Linux mmc驱动框架

• Host驱动设备树
• Host驱动
• • platform_driver数据结构
  • 控制器驱动初始化函数
  • • `sunxi_mmc_probe->mmc_add_host`
    • `sunxi_mmc_probe->mmc_add_host->mmc_start_host`
    • `sunxi_mmc_probe->mmc_add_host->mmc_start_host-> _mmc_detect_change`
    • `sunxi_mmc_probe->mmc_add_host->mmc_start_host-> _mmc_detect_change-> mmc_schedule_delayed_work`
    • `sunxi_mmc_probe->mmc_alloc_host`

1. 通过mmc_alloc_host分配一个mmc_host结构体
2. 定义实现mmc_host_ops数据结构, 并赋值给上面的mmc_host->mmc_host_ops成员变量
3. 给mmc_host成员变量赋值, 如ocr_avail、caps等成员变量
4. 调用mmc_add_host注册该Host

Host驱动设备树

  host驱动设备树用于匹配host驱动，host驱动匹配上设备树，初始化流程才能开始。本文举例全志H3设备树以及mmc控制器驱动。
  下面的代码段都是一些基本配置，compatible用于与驱动匹配，reg为控制器IO内存地址。interrupt为中断参数，GIC控制器，中断号等。以及mmc控制器用到的时钟参数。

mmc0: mmc@01c0f000 {
	/* compatible and clocks are in per SoC .dtsi file */
	compatible = "allwinner,sun7i-a20-mmc";
	reg = <0x01c0f000 0x1000>;
	resets = <&ccu RST_BUS_MMC0>;
	reset-names = "ahb";
	interrupts = <GIC_SPI 60 IRQ_TYPE_LEVEL_HIGH>;
	status = "disabled";
	#address-cells = <1>;
	#size-cells = <0>;
	clocks = <&ccu CLK_BUS_MMC0>,
		 <&ccu CLK_MMC0>,
		 <&ccu CLK_MMC0_OUTPUT>,
		 <&ccu CLK_MMC0_SAMPLE>;
	clock-names = "ahb",
		      "mmc",
		      "output",
		      "sample";
};

   
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Host驱动

platform_driver数据结构

static struct platform_driver sunxi_mmc_driver = {
	.driver = {
		.name	= "sunxi-mmc",
		.of_match_table = of_match_ptr(sunxi_mmc_of_match),
		.pm = &sunxi_mmc_pm_ops,
	},
	.probe		= sunxi_mmc_probe,
	.remove		= sunxi_mmc_remove,
};

static const struct of_device_id sunxi_mmc_of_match[] = {
{ .compatible = “allwinner,sun4i-a10-mmc”, .data = &sun4i_a10_cfg },
{ .compatible = “allwinner,sun5i-a13-mmc”, .data = &sun5i_a13_cfg },
{ .compatible = “allwinner,sun7i-a20-mmc”, .data = &sun7i_a20_cfg }, (1)
{ .compatible = “allwinner,sun8i-a83t-emmc”, .data = &sun8i_a83t_emmc_cfg },
{ .compatible = “allwinner,sun9i-a80-mmc”, .data = &sun9i_a80_cfg },
{ .compatible = “allwinner,sun50i-a64-mmc”, .data = &sun50i_a64_cfg },
{ .compatible = “allwinner,sun50i-a64-emmc”, .data = &sun50i_a64_emmc_cfg },
{ /* sentinel */ }
};

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（1）这里的compatible和设备树中对应，内核初始化时驱动匹配上设备树，会调用platform_driver 的probe函数。

控制器驱动初始化函数

  首先来看控制器驱动的probe函数：

static int sunxi_mmc_probe(struct platform_device *pdev)
{
	struct sunxi_mmc_host *host;
	struct mmc_host *mmc;
	int ret;
mmc <span class="token operator">=</span> <span class="token function">mmc_alloc_host</span><span class="token punctuation">(</span><span class="token keyword">sizeof</span><span class="token punctuation">(</span><span class="token keyword">struct</span> sunxi_mmc_host<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token operator">&amp;</span>pdev<span class="token operator">-&gt;</span>dev<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>mmc<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	<span class="token function">dev_err</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>pdev<span class="token operator">-&gt;</span>dev<span class="token punctuation">,</span> <span class="token string">"mmc alloc host failed\n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token keyword">return</span> <span class="token operator">-</span>ENOMEM<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
mmc<span class="token operator">-&gt;</span>ops		<span class="token operator">=</span> <span class="token operator">&amp;</span>sunxi_mmc_ops<span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
ret <span class="token operator">=</span> <span class="token function">sunxi_mmc_init_host</span><span class="token punctuation">(</span>host<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>ret<span class="token punctuation">)</span>
	<span class="token keyword">goto</span> error_free_dma<span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
ret <span class="token operator">=</span> <span class="token function">mmc_add_host</span><span class="token punctuation">(</span>mmc<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">return</span> ret<span class="token punctuation">;</span>

}

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  probe函数中首先会申请mmc_host数据结构，调用mmc_alloc_host函数申请数据结构内存，并设置部分mmc_host数据结构参数。
  随后设置struct mmc_host的struct mmc_host_ops数据结构。下面来看下sunxi_mmc_ops数据结构：

static const struct mmc_host_ops sunxi_mmc_ops = {
	.request	 = sunxi_mmc_request,
	.set_ios	 = sunxi_mmc_set_ios,
	.get_ro		 = mmc_gpio_get_ro,
	.get_cd		 = mmc_gpio_get_cd,
	.enable_sdio_irq = sunxi_mmc_enable_sdio_irq,
	.start_signal_voltage_switch = sunxi_mmc_volt_switch,
	.hw_reset	 = sunxi_mmc_hw_reset,
	.card_busy	 = sunxi_mmc_card_busy,
};

 
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  struct mmc_host_ops数据结构用来描述卡控制器操作接口函数功能，用于从主机控制器层向 core 层注册操作函数，从而将core 层与具体的主机控制器隔离。
  core 要操作主机控制器，就用这个 ops 当中给的函数指针操作，不能直接调用具体主控制器的函数，从而实现逻辑层和硬件驱动层的分离。

  再继续看sunxi_mmc_probe函数，ret = sunxi_mmc_init_host(host);这部分代码，主要是涉及到硬件相关的mmc控制器初始化代码，这里就不展开了。
  最后调用mmc_add_host，顾名思义，添加一个 mmc_host 。下面来看一下mmc_add_host代码。

sunxi_mmc_probe->mmc_add_host

int mmc_add_host(struct mmc_host *host)
{
	int err;
<span class="token function">WARN_ON</span><span class="token punctuation">(</span><span class="token punctuation">(</span>host<span class="token operator">-&gt;</span>caps <span class="token operator">&amp;</span> MMC_CAP_SDIO_IRQ<span class="token punctuation">)</span> <span class="token operator">&amp;&amp;</span>
	<span class="token operator">!</span>host<span class="token operator">-&gt;</span>ops<span class="token operator">-&gt;</span>enable_sdio_irq<span class="token punctuation">)</span><span class="token punctuation">;</span>

err <span class="token operator">=</span> <span class="token function">device_add</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>host<span class="token operator">-&gt;</span>class_dev<span class="token punctuation">)</span><span class="token punctuation">;</span>						<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>err<span class="token punctuation">)</span>
	<span class="token keyword">return</span> err<span class="token punctuation">;</span>

<span class="token function">led_trigger_register_simple</span><span class="token punctuation">(</span><span class="token function">dev_name</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>host<span class="token operator">-&gt;</span>class_dev<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token operator">&amp;</span>host<span class="token operator">-&gt;</span>led<span class="token punctuation">)</span><span class="token punctuation">;</span>

#ifdef CONFIG_DEBUG_FS
mmc_add_host_debugfs(host);
#endif

<span class="token function">mmc_start_host</span><span class="token punctuation">(</span>host<span class="token punctuation">)</span><span class="token punctuation">;</span>									<span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span>
<span class="token function">mmc_register_pm_notifier</span><span class="token punctuation">(</span>host<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>

}

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  很简单，就是增加了一个 device ，然后就调用 mmc_start_host 了，下面来看 mmc_start_host。

sunxi_mmc_probe->mmc_add_host->mmc_start_host

void mmc_start_host(struct mmc_host *host)
{
	host->f_init = max(freqs[0], host->f_min);
	host->rescan_disable = 0;
	host->ios.power_mode = MMC_POWER_UNDEFINED;
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token punctuation">(</span>host<span class="token operator">-&gt;</span>caps2 <span class="token operator">&amp;</span> MMC_CAP2_NO_PRESCAN_POWERUP<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	<span class="token function">mmc_claim_host</span><span class="token punctuation">(</span>host<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token function">mmc_power_up</span><span class="token punctuation">(</span>host<span class="token punctuation">,</span> host<span class="token operator">-&gt;</span>ocr_avail<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token function">mmc_release_host</span><span class="token punctuation">(</span>host<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token function">mmc_gpiod_request_cd_irq</span><span class="token punctuation">(</span>host<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">_mmc_detect_change</span><span class="token punctuation">(</span>host<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> false<span class="token punctuation">)</span><span class="token punctuation">;</span>

}

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sunxi_mmc_probe->mmc_add_host->mmc_start_host-> _mmc_detect_change

static void _mmc_detect_change(struct mmc_host *host, unsigned long delay,
				bool cd_irq)
{
	if (cd_irq && !(host->caps & MMC_CAP_NEEDS_POLL) &&
		device_can_wakeup(mmc_dev(host)))
		pm_wakeup_event(mmc_dev(host), 5000);
host<span class="token operator">-&gt;</span>detect_change <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token function">mmc_schedule_delayed_work</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>host<span class="token operator">-&gt;</span>detect<span class="token punctuation">,</span> delay<span class="token punctuation">)</span><span class="token punctuation">;</span>

}

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sunxi_mmc_probe->mmc_add_host->mmc_start_host-> _mmc_detect_change-> mmc_schedule_delayed_work

static int mmc_schedule_delayed_work(struct delayed_work *work,
				     unsigned long delay)
{
	return queue_delayed_work(system_freezable_wq, work, delay);
}

 
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  mmc_start_host代码很简单，主要代码为调用了_mmc_detect_change函数。
  _mmc_detect_change函数调用mmc_schedule_delayed_work。
  mmc_schedule_delayed_work函数最终调用了queue_delayed_work
  queue_delayed_work具体是干嘛的可以百度，这里
  这几个代码告诉我们在 workqueue 这个工作队列当中添加一个延迟的工作任务，而这个工作任务就是由 host->detect 来描述的，在随后的 delay 个 jiffies 后会有一个记录在 host->detect 里面的函数被执行，上面可以看到_mmc_detect_change传递的delay参数为0，意思是不延迟？大概是为了预留需要延迟检测卡的情况。
  代码执行到这里 sunxi_mmc_probe这个函数基本上执行完成了，host（控制器）的初始化完成了。
  但事情还没有完， workqueue 这个工作队列还在忙，不一会儿它就会调用 host->detect 里面那个函数，这个函数到底是哪个函数，到底是用来干什么的呢？好像没有看到，detect 包含在 host 里面，那估计是在刚才那个申请的地方设置的那个函数，回过头来看一下 mmc_alloc_host：

sunxi_mmc_probe->mmc_alloc_host

struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
{
	struct mmc_host *host;
host <span class="token operator">=</span> <span class="token function">kzalloc</span><span class="token punctuation">(</span><span class="token keyword">sizeof</span><span class="token punctuation">(</span><span class="token keyword">struct</span> mmc_host<span class="token punctuation">)</span> <span class="token operator">+</span> extra<span class="token punctuation">,</span> GFP_KERNEL<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>host<span class="token punctuation">)</span>
	<span class="token keyword">return</span> <span class="token constant">NULL</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token function">INIT_DELAYED_WORK</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>host<span class="token operator">-&gt;</span>detect<span class="token punctuation">,</span> mmc_rescan<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">return</span> host<span class="token punctuation">;</span>

}

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  INIT_DELAYED_WORK初始化延迟工作队列，延时结束后调用工作队列函数，这里是mmc_rescan，这个函数是用来检测卡的。