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<div class=" wh_topic_content body "><main role="main"><article class="- topic/topic concept/concept topic concept" role="article" aria-labelledby="ariaid-title1"><span class="edit-link" style="font-size:12px; opacity:0.6; text-align:right; vertical-align:middle"><a target="_blank" href="http://172.16.35.88/tasks/jdssno1uvvbf2mltu9kb9v3if05d5gopuakboe8hlud18rma/edit/F:/aicdita/aicdita-cn/topics/sdk/boot/uboot-pre-init.dita">Edit online</a></span><h1 class="- topic/title title topictitle1" id="ariaid-title1">前初始化</h1><div class="date inPage">4 Dec 2024</div><div style="color: gray;">
Read time: 4 minute(s)
</div><div class="- topic/body concept/conbody body conbody"><p class="- topic/p p" data-ofbid="d212503e23__20250121171640">U-Boot 的前初始化是指执行代码重定位之前的初始化,此时 U-Boot 在 DRAM 的前端空间执行。</p><p class="- topic/p p" data-ofbid="d212503e25__20250121171640">前初始化分为两个阶段:</p><ol class="- topic/ol ol" id="concept_qh4_1l3_pzb__ol_y1p_sbh_bzb" data-ofbid="concept_qh4_1l3_pzb__ol_y1p_sbh_bzb"><li class="- topic/li li" data-ofbid="d212503e28__20250121171640">
<p class="- topic/p p" data-ofbid="d212503e30__20250121171640">芯片架构相关的初始化代码</p>
</li><li class="- topic/li li" data-ofbid="d212503e33__20250121171640">
<p class="- topic/p p" data-ofbid="d212503e35__20250121171640">板子相关的前初始化代码</p>
</li></ol><p class="- topic/p p" data-ofbid="d212503e38__20250121171640"><strong class="+ topic/ph hi-d/b ph b">阶段一:</strong> 芯片架构相关初始化</p><div class="- topic/p p" data-ofbid="d212503e42__20250121171640">这个阶段主要是对 CPU 进行了基本的初始化,并且将上一级引导程序传递过来的参数保存起来。 ArtInChip 平台上实现了对应的
<span class="+ topic/keyword pr-d/apiname keyword apiname">save_boot_params</span> 处理函数,并且将调用现场的关键寄存器信息保存到
<span class="+ topic/keyword pr-d/apiname keyword apiname">boot_params_stash</span>
全局变量中。<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_qh4_1l3_pzb__codeblock_cqh_2mr_c1c" data-ofbid="concept_qh4_1l3_pzb__codeblock_cqh_2mr_c1c">_start <em class="hl-comment">// arch/riscv/cpu/start.S</em>
|-&gt; save_boot_params <em class="hl-comment">// arch/riscv/mach-artinchip/lowlevel_init.S</em>
| <em class="hl-comment">// BROM 或者 SPL 跳转到 U-Boot 执行的时候,传递了一些参数,这里首先将这</em>
| <em class="hl-comment">// 些参数保存起来。</em>
|
|-&gt; la t0, trap_entry <em class="hl-comment">// 设置异常处理</em>
|-&gt; li t1, CONFIG_SYS_INIT_SP_ADDR <em class="hl-comment">// 设置初始栈</em>
|-&gt; jal board_init_f_alloc_reserve
|-&gt; jal harts_early_init</pre></div><p class="- topic/p p" data-ofbid="d212503e52__20250121171640">后续的程序在需要了解当前的启动介质时,可以从中读取相关的信息。</p><div class="- topic/p p" data-ofbid="d212503e54__20250121171640"><strong class="+ topic/ph hi-d/b ph b">阶段二:</strong>
板子相关的前初始化<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_qh4_1l3_pzb__codeblock_ttw_fmr_c1c" data-ofbid="concept_qh4_1l3_pzb__codeblock_ttw_fmr_c1c">_start <em class="hl-comment">// arch/riscv/cpu/start.S</em>
|-&gt; save_boot_params <em class="hl-comment">// arch/riscv/mach-artinchip/lowlevel_init.S</em>
|-&gt; ...
|-&gt; la t5, board_init_f</pre></div><div class="- topic/p p" data-ofbid="d212503e60__20250121171640"><span class="+ topic/keyword pr-d/apiname keyword apiname">board_init_f()</span> 函数内逐个调用初始化函数列表 <span class="+ topic/keyword pr-d/apiname keyword apiname">init_sequence_f</span>
中的函数:<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_qh4_1l3_pzb__codeblock_zmq_gmr_c1c" data-ofbid="concept_qh4_1l3_pzb__codeblock_zmq_gmr_c1c"><strong class="hl-keyword">static</strong> <strong class="hl-keyword">const</strong> init_fnc_t init_sequence_f[] = {
setup_mon_len,
#ifdef CONFIG_OF_CONTROL
fdtdec_setup,
#endif
initf_malloc,
log_init,
initf_bootstage, <em class="hl-comment">/* uses its own timer, so does not need DM */</em>
setup_spl_handoff,
initf_console_record,
arch_cpu_init, <em class="hl-comment">/* basic arch cpu dependent setup */</em>
mach_cpu_init, <em class="hl-comment">/* SoC/machine dependent CPU setup */</em>
initf_dm,
arch_cpu_init_dm,
#<strong class="hl-keyword">if</strong> defined(CONFIG_BOARD_EARLY_INIT_F)
board_early_init_f,
#endif
env_init, <em class="hl-comment">/* initialize environment */</em>
init_baud_rate, <em class="hl-comment">/* initialze baudrate settings */</em>
serial_init, <em class="hl-comment">/* serial communications setup */</em>
console_init_f, <em class="hl-comment">/* stage 1 init of console */</em>
display_options, <em class="hl-comment">/* say that we are here */</em>
display_text_info, <em class="hl-comment">/* show debugging info if required */</em>
INIT_FUNC_WATCHDOG_INIT
#<strong class="hl-keyword">if</strong> defined(CONFIG_MISC_INIT_F)
misc_init_f,
#endif
INIT_FUNC_WATCHDOG_RESET
#<strong class="hl-keyword">if</strong> defined(CONFIG_SYS_I2C)
init_func_i2c,
#endif
announce_dram_init,
dram_init, <em class="hl-comment">/* configure available RAM banks */</em>
setup_dest_addr,
reserve_round_<span class="hl-number">4</span>k,
#ifdef CONFIG_ARM
reserve_mmu,
#endif
reserve_video,
reserve_trace,
reserve_uboot,
reserve_malloc,
reserve_board,
setup_machine,
reserve_global_data,
reserve_fdt,
reserve_bootstage,
reserve_bloblist,
reserve_arch,
reserve_stacks,
dram_init_banksize,
show_dram_config,
display_new_sp,
#ifdef CONFIG_OF_BOARD_FIXUP
fix_fdt,
#endif
INIT_FUNC_WATCHDOG_RESET
reloc_fdt,
reloc_bootstage,
reloc_bloblist,
setup_reloc,
NULL,
};</pre></div><p class="- topic/p p" data-ofbid="d212503e69__20250121171640">由于 DRAM 在 PBP 阶段已经初始化,这里的 <span class="+ topic/keyword pr-d/apiname keyword apiname">dram_init</span> 只是初始化 DRAM 驱动, 用于获取 DRAM 基本信息。</p><div class="- topic/p p" data-ofbid="d212503e74__20250121171640">DTS 相关的流程可参考 <span class="+ topic/keyword pr-d/apiname keyword apiname">fdtdec_setup</span><span class="+ topic/keyword pr-d/apiname keyword apiname">initf_dm</span>
<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_qh4_1l3_pzb__codeblock_f1d_dmr_c1c" data-ofbid="concept_qh4_1l3_pzb__codeblock_f1d_dmr_c1c">fdtdec_setup(); <em class="hl-comment">// lib/fdtdec.c</em>
|-&gt; gd-&gt;fdt_blob = board_fdt_blob_setup(); <em class="hl-comment">// lib/fdtdec.c</em>
| <em class="hl-comment">// 对于 U-Boot, DTB 的位置是 _end 开始的位置,此处加载 dtb</em>
|-&gt; fdtdec_prepare_fdt();
|-&gt; fdt_check_header(gd-&gt;fdt_blob);</pre><pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_qh4_1l3_pzb__codeblock_zhq_hmr_c1c" data-ofbid="concept_qh4_1l3_pzb__codeblock_zhq_hmr_c1c">initf_dm(); <em class="hl-comment">// common/board_f.c</em>
|-&gt; dm_init_and_scan(true); <em class="hl-comment">// drivers/core/root.c</em>
|-&gt; dm_init(IS_ENABLED(CONFIG_OF_LIVE)); <em class="hl-comment">// drivers/core/root.c</em>
|-&gt; dm_scan_platdata(pre_reloc_only=true);
|-&gt; dm_extended_scan_fdt(gd-&gt;fdt_blob, pre_reloc_only=true);
| |-&gt; dm_scan_fdt(blob, pre_reloc_only);
| | |-&gt; dm_scan_fdt_node(gd-&gt;dm_root, blob, <span class="hl-number">0</span>, true);
| | |-&gt; lists_bind_fdt(parent, offset_to_ofnode(offset), NULL,true);
| | | <em class="hl-comment">// drivers/core/lists.c</em>
| | | <em class="hl-comment">// 此阶段仅处理设置了 "u-boot,dm-pre-reloc" 的并且</em>
| | | <em class="hl-comment">// 对应驱动也是设置了 DM_FLAG_PRE_RELOC 的设备和驱动的绑定</em>
| | |
| | |-&gt; device_bind_with_driver_data(parent, entry, name,id-&gt;data,
| | | node, &amp;dev);
| | |-&gt; device_bind_common(...)
| | | <em class="hl-comment">// dev = calloc(1, sizeof(struct udevice));</em>
| | | <em class="hl-comment">//</em>
| | | <em class="hl-comment">// dev-&gt;platdata = platdata;</em>
| | | <em class="hl-comment">// dev-&gt;driver_data = driver_data;</em>
| | | <em class="hl-comment">// dev-&gt;name = name;</em>
| | | <em class="hl-comment">// dev-&gt;node = node;</em>
| | | <em class="hl-comment">// dev-&gt;parent = parent;</em>
| | | <em class="hl-comment">// dev-&gt;driver = drv;</em>
| | | <em class="hl-comment">// dev-&gt;uclass = uc;</em>
| | | <em class="hl-comment">// 创建 udevice并将 driver 挂上</em>
| | |
| | |-&gt; uclass_bind_device(dev);
| |-&gt; dm_scan_fdt_ofnode_path(<span class="hl-string">"/clocks"</span>, pre_reloc_only);
| |-&gt; dm_scan_fdt_ofnode_path(<span class="hl-string">"/firmware"</span>, pre_reloc_only);
|-&gt; dm_scan_other(pre_reloc_only);</pre></div><p class="- topic/p p" data-ofbid="d212503e86__20250121171640">此阶段并没有对 DTS 中列出的所有设备和驱动进行初始化处理,仅对标记了 “u-boot,dm-pre-reloc” 的设备, 以及驱动中标记了
DM_FLAG_PRE_RELOC 的驱动进行处理,以缩短这个阶段的处理时间。</p><div class="- topic/note note note note_note" id="concept_qh4_1l3_pzb__note_izk_5bh_bzb" data-ofbid="concept_qh4_1l3_pzb__note_izk_5bh_bzb"><span class="note__title">注:</span>
<p class="- topic/p p" data-ofbid="d212503e91__20250121171640">initf_dm 和 initr_dm 都会搜索一遍 DTB花费的时间比较多如果这里能够节省搜索的数量 对于快速启动会有比较大的帮助。</p>
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