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77 lines
2.0 KiB
77 lines
2.0 KiB
#include <string.h>
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#include "uart16550.h"
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#include "fdt.h"
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volatile uint8_t* uart16550;
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#define UART_REG_QUEUE 0
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#define UART_REG_LINESTAT 5
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#define UART_REG_STATUS_RX 0x01
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#define UART_REG_STATUS_TX 0x20
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void uart16550_putchar(uint8_t ch)
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{
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while ((uart16550[UART_REG_LINESTAT] & UART_REG_STATUS_TX) == 0);
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uart16550[UART_REG_QUEUE] = ch;
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}
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int uart16550_getchar()
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{
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if (uart16550[UART_REG_LINESTAT] & UART_REG_STATUS_RX)
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return uart16550[UART_REG_QUEUE];
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return -1;
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}
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struct uart16550_scan
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{
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int compat;
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uint64_t reg;
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};
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static void uart16550_open(const struct fdt_scan_node *node, void *extra)
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{
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struct uart16550_scan *scan = (struct uart16550_scan *)extra;
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memset(scan, 0, sizeof(*scan));
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}
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static void uart16550_prop(const struct fdt_scan_prop *prop, void *extra)
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{
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struct uart16550_scan *scan = (struct uart16550_scan *)extra;
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if (!strcmp(prop->name, "compatible") && !strcmp((const char*)prop->value, "ns16550a")) {
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scan->compat = 1;
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} else if (!strcmp(prop->name, "reg")) {
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fdt_get_address(prop->node->parent, prop->value, &scan->reg);
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}
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}
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static void uart16550_done(const struct fdt_scan_node *node, void *extra)
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{
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struct uart16550_scan *scan = (struct uart16550_scan *)extra;
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if (!scan->compat || !scan->reg || uart16550) return;
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uart16550 = (void*)(uintptr_t)scan->reg;
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// http://wiki.osdev.org/Serial_Ports
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uart16550[1] = 0x00; // Disable all interrupts
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uart16550[3] = 0x80; // Enable DLAB (set baud rate divisor)
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uart16550[0] = 0x03; // Set divisor to 3 (lo byte) 38400 baud
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uart16550[1] = 0x00; // (hi byte)
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uart16550[3] = 0x03; // 8 bits, no parity, one stop bit
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uart16550[2] = 0xC7; // Enable FIFO, clear them, with 14-byte threshold
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uart16550[4] = 0x0B;
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uart16550[1] = 0x01; // Enable interrupt
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}
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void query_uart16550(uintptr_t fdt)
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{
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struct fdt_cb cb;
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struct uart16550_scan scan;
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memset(&cb, 0, sizeof(cb));
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cb.open = uart16550_open;
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cb.prop = uart16550_prop;
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cb.done = uart16550_done;
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cb.extra = &scan;
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fdt_scan(fdt, &cb);
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}
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