cvw/fpga/zsbl/uart.c

#include "uart.h"


void write_reg_u8(uintptr_t addr, uint8_t value)
{
  volatile uint8_t *loc_addr = (volatile uint8_t *)addr;
  *loc_addr = value;
}

uint8_t read_reg_u8(uintptr_t addr)
{
  return *(volatile uint8_t *)addr;
}

int is_transmit_empty()
{
  return read_reg_u8(UART_LSR) & 0x20;
}

int is_receive_empty()
{
  return !(read_reg_u8(UART_LSR) & 0x1);
}

void write_serial(char a)
{
  while (is_transmit_empty() == 0) {};

  write_reg_u8(UART_THR, a);
}

void init_uart(uint32_t freq, uint32_t baud)
{
  // Alternative divisor calculation. From OpenSBI code.
  // Reduces error for every possible frequency.
  uint32_t divisor = (freq + 8 * baud) /(baud << 4);

  write_reg_u8(UART_IER, 0x00);                   // Disable all interrupts
  write_reg_u8(UART_LCR, 0x80);                   // Enable DLAB (set baud rate divisor)
  write_reg_u8(UART_DLL, divisor & 0xFF);         // divisor (lo byte)
  write_reg_u8(UART_DLM, (divisor >> 8) & 0xFF);  // divisor (hi byte)
  write_reg_u8(UART_LCR, 0x03);                   // 8 bits, no parity, one stop bit
  write_reg_u8(UART_FCR, 0xC7);                   // Enable FIFO, clear them, with 14-byte threshold
}

void print_uart(const char *str)
{
  const char *cur = &str[0];
  while (*cur != '\0') {
    write_serial((uint8_t)*cur);
    ++cur;
  }
}

uint8_t bin_to_hex_table[16] = {
  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

void bin_to_hex(uint8_t inp, uint8_t res[2])
{
  res[1] = bin_to_hex_table[inp & 0xf];
  res[0] = bin_to_hex_table[(inp >> 4) & 0xf];
  return;
}

void print_uart_int(uint32_t addr)
{
  int i;
  for (i = 3; i > -1; i--)  {
    uint8_t cur = (addr >> (i * 8)) & 0xff;
    uint8_t hex[2];
    bin_to_hex(cur, hex);
    write_serial(hex[0]);
    write_serial(hex[1]);
  }
}

void print_uart_addr(uint64_t addr)
{
  int i;
  for (i = 7; i > -1; i--) {
    uint8_t cur = (addr >> (i * 8)) & 0xff;
    uint8_t hex[2];
    bin_to_hex(cur, hex);
    write_serial(hex[0]);
    write_serial(hex[1]);
  }
}

void print_uart_byte(uint8_t byte)
{
  uint8_t hex[2];
  bin_to_hex(byte, hex);
  write_serial(hex[0]);
  write_serial(hex[1]);
}