endif
1:  wsr     a3, EPC_1                   /* update PC            */

    /* Restore interruptee's context and return from exception. */
    #ifdef __XTENSA_CALL0_ABI__
    l32i    a2, sp, 8
    l32i    a3, sp, 12
    addi    sp, sp, 16
    #else
    call0   _xt_context_restore
    addi    sp, sp, XT_STK_FRMSZ
    #endif
    movi    a0, -1
    movnez  a2, a0, a2              /* return -1 if not syscall 0 */
    rsr     a0, EXCSAVE_1
    rfe

/*
 * Co-Processor Exception Handler (jumped to from User Exception Handler).
 *
 * These exceptions are generated by co-processor instructions, which are only
 * allowed in thread code (not in interrupts or kernel code). This restriction
 * is deliberately imposed to reduce the burden of state-save/restore in
 * interrupts.
 */
#if XCHAL_CP_NUM > 0

    .section .rodata, "a"

/* Offset to CP n save area in thread's CP save area. */
    .global _xt_coproc_sa_offset
    .type   _xt_coproc_sa_offset,@object
    .align  16              /* minimize crossing cache boundaries */
_xt_coproc_sa_offset:
    .word   XT_CP0_SA, XT_CP1_SA, XT_CP2_SA, XT_CP3_SA
    .word   XT_CP4_SA, XT_CP5_SA, XT_CP6_SA, XT_CP7_SA

/* Bitmask for CP n's CPENABLE bit. */
    .type   _xt_coproc_mask,@object
    .align  16,,8           /* try to keep it all in one cache line */
    .set    i, 0
_xt_coproc_mask:
    .rept   XCHAL_CP_MAX
    .long   (i<<16) | (1<<i)    /* upper 16-bits = i, lower = bitmask */
    .set    i, i+1
    .endr

    .data

/* Owner thread of CP n, identified by thread's CP save area (0 = unowned). */
    .global _xt_coproc_owner_sa
    .type   _xt_coproc_owner_sa,@object
    .align  16,,XCHAL_CP_MAX<<2     /* minimize crossing cache boundaries */
_xt_coproc_owner_sa:
    .space  XCHAL_CP_MAX << 2

    .text


    .align  4
.L_goto_invalid:
    j   .L_xt_coproc_invalid    /* not in a thread (invalid) */
    .align  4
.L_goto_done:
    j   .L_xt_coproc_done


/*
 * Coprocessor exception handler.
 *
 * At entry, only a0 has been saved (in EXCSAVE_1).
 */

    .type   _xt_coproc_exc,@function
    .align  4

_xt_coproc_exc:

    /* Allocate interrupt stack frame and save minimal context. */
    mov     a0, sp                      /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ       /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1           /* save pre-interrupt SP */
    #if XCHAL_HAVE_WINDOWED
    s32e    a0, sp, -12                 /* for debug backtrace */
    #endif
    rsr     a0, PS                      /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_1                   /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_1               /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    #if XCHAL_HAVE_WINDOWED
    s32e    a0, sp, -16                 /* for debug backtrace */
    #endif
    movi    a0, _xt_user_exit           /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    rsr     a0, EXCCAUSE
    s32i    a5, sp, XT_STK_a5               /* save a5 */
    addi    a5, a0, -EXCCAUSE_CP0_DISABLED  /* a5 = CP index */

    /* Save a few more of interruptee's registers (a5 was already saved). */
    s32i    a2,  sp, XT_STK_a2
    s32i    a3,  sp, XT_STK_a3
    s32i    a4,  sp, XT_STK_a4
    s32i    a15, sp, XT_STK_a15

    /* Get co-processor state save area of new owner thread. */
    call0   XT_RTOS_CP_STATE            /* a15 = new owner's save area */
    beqz    a15, .L_goto_invalid        /* not in a thread (invalid) */

    /* Enable the co-processor's bit in CPENABLE. */
    movi    a0, _xt_coproc_mask
    rsr     a4, CPENABLE                /* a4 = CPENABLE */
    addx4   a0, a5, a0                  /* a0 = &_xt_coproc_mask[n] */
    l32i    a0, a0, 0                   /* a0 = (n << 16) | (1 << n) */
    movi    a3, _xt_coproc_owner_sa     /* (placed here for load slot) */
    extui   a2, a0, 0, 16               /* coprocessor bitmask portion */
    or      a4, a4, a2                  /* a4 = CPENABLE | (1 << n) */
    wsr     a4, CPENABLE

    /* Get old coprocessor owner thread (save area ptr) and assign new
     * one.
     */
    addx4   a3,  a5, a3             /* a3 = &_xt_coproc_owner_sa[n] */
    l32i    a2,  a3, 0              /* a2 = old owner's save area */
    s32i    a15, a3, 0              /* _xt_coproc_owner_sa[n] = new */
    rsync                           /* ensure wsr.CPENABLE is complete */

    /* Only need to context switch if new owner != old owner. */
    beq     a15, a2, .L_goto_done       /* new owner == old, we're done */

    /* If no old owner then nothing to save. */
    beqz    a2, .L_check_new

    /* If old owner not actively using CP then nothing to save. */
    l16ui   a4,  a2,  XT_CPENABLE       /* a4 = old owner's CPENABLE */
    bnone   a4,  a0,  .L_check_new      /* old owner not using CP    */

.L_save_old:
    /* Save old owner's coprocessor state. */

    movi    a5, _xt_coproc_sa_offset

    /* Mark old owner state as no longer active (CPENABLE bit n clear). */
    xor     a4,  a4,  a0                /* clear CP bit in CPENABLE    */
    s16i    a4,  a2,  XT_CPENABLE       /* update old owner's CPENABLE */

    extui   a4,  a0,  16,  5            /* a4 = CP index = n */
    addx4   a5,  a4,  a5                /* a5 = &_xt_coproc_sa_offset[n] */

    /* Mark old owner state as saved (CPSTORED bit n set). */
    l16ui   a4,  a2,  XT_CPSTORED   /* a4 = old owner's CPSTORED */
    l32i    a5,  a5,  0             /* a5 = XT_CP[n]_SA offset */
    or      a4,  a4,  a0            /* set CP in old owner's CPSTORED */
    s16i    a4,  a2,  XT_CPSTORED   /* update old owner's CPSTORED */
    l32i    a2, a2, XT_CP_ASA       /* ptr to actual (aligned) save area */
    extui   a3, a0, 16, 5           /* a3 = CP index = n */
    add     a2, a2, a5              /* a2 = old owner's area for CP n */

    /* The config-specific HAL macro invoked below destroys a2-5, preserves
     * a0-1. It is theoretically possible for Xtensa processor designers to
     * write TIE that causes more address registers to be affected, but it
     * is generally unlikely. If that ever happens, more registers needs to
     * be saved/restored around this macro invocation, and the value in a15
     * needs to be recomputed.
     */
    xchal_cpi_store_funcbody

.L_check_new:
    /* Check if any state has to be restored for new owner. */
    /* NOTE: a15 = new owner's save area, cannot be zero when we get
     * here. */

    l16ui   a3,  a15, XT_CPSTORED   /* a3 = new owner's CPSTORED */
    movi    a4, _xt_coproc_sa_offset
    /* full CP not saved, check callee-saved */
    bnone   a3,  a0,  .L_check_cs
    xor     a3,  a3,  a0            /* CPSTORED bit is set, clear it */
    s16i    a3,  a15, XT_CPSTORED   /* update new owner's CPSTORED */

    /* Adjust new owner's save area pointers to area for CP n. */
    extui   a3,  a0, 16, 5          /* a3 = CP index = n */
    addx4   a4,  a3, a4             /* a4 = &_xt_coproc_sa_offset[n] */
    l32i    a4,  a4, 0              /* a4 = XT_CP[n]_SA */
    l32i    a5, a15, XT_CP_ASA      /* ptr to actual (aligned) save area */
    add     a2,  a4, a5             /* a2 = new owner's area for CP */

    /* The config-specific HAL macro invoked below destroys a2-5, preserves
     * a0-1. It is theoretically possible for Xtensa processor designers to
     * write TIE that causes more address registers to be affected, but it
     * is generally unlikely. If that ever happens, more registers needs to
     * be saved/restored around this macro invocation.
     */
    xchal_cpi_load_funcbody

    /* Restore interruptee's saved registers. */
    /* Can omit rsync for wsr.CPENABLE here because _xt_user_exit does
     * it.
     */
.L_xt_coproc_done:
    l32i    a15, sp, XT_STK_a15
    l32i    a5,  sp, XT_STK_a5
    l32i    a4,  sp, XT_STK_a4
    l32i    a3,  sp, XT_STK_a3
    l32i    a2,  sp, XT_STK_a2
    call0   _xt_user_exit           /* return via exit dispatcher */
    /* Never returns here - call0 is used as a jump (see note at top) */

.L_check_cs:
    /* a0 = CP mask in low bits, a15 = new owner's save area */
    l16ui   a2, a15, XT_CP_CS_ST            /* a2 = mask of CPs saved    */
    bnone   a2,  a0, .L_xt_coproc_done      /* if no match then done     */
    and     a2,  a2, a0                     /* a2 = which CPs to restore */
    extui   a2,  a2, 0, 8                   /* extract low 8 bits        */
    s32i    a6,  sp, XT_STK_a6              /* save extra needed regs    */
    s32i    a7,  sp, XT_STK_a7
    s32i    a13, sp, XT_STK_a13
    s32i    a14, sp, XT_STK_a14
    call0   _xt_coproc_restorecs            /* restore CP registers      */
    l32i    a6,  sp, XT_STK_a6              /* restore saved registers   */
    l32i    a7,  sp, XT_STK_a7
    l32i    a13, sp, XT_STK_a13
    l32i    a14, sp, XT_STK_a14
    j       .L_xt_coproc_done

    /* Co-processor exception occurred outside a thread (not supported). */
.L_xt_coproc_invalid:
    #if XCHAL_HAVE_DEBUG
    break   1, 1                            /* unhandled user exception */
    #endif
    call0   _xt_panic                       /* not in a thread (invalid) */
    /* never returns */


#endif /* XCHAL_CP_NUM */


/*
 * Level 1 interrupt dispatch. Assumes stack frame has not been allocated yet.
 */

    .text
    .type       _xt_lowint1,@function
    .align      4

_xt_lowint1:
    mov     a0, sp                  /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1       /* save pre-interrupt SP */
    rsr     a0, PS                  /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_1               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_1           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    movi    a0, _xt_user_exit       /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    /* Save rest of interrupt context and enter RTOS. */
    call0   XT_RTOS_INT_ENTER       /* common RTOS interrupt entry */

    /* !! We are now on the RTOS system stack !! */

    /* Set up PS for C, enable interrupts above this level and clear
     * EXCM.
     */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(1) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(1) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS
    rsync

    /* OK to call C code at this point, dispatch user ISRs */

    dispatch_c_isr 1 XCHAL_INTLEVEL1_MASK

    /* Done handling interrupts, transfer control to OS. */
    call0   XT_RTOS_INT_EXIT        /* does not return directly here */


/* MEDIUM PRIORITY (LEVEL 2+) INTERRUPT VECTORS AND LOW LEVEL HANDLERS.
 *
 * Medium priority interrupts are by definition those with priority greater
 * than 1 and not greater than XCHAL_EXCM_LEVEL. These are disabled by setting
 * PS.EXCM and therefore can easily support a C environment for handlers in C,
 * and interact safely with an RTOS.
 *
 * Each vector goes at a predetermined location according to the Xtensa
 * hardware configuration, which is ensured by its placement in a special
 * section known to the Xtensa linker support package (LSP). It performs the
 * minimum necessary before jumping to the handler in the .text section.
 *
 * The corresponding handler goes in the normal .text section. It sets up the
 * appropriate stack frame, saves a few vector-specific registers and calls
 * XT_RTOS_INT_ENTER to save the rest of the interrupted context and enter the
 * RTOS, then sets up a C environment. It then calls the user's interrupt
 * handler code (which may be coded in C) and finally calls XT_RTOS_INT_EXIT to
 * transfer control to the RTOS for scheduling.
 *
 * While XT_RTOS_INT_EXIT does not return directly to the interruptee,
 * eventually the RTOS scheduler will want to dispatch the interrupted task or
 * handler. The scheduler will return to the exit point that was saved in the
 * interrupt stack frame at XT_STK_EXIT.
 *
 * FIXME: Make this a macro or something so almost-identical code isn't
 * repeated 5 times!!
 */

#if GEN_MED_INTERRUPT(2)

    .begin      literal_prefix .Level2InterruptVector
    .section    .Level2InterruptVector.text, "ax"
    .global     _Level2Vector
    .type       _Level2Vector,@function
    .align      4
_Level2Vector:
    wsr     a0, EXCSAVE_2                   /* preserve a0 */
    call0   _xt_medint2                     /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_medint2,@function
    .align      4
_xt_medint2:
    mov     a0, sp                  /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1       /* save pre-interrupt SP */
    rsr     a0, EPS_2               /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_2               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_2           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    movi    a0, _xt_medint2_exit    /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    /* Save rest of interrupt context and enter RTOS. */
    call0   XT_RTOS_INT_ENTER       /* common RTOS interrupt entry */

    /* !! We are now on the RTOS system stack !! */

    /* Set up PS for C, enable interrupts above this level and clear
     * EXCM.
     */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(2) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(2) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS
    rsync

    /* OK to call C code at this point, dispatch user ISRs */

    dispatch_c_isr 2 XCHAL_INTLEVEL2_MASK

    /* Done handling interrupts, transfer control to OS */
    call0   XT_RTOS_INT_EXIT        /* does not return directly here */

    /* Exit point for dispatch. Saved in interrupt stack frame at
     * XT_STK_EXIT on entry and used to return to a thread or interrupted
     * interrupt handler.
     */
    .global     _xt_medint2_exit
    .type       _xt_medint2_exit,@function
    .align      4
_xt_medint2_exit:
    /* Restore only level-specific regs (the rest were already restored) */
    l32i    a0, sp, XT_STK_ps       /* retrieve interruptee's PS */
    wsr     a0, EPS_2
    l32i    a0, sp, XT_STK_pc       /* retrieve interruptee's PC */
    wsr     a0, EPC_2
    l32i    a0, sp, XT_STK_a0       /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1       /* remove interrupt stack frame */
    rsync                           /* ensure EPS and EPC written */
    rfi     2

#endif  /* Level 2 */

#if GEN_MED_INTERRUPT(3)

    .begin      literal_prefix .Level3InterruptVector
    .section    .Level3InterruptVector.text, "ax"
    .global     _Level3Vector
    .type       _Level3Vector,@function
    .align      4
_Level3Vector:
    wsr     a0, EXCSAVE_3                   /* preserve a0 */
    call0   _xt_medint3                     /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_medint3,@function
    .align      4
_xt_medint3:
    mov     a0, sp                  /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1       /* save pre-interrupt SP */
    rsr     a0, EPS_3               /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_3               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_3           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    movi    a0, _xt_medint3_exit    /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    /* Save rest of interrupt context and enter RTOS. */
    call0   XT_RTOS_INT_ENTER       /* common RTOS interrupt entry */

    /* !! We are now on the RTOS system stack !! */

    /* Set up PS for C, enable interrupts above this level and clear
     * EXCM.
     */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(3) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(3) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS
    rsync

    /* OK to call C code at this point, dispatch user ISRs */

    dispatch_c_isr 3 XCHAL_INTLEVEL3_MASK

    /* Done handling interrupts, transfer control to OS */
    call0   XT_RTOS_INT_EXIT        /* does not return directly here */

    /* Exit point for dispatch. Saved in interrupt stack frame at
     * XT_STK_EXITon entry and used to return to a thread or interrupted
     * interrupt handler.
    */
    .global     _xt_medint3_exit
    .type       _xt_medint3_exit,@function
    .align      4
_xt_medint3_exit:
    /* Restore only level-specific regs (the rest were already restored) */
    l32i    a0, sp, XT_STK_ps       /* retrieve interruptee's PS */
    wsr     a0, EPS_3
    l32i    a0, sp, XT_STK_pc       /* retrieve interruptee's PC */
    wsr     a0, EPC_3
    l32i    a0, sp, XT_STK_a0       /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1       /* remove interrupt stack frame */
    rsync                           /* ensure EPS and EPC written */
    rfi     3

#endif  /* Level 3 */

#if GEN_MED_INTERRUPT(4)

    .begin      literal_prefix .Level4InterruptVector
    .section    .Level4InterruptVector.text, "ax"
    .global     _Level4Vector
    .type       _Level4Vector,@function
    .align      4
_Level4Vector:
    wsr     a0, EXCSAVE_4           /* preserve a0 */
    call0   _xt_medint4             /* load interrupt handler */

    .end        literal_prefix

    .text
    .type       _xt_medint4,@function
    .align      4
_xt_medint4:
    mov     a0, sp                  /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1       /* save pre-interrupt SP */
    rsr     a0, EPS_4               /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_4               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_4           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    movi    a0, _xt_medint4_exit    /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    /* Save rest of interrupt context and enter RTOS. */
    call0   XT_RTOS_INT_ENTER       /* common RTOS interrupt entry */

    /* !! We are now on the RTOS system stack !! */

    /* Set up PS for C, enable interrupts above this level and clear
     * EXCM.
     */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(4) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(4) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS
    rsync

    /* OK to call C code at this point, dispatch user ISRs */

    dispatch_c_isr 4 XCHAL_INTLEVEL4_MASK

    /* Done handling interrupts, transfer control to OS */
    call0   XT_RTOS_INT_EXIT        /* does not return directly here */

    /* Exit point for dispatch. Saved in interrupt stack frame at
     * XT_STK_EXIT on entry and used to return to a thread or interrupted
     * interrupt handler.
    */
    .global     _xt_medint4_exit
    .type       _xt_medint4_exit,@function
    .align      4
_xt_medint4_exit:
    /* Restore only level-specific regs (the rest were already restored) */
    l32i    a0, sp, XT_STK_ps       /* retrieve interruptee's PS */
    wsr     a0, EPS_4
    l32i    a0, sp, XT_STK_pc       /* retrieve interruptee's PC */
    wsr     a0, EPC_4
    l32i    a0, sp, XT_STK_a0       /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1       /* remove interrupt stack frame */
    rsync                           /* ensure EPS and EPC written */
    rfi     4

#endif  /* Level 4 */

#if GEN_MED_INTERRUPT(5)

    .begin      literal_prefix .Level5InterruptVector
    .section    .Level5InterruptVector.text, "ax"
    .global     _Level5Vector
    .type       _Level5Vector,@function
    .align      4
_Level5Vector:
    wsr     a0, EXCSAVE_5           /* preserve a0 */
    call0   _xt_medint5             /* load interrupt handler */

    .end        literal_prefix

    .text
    .type       _xt_medint5,@function
    .align      4
_xt_medint5:
    mov     a0, sp                  /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1       /* save pre-interrupt SP */
    rsr     a0, EPS_5               /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_5               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_5           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    movi    a0, _xt_medint5_exit    /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    /* Save rest of interrupt context and enter RTOS. */
    call0   XT_RTOS_INT_ENTER       /* common RTOS interrupt entry */

    /* !! We are now on the RTOS system stack !! */

    /* Set up PS for C, enable interrupts above this level and clear
     * EXCM.
     */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(5) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(5) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS
    rsync

    /* OK to call C code at this point, dispatch user ISRs */

    dispatch_c_isr 5 XCHAL_INTLEVEL5_MASK

    /* Done handling interrupts, transfer control to OS */
    call0   XT_RTOS_INT_EXIT        /* does not return directly here */

    /* Exit point for dispatch. Saved in interrupt stack frame at
     * XT_STK_EXITon entry and used to return to a thread or interrupted
     * interrupt handler.
    */
    .global     _xt_medint5_exit
    .type       _xt_medint5_exit,@function
    .align      4
_xt_medint5_exit:
    /* Restore only level-specific regs (the rest were already restored) */
    l32i    a0, sp, XT_STK_ps       /* retrieve interruptee's PS */
    wsr     a0, EPS_5
    l32i    a0, sp, XT_STK_pc       /* retrieve interruptee's PC */
    wsr     a0, EPC_5
    l32i    a0, sp, XT_STK_a0       /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1       /* remove interrupt stack frame */
    rsync                           /* ensure EPS and EPC written */
    rfi     5

#endif  /* Level 5 */

#if GEN_MED_INTERRUPT(6)

    .begin      literal_prefix .Level6InterruptVector
    .section    .Level6InterruptVector.text, "ax"
    .global     _Level6Vector
    .type       _Level6Vector,@function
    .align      4
_Level6Vector:
    wsr     a0, EXCSAVE_6           /* preserve a0 */
    call0   _xt_medint6             /* load interrupt handler */

    .end        literal_prefix

    .text
    .type       _xt_medint6,@function
    .align      4
_xt_medint6:
    mov     a0, sp                  /* sp == a1 */
    addi    sp, sp, -XT_STK_FRMSZ   /* allocate interrupt stack frame */
    s32i    a0, sp, XT_STK_a1       /* save pre-interrupt SP */
    rsr     a0, EPS_6               /* save interruptee's PS */
    s32i    a0, sp, XT_STK_ps
    rsr     a0, EPC_6               /* save interruptee's PC */
    s32i    a0, sp, XT_STK_pc
    rsr     a0, EXCSAVE_6           /* save interruptee's a0 */
    s32i    a0, sp, XT_STK_a0
    movi    a0, _xt_medint6_exit    /* save exit point for dispatch */
    s32i    a0, sp, XT_STK_exit

    /* Save rest of interrupt context and enter RTOS. */
    call0   XT_RTOS_INT_ENTER       /* common RTOS interrupt entry */

    /* !! We are now on the RTOS system stack !! */

    /* Set up PS for C, enable interrupts above this level and clear
     * EXCM.
     */
    #ifdef __XTENSA_CALL0_ABI__
    movi    a0, PS_INTLEVEL(6) | PS_UM
    #else
    movi    a0, PS_INTLEVEL(6) | PS_UM | PS_WOE
    #endif
    wsr     a0, PS
    rsync

    /* OK to call C code at this point, dispatch user ISRs */

    dispatch_c_isr 6 XCHAL_INTLEVEL6_MASK

    /* Done handling interrupts, transfer control to OS */
    call0   XT_RTOS_INT_EXIT        /* does not return directly here */

    /* Exit point for dispatch. Saved in interrupt stack frame at
     * XT_STK_EXIT on entry and used to return to a thread or interrupted
     * interrupt handler.
     */
    .global     _xt_medint6_exit
    .type       _xt_medint6_exit,@function
    .align      4
_xt_medint6_exit:
    /* Restore only level-specific regs (the rest were already restored) */
    l32i    a0, sp, XT_STK_ps       /* retrieve interruptee's PS */
    wsr     a0, EPS_6
    l32i    a0, sp, XT_STK_pc       /* retrieve interruptee's PC */
    wsr     a0, EPC_6
    l32i    a0, sp, XT_STK_a0       /* retrieve interruptee's A0 */
    l32i    sp, sp, XT_STK_a1       /* remove interrupt stack frame */
    rsync                           /* ensure EPS and EPC written */
    rfi     6

#endif  /* Level 6 */


/*
 * HIGH PRIORITY (LEVEL > XCHAL_EXCM_LEVEL) INTERRUPT VECTORS AND HANDLERS
 *
 * High priority interrupts are by definition those with priorities greater
 * than XCHAL_EXCM_LEVEL. This includes non-maskable (NMI). High priority
 * interrupts cannot interact with the RTOS, that is they must save all regs
 * they use and not call any RTOS function.
 *
 * A further restriction imposed by the Xtensa windowed architecture is that
 * high priority interrupts must not modify the stack area even logically
 * "above" the top of the interrupted stack (they need to provide their own
 * stack or static save area).
 *
 * Cadence Design Systems recommends high priority interrupt handlers be coded
 * in assembly and used for purposes requiring very short service times.
 *
 * Here are templates for high priority (level 2+) interrupt vectors. They
 * assume only one interrupt per level to avoid the burden of identifying which
 * interrupts at this level are pending and enabled. This allows for minimum
 * latency and avoids having to save/restore a2 in addition to a0. If more than
 * one interrupt per high priority level is configured, this burden is on the
 * handler which in any case must provide a way to save and restore registers
 * it uses without touching the interrupted stack.
 *
 * Each vector goes at a predetermined location according to the Xtensa
 * hardware configuration, which is ensured by its placement in a special
 * section known to the Xtensa linker support package (LSP). It performs the
 * minimum necessary before jumping to the handler in the .text section.
 */

/* Currently only shells for high priority interrupt handlers are provided
 * here. However a template and example can be found in the Cadence Design
 * Systems tools documentation: "Microprocessor Programmer's Guide".
 */

#if GEN_HIGH_INTERRUPT(2)

    .begin      literal_prefix .Level2InterruptVector
    .section    .Level2InterruptVector.text, "ax"
    .global     _Level2Vector
    .type       _Level2Vector,@function
    .align      4
_Level2Vector:
    wsr     a0, EXCSAVE_2                   /* preserve a0 */
    call0   _xt_highint2                    /* load interrupt handler */

    .end        literal_prefix

    .text
    .type       _xt_highint2,@function
    .align      4
_xt_highint2:

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a0, _xt_intexc_hooks
    l32i    a0, a0, 2<<2
    beqz    a0, 1f
.Ln_xt_highint2_call_hook:
    callx0  a0                              /* must NOT disturb stack! */
1:
    #endif

    /* USER_EDIT: ADD HIGH PRIORITY LEVEL 2 INTERRUPT HANDLER CODE HERE. */

    .align  4
.L_xt_highint2_exit:
    rsr     a0, EXCSAVE_2                   /* restore a0 */
    rfi     2

#endif  /* Level 2 */

#if GEN_HIGH_INTERRUPT(3)

    .begin      literal_prefix .Level3InterruptVector
    .section    .Level3InterruptVector.text, "ax"
    .global     _Level3Vector
    .type       _Level3Vector,@function
    .align      4
_Level3Vector:
    wsr     a0, EXCSAVE_3                   /* preserve a0 */
    call0   _xt_highint3                    /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_highint3,@function
    .align      4
_xt_highint3:

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a0, _xt_intexc_hooks
    l32i    a0, a0, 3<<2
    beqz    a0, 1f
.Ln_xt_highint3_call_hook:
    callx0  a0                              /* must NOT disturb stack! */
1:
    #endif

    /* USER_EDIT: ADD HIGH PRIORITY LEVEL 3 INTERRUPT HANDLER CODE HERE. */

    .align  4
.L_xt_highint3_exit:
    rsr     a0, EXCSAVE_3                   /* restore a0 */
    rfi     3

#endif  /* Level 3 */

#if GEN_HIGH_INTERRUPT(4)

    .begin      literal_prefix .Level4InterruptVector
    .section    .Level4InterruptVector.text, "ax"
    .global     _Level4Vector
    .type       _Level4Vector,@function
    .align      4
_Level4Vector:
    wsr     a0, EXCSAVE_4                   /* preserve a0 */
    call0   _xt_highint4                    /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_highint4,@function
    .align      4
_xt_highint4:

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a0, _xt_intexc_hooks
    l32i    a0, a0, 4<<2
    beqz    a0, 1f
.Ln_xt_highint4_call_hook:
    callx0  a0                              /* must NOT disturb stack! */
1:
    #endif

    /* USER_EDIT: ADD HIGH PRIORITY LEVEL 4 INTERRUPT HANDLER CODE HERE. */

    .align  4
.L_xt_highint4_exit:
    rsr     a0, EXCSAVE_4                   /* restore a0 */
    rfi     4

#endif  /* Level 4 */

#if GEN_HIGH_INTERRUPT(5)
    .begin      literal_prefix .Level5InterruptVector
    .section    .Level5InterruptVector.text, "ax"
    .global     _Level5Vector
    .type       _Level5Vector,@function
    .align      4
_Level5Vector:
    wsr     a0, EXCSAVE_5                   /* preserve a0 */
    call0   _xt_highint5                    /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_highint5,@function
    .align      4
_xt_highint5:

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a0, _xt_intexc_hooks
    l32i    a0, a0, 5<<2
    beqz    a0, 1f
.Ln_xt_highint5_call_hook:
    callx0  a0                              /* must NOT disturb stack! */
1:
    #endif

    /* USER_EDIT:
     * ADD HIGH PRIORITY LEVEL 5 INTERRUPT HANDLER CODE HERE.
     */

    .align  4
.L_xt_highint5_exit:
    rsr     a0, EXCSAVE_5                   /* restore a0 */
    rfi     5

#endif  /* Level 5 */

#if GEN_HIGH_INTERRUPT(6)

    .begin      literal_prefix .Level6InterruptVector
    .section    .Level6InterruptVector.text, "ax"
    .global     _Level6Vector
    .type       _Level6Vector,@function
    .align      4
_Level6Vector:
    wsr     a0, EXCSAVE_6                   /* preserve a0 */
    call0   _xt_highint6                    /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_highint6,@function
    .align      4
_xt_highint6:

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a0, _xt_intexc_hooks
    l32i    a0, a0, 6<<2
    beqz    a0, 1f
.Ln_xt_highint6_call_hook:
    callx0  a0                              /* must NOT disturb stack! */
1:
    #endif

    /* USER_EDIT:
     * ADD HIGH PRIORITY LEVEL 6 INTERRUPT HANDLER CODE HERE.
     */

    .align  4
.L_xt_highint6_exit:
    rsr     a0, EXCSAVE_6                   /* restore a0 */
    rfi     6

#endif  /* Level 6 */

#if XCHAL_HAVE_NMI

    .begin      literal_prefix .NMIExceptionVector
    .section    .NMIExceptionVector.text, "ax"
    .global     _NMIExceptionVector
    .type       _NMIExceptionVector,@function
    .align      4
_NMIExceptionVector:
    wsr     a0, EXCSAVE + XCHAL_NMILEVEL  _ /* preserve a0 */
    call0   _xt_nmi                         /* load interrupt handler */
    /* never returns here - call0 is used as a jump (see note at top) */

    .end        literal_prefix

    .text
    .type       _xt_nmi,@function
    .align      4
_xt_nmi:

    #ifdef XT_INTEXC_HOOKS
    /* Call interrupt hook if present to (pre)handle interrupts. */
    movi    a0, _xt_intexc_hooks
    l32i    a0, a0, XCHAL_NMILEVEL<<2
    beqz    a0, 1f
.Ln_xt_nmi_call_hook:
    callx0  a0                              /* must NOT disturb stack! */
1:
    #endif

    /* USER_EDIT:
     * ADD HIGH PRIORITY NON-MASKABLE INTERRUPT (NMI) HANDLER CODE HERE.
     */

    .align  4
.L_xt_nmi_exit:
    rsr     a0, EXCSAVE + XCHAL_NMILEVEL    /* restore a0 */
    rfi     XCHAL_NMILEVEL

#endif  /* NMI */