Blink an LED on pi

.gitignore

@@ -1 +1,2 @@
 /target
+kernel8.img

config.txt

@@ -0,0 +1,3 @@
+kernel=kernel8.img
+arm_64bit=1
+enable_uart=1

link.ld

@@ -1,7 +1,7 @@
 SECTIONS
 {
-    . = 0x80000;     /* Kernel load address for AArch64 */
-    .text : { KEEP(*(.text.boot)) *(.text .text.* .gnu.linkonce.t*) }
+    . = 0x80000;
+    .text : { KEEP(*(.text._start)) *(.text .text.* .gnu.linkonce.t*) }
     .rodata : { *(.rodata .rodata.* .gnu.linkonce.r*) }
     PROVIDE(_data = .);
     .data : { *(.data .data.* .gnu.linkonce.d*) }

src/gpio.rs

@@ -3,66 +3,28 @@ use crate::{
     uart::{self},
 };
 
+const GPFSEL2: u32 = 0x3F20_0008; //GPIO 20-29
 const GPFSEL4: u32 = 0x3F20_0010; //GPIO 40-49
-const GPPUD: u32 = 0x3F20_0094;
-const GPPUD_CLK: u32 = 0x3F20_0098; // GPIO 32-53
+const GPSET0: u32 = 0x3F20_001C;
+const GPCLR0: u32 = 0x3F20_0028;
 
-unsafe fn set_gpio47_to_output() {
-    let value: u32 = 0b001 << 21;
+unsafe fn set_gpio29_to_output() {
+    let value: u32 = 0b001 << 27;
 
-    core::ptr::write_volatile(GPFSEL4 as *mut u32, value);
+    core::ptr::write_volatile(GPFSEL2 as *mut u32, value);
 }
 
-unsafe fn enable_pull_up() {
-    let value: u32 = 0b10;
-
-    core::ptr::write_volatile(GPPUD as *mut u32, value);
-}
-
-unsafe fn enable_pull_down() {
-    let value: u32 = 0b01;
-
-    core::ptr::write_volatile(GPPUD as *mut u32, value);
-}
-
-unsafe fn disable_GPPUD() {
-    core::ptr::write_volatile(GPPUD as *mut u32, 0);
-}
-
-unsafe fn enable_clock_gpio47() {
-    let value: u32 = 0b1 << 13;
-
-    core::ptr::write_volatile(GPPUD as *mut u32, value);
-}
-
-unsafe fn disable_GPPUD_CLK() {
-    core::ptr::write_volatile(GPPUD as *mut u32, 0);
-}
-
-pub fn pull_up_gpio47() {
+pub fn pull_up_gpio29() {
     unsafe {
         uart::print("Pull Up\n");
-        set_gpio47_to_output();
-        enable_pull_up();
-        // Wait 150 cycles
-        delay(150);
-        enable_clock_gpio47();
-        delay(150);
-        disable_GPPUD();
-        disable_GPPUD_CLK();
+        set_gpio29_to_output();
+        core::ptr::write_volatile(GPSET0 as *mut u32, 1 << 29);
     }
 }
 
-pub fn pull_down_gpio47() {
+pub fn pull_down_gpio29() {
     unsafe {
         uart::print("Pull Down\n");
-        set_gpio47_to_output();
-        enable_pull_down();
-        // Wait 150 cycles
-        delay(150);
-        enable_clock_gpio47();
-        delay(150);
-        disable_GPPUD();
-        disable_GPPUD_CLK();
+        core::ptr::write_volatile(GPCLR0 as *mut u32, 1 << 29);
     }
 }

src/main.rs

@@ -2,9 +2,9 @@
 #![no_std]
 #![feature(asm_experimental_arch)]
 
-use core::panic::PanicInfo;
+use core::{arch::asm, panic::PanicInfo};
 
-use gpio::{pull_down_gpio47, pull_up_gpio47};
+use gpio::{pull_down_gpio29, pull_up_gpio29};
 
 mod gpio;
 mod uart;
@@ -12,18 +12,20 @@ mod uart;
 #[panic_handler]
 fn panic(_panic: &PanicInfo) -> ! {
     loop {
+        pull_up_gpio29();
         uart::print("Panic");
     }
 }
 
 #[no_mangle]
-#[unsafe(naked)]
-pub extern "C" fn _start() -> ! {
-    core::arch::naked_asm!("mov sp, #0x80000", "bl main");
+#[link_section = ".text._start"]
+pub unsafe extern "C" fn _start() {
+    asm!("ldr x0, =0x8004000", "mov sp, x0");
+    main();
 }
 
 #[no_mangle]
-fn main() {
+extern "C" fn main() {
     uart::configure_uart();
 
     // Delay so clock speed can stabilize
@@ -31,10 +33,10 @@ fn main() {
     uart::print("Hello World!\n");
 
     loop {
-        pull_up_gpio47();
-        unsafe { delay(10_000_000) } // ~0.5s
-        pull_down_gpio47();
-        unsafe { delay(10_000_000) }
+        pull_up_gpio29();
+        unsafe { delay(1_000_000) }
+        pull_down_gpio29();
+        unsafe { delay(1_000_000) }
     }
 }
 

tools/build_debug.sh

@@ -0,0 +1,4 @@
+cd "$(dirname "$0")"
+cd ".."
+
+cargo build --target aarch64-unknown-none

tools/build_release.sh

@@ -0,0 +1,4 @@
+cd "$(dirname "$0")"
+cd ".."
+
+cargo build --target aarch64-unknown-none --release

tools/generate_kernel.sh

@@ -0,0 +1,3 @@
+cd "$(dirname "$0")"
+
+llvm-objcopy -O binary ../target/aarch64-unknown-none/release/nova ../kernel8.img

tools/start_simulator.sh

@@ -1,3 +1,3 @@
 cd "$(dirname "$0")"
 
-qemu-system-aarch64 -M raspi3b -cpu cortex-a53 -serial stdio -display none -kernel ../target/aarch64-unknown-none/debug/nova -s
+qemu-system-aarch64 -M raspi3b -cpu cortex-a53 -serial stdio -display none -kernel ../target/aarch64-unknown-none/release/nova -s

tools/start_simulator_debug.sh

@@ -0,0 +1,3 @@
+cd "$(dirname "$0")"
+
+qemu-system-aarch64 -M raspi3b -cpu cortex-a53 -serial stdio -display none -kernel ../target/aarch64-unknown-none/debug/nova -s