--- /dev/null
+/*
+ * crt0 - C-runtime startup Code for ARM U-Boot
+ *
+ * Copyright (c) 2012 Albert ARIBAUD <albert.u.boot@aribaud.net>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <config.h>
+#include <asm-offsets.h>
+#include <linux/linkage.h>
+
+/*
+ * This file handles the target-independent stages of the U-Boot
+ * start-up where a C runtime environment is needed. Its entry point
+ * is _main and is branched into from the target's start.S file.
+ *
+ * _main execution sequence is:
+ *
+ * 1. Set up initial environment for calling board_init_f().
+ * This environment only provides a stack and a place to store
+ * the GD ('global data') structure, both located in some readily
+ * available RAM (SRAM, locked cache...). In this context, VARIABLE
+ * global data, initialized or not (BSS), are UNAVAILABLE; only
+ * CONSTANT initialized data are available.
+ *
+ * 2. Call board_init_f(). This function prepares the hardware for
+ * execution from system RAM (DRAM, DDR...) As system RAM may not
+ * be available yet, , board_init_f() must use the current GD to
+ * store any data which must be passed on to later stages. These
+ * data include the relocation destination, the future stack, and
+ * the future GD location.
+ *
+ * (the following applies only to non-SPL builds)
+ *
+ * 3. Set up intermediate environment where the stack and GD are the
+ * ones allocated by board_init_f() in system RAM, but BSS and
+ * initialized non-const data are still not available.
+ *
+ * 4. Call relocate_code(). This function relocates U-Boot from its
+ * current location into the relocation destination computed by
+ * board_init_f().
+ *
+ * 5. Set up final environment for calling board_init_r(). This
+ * environment has BSS (initialized to 0), initialized non-const
+ * data (initialized to their intended value), and stack in system
+ * RAM. GD has retained values set by board_init_f(). Some CPUs
+ * have some work left to do at this point regarding memory, so
+ * call c_runtime_cpu_setup.
+ *
+ * 6. Branch to board_init_r().
+ */
+
+/*
+ * entry point of crt0 sequence
+ */
+
+ENTRY(_main)
+
+/*
+ * Set up initial C runtime environment and call board_init_f(0).
+ */
+
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
+ ldr sp, =(CONFIG_SPL_STACK)
+#else
+ ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
+#endif
+ bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
+ sub sp, sp, #GD_SIZE /* allocate one GD above SP */
+ bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
+ mov r9, sp /* GD is above SP */
+ mov r0, #0
+ bl board_init_f
+
+#if ! defined(CONFIG_SPL_BUILD)
+
+/*
+ * Set up intermediate environment (new sp and gd) and call
+ * relocate_code(addr_moni). Trick here is that we'll return
+ * 'here' but relocated.
+ */
+
+ ldr sp, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */
+ bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
+ ldr r9, [r9, #GD_BD] /* r9 = gd->bd */
+ sub r9, r9, #GD_SIZE /* new GD is below bd */
+
+ adr lr, here
+ ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */
+ add lr, lr, r0
+ ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
+ b relocate_code
+here:
+
+/* Set up final (full) environment */
+
+ bl c_runtime_cpu_setup /* we still call old routine here */
+
+ ldr r0, =__bss_start /* this is auto-relocated! */
+ ldr r1, =__bss_end /* this is auto-relocated! */
+
+ mov r2, #0x00000000 /* prepare zero to clear BSS */
+
+clbss_l:cmp r0, r1 /* while not at end of BSS */
+ strlo r2, [r0] /* clear 32-bit BSS word */
+ addlo r0, r0, #4 /* move to next */
+ blo clbss_l
+
+ bl coloured_LED_init
+ bl red_led_on
+
+ /* call board_init_r(gd_t *id, ulong dest_addr) */
+ mov r0, r9 /* gd_t */
+ ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */
+ /* call board_init_r */
+ ldr pc, =board_init_r /* this is auto-relocated! */
+
+ /* we should not return here. */
+
+#endif
+
+ENDPROC(_main)
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