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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/sdmc/sdmc-request-processing-procedures.dita">Edit online</a></span><h1 class="- topic/title title topictitle1" id="ariaid-title1">请求处理流程</h1><div class="date inPage">15 Nov 2024</div><div style="color: gray;">
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Read time: 1 minute(s)
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</div><div class="- topic/body concept/conbody body conbody"><p class="- topic/p p" data-ofbid="d338647e23__20250121171855">对于应用程序，通过读写的接口访问文件系统，文件系统访问块设备，MMC 设备在内核中被注册为一个块设备，当读写的操作传入到 MMC 块设备后，通过 MMC 子系统处理相关操作，对于 MMC 子系统其处理皆以请求的方式实现。</p><section class="- topic/section section" id="sdmc_request_processing_procedures__section_dmm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__section_dmm_gst_c1c"><h2 class="- topic/title title sectiontitle">块层以上系统读写调用流程</h2>
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<p class="- topic/p p" data-ofbid="d338647e30__20250121171855">在块层以上，通常是用户空间调用读写接口访问 MMC 设备，主要流程如下：</p>
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<figure class="- topic/fig fig fignone" id="sdmc_request_processing_procedures__fig_ltk_kst_c1c" data-ofbid="sdmc_request_processing_procedures__fig_ltk_kst_c1c"><br/><div class="imagecenter"><img class="- topic/image image imagecenter" id="sdmc_request_processing_procedures__image_emm_gst_c1c" src="../../../images/memory/blkdev_access_flow.png" alt="blkdev_access_flow"/></div><br/><figcaption data-caption-side="bottom" class="- topic/title title figcapcenter"><span class="figtitleprefix fig--title-label">图<span class="fig--title-label-number"> 1</span><span class="fig--title-label-punctuation">. </span></span><span class="fig--title">通用块设备的访问流程</span></figcaption></figure>
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<ol class="- topic/ol ol" id="sdmc_request_processing_procedures__ol_fmm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__ol_fmm_gst_c1c"><li class="- topic/li li" data-ofbid="d338647e41__20250121171855">在用户空间，应用程序调用 read/write 接口</li><li class="- topic/li li" data-ofbid="d338647e43__20250121171855">然后通过虚拟文件系统</li><li class="- topic/li li" data-ofbid="d338647e45__20250121171855">调用通用块层的接口对块设备进行 IO 请求</li><li class="- topic/li li" data-ofbid="d338647e47__20250121171855">IO 调度层负责使用特定算法对这些请求进行调度</li><li class="- topic/li li" data-ofbid="d338647e49__20250121171855">块设备驱动层调用具体的块设备接口访问设备</li></ol>
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</section><section class="- topic/section section" id="sdmc_request_processing_procedures__section_gmm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__section_gmm_gst_c1c"><h2 class="- topic/title title sectiontitle">MMC 子系统请求处理流程</h2>
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<p class="- topic/p p" data-ofbid="d338647e57__20250121171855">MMC 子系统被抽象成一个块设备，通用块层将 IO 请求调用到具体的块设备驱动层，在 MMC 块设备驱动中的请求处理流程如下：</p>
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<figure class="- topic/fig fig fignone" id="sdmc_request_processing_procedures__fig_fnt_3st_c1c" data-ofbid="sdmc_request_processing_procedures__fig_fnt_3st_c1c"><br/><div class="imagecenter"><img class="- topic/image image imagecenter" id="sdmc_request_processing_procedures__image_hmm_gst_c1c" src="../../../images/emmc/mmc_request_flow.png" alt="mmc_request_flow"/></div><br/><figcaption data-caption-side="bottom" class="- topic/title title figcapcenter"><span class="figtitleprefix fig--title-label">图<span class="fig--title-label-number"> 2</span><span class="fig--title-label-punctuation">. </span></span><span class="fig--title">MMC 数据请求的处理流程</span></figcaption></figure>
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<ol class="- topic/ol ol" id="sdmc_request_processing_procedures__ol_imm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__ol_imm_gst_c1c"><li class="- topic/li li" data-ofbid="d338647e68__20250121171855">由于会有多个请求，在 block 中以队列的形式处理，在请求到达时，唤醒 mmc_queue_thread。</li><li class="- topic/li li" data-ofbid="d338647e70__20250121171855">调用 block 的请求处理，发出 request。</li><li class="- topic/li li" data-ofbid="d338647e72__20250121171855">block 的 request 会由 core 来实现。</li><li class="- topic/li li" data-ofbid="d338647e74__20250121171855">core 层会根据当前 host 驱动调用对应 host 的 ops 中的 request 接口去操作 controller。</li></ol>
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<p class="- topic/p p" data-ofbid="d338647e77__20250121171855">函数调用关系：</p>
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<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="sdmc_request_processing_procedures__pre_jmm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__pre_jmm_gst_c1c">mmc_wait_for_req
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|--__mmc_start_req
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|--init_completion
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|--mmc_start_request
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|--mmc_mrq_prep
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|--__mmc_start_request
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|--trace_mmc_request_start
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|--host->ops->request （即 request）
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</pre>
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</section><section class="- topic/section section" id="sdmc_request_processing_procedures__section_kmm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__section_kmm_gst_c1c"><h2 class="- topic/title title sectiontitle">Host 层驱动请求处理流程</h2>
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<p class="- topic/p p" data-ofbid="d338647e89__20250121171855">在访问 MMC 外设时，都是通过发送 CMD 的方式，在 host 层驱动中需要通过操作 controller 去实现 core 层的 request，主要流程如下：</p>
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<figure class="- topic/fig fig fignone" id="sdmc_request_processing_procedures__fig_zkr_hst_c1c" data-ofbid="sdmc_request_processing_procedures__fig_zkr_hst_c1c"><br/><div class="imagecenter"><img class="- topic/image image imagecenter" id="sdmc_request_processing_procedures__image_lmm_gst_c1c" src="../../../images/sdmc/host_request_flow.png" alt="host_request_flow"/></div><br/><figcaption data-caption-side="bottom" class="- topic/title title figcapcenter"><span class="figtitleprefix fig--title-label">图<span class="fig--title-label-number"> 3</span><span class="fig--title-label-punctuation">. </span></span><span class="fig--title">Host 层驱动的请求处理流程</span></figcaption></figure>
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<ol class="- topic/ol ol" id="sdmc_request_processing_procedures__ol_mmm_gst_c1c" data-ofbid="sdmc_request_processing_procedures__ol_mmm_gst_c1c"><li class="- topic/li li" data-ofbid="d338647e100__20250121171855">检测卡设备，需要判断当前卡设备是否被拔出。</li><li class="- topic/li li" data-ofbid="d338647e102__20250121171855">判断传输状态，如果当前传输状态不是 idle，那么将会将该请求放在请求队列里。</li><li class="- topic/li li" data-ofbid="d338647e104__20250121171855">处理 data，如果当前请求需要处理数据，则将数据先行处理，如果不需要处理数据则跳过。</li><li class="- topic/li li" data-ofbid="d338647e106__20250121171855">发送 CMD，解析请求中的 CMD 和参数，将其写入寄存器，然后触发 CMD 的发送。</li><li class="- topic/li li" data-ofbid="d338647e108__20250121171855">中断处理，在发送完 CMD 后，后续的工作需要等待中断的触发，在中断处理中会对外设返回的数据和状态进行处理。</li><li class="- topic/li li" data-ofbid="d338647e110__20250121171855">如果需要，发送 stop 命令，结束该次传输。</li></ol>
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<div class="- topic/p p" data-ofbid="d338647e113__20250121171855">Host 层函数调用关系：<pre class="+ topic/pre pr-d/codeblock pre codeblock language-c" id="sdmc_request_processing_procedures__codeblock_jrx_gst_c1c" data-ofbid="sdmc_request_processing_procedures__codeblock_jrx_gst_c1c">artinchip_mmc_request
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|--artinchip_mmc_get_cd
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|--artinchip_mmc_queue_request
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|--artinchip_mmc_start_request
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|--artinchip_mmc_prepare_command
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|--artinchip_mmc_submit_data
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|--artinchip_mmc_start_command
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|--artinchip_mmc_prep_stop_abort</pre></div>
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<div class=" wh_topic_toc "><div class="wh_topic_label">在本页上</div><ul><li class="section-item"><div class="section-title"><a href="#sdmc_request_processing_procedures__section_dmm_gst_c1c" data-tocid="sdmc_request_processing_procedures__section_dmm_gst_c1c">块层以上系统读写调用流程</a></div></li><li class="section-item"><div class="section-title"><a href="#sdmc_request_processing_procedures__section_gmm_gst_c1c" data-tocid="sdmc_request_processing_procedures__section_gmm_gst_c1c">MMC 子系统请求处理流程</a></div></li><li class="section-item"><div class="section-title"><a href="#sdmc_request_processing_procedures__section_kmm_gst_c1c" data-tocid="sdmc_request_processing_procedures__section_kmm_gst_c1c">Host 层驱动请求处理流程</a></div></li></ul></div>
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