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role="treeitem" aria-expanded="false"><div data-tocid="chapter-memory-d4445e4054" class="topicref" data-id="chapter-memory" data-state="not-ready"><span role="button" tabindex="0" aria-labelledby="button-expand-action chapter-memory-d4445e4054-link" class="wh-expand-btn"></span><div class="title"><a href="../../../topics/chapter-title/chapter-memory-sdk.html" id="chapter-memory-d4445e4054-link">存储</a><div class="wh-tooltip"><p class="shortdesc">SDMC、SPI NAND、SPI NOR 等存储模块的介绍和使用说明。</p></div></div></div></li><li role="treeitem" aria-expanded="false"><div data-tocid="concept_mcc_32s_nbc-d4445e4438" class="topicref" data-id="concept_mcc_32s_nbc" data-state="not-ready"><span role="button" tabindex="0" aria-labelledby="button-expand-action concept_mcc_32s_nbc-d4445e4438-link" class="wh-expand-btn"></span><div class="title"><a href="../../../topics/chapter-title/chapter-multi-media-sdk.html" id="concept_mcc_32s_nbc-d4445e4438-link">多媒体</a><div class="wh-tooltip"><p class="shortdesc">GE、VE、Display、DVP、MPP、MPP 播放器等多媒体模块的介绍和使用说明。</p></div></div></div></li><li role="treeitem" aria-expanded="false"><div data-tocid="concept_nww_hzh_pzb-d4445e5947" class="topicref" data-id="concept_nww_hzh_pzb" data-state="not-ready"><span role="button" tabindex="0" aria-labelledby="button-expand-action concept_nww_hzh_pzb-d4445e5947-link" class="wh-expand-btn"></span><div class="title"><a href="../../../topics/chapter-title/chapter-interface-sdk.html" id="concept_nww_hzh_pzb-d4445e5947-link">接口</a><div class="wh-tooltip"><p class="shortdesc">CAN、CIR、GPAI、GPIO、I2C、PSADC、PWM 等接口模块的介绍和使用说明。</p></div></div></div></li><li role="treeitem" aria-expanded="false"><div data-tocid="chapter-safety-d4445e7944" class="topicref" data-id="chapter-safety" data-state="not-ready"><span role="button" tabindex="0" aria-labelledby="button-expand-action chapter-safety-d4445e7944-link" class="wh-expand-btn"></span><div class="title"><a 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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">
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<span class="edit-link" style="font-size:12px; opacity:0.6; text-align:right; vertical-align:middle"><a target="_blank" title="Edit this document" href="http://172.16.35.88/tasks/jdssno1uvvbf2mltu9kb9v3if05d5gopuakboe8hlud18rma/edit/F:/aicdita/aicdita-cn/topics/sdk/boot/uboot-load-env-variables.dita">Edit online</a></span><h1 class="- topic/title title topictitle1" id="ariaid-title1">环境变量加载</h1>
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<div class="date inPage">15 Jan 2024</div><div style="color: gray;">
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Read time: 2 minute(s)
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</div>
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<div class="- topic/body concept/conbody body conbody">
|
||
<div class="- topic/p p" data-ofbid="d148996e33__20250123155214">
|
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<div class="- topic/div div">
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<p class="- topic/p p" data-ofbid="d148996e37__20250123155214">如前面所述，环境变量的处理有两个阶段：</p>
|
||
<ol class="- topic/ol ol" id="concept_tyf_bm3_pzb__ol_vng_wbh_bzb" data-ofbid="concept_tyf_bm3_pzb__ol_vng_wbh_bzb">
|
||
<li class="- topic/li li" data-ofbid="d148996e42__20250123155214">
|
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<p class="- topic/p p" data-ofbid="d148996e44__20250123155214">环境变量初始</p>
|
||
</li>
|
||
<li class="- topic/li li" data-ofbid="d148996e48__20250123155214">
|
||
<p class="- topic/p p" data-ofbid="d148996e50__20250123155214">环境变量读取</p>
|
||
</li>
|
||
</ol>
|
||
<div class="- topic/p p" data-ofbid="d148996e55__20250123155214">如下面的调用流程， <span class="+ topic/keyword pr-d/apiname keyword apiname">env_init()</span> 在 <span class="+ topic/keyword pr-d/apiname keyword apiname">board_init_f()</span>
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阶段执行，但具体的加载过程 在 <span class="+ topic/keyword pr-d/apiname keyword apiname">board_init_r()</span>
|
||
阶段执行。<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_tyf_bm3_pzb__codeblock_fkq_nmr_c1c" data-ofbid="concept_tyf_bm3_pzb__codeblock_fkq_nmr_c1c"><code>reset <em class="hl-comment">// arch/riscv/cpu/start.S</em>
|
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|-> save_boot_params <em class="hl-comment">// arch/riscv/mach-artinchip/lowlevel_init.S</em>
|
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|-> ...
|
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|-> board_init_f(); <em class="hl-comment">// common/board_f.c</em>
|
||
|-> setup_reloc(); <em class="hl-comment">// common/board_f.c</em>
|
||
|-> jump_to_copy(); <em class="hl-comment">// common/board_f.c</em>
|
||
|-> relocate_code(); <em class="hl-comment">// arch/riscv/cpu/start.S</em>
|
||
|-> invalidate_icache_all()
|
||
|-> flush_dcache_all()
|
||
|-> board_init_r();
|
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| <em class="hl-comment">// 逐个调用 init_sequence_r 里面的函数，其中包括 initr_env</em>
|
||
|-> initr_env(); <em class="hl-comment">// common/board_r.c</em>
|
||
|-> should_load_env(<strong class="hl-keyword">void</strong>);<em class="hl-comment">// common/board_r.c</em>
|
||
| <em class="hl-comment">// 由于没有在 DTS 中进行配置，总是返回 1</em>
|
||
| <em class="hl-comment">// fdtdec_get_config_int(gd->fdt_blob, "load-environment", 1);</em>
|
||
|-> env_relocate(); <em class="hl-comment">// env/common.c</em>
|
||
|-> env_load(); <em class="hl-comment">// env/env.c</em></code></pre></div>
|
||
<p class="- topic/p p" data-ofbid="d148996e69__20250123155214">U-Boot 支持在多种存储介质中保存环境变量，并且提供了一个插拔式的机制，用于实现从 不同的存储介质中加载环境变量内容。</p>
|
||
<div class="- topic/p p" data-ofbid="d148996e72__20250123155214">在添加新的环境变量加载器时，只需要实现对应存储介质的 <span class="+ topic/keyword pr-d/apiname keyword apiname">load</span> 和 <span class="+ topic/keyword pr-d/apiname keyword apiname">save</span> 函数，
|
||
然后通过宏 <span class="+ topic/keyword pr-d/apiname keyword apiname">U_BOOT_ENV_LOCATION</span> 将对应的信息添加到
|
||
<code class="+ topic/ph pr-d/codeph ph codeph">.u_boot_list_2</code> 链接段中。 比如下面的定义，将生成
|
||
<code class="+ topic/ph pr-d/codeph ph codeph">.u_boot_list_2_env_driver_2_spinand</code>
|
||
信息。<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_tyf_bm3_pzb__codeblock_djh_4mr_c1c" data-ofbid="concept_tyf_bm3_pzb__codeblock_djh_4mr_c1c"><code>U_BOOT_ENV_LOCATION(spinand) = {
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||
.location = ENVL_SPINAND,
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||
ENV_NAME(<span class="hl-string">"SPINAND"</span>)
|
||
.load = env_spinand_load,
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||
#<strong class="hl-keyword">if</strong> defined(CMD_SAVEENV)
|
||
.save = env_save_ptr(env_spinand_save),
|
||
#endif
|
||
};</code></pre></div>
|
||
<div class="- topic/p p" data-ofbid="d148996e94__20250123155214"><span class="+ topic/keyword pr-d/apiname keyword apiname">env_driver_lookup()</span> 函数首先通过检查当前的启动设备，然后从
|
||
<code class="+ topic/ph pr-d/codeph ph codeph">.u_boot_list_2</code> 段中查找对应启动设备的 ENV
|
||
加载驱动，最后调用对应的驱动读取并导入环境变量内容。<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="concept_tyf_bm3_pzb__codeblock_jd5_4mr_c1c" data-ofbid="concept_tyf_bm3_pzb__codeblock_jd5_4mr_c1c"><code>env_load(); <em class="hl-comment">// env/env.c</em>
|
||
|-> env_driver_lookup(ENVOP_LOAD, prio);
|
||
| |-> loc = env_get_location(); <em class="hl-comment">// board/artinchip/d211/env_location.c</em>
|
||
| | |-> bd = aic_get_boot_device(); <em class="hl-comment">// 获取当前的启动设备</em>
|
||
| |
|
||
| |-> _env_driver_lookup(loc);
|
||
| |-> drv = ll_entry_start();
|
||
| <em class="hl-comment">// 查找指定存储介质的 env 加载驱动</em>
|
||
|
|
||
|-> drv->load();
|
||
<em class="hl-comment">// 此处调用个存储介质的对应函数</em>
|
||
env_ram_load(); <em class="hl-comment">// board/artinchip/d211/env_location.c</em>
|
||
env_spinand_load(); <em class="hl-comment">// env/spinand.c</em>
|
||
env_sf_load(); <em class="hl-comment">// env/sf.c</em>
|
||
env_mmc_load(); <em class="hl-comment">// env/mmc.c</em></code></pre></div>
|
||
<p class="- topic/p p" data-ofbid="d148996e104__20250123155214">具体各种存储介质中，环境变量保存的位置可参考<a xml:lang="zh-CN" lang="zh-CN" class="- topic/xref xref" href="save-env-variable-on-memory-medium.html">存储介质上的保存</a>。</p>
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