avionic design with actual uboot and tooling

submodule of avionic design uboot bootloader and with included tools to
get you started , read readme.md and readme-tk1-loader.md

u-boot/arch/arm/cpu/arm1136/start.S

@@ -0,0 +1,95 @@
+/*
+ *  armboot - Startup Code for OMP2420/ARM1136 CPU-core
+ *
+ *  Copyright (c) 2004	Texas Instruments <r-woodruff2@ti.com>
+ *
+ *  Copyright (c) 2001	Marius Gröger <mag@sysgo.de>
+ *  Copyright (c) 2002	Alex Züpke <azu@sysgo.de>
+ *  Copyright (c) 2002	Gary Jennejohn <garyj@denx.de>
+ *  Copyright (c) 2003	Richard Woodruff <r-woodruff2@ti.com>
+ *  Copyright (c) 2003	Kshitij <kshitij@ti.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <asm-offsets.h>
+#include <config.h>
+
+/*
+ *************************************************************************
+ *
+ * Startup Code (reset vector)
+ *
+ * do important init only if we don't start from memory!
+ * setup Memory and board specific bits prior to relocation.
+ * relocate armboot to ram
+ * setup stack
+ *
+ *************************************************************************
+ */
+
+	.globl	reset
+
+reset:
+	/*
+	 * set the cpu to SVC32 mode
+	 */
+	mrs	r0,cpsr
+	bic	r0,r0,#0x1f
+	orr	r0,r0,#0xd3
+	msr	cpsr,r0
+
+	/* the mask ROM code should have PLL and others stable */
+#ifndef CONFIG_SKIP_LOWLEVEL_INIT
+	bl  cpu_init_crit
+#endif
+
+	bl	_main
+
+/*------------------------------------------------------------------------------*/
+
+	.globl	c_runtime_cpu_setup
+c_runtime_cpu_setup:
+
+	bx	lr
+
+/*
+ *************************************************************************
+ *
+ * CPU_init_critical registers
+ *
+ * setup important registers
+ * setup memory timing
+ *
+ *************************************************************************
+ */
+#ifndef CONFIG_SKIP_LOWLEVEL_INIT
+cpu_init_crit:
+	/*
+	 * flush v4 I/D caches
+	 */
+	mov	r0, #0
+	mcr	p15, 0, r0, c7, c7, 0	/* Invalidate I+D+BTB caches */
+	mcr	p15, 0, r0, c8, c7, 0	/* Invalidate Unified TLB */
+
+	/*
+	 * disable MMU stuff and caches
+	 */
+	mrc	p15, 0, r0, c1, c0, 0
+	bic	r0, r0, #0x00002300	@ clear bits 13, 9:8 (--V- --RS)
+	bic	r0, r0, #0x00000087	@ clear bits 7, 2:0 (B--- -CAM)
+	orr	r0, r0, #0x00000002	@ set bit 1 (A) Align
+	orr	r0, r0, #0x00001000	@ set bit 12 (I) I-Cache
+	mcr	p15, 0, r0, c1, c0, 0
+
+#ifndef CONFIG_SKIP_LOWLEVEL_INIT_ONLY
+	/*
+	 * Jump to board specific initialization... The Mask ROM will have already initialized
+	 * basic memory.  Go here to bump up clock rate and handle wake up conditions.
+	 */
+	mov	ip, lr		/* persevere link reg across call */
+	bl	lowlevel_init	/* go setup pll,mux,memory */
+	mov	lr, ip		/* restore link */
+#endif
+	mov	pc, lr		/* back to my caller */
+#endif /* CONFIG_SKIP_LOWLEVEL_INIT */