Add uart

exosphere/uart.c

@@ -0,0 +1,33 @@
+#include "uart.h"
+
+volatile void *g_uart_registers = NULL;
+
+void set_uart_address(void *uart_base) {
+    g_uart_registers = uart_base;
+}
+
+inline void *get_uart_address(void) {
+    return g_uart_registers;
+}
+
+void uart_initialize(uint16_t divider) {
+    /* Setup UART in 16450 mode. We assume the relevant UART clock has been enabled. */
+
+    /* Disable FIFO */
+    UART_IIR_FCR_0 = 0x00;
+
+    /* Set DLAB */
+    UART_LCR_0 = 0x80;
+    UART_THR_DLAB_0_0 = (uint8_t)divider;
+    UART_IER_DLAB_0_0 = (uint8_t)(divider >> 8);
+
+    /* 8N1 mode */
+    UART_LCR_0 = 0x03;
+}
+
+void uart_transmit_char(char ch) {
+    /* Wait for THR to be empty */
+    while (!(UART_LSR_0 & 0x20)) {}
+
+    UART_THR_DLAB_0_0 = ch;
+}

exosphere/uart.h

@@ -0,0 +1,20 @@
+#ifndef EXOSPHERE_UART_H
+#define EXOSPHERE_UART_H
+
+#include <stdint.h>
+
+/* Exosphere driver for the Tegra X1 UARTs. */
+
+void set_uart_address(void *uart_base);
+void *get_uart_address(void); /* This is inlined in uart.c */
+
+#define UART_THR_DLAB_0_0 (*((volatile uint32_t *)(get_uart_address() + 0x0)))
+#define UART_IER_DLAB_0_0 (*((volatile uint32_t *)(get_uart_address() + 0x4)))
+#define UART_IIR_FCR_0 (*((volatile uint32_t *)(get_uart_address() + 0x8)))
+#define UART_LCR_0 (*((volatile uint32_t *)(get_uart_address() + 0xC)))
+#define UART_LSR_0 (*((volatile uint32_t *)(get_uart_address() + 0x14)))
+
+void uart_initialize(uint16_t divider);
+void uart_transmit_char(char ch);
+
+#endif