详解linux 驱动编写（sd卡驱动）
<p>随着sd卡的流行，sd卡在嵌入式设备上使用的场景也越来越多。那下面我们可以看一下，linux驱动框架上是怎么处理sd卡驱动的？</p>
<p>
1、代码目录地址</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterplain" id="highlighter_229448">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="plain plain">drivers/mmc</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
2、基本结构</p>
<p>
从mmc的代码结构可以看得出，主要分为两个部分，其中core为协议部分，host为各个soc的适配部分</p>
<p>
host是我们需要真正关心的代码</p>
<p>
3、以s3c为例，观察makefile</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterplain" id="highlighter_463098">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="plain plain">obj-$(CONFIG_MMC_SDHCI_S3C) += sdhci-s3c.o </code>
</div>
<div class="line number2 index1 alt1">
<code class="plain plain">...... </code>
</div>
<div class="line number3 index2 alt2">
<code class="plain plain">obj-$(CONFIG_MMC_S3C) += s3cmci.o</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
4、根据s3c阅读Kconfig，确认s3c下的sd卡还依赖哪些文件</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterplain" id="highlighter_730595">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
<div class="line number9 index8 alt2">
9</div>
<div class="line number10 index9 alt1">
10</div>
<div class="line number11 index10 alt2">
11</div>
<div class="line number12 index11 alt1">
12</div>
<div class="line number13 index12 alt2">
13</div>
<div class="line number14 index13 alt1">
14</div>
<div class="line number15 index14 alt2">
15</div>
<div class="line number16 index15 alt1">
16</div>
<div class="line number17 index16 alt2">
17</div>
<div class="line number18 index17 alt1">
18</div>
<div class="line number19 index18 alt2">
19</div>
<div class="line number20 index19 alt1">
20</div>
<div class="line number21 index20 alt2">
21</div>
<div class="line number22 index21 alt1">
22</div>
<div class="line number23 index22 alt2">
23</div>
<div class="line number24 index23 alt1">
24</div>
<div class="line number25 index24 alt2">
25</div>
<div class="line number26 index25 alt1">
26</div>
<div class="line number27 index26 alt2">
27</div>
<div class="line number28 index27 alt1">
28</div>
<div class="line number29 index28 alt2">
29</div>
<div class="line number30 index29 alt1">
30</div>
<div class="line number31 index30 alt2">
31</div>
<div class="line number32 index31 alt1">
32</div>
<div class="line number33 index32 alt2">
33</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="plain plain">config MMC_SDHCI_S3C </code>
</div>
<div class="line number2 index1 alt1">
<code class="plain spaces"> </code><code class="plain plain">tristate "SDHCI support on Samsung S3C SoC" </code>
</div>
<div class="line number3 index2 alt2">
<code class="plain spaces"> </code><code class="plain plain">depends on MMC_SDHCI && PLAT_SAMSUNG </code>
</div>
<div class="line number4 index3 alt1">
<code class="plain spaces"> </code><code class="plain plain">help </code>
</div>
<div class="line number5 index4 alt2">
<code class="plain spaces"> </code><code class="plain plain">This selects the Secure Digital Host Controller Interface (SDHCI) </code>
</div>
<div class="line number6 index5 alt1">
<code class="plain spaces"> </code><code class="plain plain">often referrered to as the HSMMC block in some of the Samsung S3C </code>
</div>
<div class="line number7 index6 alt2">
<code class="plain spaces"> </code><code class="plain plain">range of SoC. </code>
</div>
<div class="line number8 index7 alt1">
<code class="plain spaces"> </code>
</div>
<div class="line number9 index8 alt2">
<code class="plain spaces"> </code><code class="plain plain">If you have a controller with this interface, say Y or M here. </code>
</div>
<div class="line number10 index9 alt1">
<code class="plain spaces"> </code>
</div>
<div class="line number11 index10 alt2">
<code class="plain spaces"> </code><code class="plain plain">If unsure, say N. </code>
</div>
<div class="line number12 index11 alt1">
<code class="plain spaces"> </code>
</div>
<div class="line number13 index12 alt2">
<code class="plain plain">config MMC_SDHCI_S3C_DMA </code>
</div>
<div class="line number14 index13 alt1">
<code class="plain spaces"> </code><code class="plain plain">bool "DMA support on S3C SDHCI" </code>
</div>
<div class="line number15 index14 alt2">
<code class="plain spaces"> </code><code class="plain plain">depends on MMC_SDHCI_S3C </code>
</div>
<div class="line number16 index15 alt1">
<code class="plain spaces"> </code><code class="plain plain">help </code>
</div>
<div class="line number17 index16 alt2">
<code class="plain spaces"> </code><code class="plain plain">Enable DMA support on the Samsung S3C SDHCI glue. The DMA </code>
</div>
<div class="line number18 index17 alt1">
<code class="plain spaces"> </code><code class="plain plain">has proved to be problematic if the controller encounters </code>
</div>
<div class="line number19 index18 alt2">
<code class="plain spaces"> </code><code class="plain plain">certain errors, and thus should be treated with care. </code>
</div>
<div class="line number20 index19 alt1">
<code class="plain spaces"> </code>
</div>
<div class="line number21 index20 alt2">
<code class="plain spaces"> </code><code class="plain plain">YMMV. </code>
</div>
<div class="line number22 index21 alt1">
<code class="plain spaces"> </code>
</div>
<div class="line number23 index22 alt2">
<code class="plain plain">config MMC_S3C </code>
</div>
<div class="line number24 index23 alt1">
<code class="plain spaces"> </code><code class="plain plain">tristate "Samsung S3C SD/MMC Card Interface support" </code>
</div>
<div class="line number25 index24 alt2">
<code class="plain spaces"> </code><code class="plain plain">depends on ARCH_S3C24XX </code>
</div>
<div class="line number26 index25 alt1">
<code class="plain spaces"> </code><code class="plain plain">depends on S3C24XX_DMAC </code>
</div>
<div class="line number27 index26 alt2">
<code class="plain spaces"> </code><code class="plain plain">help </code>
</div>
<div class="line number28 index27 alt1">
<code class="plain spaces"> </code><code class="plain plain">This selects a driver for the MCI interface found in </code>
</div>
<div class="line number29 index28 alt2">
<code class="plain spaces"> </code><code class="plain plain">Samsung's S3C2410, S3C2412, S3C2440, S3C2442 CPUs. </code>
</div>
<div class="line number30 index29 alt1">
<code class="plain spaces"> </code><code class="plain plain">If you have a board based on one of those and a MMC/SD </code>
</div>
<div class="line number31 index30 alt2">
<code class="plain spaces"> </code><code class="plain plain">slot, say Y or M here. </code>
</div>
<div class="line number32 index31 alt1">
<code class="plain spaces"> </code>
</div>
<div class="line number33 index32 alt2">
<code class="plain spaces"> </code><code class="plain plain">If unsure, say N. </code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
5、MMC_S3C和MMC_SDHCI_S3C是主要的macro，接着了解两个macro对应文件的数据结构</p>
<p>
首先看一下s3cmci.c文件，</p>
<div class="jb51code">
<div>
<div class="syntaxhighlightercpp" id="highlighter_855219">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">const</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">mmc_host_ops s3cmci_ops = { </code>
</div>
<div class="line number2 index1 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.request = s3cmci_request, </code>
</div>
<div class="line number3 index2 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.set_ios = s3cmci_set_ios, </code>
</div>
<div class="line number4 index3 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.get_ro = mmc_gpio_get_ro, </code>
</div>
<div class="line number5 index4 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.get_cd = mmc_gpio_get_cd, </code>
</div>
<div class="line number6 index5 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.enable_sdio_irq = s3cmci_enable_sdio_irq, </code>
</div>
<div class="line number7 index6 alt2">
<code class="cpp plain">};</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
再看一下sdhci-s3c.c文件，</p>
<div class="jb51code">
<div>
<div class="syntaxhighlightercpp" id="highlighter_4488">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="cpp keyword bold">static</code> <code class="cpp keyword bold">struct</code> <code class="cpp plain">sdhci_ops sdhci_s3c_ops = { </code>
</div>
<div class="line number2 index1 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.get_max_clock = sdhci_s3c_get_max_clk, </code>
</div>
<div class="line number3 index2 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.set_clock = sdhci_s3c_set_clock, </code>
</div>
<div class="line number4 index3 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.get_min_clock = sdhci_s3c_get_min_clock, </code>
</div>
<div class="line number5 index4 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.set_bus_width = sdhci_set_bus_width, </code>
</div>
<div class="line number6 index5 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">.reset = sdhci_reset, </code>
</div>
<div class="line number7 index6 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">.set_uhs_signaling = sdhci_set_uhs_signaling, </code>
</div>
<div class="line number8 index7 alt1">
<code class="cpp plain">};</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
6 、从host角度来说，有了platform driver和上面的host driver，驱动流程就算搞清楚了。</p>
<p>
但是如果深入下去的话，还是需要好好读一下sd协议，这里面花的时间最多。</p>
<p>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。</p>
<p>
原文链接：https://blog.csdn.net/feixiaoxing/article/details/79847066</p>
頁:
[1]