/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * Vineetg: March 2009 (Supporting 2 levels of Interrupts)
 *  Stack switching code can no longer reliably rely on the fact that
 *  if we are NOT in user mode, stack is switched to kernel mode.
 *  e.g. L2 IRQ interrupted a L1 ISR which had not yet completed
 *  it's prologue including stack switching from user mode
 *
 * Vineetg: Aug 28th 2008: Bug #94984
 *  -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap
 *   Normally CPU does this automatically, however when doing FAKE rtie,
 *   we also need to explicitly do this. The problem in macros
 *   FAKE_RET_FROM_EXCPN and FAKE_RET_FROM_EXCPN_LOCK_IRQ was that this bit
 *   was being "CLEARED" rather then "SET". Actually "SET" clears ZOL context
 *
 * Vineetg: May 5th 2008
 *  -Modified CALLEE_REG save/restore macros to handle the fact that
 *      r25 contains the kernel current task ptr
 *  - Defined Stack Switching Macro to be reused in all intr/excp hdlrs
 *  - Shaved off 11 instructions from RESTORE_ALL_INT1 by using the
 *      address Write back load ld.ab instead of seperate ld/add instn
 *
 * Amit Bhor, Sameer Dhavale: Codito Technologies 2004
 */

#ifndef __ASM_ARC_ENTRY_COMPACT_H
#define __ASM_ARC_ENTRY_COMPACT_H

#include <asm/asm-offsets.h>
#include <asm/irqflags-compact.h>
#include <asm/thread_info.h>    /* For THREAD_SIZE */

/*--------------------------------------------------------------
 * Switch to Kernel Mode stack if SP points to User Mode stack
 *
 * Entry   : r9 contains pre-IRQ/exception/trap status32
 * Exit    : SP set to K mode stack
 *           SP at the time of entry (K/U) saved @ pt_regs->sp
 * Clobbers: r9
 *-------------------------------------------------------------*/

.macro SWITCH_TO_KERNEL_STK

        /* User Mode when this happened ? Yes: Proceed to switch stack */
        bbit1   r9, STATUS_U_BIT, 88f

        /* OK we were already in kernel mode when this event happened, thus can
         * assume SP is kernel mode SP. _NO_ need to do any stack switching
         */

#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
        /* However....
         * If Level 2 Interrupts enabled, we may end up with a corner case:
         * 1. User Task executing
         * 2. L1 IRQ taken, ISR starts (CPU auto-switched to KERNEL mode)
         * 3. But before it could switch SP from USER to KERNEL stack
         *      a L2 IRQ "Interrupts" L1
         * Thay way although L2 IRQ happened in Kernel mode, stack is still
         * not switched.
         * To handle this, we may need to switch stack even if in kernel mode
         * provided SP has values in range of USER mode stack ( < 0x7000_0000 )
         */
        brlo sp, VMALLOC_START, 88f

        /* TODO: vineetg:
         * We need to be a bit more cautious here. What if a kernel bug in
         * L1 ISR, caused SP to go whaco (some small value which looks like
         * USER stk) and then we take L2 ISR.
         * Above brlo alone would treat it as a valid L1-L2 scenario
         * instead of shouting around
         * The only feasible way is to make sure this L2 happened in
         * L1 prelogue ONLY i.e. ilink2 is less than a pre-set marker in
         * L1 ISR before it switches stack
         */

#endif

    /*------Intr/Ecxp happened in kernel mode, SP already setup ------ */
        /* save it nevertheless @ pt_regs->sp for uniformity */

        b.d     66f
        st      sp, [sp, PT_sp - SZ_PT_REGS]

88: /*------Intr/Ecxp happened in user mode, "switch" stack ------ */

        GET_CURR_TASK_ON_CPU   r9

        /* With current tsk in r9, get it's kernel mode stack base */
        GET_TSK_STACK_BASE  r9, r9

        /* save U mode SP @ pt_regs->sp */
        st      sp, [r9, PT_sp - SZ_PT_REGS]

        /* final SP switch */
        mov     sp, r9
66:
.endm

/*------------------------------------------------------------
 * "FAKE" a rtie to return from CPU Exception context
 * This is to re-enable Exceptions within exception
 * Look at EV_ProtV to see how this is actually used
 *-------------------------------------------------------------*/

.macro FAKE_RET_FROM_EXCPN

        lr      r9, [status32]
        bclr    r9, r9, STATUS_AE_BIT
        or      r9, r9, (STATUS_E1_MASK|STATUS_E2_MASK)
        sr      r9, [erstatus]
        mov     r9, 55f
        sr      r9, [eret]
        rtie
55:
.endm

/*--------------------------------------------------------------
 * For early Exception/ISR Prologue, a core reg is temporarily needed to
 * code the rest of prolog (stack switching). This is done by stashing
 * it to memory (non-SMP case) or SCRATCH0 Aux Reg (SMP).
 *
 * Before saving the full regfile - this reg is restored back, only
 * to be saved again on kernel mode stack, as part of pt_regs.
 *-------------------------------------------------------------*/
.macro PROLOG_FREEUP_REG        reg, mem
        st  \reg, [\mem]
.endm

.macro PROLOG_RESTORE_REG       reg, mem
        ld  \reg, [\mem]
.endm

/*--------------------------------------------------------------
 * Exception Entry prologue
 * -Switches stack to K mode (if not already)
 * -Saves the register file
 *
 * After this it is safe to call the "C" handlers
 *-------------------------------------------------------------*/
.macro EXCEPTION_PROLOGUE

        /* Need at least 1 reg to code the early exception prologue */
        PROLOG_FREEUP_REG r9, @ex_saved_reg1

        /* U/K mode at time of exception (stack not switched if already K) */
        lr  r9, [erstatus]

        /* ARC700 doesn't provide auto-stack switching */
        SWITCH_TO_KERNEL_STK

#ifdef CONFIG_ARC_CURR_IN_REG
        /* Treat r25 as scratch reg (save on stack) and load with "current" */
        PUSH    r25
        GET_CURR_TASK_ON_CPU   r25
#else
        sub     sp, sp, 4
#endif

        st.a    r0, [sp, -8]    /* orig_r0 needed for syscall (skip ECR slot) */
        sub     sp, sp, 4       /* skip pt_regs->sp, already saved above */

        /* Restore r9 used to code the early prologue */
        PROLOG_RESTORE_REG  r9, @ex_saved_reg1

        /* now we are ready to save the regfile */
        SAVE_R0_TO_R12
        PUSH    gp
        PUSH    fp
        PUSH    blink
        PUSHAX  eret
        PUSHAX  erstatus
        PUSH    lp_count
        PUSHAX  lp_end
        PUSHAX  lp_start
        PUSHAX  erbta

        lr      r10, [ecr]
        st      r10, [sp, PT_event]    /* EV_Trap expects r10 to have ECR */
.endm

/*--------------------------------------------------------------
 * Restore all registers used by system call or Exceptions
 * SP should always be pointing to the next free stack element
 * when entering this macro.
 *
 * NOTE:
 *
 * It is recommended that lp_count/ilink1/ilink2 not be used as a dest reg
 * for memory load operations. If used in that way interrupts are deffered
 * by hardware and that is not good.
 *-------------------------------------------------------------*/
.macro EXCEPTION_EPILOGUE

        POPAX   erbta
        POPAX   lp_start
        POPAX   lp_end

        POP     r9
        mov     lp_count, r9    ;LD to lp_count is not allowed

        POPAX   erstatus
        POPAX   eret
        POP     blink
        POP     fp
        POP     gp
        RESTORE_R12_TO_R0

#ifdef CONFIG_ARC_CURR_IN_REG
        ld      r25, [sp, 12]
#endif
        ld  sp, [sp] /* restore original sp */
        /* orig_r0, ECR, user_r25 skipped automatically */
.endm

/* Dummy ECR values for Interrupts */
#define event_IRQ1              0x0031abcd
#define event_IRQ2              0x0032abcd

.macro INTERRUPT_PROLOGUE  LVL

        /* free up r9 as scratchpad */
        PROLOG_FREEUP_REG r9, @int\LVL\()_saved_reg

        /* Which mode (user/kernel) was the system in when intr occurred */
        lr  r9, [status32_l\LVL\()]

        SWITCH_TO_KERNEL_STK

#ifdef CONFIG_ARC_CURR_IN_REG
        /* Treat r25 as scratch reg (save on stack) and load with "current" */
        PUSH    r25
        GET_CURR_TASK_ON_CPU   r25
#else
        sub     sp, sp, 4
#endif

        PUSH    0x003\LVL\()abcd    /* Dummy ECR */
        sub     sp, sp, 8           /* skip orig_r0 (not needed)
                                       skip pt_regs->sp, already saved above */

        /* Restore r9 used to code the early prologue */
        PROLOG_RESTORE_REG  r9, @int\LVL\()_saved_reg

        SAVE_R0_TO_R12
        PUSH    gp
        PUSH    fp
        PUSH    blink
        PUSH    ilink\LVL\()
        PUSHAX  status32_l\LVL\()
        PUSH    lp_count
        PUSHAX  lp_end
        PUSHAX  lp_start
        PUSHAX  bta_l\LVL\()

.endm

/*--------------------------------------------------------------
 * Restore all registers used by interrupt handlers.
 *
 * NOTE:
 *
 * It is recommended that lp_count/ilink1/ilink2 not be used as a dest reg
 * for memory load operations. If used in that way interrupts are deffered
 * by hardware and that is not good.
 *-------------------------------------------------------------*/
.macro INTERRUPT_EPILOGUE  LVL

        POPAX   bta_l\LVL\()
        POPAX   lp_start
        POPAX   lp_end

        POP     r9
        mov     lp_count, r9    ;LD to lp_count is not allowed

        POPAX   status32_l\LVL\()
        POP     ilink\LVL\()
        POP     blink
        POP     fp
        POP     gp
        RESTORE_R12_TO_R0

#ifdef CONFIG_ARC_CURR_IN_REG
        ld      r25, [sp, 12]
#endif
        ld  sp, [sp] /* restore original sp */
        /* orig_r0, ECR, user_r25 skipped automatically */
.endm

/* Get thread_info of "current" tsk */
.macro GET_CURR_THR_INFO_FROM_SP  reg
        bic \reg, sp, (THREAD_SIZE - 1)
.endm

/* Get CPU-ID of this core */
.macro  GET_CPU_ID  reg
        lr  \reg, [identity]
        lsr \reg, \reg, 8
        bmsk \reg, \reg, 7
.endm

#endif  /* __ASM_ARC_ENTRY_COMPACT_H */