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/sa1100/Makefile

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+#
+# (C) Copyright 2000-2006
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+extra-y	= start.o
+
+obj-y	+= cpu.o
+obj-y	+= timer.o

u-boot/arch/arm/cpu/sa1100/cpu.c

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+/*
+ * (C) Copyright 2002
+ * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
+ * Marius Groeger <mgroeger@sysgo.de>
+ *
+ * (C) Copyright 2002
+ * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
+ * Alex Zuepke <azu@sysgo.de>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+/*
+ * CPU specific code
+ */
+
+#include <common.h>
+#include <command.h>
+#include <asm/system.h>
+#include <asm/io.h>
+
+#ifdef CONFIG_USE_IRQ
+DECLARE_GLOBAL_DATA_PTR;
+#endif
+
+static void cache_flush(void);
+
+int cleanup_before_linux (void)
+{
+	/*
+	 * this function is called just before we call linux
+	 * it prepares the processor for linux
+	 *
+	 * just disable everything that can disturb booting linux
+	 */
+
+	disable_interrupts ();
+
+	/* turn off I-cache */
+	icache_disable();
+	dcache_disable();
+
+	/* flush I-cache */
+	cache_flush();
+
+	return (0);
+}
+
+/* flush I/D-cache */
+static void cache_flush (void)
+{
+	unsigned long i = 0;
+
+	asm ("mcr p15, 0, %0, c7, c5, 0": :"r" (i));
+}
+
+#define RST_BASE 0x90030000
+#define RSRR	0x00
+#define RCSR	0x04
+
+__attribute__((noreturn)) void reset_cpu(ulong addr __attribute__((unused)))
+{
+	/* repeat endlessly */
+	while (1) {
+		writel(0, RST_BASE + RCSR);
+		writel(1, RST_BASE + RSRR);
+	}
+}

u-boot/arch/arm/cpu/sa1100/start.S

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+/*
+ *  armboot - Startup Code for SA1100 CPU
+ *
+ *  Copyright (C) 1998	Dan Malek <dmalek@jlc.net>
+ *  Copyright (C) 1999	Magnus Damm <kieraypc01.p.y.kie.era.ericsson.se>
+ *  Copyright (C) 2000	Wolfgang Denk <wd@denx.de>
+ *  Copyright (c) 2001	Alex Züpke <azu@sysgo.de>
+ *
+ * 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!
+ * relocate armboot to ram
+ * setup stack
+ * jump to second stage
+ *
+ *************************************************************************
+ */
+
+	.globl	reset
+
+reset:
+	/*
+	 * set the cpu to SVC32 mode
+	 */
+	mrs	r0,cpsr
+	bic	r0,r0,#0x1f
+	orr	r0,r0,#0xd3
+	msr	cpsr,r0
+
+	/*
+	 * we do sys-critical inits only at reboot,
+	 * not when booting from ram!
+	 */
+#ifndef CONFIG_SKIP_LOWLEVEL_INIT
+	bl	cpu_init_crit
+#endif
+
+	bl	_main
+
+/*------------------------------------------------------------------------------*/
+
+	.globl	c_runtime_cpu_setup
+c_runtime_cpu_setup:
+
+	mov	pc, lr
+
+/*
+ *************************************************************************
+ *
+ * CPU_init_critical registers
+ *
+ * setup important registers
+ * setup memory timing
+ *
+ *************************************************************************
+ */
+
+
+/* Interrupt-Controller base address */
+IC_BASE:	.word	0x90050000
+#define ICMR	0x04
+
+
+/* Reset-Controller */
+RST_BASE:		.word   0x90030000
+#define RSRR	0x00
+#define RCSR	0x04
+
+
+/* PWR */
+PWR_BASE:		.word   0x90020000
+#define PSPR    0x08
+#define PPCR    0x14
+cpuspeed:		.word   CONFIG_SYS_CPUSPEED
+
+
+cpu_init_crit:
+	/*
+	 * mask all IRQs
+	 */
+	ldr	r0, IC_BASE
+	mov	r1, #0x00
+	str	r1, [r0, #ICMR]
+
+	/* set clock speed */
+	ldr	r0, PWR_BASE
+	ldr	r1, cpuspeed
+	str	r1, [r0, #PPCR]
+
+#ifndef CONFIG_SKIP_LOWLEVEL_INIT_ONLY
+	/*
+	 * before relocating, we have to setup RAM timing
+	 * because memory timing is board-dependend, you will
+	 * find a lowlevel_init.S in your board directory.
+	 */
+	mov	ip,	lr
+	bl	lowlevel_init
+	mov	lr,	ip
+#endif
+
+	/*
+	 * disable MMU stuff and enable I-cache
+	 */
+	mrc	p15,0,r0,c1,c0
+	bic	r0, r0, #0x00002000	@ clear bit 13 (X)
+	bic	r0, r0, #0x0000000f	@ clear bits 3-0 (WCAM)
+	orr	r0, r0, #0x00001000	@ set bit 12 (I) Icache
+	orr	r0, r0, #0x00000002	@ set bit 1 (A) Align
+	mcr	p15,0,r0,c1,c0
+
+	/*
+	 * flush v4 I/D caches
+	 */
+	mov	r0, #0
+	mcr	p15, 0, r0, c7, c7, 0	/* flush v3/v4 cache */
+	mcr	p15, 0, r0, c8, c7, 0	/* flush v4 TLB */
+
+	mov	pc, lr

u-boot/arch/arm/cpu/sa1100/timer.c

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+/*
+ * (C) Copyright 2002
+ * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
+ * Marius Groeger <mgroeger@sysgo.de>
+ *
+ * (C) Copyright 2002
+ * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
+ * Alex Zuepke <azu@sysgo.de>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <SA-1100.h>
+
+ulong get_timer (ulong base)
+{
+	return get_timer_masked ();
+}
+
+void __udelay (unsigned long usec)
+{
+	udelay_masked (usec);
+}
+
+ulong get_timer_masked (void)
+{
+	return OSCR;
+}
+
+void udelay_masked (unsigned long usec)
+{
+	ulong tmo;
+	ulong endtime;
+	signed long diff;
+
+	if (usec >= 1000) {
+		tmo = usec / 1000;
+		tmo *= CONFIG_SYS_HZ;
+		tmo /= 1000;
+	} else {
+		tmo = usec * CONFIG_SYS_HZ;
+		tmo /= (1000*1000);
+	}
+
+	endtime = get_timer_masked () + tmo;
+
+	do {
+		ulong now = get_timer_masked ();
+		diff = endtime - now;
+	} while (diff >= 0);
+}
+
+/*
+ * This function is derived from PowerPC code (read timebase as long long).
+ * On ARM it just returns the timer value.
+ */
+unsigned long long get_ticks(void)
+{
+	return get_timer(0);
+}
+
+/*
+ * This function is derived from PowerPC code (timebase clock frequency).
+ * On ARM it returns the number of timer ticks per second.
+ */
+ulong get_tbclk (void)
+{
+	ulong tbclk;
+
+	tbclk = CONFIG_SYS_HZ;
+	return tbclk;
+}