Linux驱动——mmc host浅析（四）

- 日理万妓 2022-09-16 15:29 590阅读 0赞

# Linux驱动——mmc host浅析（四） #

备注：  
  1. Kernel版本：5.4  
  2. 使用工具：Source Insight 4.0  
  3. 参考博客：  
[4. \[mmc subsystem\] mmc core（第四章）——host模块说明][4. _mmc subsystem_ mmc core_host]

### 文章目录 ###

*  Linux驱动——mmc host浅析（四）
 *   *  概述
     *  API预览
     *   *  mmc host分配、注册相关
         *  mmc host class相关
         *  mmc host属性解析相关
     *  核心接口函数实现
     *   *  mmc\_register\_host\_class实现
         *  mmc\_alloc\_host实现
         *  mmc\_add\_host实现
         *  mmc\_of\_parse实现

## 概述 ##

对应代码drivers/mmc/core/host.c，drivers/mmc/core/host.h。为底层host controller driver实现mmc host的申请以及注册的API等等，以及host相关属性的实现。

## API预览 ##

### mmc host分配、注册相关 ###

*  mmc\_alloc\_host & mmc\_free\_host

底层host controller驱动调用，用来分配或者释放一个struct mmc\_host结构体，将其于mmc\_host\_class关联，并且做部分初始化操作。

// 参数说明：
    // extra——>mmc_host的私有数据的长度，
    //         会和mmc_host结构体一起分配，
    //   dev——>底层host controller的device结构体，
    //         用于作为mmc_host的device的父设备
    struct mmc_host *mmc_alloc_host(int extra, struct device *dev)；
    
    void mmc_free_host(struct mmc_host *host)；

*  mmc\_add\_host & mmc\_remove\_host

底层host controller驱动调用，注册或者卸载mmc\_host到设备驱动中，添加到sys类下面，并设置相应的debug目录。然后启动mmc\_host。

int mmc_add_host(struct mmc_host *host);
    void mmc_remove_host(struct mmc_host *host);

### mmc host class相关 ###

*  mmc\_register\_host\_class & mmc\_unregister\_host\_class

int mmc_register_host_class(void);
    void mmc_unregister_host_class(void);

### mmc host属性解析相关 ###

*  mmc\_of\_parse

底层host controller驱动调用，解析mmc\_host的dtsi节点的部分属性。

void mmc_of_parse(struct mmc_host *host);

## 核心接口函数实现 ##

### mmc\_register\_host\_class实现 ###

注册mmc\_host class。

int mmc_register_host_class(void)
    {
        // 注册mmc_host类
        return class_register(&mmc_host_class);   
    }

void mmc_unregister_host_class(void)
    {
    	// 卸载mmc_host类
    	class_unregister(&mmc_host_class);
    }

### mmc\_alloc\_host实现 ###

底层host controller驱动调用，用来分配一个struct mmc\_host结构体，将其于mmc\_host\_class关联，并且做部分初始化操作。

*  主要工作：  
    分配内存空间初始化其class device（对应/sys/class/mmc0节点）  
    初始化detect成员（也就是检测工作）为mmc\_rescan  
    初始化 max\_segs、max\_req\_size等

/**
     *	mmc_alloc_host - initialise the per-host structure.
     *	@extra: sizeof private data structure
     *	@dev: pointer to host device model structure
     *
     *	Initialise the per-host structure.
     */
    // 参数说明：
    // extra——>mmc_host的私有数据的长度，
    //         会和mmc_host结构体一起分配，
    //   dev——>底层host controller的device结构体，
    //         用于作为mmc_host的device的父设备
    struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
    {
    	int err;
    	struct mmc_host *host;
    	// 申请mmc_host内存，预申请私有数据的内存
    	host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
    	if (!host)
    		return NULL;
    
    	/* scanning will be enabled when we're ready */
    	/* 
    	 * 因为只是分配了一个mmc_host，host还没有准备好，
    	 * 所以这里禁用rescan，也就是设置mmc_host->rescan_disable 
    	 */
    	host->rescan_disable = 1; // 在在mmc_start_host中会去使能
    
    	// 为该mmc_host分配一个唯一的id号，设置到host->index
    	err = ida_simple_get(&mmc_host_ida, 0, 0, GFP_KERNEL);
    	if (err < 0) {
    		kfree(host);
    		return NULL;
    	}
    
    	host->index = err;
    	/* 设置mmc_host name */
    	// 以mmc_host的id号构成mmc_host的name，例如mmc0、mmc1
    	dev_set_name(&host->class_dev, "mmc%d", host->index);
    
    	/* 关联mmc_host class_dev并进行初始化 */
    	/* class_dev就代表了mmc_host 的device结构体，是其在设备驱动模型中的体现 */
    	// 将mmc_host的parent设置成对应host controller节点转化出来的device
    	host->parent = dev;
    	host->class_dev.parent = dev;
    	host->class_dev.class = &mmc_host_class;
    	device_initialize(&host->class_dev); // 初始化mmc_host->class_dev
    	device_enable_async_suspend(&host->class_dev);
    
    	// 申请cd-gpio、ro-gpio
    	if (mmc_gpio_alloc(host)) {
    		put_device(&host->class_dev);
    		return NULL;
    	}
    
    	spin_lock_init(&host->lock);
    	init_waitqueue_head(&host->wq);
    
    	// 初始化detect工作为mmc_rescan，
    	// 后续调度host->detect来检测是否有card插入时，
    	// 就会调用到mmc_rescan
    	INIT_DELAYED_WORK(&host->detect, mmc_rescan);
    
    	// 创建 irq work task
    	INIT_DELAYED_WORK(&host->sdio_irq_work, sdio_irq_work);
    	timer_setup(&host->retune_timer, mmc_retune_timer, 0);
    
    	/*
    	 * By default, hosts do not support SGIO or large requests.
    	 * They have to set these according to their abilities.
    	 */
    	/* 初始化 host 基本参数 */
    	host->max_segs = 1;
    	host->max_seg_size = PAGE_SIZE;
    
    	host->max_req_size = PAGE_SIZE;
    	host->max_blk_size = 512;
    	host->max_blk_count = PAGE_SIZE / 512;
    
    	host->fixed_drv_type = -EINVAL;
    	host->ios.power_delay_ms = 10;
    
    	return host;
    }

### mmc\_add\_host实现 ###

底层host controller驱动调用，注册mmc\_host到设备驱动中，添加到sys类下面，并设置相应的debug目录。然后启动mmc\_host。

*  主要工作：  
    将mmc\_host的class\_dev添加到设备驱动模型中，在sysfs中生成相应的节点  
    初始化mmc\_host相关的debug目录  
    设置mmc\_host的class\_dev的属性  
    调用mmc\_start\_host启动host

/**
     *	mmc_add_host - initialise host hardware
     *	@host: mmc host
     *
     *	Register the host with the driver model. The host must be
     *	prepared to start servicing requests before this function
     *	completes.
     */
    int mmc_add_host(struct mmc_host *host)
    {
    	int err;
    
    	// 检查 MMC_CAP_SDIO_IRQ 属性
    	WARN_ON((host->caps & MMC_CAP_SDIO_IRQ) &&
    		!host->ops->enable_sdio_irq);
    
    	/* 
    	 * 通过device_add将mmc_host->class_dev添加到设备驱动模型中，
    	 * 在sys下生成相应节点 
    	 */
    	err = device_add(&host->class_dev);
    	if (err)
    		return err;
    
    	led_trigger_register_simple(dev_name(&host->class_dev), &host->led);
    
    #ifdef CONFIG_DEBUG_FS
    	/* 设置mmc_host的debugfs节点 */
    	mmc_add_host_debugfs(host);
    #endif
    
    	mmc_start_host(host);//启动host，卡识别等
    	mmc_register_pm_notifier(host);
    
    	return 0;
    }

### mmc\_of\_parse实现 ###

解析mmc\_host的dtsi节点的部分属性。  
  mmc\_of\_parse提供了通用的、解析host controller dtsi节点的属性的方法，这就要依赖于dtsi的属性是否符合规范。  
  但是host controller driver并一定要使用这个，也可以使用自己一套解析的方法。

/**
     *	mmc_of_parse() - parse host's device-tree node
     *	@host: host whose node should be parsed.
     *
     * To keep the rest of the MMC subsystem unaware of whether DT has been
     * used to to instantiate and configure this host instance or not, we
     * parse the properties and set respective generic mmc-host flags and
     * parameters.
     */
    int mmc_of_parse(struct mmc_host *host)
    {
    	struct device *dev = host->parent;
    	u32 bus_width, drv_type, cd_debounce_delay_ms;
    	int ret;
    	bool cd_cap_invert, cd_gpio_invert = false;
    
    	if (!dev || !dev_fwnode(dev))
    		return 0;
    
    	/* "bus-width" is translated to MMC_CAP_*_BIT_DATA flags */
    	// 获取数据线宽度
    	if (device_property_read_u32(dev, "bus-width", &bus_width) < 0) {
    		dev_dbg(host->parent,
    			"\"bus-width\" property is missing, assuming 1 bit.\n");
    		bus_width = 1;
    	}
    
    	switch (bus_width) {
    	case 8:
    		host->caps |= MMC_CAP_8_BIT_DATA;
    		/* fall through - Hosts capable of 8-bit can also do 4 bits */
    	case 4:
    		host->caps |= MMC_CAP_4_BIT_DATA;
    		break;
    	case 1:
    		break;
    	default:
    		dev_err(host->parent,
    			"Invalid \"bus-width\" value %u!\n", bus_width);
    		return -EINVAL;
    	}
    
    	/* f_max is obtained from the optional "max-frequency" property */
    	// 获取最大频率
    	device_property_read_u32(dev, "max-frequency", &host->f_max);
    
    	/*
    	 * Configure CD and WP pins. They are both by default active low to
    	 * match the SDHCI spec. If GPIOs are provided for CD and / or WP, the
    	 * mmc-gpio helpers are used to attach, configure and use them. If
    	 * polarity inversion is specified in DT, one of MMC_CAP2_CD_ACTIVE_HIGH
    	 * and MMC_CAP2_RO_ACTIVE_HIGH capability-2 flags is set. If the
    	 * "broken-cd" property is provided, the MMC_CAP_NEEDS_POLL capability
    	 * is set. If the "non-removable" property is found, the
    	 * MMC_CAP_NONREMOVABLE capability is set and no card-detection
    	 * configuration is performed.
    	 */
    
    	/* Parse Card Detection */
    	// 获取卡不可移除标志
    	if (device_property_read_bool(dev, "non-removable")) {
    		host->caps |= MMC_CAP_NONREMOVABLE;
    	} else {
    		cd_cap_invert = device_property_read_bool(dev, "cd-inverted");
    
    		if (device_property_read_u32(dev, "cd-debounce-delay-ms",
    					     &cd_debounce_delay_ms))
    			cd_debounce_delay_ms = 200;
    
    		// 获取轮询查询卡状态标志
    		if (device_property_read_bool(dev, "broken-cd"))
    			host->caps |= MMC_CAP_NEEDS_POLL;
    
    		// 申请cd-gpio管脚
    		ret = mmc_gpiod_request_cd(host, "cd", 0, false,
    					   cd_debounce_delay_ms * 1000,
    					   &cd_gpio_invert);
    		if (!ret)
    			dev_info(host->parent, "Got CD GPIO\n");
    		else if (ret != -ENOENT && ret != -ENOSYS)
    			return ret;
    
    		/*
    		 * There are two ways to flag that the CD line is inverted:
    		 * through the cd-inverted flag and by the GPIO line itself
    		 * being inverted from the GPIO subsystem. This is a leftover
    		 * from the times when the GPIO subsystem did not make it
    		 * possible to flag a line as inverted.
    		 *
    		 * If the capability on the host AND the GPIO line are
    		 * both inverted, the end result is that the CD line is
    		 * not inverted.
    		 */
    		if (cd_cap_invert ^ cd_gpio_invert)
    			host->caps2 |= MMC_CAP2_CD_ACTIVE_HIGH;
    	}
    
    	/* Parse Write Protection */
    	// 获取写保护标志
    	if (device_property_read_bool(dev, "wp-inverted"))
    		host->caps2 |= MMC_CAP2_RO_ACTIVE_HIGH;
    
    	ret = mmc_gpiod_request_ro(host, "wp", 0, 0, NULL);
    	if (!ret)
    		dev_info(host->parent, "Got WP GPIO\n");
    	else if (ret != -ENOENT && ret != -ENOSYS)
    		return ret;
    
    	if (device_property_read_bool(dev, "disable-wp"))
    		host->caps2 |= MMC_CAP2_NO_WRITE_PROTECT;
    
    	// 获取sd highspeed标志
    	if (device_property_read_bool(dev, "cap-sd-highspeed"))
    		host->caps |= MMC_CAP_SD_HIGHSPEED;
    
    	// 获取mmc highspeed标志
    	if (device_property_read_bool(dev, "cap-mmc-highspeed"))
    		host->caps |= MMC_CAP_MMC_HIGHSPEED;
    	if (device_property_read_bool(dev, "sd-uhs-sdr12"))
    		host->caps |= MMC_CAP_UHS_SDR12;
    	if (device_property_read_bool(dev, "sd-uhs-sdr25"))
    		host->caps |= MMC_CAP_UHS_SDR25;
    	if (device_property_read_bool(dev, "sd-uhs-sdr50"))
    		host->caps |= MMC_CAP_UHS_SDR50;
    	if (device_property_read_bool(dev, "sd-uhs-sdr104"))
    		host->caps |= MMC_CAP_UHS_SDR104;
    	if (device_property_read_bool(dev, "sd-uhs-ddr50"))
    		host->caps |= MMC_CAP_UHS_DDR50;
    
    	// 获取card 可掉电标志
    	if (device_property_read_bool(dev, "cap-power-off-card"))
    		host->caps |= MMC_CAP_POWER_OFF_CARD;
    
    	// 获取card 硬件复位标志
    	if (device_property_read_bool(dev, "cap-mmc-hw-reset"))
    		host->caps |= MMC_CAP_HW_RESET;
    
    	// 获取sdio hw irq标志
    	if (device_property_read_bool(dev, "cap-sdio-irq"))
    		host->caps |= MMC_CAP_SDIO_IRQ;
    	if (device_property_read_bool(dev, "full-pwr-cycle"))
    		host->caps2 |= MMC_CAP2_FULL_PWR_CYCLE;
    
    	// 在suspend模式下，应保持上电
    	if (device_property_read_bool(dev, "keep-power-in-suspend"))
    		host->pm_caps |= MMC_PM_KEEP_POWER;
    
    	// 获取唤醒源标志
    	if (device_property_read_bool(dev, "wakeup-source") ||
    	    device_property_read_bool(dev, "enable-sdio-wakeup")) /* legacy */
    		host->pm_caps |= MMC_PM_WAKE_SDIO_IRQ;
    	if (device_property_read_bool(dev, "mmc-ddr-3_3v"))
    		host->caps |= MMC_CAP_3_3V_DDR;
    	if (device_property_read_bool(dev, "mmc-ddr-1_8v"))
    		host->caps |= MMC_CAP_1_8V_DDR;
    	if (device_property_read_bool(dev, "mmc-ddr-1_2v"))
    		host->caps |= MMC_CAP_1_2V_DDR;
    	if (device_property_read_bool(dev, "mmc-hs200-1_8v"))
    		host->caps2 |= MMC_CAP2_HS200_1_8V_SDR;
    	if (device_property_read_bool(dev, "mmc-hs200-1_2v"))
    		host->caps2 |= MMC_CAP2_HS200_1_2V_SDR;
    	if (device_property_read_bool(dev, "mmc-hs400-1_8v"))
    		host->caps2 |= MMC_CAP2_HS400_1_8V | MMC_CAP2_HS200_1_8V_SDR;
    	if (device_property_read_bool(dev, "mmc-hs400-1_2v"))
    		host->caps2 |= MMC_CAP2_HS400_1_2V | MMC_CAP2_HS200_1_2V_SDR;
    	if (device_property_read_bool(dev, "mmc-hs400-enhanced-strobe"))
    		host->caps2 |= MMC_CAP2_HS400_ES;
    
    	// 获取 host不支持的card标志
    	if (device_property_read_bool(dev, "no-sdio"))
    		host->caps2 |= MMC_CAP2_NO_SDIO;
    	if (device_property_read_bool(dev, "no-sd"))
    		host->caps2 |= MMC_CAP2_NO_SD;
    	if (device_property_read_bool(dev, "no-mmc"))
    		host->caps2 |= MMC_CAP2_NO_MMC;
    
    	/* Must be after "non-removable" check */
    	if (device_property_read_u32(dev, "fixed-emmc-driver-type", &drv_type) == 0) {
    		if (host->caps & MMC_CAP_NONREMOVABLE)
    			host->fixed_drv_type = drv_type;
    		else
    			dev_err(host->parent,
    				"can't use fixed driver type, media is removable\n");
    	}
    
    	host->dsr_req = !device_property_read_u32(dev, "dsr", &host->dsr);
    	if (host->dsr_req && (host->dsr & ~0xffff)) {
    		dev_err(host->parent,
    			"device tree specified broken value for DSR: 0x%x, ignoring\n",
    			host->dsr);
    		host->dsr_req = 0;
    	}
    
    	device_property_read_u32(dev, "post-power-on-delay-ms",
    				 &host->ios.power_delay_ms);
    
    	return mmc_pwrseq_alloc(host);
    }

[4. _mmc subsystem_ mmc core_host]: https://www.cnblogs.com/linhaostudy/p/10790541.htmll