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// See LICENSE for license details.
#include <string.h>
#include "uart16550.h"
#include "fdt.h"
volatile uint8_t* uart16550;
#define UART_REG_QUEUE 0
#define UART_REG_LINESTAT 5
#define UART_REG_STATUS_RX 0x01
#define UART_REG_STATUS_TX 0x20
void uart16550_putchar(uint8_t ch)
{
while ((uart16550[UART_REG_LINESTAT] & UART_REG_STATUS_TX) == 0);
uart16550[UART_REG_QUEUE] = ch;
}
int uart16550_getchar()
{
if (uart16550[UART_REG_LINESTAT] & UART_REG_STATUS_RX)
return uart16550[UART_REG_QUEUE];
return -1;
}
struct uart16550_scan
{
int compat;
uint64_t reg;
};
static void uart16550_open(const struct fdt_scan_node *node, void *extra)
{
struct uart16550_scan *scan = (struct uart16550_scan *)extra;
memset(scan, 0, sizeof(*scan));
}
static void uart16550_prop(const struct fdt_scan_prop *prop, void *extra)
{
struct uart16550_scan *scan = (struct uart16550_scan *)extra;
if (!strcmp(prop->name, "compatible") && !strcmp((const char*)prop->value, "ns16550a")) {
scan->compat = 1;
} else if (!strcmp(prop->name, "reg")) {
fdt_get_address(prop->node->parent, prop->value, &scan->reg);
}
}
static void uart16550_done(const struct fdt_scan_node *node, void *extra)
{
struct uart16550_scan *scan = (struct uart16550_scan *)extra;
if (!scan->compat || !scan->reg || uart16550) return;
uart16550 = (void*)(uintptr_t)scan->reg;
// http://wiki.osdev.org/Serial_Ports
uart16550[1] = 0x00; // Disable all interrupts
uart16550[3] = 0x80; // Enable DLAB (set baud rate divisor)
uart16550[0] = 0x03; // Set divisor to 3 (lo byte) 38400 baud
uart16550[1] = 0x00; // (hi byte)
uart16550[3] = 0x03; // 8 bits, no parity, one stop bit
uart16550[2] = 0xC7; // Enable FIFO, clear them, with 14-byte threshold
}
void query_uart16550(uintptr_t fdt)
{
struct fdt_cb cb;
struct uart16550_scan scan;
memset(&cb, 0, sizeof(cb));
cb.open = uart16550_open;
cb.prop = uart16550_prop;
cb.done = uart16550_done;
cb.extra = &scan;
fdt_scan(fdt, &cb);
}
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