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--- u-boot_boot_sequence [2019/12/27 17:39] – rpjday
+++ u-boot_boot_sequence [2019/12/28 08:33] (current) – [1.] rpjday
@@ Line 19: / Line 19: @@
 ===== arch/arm/lib/crt0_64.S [ENTRY(_main)] =====
+==== Prologue ====
+<code>
+ * 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.
+</code>
-===== common/board_f.c =====
+==== 1. ====
-===== common/board_r.c (only most common) =====
+<code>
+ * 1. Set up initial environment for calling board_init_f().
-==== initr_dm() [C] ====
+ *    This environment only provides a stack and a place to store
-==== board_init() [A,B] ====
+ *    the GD ('global data') structure, both located in some readily
+ *    available RAM (SRAM, locked cache...). In this context, VARIABLE
-==== board_early_init_r() (not for Zynq) ====
+ *    global data, initialized or not (BSS), are UNAVAILABLE; only
+ *    CONSTANT initialized data are available. GD should be zeroed
-==== arch_early_init_r() [A] ====
+ *    before board_init_f() is called.
+</code>
-  * arch/arm/mach-zynq/cpu.c
-  * arch/arm/mach-zynq/spl.c
 <code>
-#if defined(CONFIG_ARCH_EARLY_INIT_R)
+ENTRY(_main)
-int arch_early_init_r(void)
-{
-#if (defined(CONFIG_FPGA) && !defined(CONFIG_SPL_BUILD)) || \
-    (defined(CONFIG_SPL_FPGA_SUPPORT) && defined(CONFIG_SPL_BUILD))
-        int cpu_id = cpu_desc_id();
-        if (cpu_id < 0)
+/*
-                return 0;
+ * Set up initial C runtime environment and call board_init_f(0).
+ */
-        fpga.size = zynq_fpga_descs[cpu_id].fpga_size;
+#if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK)
-        fpga.name = zynq_fpga_descs[cpu_id].devicename;
+        ldr     x0, =(CONFIG_TPL_STACK)
-        fpga_init();
+#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
-        fpga_add(fpga_xilinx, &fpga);
+        ldr     x0, =(CONFIG_SPL_STACK)
-#endif
+#elif defined(CONFIG_INIT_SP_RELATIVE)
-        return 0;
+        adr     x0, __bss_start
-}
+        add     x0, x0, #CONFIG_SYS_INIT_SP_BSS_OFFSET
+#else
+        ldr     x0, =(CONFIG_SYS_INIT_SP_ADDR)
 #endif
+        bic     sp, x0, #0xf    /* 16-byte alignment for ABI compliance */
+        mov     x0, sp
+        bl      board_init_f_alloc_reserve
+        mov     sp, x0
+        /* set up gd here, outside any C code */
+        mov     x18, x0
+        bl      board_init_f_init_reserve
 </code>
-==== initr_mmc() [C] ====
+==== 2. ====
 <code>
-#ifdef CONFIG_MMC
+ * 2. Call board_init_f(). This function prepares the hardware for
-static int initr_mmc(void)
+ *    execution from system RAM (DRAM, DDR...) As system RAM may not
-{
+ *    be available yet, , board_init_f() must use the current GD to
-        puts("MMC:   ");
+ *    store any data which must be passed on to later stages. These
-        mmc_initialize(gd->bd);
+ *    data include the relocation destination, the future stack, and
-        return 0;
+ *    the future GD location.
-}
-#endif
 </code>
-==== initr_env() [C] ====
 <code>
-static int initr_env(void)
+        mov     x0, #0
-{
+        bl      board_init_f
-        /* initialize environment */
+</code>
-        if (should_load_env())
-                env_relocate();
-        else
-                set_default_env(NULL, 0);
-#ifdef CONFIG_OF_CONTROL
-        env_set_hex("fdtcontroladdr",
-                    (unsigned long)map_to_sysmem(gd->fdt_blob));
-#endif
-        /* Initialize from environment */
+==== 3. ====
-        load_addr = env_get_ulong("loadaddr", 16, load_addr);
-        return 0;
+<code>
-}
+ * 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.
 </code>
-==== show_board_info() [C] ====
-From ''common/board_info.c'':
 <code>
-int __weak checkboard(void)
+#if !defined(CONFIG_SPL_BUILD)
-{
-        return 0;
-}
 /*
- * If the root node of the DTB has a "model" property, show it.
+ * Set up intermediate environment (new sp and gd) and call
- * Then call checkboard().
+ * relocate_code(addr_moni). Trick here is that we'll return
+ * 'here' but relocated.
  */
-int __weak show_board_info(void)
+        ldr     x0, [x18, #GD_START_ADDR_SP]    /* x0 <- gd->start_addr_sp */
-{
+        bic     sp, x0, #0xf    /* 16-byte alignment for ABI compliance */
-#ifdef CONFIG_OF_CONTROL
+        ldr     x18, [x18, #GD_NEW_GD]          /* x18 <- gd->new_gd */
-        DECLARE_GLOBAL_DATA_PTR;
-        const char *model;
-        model = fdt_getprop(gd->fdt_blob, 0, "model", NULL);
+        adr     lr, relocation_return
+#if CONFIG_POSITION_INDEPENDENT
-        if (model)
+        /* Add in link-vs-runtime offset */
-                printf("Model: %s\n", model);
+        adr     x0, _start              /* x0 <- Runtime value of _start */
+        ldr     x9, _TEXT_BASE          /* x9 <- Linked value of _start */
+        sub     x9, x9, x0              /* x9 <- Run-vs-link offset */
+        add     lr, lr, x9
 #endif
+        /* Add in link-vs-relocation offset */
-        return checkboard();
+        ldr     x9, [x18, #GD_RELOC_OFF]        /* x9 <- gd->reloc_off */
-}
+        add     lr, lr, x9      /* new return address after relocation */
+        ldr     x0, [x18, #GD_RELOCADDR]        /* x0 <- gd->relocaddr */
 </code>
+==== 4a. ====
-For ''zynqmp.c'':
+<code>
+ * 4a.For U-Boot proper (not SPL), call relocate_code(). This function
+ *    relocates U-Boot from its current location into the relocation
+ *    destination computed by board_init_f().
+</code>
 <code>
-int checkboard(void)
+        b       relocate_code
-{
-        puts("Board: Xilinx ZynqMP\n");
+relocation_return:
-        return 0;
-}
 </code>
-==== arch_misc_init() ====
+==== 4b. ====
-Some arches and boards, not Zynq.
 <code>
-#ifdef CONFIG_ARCH_MISC_INIT
+ * 4b.For SPL, board_init_f() just returns (to crt0). There is no
-        arch_misc_init,
+ *    code relocation in SPL.
-#endif
 </code>
-==== misc_init_r() ====
+==== 5. ====
 <code>
-#ifdef CONFIG_MISC_INIT_R
+ * 5. Set up final environment for calling board_init_r(). This
-        misc_init_r,
+ *    environment has BSS (initialized to 0), initialized non-const
-#endif
+ *    data (initialized to their intended value), and stack in system
+ *    RAM (for SPL moving the stack and GD into RAM is optional - see
+ *    CONFIG_SPL_STACK_R). GD has retained values set by board_init_f().
 </code>
-==== initr_enable_interrupts() ====
+==== 6. ====
 <code>
-#ifdef CONFIG_ARM
+ * 6. For U-Boot proper (not SPL), some CPUs have some work left to do
-static int initr_enable_interrupts(void)
+ *    at this point regarding memory, so call c_runtime_cpu_setup.
-{
-        enable_interrupts();
-        return 0;
-}
-#endif
 </code>
-From ''arch/arm/lib/interrupts.c'':
 <code>
-int interrupt_init (void)
+/*
-{
+ * Set up final (full) environment
+ */
+        bl      c_runtime_cpu_setup             /* still call old routine */
+#endif /* !CONFIG_SPL_BUILD */
+#if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK)
+#if defined(CONFIG_SPL_BUILD)
+        bl      spl_relocate_stack_gd           /* may return NULL */
+        /* set up gd here, outside any C code, if new stack is returned */
+        cmp     x0, #0
+        csel    x18, x0, x18, ne
         /*
-         * setup up stacks if necessary
+         * Perform 'sp = (x0 != NULL) ? x0 : sp' while working
+         * around the constraint that conditional moves can not
+         * have 'sp' as an operand
          */
-        IRQ_STACK_START_IN = gd->irq_sp + 8;
+        mov     x1, sp
+        cmp     x0, #0
+        csel    x0, x0, x1, ne
+        mov     sp, x0
+#endif
-        return 0;
+/*
-}
+ * Clear BSS section
+ */
+        ldr     x0, =__bss_start                /* this is auto-relocated! */
+        ldr     x1, =__bss_end                  /* this is auto-relocated! */
+clear_loop:
+        str     xzr, [x0], #8
+        cmp     x0, x1
+        b.lo    clear_loop
-void enable_interrupts (void)
+        /* call board_init_r(gd_t *id, ulong dest_addr) */
-{
+        mov     x0, x18                         /* gd_t */
-        return;
+        ldr     x1, [x18, #GD_RELOCADDR]        /* dest_addr */
-}
-int disable_interrupts (void)
-{
-        return 0;
-}
 </code>
-==== initr_ethaddr() [C] ====
+==== 7. ====
 <code>
-#ifdef CONFIG_CMD_NET
+ * 7. Branch to board_init_r().
-        initr_ethaddr,
-#endif
 </code>
 <code>
-#ifdef CONFIG_CMD_NET
+        b       board_init_r                    /* PC relative jump */
-static int initr_ethaddr(void)
-{
-        bd_t *bd = gd->bd;
-        /* kept around for legacy kernels only ... ignore the next section */
+        /* NOTREACHED - board_init_r() does not return */
-        eth_env_get_enetaddr("ethaddr", bd->bi_enetaddr);
-#ifdef CONFIG_HAS_ETH1
-        eth_env_get_enetaddr("eth1addr", bd->bi_enet1addr);
-#endif
-#ifdef CONFIG_HAS_ETH2
-        eth_env_get_enetaddr("eth2addr", bd->bi_enet2addr);
-#endif
-#ifdef CONFIG_HAS_ETH3
-        eth_env_get_enetaddr("eth3addr", bd->bi_enet3addr);
-#endif
-#ifdef CONFIG_HAS_ETH4
-        eth_env_get_enetaddr("eth4addr", bd->bi_enet4addr);
-#endif
-#ifdef CONFIG_HAS_ETH5
-        eth_env_get_enetaddr("eth5addr", bd->bi_enet5addr);
-#endif
-        return 0;
-}
-#endif /* CONFIG_CMD_NET */
 </code>
-==== board_late_init() [B] ====
+===== common/board_f.c =====
-(Defined in board/xilinx/zynq/board.c.)
 <code>
-#ifdef CONFIG_BOARD_LATE_INIT
+void board_init_f(ulong boot_flags)
-        board_late_init,
+{
-#endif
+        gd->flags = boot_flags;
+        gd->have_console = 0;
+        if (initcall_run_list(init_sequence_f))
+                hang();
+                ...
 </code>
-==== initr_net() ====
+===== common/board_r.c =====
 <code>
-#ifdef CONFIG_CMD_NET
+void board_init_r(gd_t *new_gd, ulong dest_addr)
-static int initr_net(void)
 {
-        puts("Net:   ");
+        /*
-        eth_initialize();
+         * Set up the new global data pointer. So far only x86 does this
-#if defined(CONFIG_RESET_PHY_R)
+         * here.
-        debug("Reset Ethernet PHY\n");
+         * TODO(sjg@chromium.org): Consider doing this for all archs, or
-        reset_phy();
+         * dropping the new_gd parameter.
+         */
+#if CONFIG_IS_ENABLED(X86_64)
+        arch_setup_gd(new_gd);
 #endif
-        return 0;
-}
+#ifdef CONFIG_NEEDS_MANUAL_RELOC
+        int i;
 #endif
-</code>
+#if !defined(CONFIG_X86) && !defined(CONFIG_ARM) && !defined(CONFIG_ARM64)
+        gd = new_gd;
+#endif
+        gd->flags &= ~GD_FLG_LOG_READY;
+#ifdef CONFIG_NEEDS_MANUAL_RELOC
+        for (i = 0; i < ARRAY_SIZE(init_sequence_r); i++)
+                init_sequence_r[i] += gd->reloc_off;
+#endif
+        if (initcall_run_list(init_sequence_r))
+                hang();
+        /* NOTREACHED - run_main_loop() does not return */
+        hang();
+</code>