From 6f1e6acb1a9775eef4b0d8879c102df86e207687 Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Thu, 18 Aug 2022 18:21:13 -0700
Subject: Assembly stuff

---
 src/_arch/arm/asm.rs          | 35 ++++++++++++++++++++++++++-
 src/bsp/raspberrypi/linker.ld |  6 +++++
 src/cpu.rs                    |  2 +-
 src/kernel.rs                 |  1 -
 src/uart.rs                   | 56 ++++++++++++++++++++++---------------------
 5 files changed, 70 insertions(+), 30 deletions(-)

diff --git a/src/_arch/arm/asm.rs b/src/_arch/arm/asm.rs
index c400f2f..c1af5b4 100644
--- a/src/_arch/arm/asm.rs
+++ b/src/_arch/arm/asm.rs
@@ -1,9 +1,42 @@
 //! Wrapping ARMv7-A Instructions
 
 /// WFE
-/// #[inline(always)]
+#[inline(always)]
 pub fn wfe() {
     unsafe {
         core::arch::asm!("wfe", options(nomem, nostack))
     }
 }
+
+/// NOP
+#[inline(always)]
+pub fn nop() {
+    unsafe {
+        core::arch::asm!("nop", options(nomem, nostack))
+    }
+}
+
+/// Store u32 to address
+#[inline]
+pub fn store32(addr: u32, value: u32) {
+	unsafe {
+		*(addr as *mut u32) = value;
+	}
+}
+
+/// Read u32 value from address
+#[inline]
+pub fn load32(addr: u32) -> u32 {
+	unsafe {
+		*(addr as *mut u32)
+	}
+}
+
+/// Wait for n cycles
+#[inline]
+pub fn spin_for_n_cycles(n: u32) {
+	unsafe {
+		core::arch::asm!("1: subs r1, #1
+				bne 1b", in("r1") n);
+	}
+}
diff --git a/src/bsp/raspberrypi/linker.ld b/src/bsp/raspberrypi/linker.ld
index aa60bbb..93ee267 100644
--- a/src/bsp/raspberrypi/linker.ld
+++ b/src/bsp/raspberrypi/linker.ld
@@ -37,4 +37,10 @@ SECTIONS
 	. = ALIGN(4096);
 	__bss_end = .;
 	__end = .;
+
+	/DISCARD/ :
+	{
+		*(.ARM.exidx);
+		*(.ARM.extab.*);
+	}
 }
diff --git a/src/cpu.rs b/src/cpu.rs
index 62fcf99..9f003f8 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -2,6 +2,6 @@
 #[cfg(target_arch = "arm")]
 #[path = "_arch/arm/cpu.rs"]
 mod arch_cpu;
-pub use arch_cpu::{wait_forever};
+pub use arch_cpu::{nop,wait_forever,spin_for_n_cycles,load32,store32};
 
 mod boot;
diff --git a/src/kernel.rs b/src/kernel.rs
index 9697ca8..a194b14 100644
--- a/src/kernel.rs
+++ b/src/kernel.rs
@@ -23,7 +23,6 @@ unsafe fn kernel_init() -> ! {
 
 fn kernel_main() -> ! {
     write_char(b'a');
-    write_char(b'b');
     loop {
     }
 }
diff --git a/src/uart.rs b/src/uart.rs
index 7c048e0..a26bb2f 100644
--- a/src/uart.rs
+++ b/src/uart.rs
@@ -1,31 +1,33 @@
-pub unsafe fn uart_init() {
-    let UART0_CR = 0x3F201030 as *mut u32;
-    let UART0_ICR = 0x3F201044 as *mut u32;
-    let UART0_IBRD = 0x3F201024 as *mut u32;
-    let UART0_FBRD = 0x3F201028 as *mut u32;
-    let UART0_LCRH = 0x3F20102C as *mut u32;
-    let UART0_IMSC = 0x3F201038 as *mut u32;
-    let GPPUD = 0x3F200094 as *mut u32;
-    let GPPUDCLK0 = 0x3F200098 as *mut u32;
-    *UART0_CR = 0;
-    *GPPUD = 0;
-    for _ in 0..150 {core::arch::asm!("nop", options(nomem, nostack));}
-    *GPPUDCLK0 = (1 << 14) | (1 << 15);
-    for _ in 0..150 {core::arch::asm!("nop", options(nomem, nostack));}
-    *GPPUDCLK0 = 0;
-    *UART0_ICR = 0x7FF;
-    *UART0_IBRD = 9;
-    *UART0_FBRD = 49;
-    *UART0_LCRH = (1<<4)|(1<<5)|(1<<6);
-    *UART0_IMSC = (1<<1)|(1<<4)|(1<<5)|(1<<6)|(1<<7)|(1<<8)|(1<<9)|(1<<10);
-    *UART0_CR = (1<<0) | (1<<8) | (1<<9);
+use crate::cpu::*;
+const UART0_DR: u32    = 0x3F201000;
+const UART0_FR: u32    = 0x3F201018;
+const UART0_CR: u32    = 0x3F201030;
+const UART0_ICR: u32   = 0x3F201044;
+const UART0_IBRD: u32  = 0x3F201024;
+const UART0_FBRD: u32  = 0x3F201028;
+const UART0_LCRH: u32  = 0x3F20102C;
+const UART0_IMSC: u32  = 0x3F201038;
+const GPPUD: u32       = 0x3F200094;
+const GPPUDCLK0: u32   = 0x3F200098;
+
+pub fn uart_init() {
+	store32(UART0_CR, 0);
+	store32(GPPUD, 0);
+	spin_for_n_cycles(150);
+	store32(GPPUDCLK0, (1 << 14) | (1 << 15));
+	spin_for_n_cycles(150);
+	store32(GPPUDCLK0, 0);
+	store32(UART0_ICR, 0x7FF);
+	store32(UART0_IBRD, 9);
+	store32(UART0_FBRD, 49);
+	store32(UART0_LCRH, (1<<4) | (1<<5) | (1<<6));
+	store32(UART0_IMSC, (1<<1) | (1<<4) | (1<<5) | (1<<6) | (1<<7) | (1<<8) | (1<<9) | (1<<10));
+	store32(UART0_CR, (1<<0) | (1<<8) | (1<<9));
 }
 
 pub fn write_char(ch: u8) {
-    let UART0_DR = 0x3F201000 as *mut u32;
-    let UART0_FR = 0x3F201018 as *mut u32;
-    unsafe {
-        while *UART0_FR & 0x20 != 0 {core::arch::asm!("nop", options(nomem, nostack));}
-        *UART0_DR = ch as u32;
-    }
+	while load32(UART0_FR) & 0x20 != 0 {
+		nop();
+	}
+	store32(UART0_DR, ch as u32);
 }
-- 
cgit v1.2.1