irq commit: this large commit gets interrupts working

Signed-off-by: Sean Cross <sean@xobs.io>

src/main.rs

@@ -2,17 +2,68 @@
 #![no_main]
 
 extern crate xous_riscv;
+mod syscalls;
+mod irq;
+
+pub use irq::sys_interrupt_claim;
 
 use core::panic::PanicInfo;
+use xous_kernel_riscv_rt::xous_kernel_entry;
+use xous_riscv::register::{mcause, mstatus, mie, vmim, vmip};
+
+
 #[panic_handler]
-fn handle_panic(arg: &PanicInfo) -> ! {
+fn handle_panic(_arg: &PanicInfo) -> ! {
     loop {}
 }
 
-use xous_riscv_rt::entry;
-#[entry]
+fn print_str(uart: *mut usize, s: &str) {
+    for c in s.bytes() {
+        unsafe { uart.write_volatile(c as usize) };
+    }
+}
+
+#[xous_kernel_entry]
 fn xous_main() -> ! {
+    unsafe {
+        vmim::write(0); // Disable all machine interrupts
+        mie::set_msoft();
+        mie::set_mtimer();
+        mie::set_mext();
+        mstatus::set_mie(); // Enable CPU interrupts
+    }
+    sys_interrupt_claim(2, |_| {
+        let uart_ptr = 0xE000_1800 as *mut usize;
+        print_str(uart_ptr, "hello, world!\r\n");
+        // Acknowledge the IRQ
+        unsafe {
+            uart_ptr.add(0).read_volatile();
+
+            // Acknowledge the event
+            uart_ptr.add(4).write_volatile(3);
+        };
+    })
+    .unwrap();
+
+    // Enable interrupts
+    let uart_ptr = 0xE000_1800 as *mut usize;
+    unsafe { uart_ptr.add(4).write_volatile(3) };
+    unsafe { uart_ptr.add(5).write_volatile(3) };
+    print_str(uart_ptr, "greetings!\r\n");
+
     loop {
         unsafe { xous_riscv::asm::wfi() };
     }
 }
+
+#[no_mangle]
+pub fn trap_handler() {
+    let mc = mcause::read();
+    let irqs_pending = vmip::read();
+
+    if mc.is_exception() {}
+
+    if irqs_pending != 0 {
+        irq::handle(irqs_pending);
+    }
+}