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// #################################################################################################

// # << NEORV32: neorv32_rte.c - NEORV32 Runtime Environment >>                                    #

// # ********************************************************************************************* #

// # BSD 3-Clause License                                                                          #

// #                                                                                               #

// # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #

// #                                                                                               #

// # Redistribution and use in source and binary forms, with or without modification, are          #

// # permitted provided that the following conditions are met:                                     #

// #                                                                                               #

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// #    conditions and the following disclaimer.                                                   #

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// #    conditions and the following disclaimer in the documentation and/or other materials        #

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// #    endorse or promote products derived from this software without specific prior written      #

// #    permission.                                                                                #

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// # ********************************************************************************************* #

// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

// #################################################################################################

/**********************************************************************//**

 * @file neorv32_rte.c

 * @author Stephan Nolting

 * @brief NEORV32 Runtime Environment.

 **************************************************************************/

#include "neorv32.h"

#include "neorv32_rte.h"

/**********************************************************************//**

 * The >private< trap vector look-up table of the NEORV32 RTE.

 **************************************************************************/

static uint32_t __neorv32_rte_vector_lut[16] __attribute__((unused)); // trap handler vector table

// private functions

static void __attribute__((__interrupt__)) __neorv32_rte_core(void) __attribute__((aligned(16))) __attribute__((unused));

static void __neorv32_rte_debug_exc_handler(void)     __attribute__((unused));

static void __neorv32_rte_print_true_false(int state) __attribute__((unused));

/**********************************************************************//**

 * Setup NEORV32 runtime environment.

 *

 * @note This function installs a debug handler for ALL exception and interrupt sources, which

 * gives detailed information about the exception/interrupt. Actual handler can be installed afterwards

 * via neorv32_rte_exception_install(uint8_t id, void (*handler)(void)).

 **************************************************************************/

void neorv32_rte_setup(void) {

  // configure trap handler base address

  uint32_t mtvec_base = (uint32_t)(&__neorv32_rte_core);

  neorv32_cpu_csr_write(CSR_MTVEC, mtvec_base);

  // install debug handler for all sources

  uint8_t id;

  for (id = 0; id < (sizeof(__neorv32_rte_vector_lut)/sizeof(__neorv32_rte_vector_lut[0])); id++) {

    neorv32_rte_exception_uninstall(id); // this will configure the debug handler

  }

}

/**********************************************************************//**

 * Install exception handler function to NEORV32 runtime environment.

 *

 * @note This function automatically activates the according CSR.mie bits when installing handlers for

 * the MTIME (MTI), CLIC (MEI), machine software interrupt (MSI) or a fast IRQ. The global interrupt enable bit mstatus.mie has

 * to be set by the user via neorv32_cpu_eint(void).

 *

 * @param[in] id Identifier (type) of the targeted exception. See #NEORV32_RTE_TRAP_enum.

 * @param[in] handler The actual handler function for the specified exception (function MUST be of type "void function(void);").

 * return 0 if success, 1 if error (invalid id or targeted exception not supported).

 **************************************************************************/

int neorv32_rte_exception_install(uint8_t id, void (*handler)(void)) {

  // id valid?

  if ((id == RTE_TRAP_I_MISALIGNED) || (id == RTE_TRAP_I_ACCESS)     || (id == RTE_TRAP_I_ILLEGAL) ||

      (id == RTE_TRAP_BREAKPOINT)   || (id == RTE_TRAP_L_MISALIGNED) || (id == RTE_TRAP_L_ACCESS)  ||

      (id == RTE_TRAP_S_MISALIGNED) || (id == RTE_TRAP_S_ACCESS)     || (id == RTE_TRAP_MENV_CALL) ||

      (id == RTE_TRAP_MSI)          || (id == RTE_TRAP_MTI)          || (id == RTE_TRAP_MEI)       ||

      (id == RTE_TRAP_FIRQ_0)       || (id == RTE_TRAP_FIRQ_1)       || (id == RTE_TRAP_FIRQ_2)    || (id == RTE_TRAP_FIRQ_3)) {

    if (id == RTE_TRAP_MSI)    { neorv32_cpu_irq_enable(CPU_MIE_MSIE); } // activate software interrupt

    if (id == RTE_TRAP_MTI)    { neorv32_cpu_irq_enable(CPU_MIE_MTIE); } // activate timer interrupt

    if (id == RTE_TRAP_MEI)    { neorv32_cpu_irq_enable(CPU_MIE_MEIE); } // activate external interrupt

    if (id == RTE_TRAP_FIRQ_0) { neorv32_cpu_irq_enable(CPU_MIE_FIRQ0E); } // activate fast interrupt channel 0

    if (id == RTE_TRAP_FIRQ_1) { neorv32_cpu_irq_enable(CPU_MIE_FIRQ1E); } // activate fast interrupt channel 1

    if (id == RTE_TRAP_FIRQ_2) { neorv32_cpu_irq_enable(CPU_MIE_FIRQ2E); } // activate fast interrupt channel 2

    if (id == RTE_TRAP_FIRQ_3) { neorv32_cpu_irq_enable(CPU_MIE_FIRQ3E); } // activate fast interrupt channel 3

    __neorv32_rte_vector_lut[id]  = (uint32_t)handler; // install handler

    return 0;

  }

  return 1;

}

/**********************************************************************//**

 * Uninstall exception handler function from NEORV32 runtime environment, which was

 * previously installed via neorv32_rte_exception_install(uint8_t id, void (*handler)(void)).

 *

 * @note This function automatically clears the according CSR.mie bits when uninstalling handlers for

 * the MTIME (MTI), CLIC (MEI), machine software interrupt (MSI) or fast IRQs. The global interrupt enable bit mstatus.mie has

 * to be cleared by the user via neorv32_cpu_dint(void).

 *

 * @param[in] id Identifier (type) of the targeted exception. See #NEORV32_RTE_TRAP_enum.

 * return 0 if success, 1 if error (invalid id or targeted exception not supported).

 **************************************************************************/

int neorv32_rte_exception_uninstall(uint8_t id) {

  // id valid?

  if ((id == RTE_TRAP_I_MISALIGNED) || (id == RTE_TRAP_I_ACCESS)     || (id == RTE_TRAP_I_ILLEGAL) ||

      (id == RTE_TRAP_BREAKPOINT)   || (id == RTE_TRAP_L_MISALIGNED) || (id == RTE_TRAP_L_ACCESS)  ||

      (id == RTE_TRAP_S_MISALIGNED) || (id == RTE_TRAP_S_ACCESS)     || (id == RTE_TRAP_MENV_CALL) ||

      (id == RTE_TRAP_MSI)          || (id == RTE_TRAP_MTI)          || (id == RTE_TRAP_MEI)       ||

      (id == RTE_TRAP_FIRQ_0)       || (id == RTE_TRAP_FIRQ_1)       || (id == RTE_TRAP_FIRQ_2)    || (id == RTE_TRAP_FIRQ_3)) {

    if (id == RTE_TRAP_MSI)    { neorv32_cpu_irq_disable(CPU_MIE_MSIE); } // deactivate software interrupt

    if (id == RTE_TRAP_MTI)    { neorv32_cpu_irq_disable(CPU_MIE_MTIE); } // deactivate timer interrupt

    if (id == RTE_TRAP_MEI)    { neorv32_cpu_irq_disable(CPU_MIE_MEIE); } // deactivate external interrupt

    if (id == RTE_TRAP_FIRQ_0) { neorv32_cpu_irq_disable(CPU_MIE_FIRQ0E); } // deactivate fast interrupt channel 0

    if (id == RTE_TRAP_FIRQ_1) { neorv32_cpu_irq_disable(CPU_MIE_FIRQ1E); } // deactivate fast interrupt channel 1

    if (id == RTE_TRAP_FIRQ_2) { neorv32_cpu_irq_disable(CPU_MIE_FIRQ2E); } // deactivate fast interrupt channel 2

    if (id == RTE_TRAP_FIRQ_3) { neorv32_cpu_irq_disable(CPU_MIE_FIRQ3E); } // deactivate fast interrupt channel 3

    __neorv32_rte_vector_lut[id] = (uint32_t)(&__neorv32_rte_debug_exc_handler); // use dummy handler in case the exception is accidently triggered

    return 0;

  }

  return 1;

}

/**********************************************************************//**

 * This is the core of the NEORV32 RTE.

 *

 * @note This function must no be explicitly used by the user.

 * @warning When using the the RTE, this function is the ONLY function that can use the 'interrupt' attribute!

 **************************************************************************/

static void __attribute__((__interrupt__)) __attribute__((aligned(16)))  __neorv32_rte_core(void) {

  register uint32_t rte_mepc   = neorv32_cpu_csr_read(CSR_MEPC);

  register uint32_t rte_mcause = neorv32_cpu_csr_read(CSR_MCAUSE);

  // compute return address

  if ((rte_mcause & 0x80000000) == 0) { // modify pc only if exception

    // get low half word of faulting instruction

    register uint32_t rte_trap_inst;

    asm volatile ("lh %[result], 0(%[input_i])" : [result] "=r" (rte_trap_inst) : [input_i] "r" (rte_mepc));

    if ((rte_trap_inst & 3) == 3) { // faulting instruction is uncompressed instruction

      rte_mepc += 4;

    }

    else { // faulting instruction is compressed instruction

      rte_mepc += 2;

    }

    // store new return address

    neorv32_cpu_csr_write(CSR_MEPC, rte_mepc);

  }

  // find according trap handler

  register uint32_t rte_handler = (uint32_t)(&__neorv32_rte_debug_exc_handler);

  switch (rte_mcause) {

    case TRAP_CODE_I_MISALIGNED: rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_I_MISALIGNED]; break;

    case TRAP_CODE_I_ACCESS:     rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_I_ACCESS]; break;

    case TRAP_CODE_I_ILLEGAL:    rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_I_ILLEGAL]; break;

    case TRAP_CODE_BREAKPOINT:   rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_BREAKPOINT]; break;

    case TRAP_CODE_L_MISALIGNED: rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_L_MISALIGNED]; break;

    case TRAP_CODE_L_ACCESS:     rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_L_ACCESS]; break;

    case TRAP_CODE_S_MISALIGNED: rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_S_MISALIGNED]; break;

    case TRAP_CODE_S_ACCESS:     rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_S_ACCESS]; break;

    case TRAP_CODE_MENV_CALL:    rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_MENV_CALL]; break;

    case TRAP_CODE_MSI:          rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_MSI]; break;

    case TRAP_CODE_MTI:          rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_MTI]; break;

    case TRAP_CODE_MEI:          rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_MEI]; break;

    case TRAP_CODE_FIRQ_0:       rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_FIRQ_0]; break;

    case TRAP_CODE_FIRQ_1:       rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_FIRQ_1]; break;

    case TRAP_CODE_FIRQ_2:       rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_FIRQ_2]; break;

    case TRAP_CODE_FIRQ_3:       rte_handler = __neorv32_rte_vector_lut[RTE_TRAP_FIRQ_3]; break;

    default: break;

  }

  // execute handler

  void (*handler_pnt)(void);

  handler_pnt = (void*)rte_handler;

  (*handler_pnt)();

}

/**********************************************************************//**

 * NEORV32 runtime environment: Debug exception handler, printing various exception/interrupt information via UART.

 * @note This function is used by neorv32_rte_exception_uninstall(void) only.

 **************************************************************************/

static void __neorv32_rte_debug_exc_handler(void) {

  neorv32_uart_printf("\n\n<< NEORV32 Runtime Environment >>\n");

  neorv32_uart_printf("System time: 0x%x_%x\n", neorv32_cpu_csr_read(CSR_TIMEH), neorv32_cpu_csr_read(CSR_TIME));

  register uint32_t trap_cause = neorv32_cpu_csr_read(CSR_MCAUSE);

  register uint32_t trap_addr  = neorv32_cpu_csr_read(CSR_MEPC);

  register uint32_t trap_inst;

  asm volatile ("lh %[result], 0(%[input_i])" : [result] "=r" (trap_inst) : [input_i] "r" (trap_addr));

  if (trap_cause & 0x80000000) {

    neorv32_uart_printf("INTERRUPT");

  }

  else {

    neorv32_uart_printf("EXCEPTION");

    if ((trap_inst & 3) == 3) {

      trap_addr -= 4;

    }

    else {

      trap_addr -= 2;

    }

  }

  neorv32_uart_printf(" at instruction address: 0x%x\n", trap_addr);

  neorv32_uart_printf("Cause: ");

  switch (trap_cause) {

    case TRAP_CODE_I_MISALIGNED: neorv32_uart_printf("Instruction address misaligned"); break;

    case TRAP_CODE_I_ACCESS:     neorv32_uart_printf("Instruction access fault"); break;

    case TRAP_CODE_I_ILLEGAL:    neorv32_uart_printf("Illegal instruction"); break;

    case TRAP_CODE_BREAKPOINT:   neorv32_uart_printf("Breakpoint (EBREAK)"); break;

    case TRAP_CODE_L_MISALIGNED: neorv32_uart_printf("Load address misaligned"); break;

    case TRAP_CODE_L_ACCESS:     neorv32_uart_printf("Load access fault"); break;

    case TRAP_CODE_S_MISALIGNED: neorv32_uart_printf("Store address misaligned"); break;

    case TRAP_CODE_S_ACCESS:     neorv32_uart_printf("Store access fault"); break;

    case TRAP_CODE_MENV_CALL:    neorv32_uart_printf("Environment call from M-mode"); break;

    case TRAP_CODE_MSI:          neorv32_uart_printf("Machine software interrupt"); break;

    case TRAP_CODE_MTI:          neorv32_uart_printf("Machine timer interrupt"); break;

    case TRAP_CODE_MEI:          neorv32_uart_printf("Machine external interrupt"); break;

    case TRAP_CODE_FIRQ_0:       neorv32_uart_printf("Fast interrupt channel 0"); break;

    case TRAP_CODE_FIRQ_1:       neorv32_uart_printf("Fast interrupt channel 1"); break;

    case TRAP_CODE_FIRQ_2:       neorv32_uart_printf("Fast interrupt channel 2"); break;

    case TRAP_CODE_FIRQ_3:       neorv32_uart_printf("Fast interrupt channel 3"); break;

    default:                     neorv32_uart_printf("Unknown (0x%x)", trap_cause); break;

  }

  // fault address

  neorv32_uart_printf("\nFaulting instruction (low half word): 0x%x", trap_inst);

  if ((trap_inst & 3) != 3) {

    neorv32_uart_printf(" (decompressed)\n");

  }

  neorv32_uart_printf("\nMTVAL: 0x%x\n", neorv32_cpu_csr_read(CSR_MTVAL));

  neorv32_uart_printf("Trying to resume application @ 0x%x...", neorv32_cpu_csr_read(CSR_MEPC));

  neorv32_uart_printf("\n<</NEORV32 Runtime Environment >>\n\n");

}

/**********************************************************************//**

 * NEORV32 runtime environment: Print hardware configuration information via UART

 **************************************************************************/

void neorv32_rte_print_hw_config(void) {

  uint32_t tmp;

  int i;

  char c;

  neorv32_uart_printf("\n\n<< NEORV32 Hardware Configuration Overview >>\n");

  // CPU configuration

  neorv32_uart_printf("\n-- Central Processing Unit --\n");

  // Hart ID

  neorv32_uart_printf("Hart ID:          %u\n", neorv32_cpu_csr_read(CSR_MHARTID));

  // Custom user code

  neorv32_uart_printf("User code:        0x%x\n", SYSINFO_USER_CODE);

  // HW version

  neorv32_uart_printf("Hardware version: ");

  neorv32_rte_print_hw_version();

  neorv32_uart_printf(" (0x%x)\n", neorv32_cpu_csr_read(CSR_MIMPID));

  // CPU architecture

  neorv32_uart_printf("Architecture:     ");

  tmp = neorv32_cpu_csr_read(CSR_MISA);

  tmp = (tmp >> 30) & 0x03;

  if (tmp == 0) {

    neorv32_uart_printf("unknown");

  }

  if (tmp == 1) {

    neorv32_uart_printf("RV32");

  }

  if (tmp == 2) {

    neorv32_uart_printf("RV64");

  }

  if (tmp == 3) {

    neorv32_uart_printf("RV128");

  }

  // CPU extensions

  neorv32_uart_printf("\nCPU extensions:   ");

  tmp = neorv32_cpu_csr_read(CSR_MISA);

  for (i=0; i<26; i++) {

    if (tmp & (1 << i)) {

      c = (char)('A' + i);

      neorv32_uart_putc(c);

      neorv32_uart_putc(' ');

    }

  }

  neorv32_uart_printf("(0x%x)\n", tmp);

  // Clock speed

  neorv32_uart_printf("Clock speed:      %u Hz\n", SYSINFO_CLK);

  // Memory configuration

  neorv32_uart_printf("\n-- Memory Configuration --\n");

  uint32_t size = SYSINFO_ISPACE_SIZE;

  uint32_t base = SYSINFO_ISPACE_BASE;

  neorv32_uart_printf("Instruction memory:   %u bytes @ 0x%x\n", size, base);

  neorv32_uart_printf("Internal IMEM:        ");

  __neorv32_rte_print_true_false(SYSINFO_FEATURES & (1 << SYSINFO_FEATURES_MEM_INT_IMEM));

  neorv32_uart_printf("Internal IMEM as ROM: ");

  __neorv32_rte_print_true_false(SYSINFO_FEATURES & (1 << SYSINFO_FEATURES_MEM_INT_IMEM_ROM));

  size = SYSINFO_DSPACE_SIZE;

  base = SYSINFO_DSPACE_BASE;

  neorv32_uart_printf("Data memory:          %u bytes @ 0x%x\n", size, base);

  neorv32_uart_printf("Internal DMEM:        ");

  __neorv32_rte_print_true_false(SYSINFO_FEATURES & (1 << SYSINFO_FEATURES_MEM_INT_DMEM));

  neorv32_uart_printf("Bootloader:           ");

  __neorv32_rte_print_true_false(SYSINFO_FEATURES & (1 << SYSINFO_FEATURES_BOOTLOADER));

  neorv32_uart_printf("External interface:   ");

  __neorv32_rte_print_true_false(SYSINFO_FEATURES & (1 << SYSINFO_FEATURES_MEM_EXT));

  // peripherals

  neorv32_uart_printf("\n-- Peripherals --\n");

  tmp = SYSINFO_FEATURES;

  neorv32_uart_printf("GPIO:    ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_GPIO));

  neorv32_uart_printf("MTIME:   ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_MTIME));

  neorv32_uart_printf("UART:    ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_UART));

  neorv32_uart_printf("SPI:     ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_SPI));

  neorv32_uart_printf("TWI:     ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_TWI));

  neorv32_uart_printf("PWM:     ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_PWM));

  neorv32_uart_printf("WDT:     ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_WDT));

  neorv32_uart_printf("TRNG:    ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_TRNG));

  neorv32_uart_printf("DEVNULL: ");

  __neorv32_rte_print_true_false(tmp & (1 << SYSINFO_FEATURES_IO_DEVNULL));

}

/**********************************************************************//**

 * NEORV32 runtime environment: Private function to print true or false.

 * @note This function is used by neorv32_rte_print_hw_config(void) only.

 *

 * @param[in] state Print TRUE when !=0, print FALSE when 0

 **************************************************************************/

static void __neorv32_rte_print_true_false(int state) {

  if (state) {

    neorv32_uart_printf("True\n");

  }

  else {

    neorv32_uart_printf("False\n");

  }

}

/**********************************************************************//**

 * NEORV32 runtime environment: Function to show the processor version in human-readable format.

 **************************************************************************/

void neorv32_rte_print_hw_version(void) {

  uint32_t i;

  char tmp, cnt;

  uint32_t version = neorv32_cpu_csr_read(CSR_MIMPID);

  for (i=0; i<4; i++) {

    tmp = (char)(version >> (24 - 8*i));

    // serial division

    cnt = 0;

    while (tmp >= 10) {

      tmp = tmp - 10;

      cnt++;

    }

    if (cnt) {

      neorv32_uart_putc('0' + cnt);

    }

    neorv32_uart_putc('0' + tmp);

    if (i < 3) {

      neorv32_uart_putc('.');

    }

  }

}

/**********************************************************************//**

 * NEORV32 runtime environment: Print project credits

 **************************************************************************/

void neorv32_rte_print_credits(void) {

  neorv32_uart_print("\n\nThe NEORV32 Processor Project\n"

                     "by Stephan Nolting\n"

                     "https://github.com/stnolting/neorv32\n"

                     "made in Hannover, Germany\n\n");

}