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147 lines
2.4 KiB
C
147 lines
2.4 KiB
C
#include <unistd.h>
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#include <string.h>
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#include <stdint.h>
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#include <stdbool.h>
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/*
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* Core UART functions to implement for a port
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*/
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static uint64_t potato_uart_base;
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#define PROC_FREQ 50000000
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#define UART_FREQ 115200
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#define UART_BASE 0xc0002000
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#define POTATO_CONSOLE_TX 0x00
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#define POTATO_CONSOLE_RX 0x08
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#define POTATO_CONSOLE_STATUS 0x10
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#define POTATO_CONSOLE_STATUS_RX_EMPTY 0x01
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#define POTATO_CONSOLE_STATUS_TX_EMPTY 0x02
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#define POTATO_CONSOLE_STATUS_RX_FULL 0x04
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#define POTATO_CONSOLE_STATUS_TX_FULL 0x08
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#define POTATO_CONSOLE_CLOCK_DIV 0x18
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#define POTATO_CONSOLE_IRQ_EN 0x20
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static uint64_t potato_uart_reg_read(int offset)
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{
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uint64_t addr;
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uint64_t val;
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addr = potato_uart_base + offset;
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val = *(volatile uint64_t *)addr;
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return val;
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}
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static void potato_uart_reg_write(int offset, uint64_t val)
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{
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uint64_t addr;
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addr = potato_uart_base + offset;
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*(volatile uint64_t *)addr = val;
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}
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static int potato_uart_rx_empty(void)
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{
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uint64_t val;
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val = potato_uart_reg_read(POTATO_CONSOLE_STATUS);
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if (val & POTATO_CONSOLE_STATUS_RX_EMPTY)
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return 1;
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return 0;
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}
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static int potato_uart_tx_full(void)
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{
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uint64_t val;
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val = potato_uart_reg_read(POTATO_CONSOLE_STATUS);
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if (val & POTATO_CONSOLE_STATUS_TX_FULL)
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return 1;
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return 0;
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}
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static char potato_uart_read(void)
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{
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uint64_t val;
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val = potato_uart_reg_read(POTATO_CONSOLE_RX);
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return (char)(val & 0x000000ff);
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}
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static void potato_uart_write(char c)
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{
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uint64_t val;
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val = c;
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potato_uart_reg_write(POTATO_CONSOLE_TX, val);
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}
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static unsigned long potato_uart_divisor(unsigned long proc_freq, unsigned long uart_freq)
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{
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return proc_freq / (uart_freq * 16) - 1;
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}
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void potato_uart_init(void)
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{
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potato_uart_base = UART_BASE;
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potato_uart_reg_write(POTATO_CONSOLE_CLOCK_DIV, potato_uart_divisor(PROC_FREQ, UART_FREQ));
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}
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int getchar(void)
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{
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while (potato_uart_rx_empty())
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/* Do nothing */ ;
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return potato_uart_read();
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}
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void putchar(unsigned char c)
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{
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while (potato_uart_tx_full())
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/* Do Nothing */;
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potato_uart_write(c);
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}
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void putstr(const char *str, unsigned long len)
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{
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for (unsigned long i = 0; i < len; i++) {
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putchar(str[i]);
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}
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}
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size_t strlen(const char *s)
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{
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size_t len = 0;
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while (*s++)
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len++;
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return len;
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}
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#define HELLO_WORLD "Hello World\r\n"
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int main(void)
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{
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potato_uart_init();
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putstr(HELLO_WORLD, strlen(HELLO_WORLD));
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while (1) {
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unsigned char c = getchar();
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putchar(c);
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}
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}
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