1 files changed, 38 insertions, 0 deletions
diff --git a/machine/uart.c b/machine/uart.c
new file mode 100644
index 0000000..28cc21c
--- /dev/null
+++ b/machine/uart.c
@@ -0,0 +1,38 @@
+#include "uart.h"
+#include "fdt.h"
+
+volatile uint32_t* uart;
+
+void uart_putchar(uint8_t ch)
+{
+#ifdef __riscv_atomic
+    int32_t r;
+    do {
+      __asm__ __volatile__ (
+        "amoor.w %0, %2, %1\n"
+        : "=r" (r), "+A" (uart[UART_REG_TXFIFO])
+        : "r" (ch));
+    } while (r < 0);
+#else
+    volatile uint32_t *tx = uart + UART_REG_TXFIFO;
+    while ((int32_t)(*tx) < 0);
+    *tx = ch;
+#endif
+}
+
+int uart_getchar()
+{
+  int32_t ch = uart[UART_REG_RXFIFO];
+  if (ch < 0) return -1;
+  return ch;
+}
+
+void query_uart(uintptr_t dtb)
+{
+  uart = 0; // (void*)fdt_get_reg(dtb, "sifive,uart0");
+  if (!uart) return;
+
+  // Enable Rx/Tx channels
+  uart[UART_REG_TXCTRL] = UART_TXEN;
+  uart[UART_REG_RXCTRL] = UART_RXEN;
+}