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// #################################################################################################
// # << NEORV32: neorv32_cpu.c - CPU Core Functions HW Driver >>                                   #
// # ********************************************************************************************* #
// # BSD 3-Clause License                                                                          #
// #                                                                                               #
// # Copyright (c) 2021, Stephan Nolting. All rights reserved.                                     #
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// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #
// #################################################################################################
 
 
/**********************************************************************//**
 * @file neorv32_cpu.c
 * @author Stephan Nolting
 * @brief CPU Core Functions HW driver source file.
 **************************************************************************/
 
#include "neorv32.h"
#include "neorv32_cpu.h"
 
 
/**********************************************************************//**
 * Unavailable extensions warning.
 **************************************************************************/
#if defined __riscv_f || (__riscv_flen == 32)
  #warning Single-precision floating-point extension <F/Zfinx> is WORK-IN-PROGRESS and NOT FULLY OPERATIONAL yet!
#endif
 
#if defined __riscv_d || (__riscv_flen == 64)
  #error Double-precision floating-point extension <D/Zdinx> is NOT supported!
#endif
 
#if (__riscv_xlen > 32)
  #error Only 32-bit <rv32> is supported!
#endif
 
#ifdef __riscv_b
  #warning Bit-manipulation extension <B> is still experimental (non-ratified) and does not support all <Zb*> subsets yet.
#endif
 
#ifdef __riscv_fdiv
  #warning Floating-point division instruction <FDIV> is NOT supported yet!
#endif
 
#ifdef __riscv_fsqrt
  #warning Floating-point square root instruction <FSQRT> is NOT supported yet!
#endif
 
 
/**********************************************************************//**
 * >Private< helper functions.
 **************************************************************************/
static int __neorv32_cpu_irq_id_check(uint8_t irq_sel);
static uint32_t __neorv32_cpu_pmp_cfg_read(uint32_t index);
static void __neorv32_cpu_pmp_cfg_write(uint32_t index, uint32_t data);
 
 
/**********************************************************************//**
 * Private function: Check IRQ id.
 *
 * @param[in] irq_sel CPU interrupt select. See #NEORV32_CSR_MIE_enum.
 * @return 0 if success, 1 if error (invalid irq_sel).
 **************************************************************************/
static int __neorv32_cpu_irq_id_check(uint8_t irq_sel) {
 
  if ((irq_sel == CSR_MIE_MSIE) || (irq_sel == CSR_MIE_MTIE) || (irq_sel == CSR_MIE_MEIE) ||
     ((irq_sel >= CSR_MIE_FIRQ0E) && (irq_sel <= CSR_MIE_FIRQ15E))) {
    return 0;
  }
  else {
    return 1;
  }
}
 
 
/**********************************************************************//**
 * Enable specific CPU interrupt.
 *
 * @note Interrupts have to be globally enabled via neorv32_cpu_eint(void), too.
 *
 * @param[in] irq_sel CPU interrupt select. See #NEORV32_CSR_MIE_enum.
 * @return 0 if success, 1 if error (invalid irq_sel).
 **************************************************************************/
int neorv32_cpu_irq_enable(uint8_t irq_sel) {
 
  // check IRQ id
  if (__neorv32_cpu_irq_id_check(irq_sel)) {
    return 1;
  }
 
  register uint32_t mask = (uint32_t)(1 << irq_sel);
  asm volatile ("csrrs zero, mie, %0" : : "r" (mask));
  return 0;
}
 
 
/**********************************************************************//**
 * Disable specific CPU interrupt.
 *
 * @param[in] irq_sel CPU interrupt select. See #NEORV32_CSR_MIE_enum.
 * @return 0 if success, 1 if error (invalid irq_sel).
 **************************************************************************/
int neorv32_cpu_irq_disable(uint8_t irq_sel) {
 
  // check IRQ id
  if (__neorv32_cpu_irq_id_check(irq_sel)) {
    return 1;
  }
 
  register uint32_t mask = (uint32_t)(1 << irq_sel);
  asm volatile ("csrrc zero, mie, %0" : : "r" (mask));
  return 0;
}
 
 
/**********************************************************************//**
 * Get cycle count from cycle[h].
 *
 * @note The cycle[h] CSR is shadowed copy of the mcycle[h] CSR.
 *
 * @return Current cycle counter (64 bit).
 **************************************************************************/
uint64_t neorv32_cpu_get_cycle(void) {
 
  union {
    uint64_t uint64;
    uint32_t uint32[sizeof(uint64_t)/2];
  } cycles;
 
  uint32_t tmp1, tmp2, tmp3;
  while(1) {
    tmp1 = neorv32_cpu_csr_read(CSR_CYCLEH);
    tmp2 = neorv32_cpu_csr_read(CSR_CYCLE);
    tmp3 = neorv32_cpu_csr_read(CSR_CYCLEH);
    if (tmp1 == tmp3) {
      break;
    }
  }
 
  cycles.uint32[0] = tmp2;
  cycles.uint32[1] = tmp3;
 
  return cycles.uint64;
}
 
 
/**********************************************************************//**
 * Set mcycle[h] counter.
 *
 * @param[in] value New value for mcycle[h] CSR (64-bit).
 **************************************************************************/
void neorv32_cpu_set_mcycle(uint64_t value) {
 
  union {
    uint64_t uint64;
    uint32_t uint32[sizeof(uint64_t)/2];
  } cycles;
 
  cycles.uint64 = value;
 
  neorv32_cpu_csr_write(CSR_MCYCLE,  0);
  neorv32_cpu_csr_write(CSR_MCYCLEH, cycles.uint32[1]);
  neorv32_cpu_csr_write(CSR_MCYCLE,  cycles.uint32[0]);
}
 
 
/**********************************************************************//**
 * Get retired instructions counter from instret[h].
 *
 * @note The instret[h] CSR is shadowed copy of the instret[h] CSR.
 *
 * @return Current instructions counter (64 bit).
 **************************************************************************/
uint64_t neorv32_cpu_get_instret(void) {
 
  union {
    uint64_t uint64;
    uint32_t uint32[sizeof(uint64_t)/2];
  } cycles;
 
  uint32_t tmp1, tmp2, tmp3;
  while(1) {
    tmp1 = neorv32_cpu_csr_read(CSR_INSTRETH);
    tmp2 = neorv32_cpu_csr_read(CSR_INSTRET);
    tmp3 = neorv32_cpu_csr_read(CSR_INSTRETH);
    if (tmp1 == tmp3) {
      break;
    }
  }
 
  cycles.uint32[0] = tmp2;
  cycles.uint32[1] = tmp3;
 
  return cycles.uint64;
}
 
 
/**********************************************************************//**
 * Set retired instructions counter minstret[h].
 *
 * @param[in] value New value for mcycle[h] CSR (64-bit).
 **************************************************************************/
void neorv32_cpu_set_minstret(uint64_t value) {
 
  union {
    uint64_t uint64;
    uint32_t uint32[sizeof(uint64_t)/2];
  } cycles;
 
  cycles.uint64 = value;
 
  neorv32_cpu_csr_write(CSR_MINSTRET,  0);
  neorv32_cpu_csr_write(CSR_MINSTRETH, cycles.uint32[1]);
  neorv32_cpu_csr_write(CSR_MINSTRET,  cycles.uint32[0]);
}
 
 
/**********************************************************************//**
 * Get current system time from time[h] CSR.
 *
 * @note This function requires the MTIME system timer to be implemented.
 *
 * @return Current system time (64 bit).
 **************************************************************************/
uint64_t neorv32_cpu_get_systime(void) {
 
  union {
    uint64_t uint64;
    uint32_t uint32[sizeof(uint64_t)/2];
  } cycles;
 
  uint32_t tmp1, tmp2, tmp3;
  while(1) {
    tmp1 = neorv32_cpu_csr_read(CSR_TIMEH);
    tmp2 = neorv32_cpu_csr_read(CSR_TIME);
    tmp3 = neorv32_cpu_csr_read(CSR_TIMEH);
    if (tmp1 == tmp3) {
      break;
    }
  }
 
  cycles.uint32[0] = tmp2;
  cycles.uint32[1] = tmp3;
 
  return cycles.uint64;
}
 
 
/**********************************************************************//**
 * Simple delay function using busy wait (simple loop).
 *
 * @warning This function is not really precise (especially if there is no M extension available)! Use a timer-based approach (using cycle or time CSRs) for precise timings.
 *
 * @param[in] time_ms Time in ms to wait (max 32767ms).
 **************************************************************************/
void neorv32_cpu_delay_ms(int16_t time_ms) {
 
  const uint32_t loop_cycles_c = 16; // clock cycles per iteration of the ASM loop
 
  // check input
  if (time_ms < 0) {
    time_ms = -time_ms;
  }
 
  uint32_t clock = SYSINFO_CLK; // clock ticks per second
  clock = clock / 1000; // clock ticks per ms
 
  uint64_t wait_cycles = ((uint64_t)clock) * ((uint64_t)time_ms);
  uint32_t ticks = (uint32_t)(wait_cycles / loop_cycles_c);
 
  asm volatile (" .balign 4                                        \n" // make sure this is 32-bit aligned
                " __neorv32_cpu_delay_ms_start:                    \n"
                " beq  %[cnt_r], zero, __neorv32_cpu_delay_ms_end  \n" // 3 cycles (not taken)
                " beq  %[cnt_r], zero, __neorv32_cpu_delay_ms_end  \n" // 3 cycles (never taken)
                " addi %[cnt_w], %[cnt_r], -1                      \n" // 2 cycles
                " nop                                              \n" // 2 cycles
                " j    __neorv32_cpu_delay_ms_start                \n" // 6 cycles
                " __neorv32_cpu_delay_ms_end: "
                : [cnt_w] "=r" (ticks) : [cnt_r] "r" (ticks));
}
 
 
/**********************************************************************//**
 * Switch from privilege mode MACHINE to privilege mode USER.
 *
 * @warning This function requires the U extension to be implemented.
 **************************************************************************/
void __attribute__((naked)) neorv32_cpu_goto_user_mode(void) {
 
  // make sure to use NO registers in here! -> naked
 
  asm volatile ("csrw mepc, ra           \n" // move return address to mepc so we can return using "mret". also, we can now use ra as general purpose register in here
                "li ra, %[input_imm]     \n" // bit mask to clear the two MPP bits
                "csrrc zero, mstatus, ra \n" // clear MPP bits -> MPP=u-mode
                "mret                    \n" // return and switch to user mode
                :  : [input_imm] "i" ((1<<CSR_MSTATUS_MPP_H) | (1<<CSR_MSTATUS_MPP_L)));
}
 
 
/**********************************************************************//**
 * Atomic compare-and-swap operation (for implemeneting semaphores and mutexes).
 *
 * @warning This function requires the A (atomic) CPU extension.
 *
 * @param[in] addr Address of memory location.
 * @param[in] expected Expected value (for comparison).
 * @param[in] desired Desired value (new value).
 * @return Returns 0 on success, 1 on failure.
 **************************************************************************/
int __attribute__ ((noinline)) neorv32_cpu_atomic_cas(uint32_t addr, uint32_t expected, uint32_t desired) {
#ifdef __riscv_atomic
 
  register uint32_t addr_reg = addr;
  register uint32_t des_reg = desired;
  register uint32_t tmp_reg;
 
  // load original value + reservation (lock)
  asm volatile ("lr.w %[result], (%[input])" : [result] "=r" (tmp_reg) : [input] "r" (addr_reg));
 
  if (tmp_reg != expected) {
    asm volatile ("lw x0, 0(%[input])" : : [input] "r" (addr_reg)); // clear reservation lock
    return 1;
  }
 
  // store-conditional
  asm volatile ("sc.w %[result], %[input_i], (%[input_j])" : [result] "=r" (tmp_reg) : [input_i] "r" (des_reg), [input_j] "r" (addr_reg));
 
  if (tmp_reg) {
    return 1;
  }
 
  return 0;
#else
  return 1; // A extension not implemented - function always fails
#endif
}
 
 
/**********************************************************************//**
 * Physical memory protection (PMP): Get number of available regions.
 *
 * @warning This function overrides all available PMPCFG* CSRs.
 * @warning This function requires the PMP CPU extension.
 *
 * @return Returns number of available PMP regions.
 **************************************************************************/
uint32_t neorv32_cpu_pmp_get_num_regions(void) {
 
  uint32_t i = 0;
 
  // try setting R bit in all PMPCFG CSRs
  const uint32_t tmp = 0x01010101;
  for (i=0; i<16; i++) {
    __neorv32_cpu_pmp_cfg_write(i, tmp);
  }
 
  // sum up all written ones (only available PMPCFG* CSRs/entries will return =! 0)
  union {
    uint32_t uint32;
    uint8_t  uint8[sizeof(uint32_t)/sizeof(uint8_t)];
  } cnt;
 
  cnt.uint32 = 0;
  for (i=0; i<16; i++) {
    cnt.uint32 += __neorv32_cpu_pmp_cfg_read(i);
  }
 
  // sum up bytes
  uint32_t num_regions = 0;
  num_regions += (uint32_t)cnt.uint8[0];
  num_regions += (uint32_t)cnt.uint8[1];
  num_regions += (uint32_t)cnt.uint8[2];
  num_regions += (uint32_t)cnt.uint8[3];
 
  return num_regions;
}
 
 
/**********************************************************************//**
 * Physical memory protection (PMP): Get minimal region size (granularity). 
 *
 * @warning This function overrides PMPCFG0[0] and PMPADDR0 CSRs.
 * @warning This function requires the PMP CPU extension.
 *
 * @return Returns minimal region size in bytes.
 **************************************************************************/
uint32_t neorv32_cpu_pmp_get_granularity(void) {
 
  // check min granulartiy
  uint32_t tmp = neorv32_cpu_csr_read(CSR_PMPCFG0);
  tmp &= 0xffffff00; // disable entry 0
  neorv32_cpu_csr_write(CSR_PMPCFG0, tmp);
  neorv32_cpu_csr_write(CSR_PMPADDR0, 0xffffffff);
  uint32_t tmp_a = neorv32_cpu_csr_read(CSR_PMPADDR0);
 
  uint32_t i;
 
  // find least-significat set bit
  for (i=31; i!=0; i--) {
    if (((tmp_a >> i) & 1) == 0) {
      break;
    }
  }
 
  return (uint32_t)(1 << (i+1+2));
}
 
 
/**********************************************************************//**
 * Physical memory protection (PMP): Configure region.
 *
 * @note Using NAPOT mode - page base address has to be naturally aligned.
 *
 * @warning This function requires the PMP CPU extension.
 * @warning Only use available PMP regions. Check before using neorv32_cpu_pmp_get_regions(void).
 *
 * @param[in] index Region number (index, 0..PMP_NUM_REGIONS-1).
 * @param[in] base Region base address (has to be naturally aligned!).
 * @param[in] size Region size, has to be a power of 2 (min 8 bytes or according to HW's PMP.granularity configuration).
 * @param[in] config Region configuration (attributes) byte (for PMPCFGx).
 * @return Returns 0 on success, 1 on failure.
 **************************************************************************/
int neorv32_cpu_pmp_configure_region(uint32_t index, uint32_t base, uint32_t size, uint8_t config) {
 
  if (size < 8) {
    return 1; // minimal region size is 8 bytes
  }
 
  if ((size & (size - 1)) != 0) {
    return 1; // region size is not a power of two
  }
 
  // pmpcfg register index
  uint32_t pmpcfg_index = index >> 4; // 4 entries per pmpcfg csr
 
  // setup configuration
  uint32_t tmp;
  uint32_t config_int  = ((uint32_t)config) << ((index%4)*8);
  uint32_t config_mask = ((uint32_t)0xFF)   << ((index%4)*8);
  config_mask = ~config_mask;
 
  // clear old configuration
  __neorv32_cpu_pmp_cfg_write(pmpcfg_index, __neorv32_cpu_pmp_cfg_read(pmpcfg_index) & config_mask);
 
 
  // set base address and region size
  uint32_t addr_mask = ~((size - 1) >> 2);
  uint32_t size_mask = (size - 1) >> 3;
 
  tmp = base & addr_mask;
  tmp = tmp | size_mask;
 
  switch(index & 63) {
    case 0:  neorv32_cpu_csr_write(CSR_PMPADDR0,  tmp); break;
    case 1:  neorv32_cpu_csr_write(CSR_PMPADDR1,  tmp); break;
    case 2:  neorv32_cpu_csr_write(CSR_PMPADDR2,  tmp); break;
    case 3:  neorv32_cpu_csr_write(CSR_PMPADDR3,  tmp); break;
    case 4:  neorv32_cpu_csr_write(CSR_PMPADDR4,  tmp); break;
    case 5:  neorv32_cpu_csr_write(CSR_PMPADDR5,  tmp); break;
    case 6:  neorv32_cpu_csr_write(CSR_PMPADDR6,  tmp); break;
    case 7:  neorv32_cpu_csr_write(CSR_PMPADDR7,  tmp); break;
    case 8:  neorv32_cpu_csr_write(CSR_PMPADDR8,  tmp); break;
    case 9:  neorv32_cpu_csr_write(CSR_PMPADDR9,  tmp); break;
    case 10: neorv32_cpu_csr_write(CSR_PMPADDR10, tmp); break;
    case 11: neorv32_cpu_csr_write(CSR_PMPADDR11, tmp); break;
    case 12: neorv32_cpu_csr_write(CSR_PMPADDR12, tmp); break;
    case 13: neorv32_cpu_csr_write(CSR_PMPADDR13, tmp); break;
    case 14: neorv32_cpu_csr_write(CSR_PMPADDR14, tmp); break;
    case 15: neorv32_cpu_csr_write(CSR_PMPADDR15, tmp); break;
    case 16: neorv32_cpu_csr_write(CSR_PMPADDR16, tmp); break;
    case 17: neorv32_cpu_csr_write(CSR_PMPADDR17, tmp); break;
    case 18: neorv32_cpu_csr_write(CSR_PMPADDR18, tmp); break;
    case 19: neorv32_cpu_csr_write(CSR_PMPADDR19, tmp); break;
    case 20: neorv32_cpu_csr_write(CSR_PMPADDR20, tmp); break;
    case 21: neorv32_cpu_csr_write(CSR_PMPADDR21, tmp); break;
    case 22: neorv32_cpu_csr_write(CSR_PMPADDR22, tmp); break;
    case 23: neorv32_cpu_csr_write(CSR_PMPADDR23, tmp); break;
    case 24: neorv32_cpu_csr_write(CSR_PMPADDR24, tmp); break;
    case 25: neorv32_cpu_csr_write(CSR_PMPADDR25, tmp); break;
    case 26: neorv32_cpu_csr_write(CSR_PMPADDR26, tmp); break;
    case 27: neorv32_cpu_csr_write(CSR_PMPADDR27, tmp); break;
    case 28: neorv32_cpu_csr_write(CSR_PMPADDR28, tmp); break;
    case 29: neorv32_cpu_csr_write(CSR_PMPADDR29, tmp); break;
    case 30: neorv32_cpu_csr_write(CSR_PMPADDR30, tmp); break;
    case 31: neorv32_cpu_csr_write(CSR_PMPADDR31, tmp); break;
    case 32: neorv32_cpu_csr_write(CSR_PMPADDR32, tmp); break;
    case 33: neorv32_cpu_csr_write(CSR_PMPADDR33, tmp); break;
    case 34: neorv32_cpu_csr_write(CSR_PMPADDR34, tmp); break;
    case 35: neorv32_cpu_csr_write(CSR_PMPADDR35, tmp); break;
    case 36: neorv32_cpu_csr_write(CSR_PMPADDR36, tmp); break;
    case 37: neorv32_cpu_csr_write(CSR_PMPADDR37, tmp); break;
    case 38: neorv32_cpu_csr_write(CSR_PMPADDR38, tmp); break;
    case 39: neorv32_cpu_csr_write(CSR_PMPADDR39, tmp); break;
    case 40: neorv32_cpu_csr_write(CSR_PMPADDR40, tmp); break;
    case 41: neorv32_cpu_csr_write(CSR_PMPADDR41, tmp); break;
    case 42: neorv32_cpu_csr_write(CSR_PMPADDR42, tmp); break;
    case 43: neorv32_cpu_csr_write(CSR_PMPADDR43, tmp); break;
    case 44: neorv32_cpu_csr_write(CSR_PMPADDR44, tmp); break;
    case 45: neorv32_cpu_csr_write(CSR_PMPADDR45, tmp); break;
    case 46: neorv32_cpu_csr_write(CSR_PMPADDR46, tmp); break;
    case 47: neorv32_cpu_csr_write(CSR_PMPADDR47, tmp); break;
    case 48: neorv32_cpu_csr_write(CSR_PMPADDR48, tmp); break;
    case 49: neorv32_cpu_csr_write(CSR_PMPADDR49, tmp); break;
    case 50: neorv32_cpu_csr_write(CSR_PMPADDR50, tmp); break;
    case 51: neorv32_cpu_csr_write(CSR_PMPADDR51, tmp); break;
    case 52: neorv32_cpu_csr_write(CSR_PMPADDR52, tmp); break;
    case 53: neorv32_cpu_csr_write(CSR_PMPADDR53, tmp); break;
    case 54: neorv32_cpu_csr_write(CSR_PMPADDR54, tmp); break;
    case 55: neorv32_cpu_csr_write(CSR_PMPADDR55, tmp); break;
    case 56: neorv32_cpu_csr_write(CSR_PMPADDR56, tmp); break;
    case 57: neorv32_cpu_csr_write(CSR_PMPADDR57, tmp); break;
    case 58: neorv32_cpu_csr_write(CSR_PMPADDR58, tmp); break;
    case 59: neorv32_cpu_csr_write(CSR_PMPADDR59, tmp); break;
    case 60: neorv32_cpu_csr_write(CSR_PMPADDR60, tmp); break;
    case 61: neorv32_cpu_csr_write(CSR_PMPADDR61, tmp); break;
    case 62: neorv32_cpu_csr_write(CSR_PMPADDR62, tmp); break;
    case 63: neorv32_cpu_csr_write(CSR_PMPADDR63, tmp); break;
    default: break;
  }
 
  // wait for HW to compute PMP-internal stuff (address masks)
  for (tmp=0; tmp<16; tmp++) {
    asm volatile ("nop");
  }
 
  // set new configuration
  __neorv32_cpu_pmp_cfg_write(pmpcfg_index, __neorv32_cpu_pmp_cfg_read(pmpcfg_index) | config_int);
 
  return 0;
}
 
 
/**********************************************************************//**
 * Internal helper function: Read PMP configuration register 0..15
 *
 * @warning This function requires the PMP CPU extension.
 *
 * @param[in] index PMP CFG configuration register ID (0..15).
 * @return PMP CFG read data.
 **************************************************************************/
static uint32_t __neorv32_cpu_pmp_cfg_read(uint32_t index) {
 
  uint32_t tmp = 0;
  switch(index & 15) {
    case 0:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG0);  break;
    case 1:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG1);  break;
    case 2:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG2);  break;
    case 3:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG3);  break;
    case 4:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG4);  break;
    case 5:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG5);  break;
    case 6:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG6);  break;
    case 7:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG7);  break;
    case 8:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG8);  break;
    case 9:  tmp = neorv32_cpu_csr_read(CSR_PMPCFG9);  break;
    case 10: tmp = neorv32_cpu_csr_read(CSR_PMPCFG10); break;
    case 11: tmp = neorv32_cpu_csr_read(CSR_PMPCFG11); break;
    case 12: tmp = neorv32_cpu_csr_read(CSR_PMPCFG12); break;
    case 13: tmp = neorv32_cpu_csr_read(CSR_PMPCFG13); break;
    case 14: tmp = neorv32_cpu_csr_read(CSR_PMPCFG14); break;
    case 15: tmp = neorv32_cpu_csr_read(CSR_PMPCFG15); break;
    default: break;
  }
 
  return tmp;
}
 
 
/**********************************************************************//**
 * Internal helper function: Write PMP configuration register 0..15
 *
 * @warning This function requires the PMP CPU extension.
 *
 * @param[in] index PMP CFG configuration register ID (0..15).
 * @param[in] data PMP CFG write data.
 **************************************************************************/
static void __neorv32_cpu_pmp_cfg_write(uint32_t index, uint32_t data) {
 
  switch(index & 15) {
    case 0:  neorv32_cpu_csr_write(CSR_PMPCFG0,  data); break;
    case 1:  neorv32_cpu_csr_write(CSR_PMPCFG1,  data); break;
    case 2:  neorv32_cpu_csr_write(CSR_PMPCFG2,  data); break;
    case 3:  neorv32_cpu_csr_write(CSR_PMPCFG3,  data); break;
    case 4:  neorv32_cpu_csr_write(CSR_PMPCFG4,  data); break;
    case 5:  neorv32_cpu_csr_write(CSR_PMPCFG5,  data); break;
    case 6:  neorv32_cpu_csr_write(CSR_PMPCFG6,  data); break;
    case 7:  neorv32_cpu_csr_write(CSR_PMPCFG7,  data); break;
    case 8:  neorv32_cpu_csr_write(CSR_PMPCFG8,  data); break;
    case 9:  neorv32_cpu_csr_write(CSR_PMPCFG9,  data); break;
    case 10: neorv32_cpu_csr_write(CSR_PMPCFG10, data); break;
    case 11: neorv32_cpu_csr_write(CSR_PMPCFG11, data); break;
    case 12: neorv32_cpu_csr_write(CSR_PMPCFG12, data); break;
    case 13: neorv32_cpu_csr_write(CSR_PMPCFG13, data); break;
    case 14: neorv32_cpu_csr_write(CSR_PMPCFG14, data); break;
    case 15: neorv32_cpu_csr_write(CSR_PMPCFG15, data); break;
    default: break;
  }
}
 
 
/**********************************************************************//**
 * Hardware performance monitors (HPM): Get number of available HPM counters.
 *
 * @warning This function overrides all available mhpmcounter* CSRs.
 *
 * @return Returns number of available HPM counters (..29).
 **************************************************************************/
uint32_t neorv32_cpu_hpm_get_counters(void) {
 
  // inhibit all HPM counters
  uint32_t tmp = neorv32_cpu_csr_read(CSR_MCOUNTINHIBIT);
  tmp |= 0xfffffff8;
  neorv32_cpu_csr_write(CSR_MCOUNTINHIBIT, tmp);
 
  // try setting all mhpmcounter* CSRs to 1
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER3,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER4,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER5,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER6,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER7,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER8,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER9,  1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER10, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER11, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER12, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER13, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER14, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER15, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER16, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER17, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER18, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER19, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER20, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER21, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER22, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER23, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER24, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER25, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER26, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER27, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER28, 1);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER29, 1);
 
  // sum up all written ones (only available HPM counter CSRs will return =! 0)
  uint32_t num_hpm_cnts = 0;
 
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER3);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER4);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER5);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER6);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER7);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER8);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER9);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER10);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER11);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER12);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER13);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER14);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER15);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER16);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER17);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER18);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER19);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER20);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER21);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER22);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER23);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER24);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER25);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER26);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER27);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER28);
  num_hpm_cnts += neorv32_cpu_csr_read(CSR_MHPMCOUNTER29);
 
  return num_hpm_cnts;
}
 
 
/**********************************************************************//**
 * Hardware performance monitors (HPM): Get total counter width
 *
 * @warning This function overrides mhpmcounter3[h] CSRs.
 *
 * @return Size of HPM counter bits (1-64).
 **************************************************************************/
uint32_t neorv32_cpu_hpm_get_size(void) {
 
  // inhibt auto-update
  asm volatile ("csrwi %[addr], %[imm]" : : [addr] "i" (CSR_MCOUNTINHIBIT), [imm] "i" (1<<CSR_MCOUNTEREN_HPM3));
 
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER3,  0xffffffff);
  neorv32_cpu_csr_write(CSR_MHPMCOUNTER3H, 0xffffffff);
 
  uint32_t tmp, size, i;
 
  if (neorv32_cpu_csr_read(CSR_MHPMCOUNTER3H) == 0) {
    size = 0;
    tmp = neorv32_cpu_csr_read(CSR_MHPMCOUNTER3);
  }
  else {
    size = 32;
    tmp = neorv32_cpu_csr_read(CSR_MHPMCOUNTER3H);
  }
 
  for (i=0; i<32; i++) {
    if (tmp & (1<<i)) {
      size++;
    }
  }
 
  return size;
}
 
 
/**********************************************************************//**
 * Check if certain Z* extension is available
 *
 * @param[in] flag Index of the Z-extension to check from #NEORV32_CSR_MZEXT_enum
 * @return 0 if extension is NOT available, != 0 if extension is available.
 **************************************************************************/
int neorv32_check_zextension(uint32_t flag) {
 
  // check if out of range
  if (flag > 31) {
    return 0;
  }
 
  uint32_t tmp = neorv32_cpu_csr_read(CSR_MZEXT);
  if ((tmp & (1 << flag)) == 0) {
    return 0;
  }
  else {
    return 1;
  }
}