commit 787b4617ae6b72dd51af61f6833f8649102b534d
Author: Mathieu Maret <mathieu.maret@gmail.com>
Date:   Mon Mar 14 07:46:32 2022 +0100

    Initial import with uart

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0986317
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,23 @@
+#CROSS=aarch64-none-elf-
+CROSS=aarch64-linux-gnu-
+CC=$(CROSS)gcc
+LD=$(CROSS)ld
+CFLAGS=-Wall -Wextra -ffreestanding -march=armv8-a+crc -mcpu=cortex-a53
+LDSCRIPT=rpi3.ld
+
+OBJS=crt0.o uart.o hello.o
+
+all:kernel.bin
+
+kernel.elf: $(OBJS) $(LDSCRIPT)
+	$(LD) -o $@ $(OBJS) -T$(LDSCRIPT) -Map kernel.map
+
+kernel.bin: kernel.elf
+	$(CROSS)objcopy -O binay -B aarch64 $< $@
+
+clean:
+	rm -rf $(OBJS) *.bin *.elf *.map
+
+run: kernel.bin
+	qemu-system-aarch64 -machine raspi3b -kernel $<
+
diff --git a/config.txt b/config.txt
new file mode 100644
index 0000000..3c49fda
--- /dev/null
+++ b/config.txt
@@ -0,0 +1,8 @@
+#bootloarder
+uart_2ndstage=1
+
+# 64bits
+arm_64bit=1
+
+# Kernel name
+kernel=kernel.bin
diff --git a/crt0.S b/crt0.S
new file mode 100644
index 0000000..90ec9b4
--- /dev/null
+++ b/crt0.S
@@ -0,0 +1,27 @@
+	.section .text.boot
+	.global __start
+	.type __start, %function
+
+__start:
+	//Use core 0 only
+	mrs	x7, mpidr_el1
+	and		x7, x7, #3
+	cbz		x7, __start_master
+0: wfe
+	b			0b
+
+__start_master:
+	//Setup stack pointer
+	ldr		x2, = __stack_start
+	mov		sp, x2
+
+	//Clear BSS
+	ldr		w0, = __bss_start
+	ldr		w1, = __bss_size
+1: cbz	x1, 2f
+	str		xzr, [x0], #8
+	sub		x1, x1, #1
+	cbnz	x1, 1b
+2:
+	bl		kernelmain
+	b			0b
diff --git a/gpio.h b/gpio.h
new file mode 100644
index 0000000..899cc97
--- /dev/null
+++ b/gpio.h
@@ -0,0 +1,9 @@
+#pragma	once
+
+#include "mmio.h"
+// GPIO Function Select 1
+#define GPFSEL1 (*(volatile unsigned *)(GP_BASE + 0x04))
+// GPIO Pin Pull-up/down Enable
+#define GPPUD   (*(volatile unsigned *)(GP_BASE + 0x94))
+// GPIO Pin Pull-up/down Enable Clock 0
+#define GPPUDCLK0   (*(volatile unsigned *)(GP_BASE + 0x98))
diff --git a/hello.c b/hello.c
new file mode 100644
index 0000000..6631ada
--- /dev/null
+++ b/hello.c
@@ -0,0 +1,6 @@
+#include "uart.h"
+
+int kernelmain(void) {
+  init_uart();
+  return 0;
+}
diff --git a/mmio.h b/mmio.h
new file mode 100644
index 0000000..3f98913
--- /dev/null
+++ b/mmio.h
@@ -0,0 +1,13 @@
+#pragma once
+
+// IO mapping
+#define IO_BASE 0x3f000000
+
+// Mini-UART mapping
+#define MU_BASE (IO_BASE + 0x215000)
+
+// GPIO mapping
+#define GP_BASE (IO_BASE + 0x200000)
+
+// videocore mbox system
+#define VCORE_MBOX (IO_BASE + 0x0000B880)
diff --git a/rpi3.ld b/rpi3.ld
new file mode 100644
index 0000000..7e6f591
--- /dev/null
+++ b/rpi3.ld
@@ -0,0 +1,32 @@
+MEMORY
+{
+	/* Load at a classic 64bit addr*/
+	/* Could be replace by . = 0x8000; before .text*/
+	RAM (rwx) : ORIGIN = 0x80000, LENGTH = 0x10000000
+}
+
+SECTIONS
+{
+	.text : { *(.text .text.*) }
+	.rodata : { *(.rodata .rodata.*) }
+	.data : { *(.data .data.*) }
+
+	.bss (NOLOAD):
+	{
+		__bss_start = ALIGN(16);
+		*(.bss .bss.*)
+		__bss_end = ALIGN(16);
+	}
+	__end =.;
+
+	. = ALIGN(16);
+	. += 0x1000;
+	__stack_start = .;
+
+	/DISCARD/ :
+	{
+		*(.comment) *(.gnu) *(.note*) *(.eh_frame*)
+	}
+}
+
+__bss_size = (__bss_end - __bss_start) >> 3;
diff --git a/uart.c b/uart.c
new file mode 100644
index 0000000..e3d1ca9
--- /dev/null
+++ b/uart.c
@@ -0,0 +1,45 @@
+#include <stdint.h>
+
+#include "uart.h"
+#include "gpio.h"
+//#include "mbox.h"
+
+
+void init_uart(void )
+{
+	//Active waiting
+	while(UART0_FR & (1<<3)){}
+
+	//Stop UART0
+	UART0_CR = 0;
+
+	//GPIO 14 and 15 in ALT0
+	GPFSEL1 &= ~((7<<12)|(7<<15));
+	GPFSEL1 |= (4<<12)|(4<<15);
+	GPPUD = 0;
+	for(uint8_t i = 0; i < 150; i++){
+		asm volatile ("nop");
+	}
+	GPPUDCLK0 = (1<<14)|(1<<5);
+	for(uint8_t i = 0; i < 150; i++){
+		asm volatile ("nop");
+	}
+
+	//CLR INTR
+	GPPUDCLK0 = 0;
+
+	// Setup for 115200bps @3Mhz
+	// 3000000 /(115200 * 16) = 1.627
+	// 0.627 * 64 + 0.5 = 40.628 -> 40
+	UART0_IBRD = 1; //int part
+	UART0_FBRD = 40; //fract part
+	UART0_LCRH = 0b11 <<5; //format 8n1
+	UART0_CR = 0x301; //Active Tx, Rx & FIFO
+}
+
+void putc(char c){
+	//FIFO Full?
+	while(UART0_FR & (1<<5)){}
+
+	UART0_DR = c;
+}
diff --git a/uart.h b/uart.h
new file mode 100644
index 0000000..c0d4777
--- /dev/null
+++ b/uart.h
@@ -0,0 +1,15 @@
+#pragma once
+#include "mmio.h"
+
+/* PL011 UART */
+#define UART0_DR (*(volatile unsigned *)(IO_BASE + 0x00201000))
+#define UART0_FR (*(volatile unsigned *)(IO_BASE + 0x00201018))
+#define UART0_IBRD (*(volatile unsigned *)(IO_BASE + 0x00201024))
+#define UART0_FBRD (*(volatile unsigned *)(IO_BASE + 0x00201028))
+#define UART0_LCRH (*(volatile unsigned *)(IO_BASE + 0x0020102C))
+#define UART0_CR (*(volatile unsigned *)(IO_BASE + 0x00201030))
+#define UART0_IMSC (*(volatile unsigned *)(IO_BASE + 0x00201038))
+#define UART0_ICR (*(volatile unsigned *)(IO_BASE + 0x00201044))
+
+void init_uart(void);
+void putc(char c);