/*
 * Copyright (c) 2019-Present Nuclei Limited. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2020/03/26     hqfang       First Nuclei RISC-V porting implementation
 */

#include "riscv_encoding.h"

.section    .text.entry
.align 8

/**
 * \brief  Global interrupt disabled
 * \details
 *  This function disable global interrupt.
 * \remarks
 *  - All the interrupt requests will be ignored by CPU.
 */
.macro DISABLE_MIE
    csrc CSR_MSTATUS, MSTATUS_MIE
.endm

/**
 * \brief  Macro for context save
 * \details
 * This macro save ABI defined caller saved registers in the stack.
 * \remarks
 * - This Macro could use to save context when you enter to interrupt
 * or exception
*/
/* Save caller registers */
.macro SAVE_CONTEXT
    csrrw sp, CSR_MSCRATCHCSWL, sp
    /* Allocate stack space for context saving */
#ifndef __riscv_32e
    addi sp, sp, -20*REGBYTES
#else
    addi sp, sp, -14*REGBYTES
#endif /* __riscv_32e */

    STORE x1, 0*REGBYTES(sp)
    STORE x4, 1*REGBYTES(sp)
    STORE x5, 2*REGBYTES(sp)
    STORE x6, 3*REGBYTES(sp)
    STORE x7, 4*REGBYTES(sp)
    STORE x10, 5*REGBYTES(sp)
    STORE x11, 6*REGBYTES(sp)
    STORE x12, 7*REGBYTES(sp)
    STORE x13, 8*REGBYTES(sp)
    STORE x14, 9*REGBYTES(sp)
    STORE x15, 10*REGBYTES(sp)
#ifndef __riscv_32e
    STORE x16, 14*REGBYTES(sp)
    STORE x17, 15*REGBYTES(sp)
    STORE x28, 16*REGBYTES(sp)
    STORE x29, 17*REGBYTES(sp)
    STORE x30, 18*REGBYTES(sp)
    STORE x31, 19*REGBYTES(sp)
#endif /* __riscv_32e */
.endm

/**
 * \brief  Macro for restore caller registers
 * \details
 * This macro restore ABI defined caller saved registers from stack.
 * \remarks
 * - You could use this macro to restore context before you want return
 * from interrupt or exeception
 */
/* Restore caller registers */
.macro RESTORE_CONTEXT
    LOAD x1, 0*REGBYTES(sp)
    LOAD x4, 1*REGBYTES(sp)
    LOAD x5, 2*REGBYTES(sp)
    LOAD x6, 3*REGBYTES(sp)
    LOAD x7, 4*REGBYTES(sp)
    LOAD x10, 5*REGBYTES(sp)
    LOAD x11, 6*REGBYTES(sp)
    LOAD x12, 7*REGBYTES(sp)
    LOAD x13, 8*REGBYTES(sp)
    LOAD x14, 9*REGBYTES(sp)
    LOAD x15, 10*REGBYTES(sp)
#ifndef __riscv_32e
    LOAD x16, 14*REGBYTES(sp)
    LOAD x17, 15*REGBYTES(sp)
    LOAD x28, 16*REGBYTES(sp)
    LOAD x29, 17*REGBYTES(sp)
    LOAD x30, 18*REGBYTES(sp)
    LOAD x31, 19*REGBYTES(sp)

    /* De-allocate the stack space */
    addi sp, sp, 20*REGBYTES
#else
    /* De-allocate the stack space */
    addi sp, sp, 14*REGBYTES
#endif /* __riscv_32e */
    csrrw sp, CSR_MSCRATCHCSWL, sp
.endm

/**
 * \brief  Macro for save necessary CSRs to stack
 * \details
 * This macro store MCAUSE, MEPC, MSUBM to stack.
 */
.macro SAVE_CSR_CONTEXT
    /* Store CSR mcause to stack using pushmcause */
    csrrwi  x0, CSR_PUSHMCAUSE, 11
    /* Store CSR mepc to stack using pushmepc */
    csrrwi  x0, CSR_PUSHMEPC, 12
    /* Store CSR msub to stack using pushmsub */
    csrrwi  x0, CSR_PUSHMSUBM, 13
.endm

/**
 * \brief  Macro for restore necessary CSRs from stack
 * \details
 * This macro restore MSUBM, MEPC, MCAUSE from stack.
 */
.macro RESTORE_CSR_CONTEXT
    LOAD x5,  13*REGBYTES(sp)
    csrw CSR_MSUBM, x5
    LOAD x5,  12*REGBYTES(sp)
    csrw CSR_MEPC, x5
    LOAD x5,  11*REGBYTES(sp)
    csrw CSR_MCAUSE, x5
.endm

/**
 * \brief  Exception/NMI Entry
 * \details
 * This function provide common entry functions for exception/nmi.
 * \remarks
 * This function provide a default exception/nmi entry.
 * ABI defined caller save register and some CSR registers
 * to be saved before enter interrupt handler and be restored before return.
 */
.section .text.trap
/* In CLIC mode, the exeception entry must be 64bytes aligned */
.align 6
.global exc_entry
exc_entry:
    /* Save the caller saving registers (context) */
    SAVE_CONTEXT
    /* Save the necessary CSR registers */
    SAVE_CSR_CONTEXT

    /*
     * Set the exception handler function arguments
     * argument 1: mcause value
     * argument 2: current stack point(SP) value
     */
    csrr a0, mcause
    mv a1, sp
    /*
     * TODO: Call the exception handler function
     * By default, the function template is provided in
     * system_Device.c, you can adjust it as you want
     */
    call core_exception_handler

    /* Restore the necessary CSR registers */
    RESTORE_CSR_CONTEXT
    /* Restore the caller saving registers (context) */
    RESTORE_CONTEXT

    /* Return to regular code */
    mret

/**
 * \brief  Non-Vector Interrupt Entry
 * \details
 * This function provide common entry functions for handling
 * non-vector interrupts
 * \remarks
 * This function provide a default non-vector interrupt entry.
 * ABI defined caller save register and some CSR registers need
 * to be saved before enter interrupt handler and be restored before return.
 */
.section      .text.irq
/* In CLIC mode, the interrupt entry must be 4bytes aligned */
.align 2
.global irq_entry
/* This label will be set to MTVT2 register */
irq_entry:
    /* Save the caller saving registers (context) */
    SAVE_CONTEXT
    /* Save the necessary CSR registers */
    SAVE_CSR_CONTEXT

    /* This special CSR read/write operation, which is actually
     * claim the CLIC to find its pending highest ID, if the ID
     * is not 0, then automatically enable the mstatus.MIE, and
     * jump to its vector-entry-label, and update the link register
     */
    csrrw ra, CSR_JALMNXTI, ra

    /* Critical section with interrupts disabled */
    DISABLE_MIE

    /* Restore the necessary CSR registers */
    RESTORE_CSR_CONTEXT
    /* Restore the caller saving registers (context) */
    RESTORE_CONTEXT

    /* Return to regular code */
    mret

/* Default Handler for Exceptions / Interrupts */
.global default_intexc_handler
Undef_Handler:
default_intexc_handler:
1:
	j 1b