Linux驱动——mmc数据结构（二）

备注：
  1. Kernel版本：5.4
  2. 使用工具：Source Insight 4.0
  3. 参考博客：
2. [mmc subsystem] mmc core数据结构和宏定义说明
Linux MMC framework(2)_host controller driver

文章目录

• Linux驱动——mmc数据结构（二）
• • 数据结构关系
  • host 相关
  • • struct mmc_host
    • struct mmc_host_ops
  • card相关
  • • struct mmc_card
  • host的总线相关
  • • struct mmc_bus_ops
    • struct mmc_ios
  • mmc请求相关
  • • struct mmc_command
    • struct mmc_data
    • struct mmc_request

数据结构关系

host 相关

struct mmc_host

  struct mmc_host是mmc core由host controller抽象出来的结构体，用于代表一个mmc host控制器。

struct mmc_host {
	struct device		*parent;	//对应的host controller的device
	struct device		class_dev;	// mmc_host的device结构体，会挂在class/mmc_host下
	int			index;				// 该host的索引号
	const struct mmc_host_ops *ops;	// 该host的操作集，由host controller设置
	struct mmc_pwrseq	*pwrseq;	// 该host电源管理有关的操作函数集
	unsigned int		f_min;		// 该host支持的最低频率
	unsigned int		f_max;		// 该host支持的最大频率
	unsigned int		f_init;		// 该host使用的初始化频率

	/*
	 * OCR（Operating Conditions Register）
	 * 是MMC/SD/SDIO卡的一个32-bit的寄存器，
	 * 其中有些bit指明了该卡的操作电压。
	 * MMC host在驱动这些卡的时候，
	 * 需要和Host自身所支持的电压范围匹配之后，
	 * 才能正常操作，这就是ocr_avail的存在意义
	 */
	u32			ocr_avail;			// 该host可支持的操作电压范围

	/* 
	 * 如果MMC host针对SDIO、SD、MMC等不同类型的卡，
	 * 所支持的电压范围不同的话，
	 * 需要通过这几个字段特别指定。
	 * 否则，不需要赋值（初始化为0）
	 */
	u32			ocr_avail_sdio;	/* SDIO-specific OCR */
	u32			ocr_avail_sd;	/* SD-specific OCR */
	u32			ocr_avail_mmc;	/* MMC-specific OCR */
#ifdef CONFIG_PM_SLEEP
	struct notifier_block	pm_notify;// 用于支持power management有关的notify实现
#endif
	u32			max_current_330;	// 3.3V时的最大电流
	u32			max_current_300;	// 3.0V时的最大电流
	u32			max_current_180;	// 1.8V时的最大电流

#define MMC_VDD_165_195		0x00000080	/* VDD voltage 1.65 - 1.95 */
#define MMC_VDD_20_21		0x00000100	/* VDD voltage 2.0 ~ 2.1 */
#define MMC_VDD_21_22		0x00000200	/* VDD voltage 2.1 ~ 2.2 */
#define MMC_VDD_22_23		0x00000400	/* VDD voltage 2.2 ~ 2.3 */
#define MMC_VDD_23_24		0x00000800	/* VDD voltage 2.3 ~ 2.4 */
#define MMC_VDD_24_25		0x00001000	/* VDD voltage 2.4 ~ 2.5 */
#define MMC_VDD_25_26		0x00002000	/* VDD voltage 2.5 ~ 2.6 */
#define MMC_VDD_26_27		0x00004000	/* VDD voltage 2.6 ~ 2.7 */
#define MMC_VDD_27_28		0x00008000	/* VDD voltage 2.7 ~ 2.8 */
#define MMC_VDD_28_29		0x00010000	/* VDD voltage 2.8 ~ 2.9 */
#define MMC_VDD_29_30		0x00020000	/* VDD voltage 2.9 ~ 3.0 */
#define MMC_VDD_30_31		0x00040000	/* VDD voltage 3.0 ~ 3.1 */
#define MMC_VDD_31_32		0x00080000	/* VDD voltage 3.1 ~ 3.2 */
#define MMC_VDD_32_33		0x00100000	/* VDD voltage 3.2 ~ 3.3 */
#define MMC_VDD_33_34		0x00200000	/* VDD voltage 3.3 ~ 3.4 */
#define MMC_VDD_34_35		0x00400000	/* VDD voltage 3.4 ~ 3.5 */
#define MMC_VDD_35_36		0x00800000	/* VDD voltage 3.5 ~ 3.6 */

	// 指示该MMC host所支持的功能特性
	u32			caps;		/* Host capabilities */

#define MMC_CAP_4_BIT_DATA	(1 << 0)	/* Can the host do 4 bit transfers */
#define MMC_CAP_MMC_HIGHSPEED	(1 << 1)	/* Can do MMC high-speed timing */
#define MMC_CAP_SD_HIGHSPEED	(1 << 2)	/* Can do SD high-speed timing */
#define MMC_CAP_SDIO_IRQ	(1 << 3)	/* Can signal pending SDIO IRQs */
#define MMC_CAP_SPI		(1 << 4)	/* Talks only SPI protocols */
#define MMC_CAP_NEEDS_POLL	(1 << 5)	/* Needs polling for card-detection */
#define MMC_CAP_8_BIT_DATA	(1 << 6)	/* Can the host do 8 bit transfers */
#define MMC_CAP_AGGRESSIVE_PM	(1 << 7)	/* Suspend (e)MMC/SD at idle  */
#define MMC_CAP_NONREMOVABLE	(1 << 8)	/* Nonremovable e.g. eMMC */
#define MMC_CAP_WAIT_WHILE_BUSY	(1 << 9)	/* Waits while card is busy */
#define MMC_CAP_ERASE		(1 << 10)	/* Allow erase/trim commands */
#define MMC_CAP_3_3V_DDR	(1 << 11)	/* Host supports eMMC DDR 3.3V */
#define MMC_CAP_1_8V_DDR	(1 << 12)	/* Host supports eMMC DDR 1.8V */
#define MMC_CAP_1_2V_DDR	(1 << 13)	/* Host supports eMMC DDR 1.2V */
#define MMC_CAP_POWER_OFF_CARD	(1 << 14)	/* Can power off after boot */
#define MMC_CAP_BUS_WIDTH_TEST	(1 << 15)	/* CMD14/CMD19 bus width ok */
#define MMC_CAP_UHS_SDR12	(1 << 16)	/* Host supports UHS SDR12 mode */
#define MMC_CAP_UHS_SDR25	(1 << 17)	/* Host supports UHS SDR25 mode */
#define MMC_CAP_UHS_SDR50	(1 << 18)	/* Host supports UHS SDR50 mode */
#define MMC_CAP_UHS_SDR104	(1 << 19)	/* Host supports UHS SDR104 mode */
#define MMC_CAP_UHS_DDR50	(1 << 20)	/* Host supports UHS DDR50 mode */
#define MMC_CAP_UHS		(MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 | \
				 MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 | \
				 MMC_CAP_UHS_DDR50)
#define MMC_CAP_SYNC_RUNTIME_PM	(1 << 21)	/* Synced runtime PM suspends. */
#define MMC_CAP_NEED_RSP_BUSY	(1 << 22)	/* Commands with R1B can't use R1. */
#define MMC_CAP_DRIVER_TYPE_A	(1 << 23)	/* Host supports Driver Type A */
#define MMC_CAP_DRIVER_TYPE_C	(1 << 24)	/* Host supports Driver Type C */
#define MMC_CAP_DRIVER_TYPE_D	(1 << 25)	/* Host supports Driver Type D */
#define MMC_CAP_DONE_COMPLETE	(1 << 27)	/* RW reqs can be completed within mmc_request_done() */
#define MMC_CAP_CD_WAKE		(1 << 28)	/* Enable card detect wake */
#define MMC_CAP_CMD_DURING_TFR	(1 << 29)	/* Commands during data transfer */
#define MMC_CAP_CMD23		(1 << 30)	/* CMD23 supported. */
#define MMC_CAP_HW_RESET	(1 << 31)	/* Hardware reset */

	// 指示该MMC host所支持的功能特性
	u32			caps2;		/* More host capabilities */

#define MMC_CAP2_BOOTPART_NOACC	(1 << 0)	/* Boot partition no access */
#define MMC_CAP2_FULL_PWR_CYCLE	(1 << 2)	/* Can do full power cycle */
#define MMC_CAP2_HS200_1_8V_SDR	(1 << 5)        /* can support */
#define MMC_CAP2_HS200_1_2V_SDR	(1 << 6)        /* can support */
#define MMC_CAP2_HS200		(MMC_CAP2_HS200_1_8V_SDR | \
				 MMC_CAP2_HS200_1_2V_SDR)
#define MMC_CAP2_CD_ACTIVE_HIGH	(1 << 10)	/* Card-detect signal active high */
#define MMC_CAP2_RO_ACTIVE_HIGH	(1 << 11)	/* Write-protect signal active high */
#define MMC_CAP2_NO_PRESCAN_POWERUP (1 << 14)	/* Don't power up before scan */
#define MMC_CAP2_HS400_1_8V	(1 << 15)	/* Can support HS400 1.8V */
#define MMC_CAP2_HS400_1_2V	(1 << 16)	/* Can support HS400 1.2V */
#define MMC_CAP2_HS400		(MMC_CAP2_HS400_1_8V | \
				 MMC_CAP2_HS400_1_2V)
#define MMC_CAP2_HSX00_1_8V	(MMC_CAP2_HS200_1_8V_SDR | MMC_CAP2_HS400_1_8V)
#define MMC_CAP2_HSX00_1_2V	(MMC_CAP2_HS200_1_2V_SDR | MMC_CAP2_HS400_1_2V)
#define MMC_CAP2_SDIO_IRQ_NOTHREAD (1 << 17)
#define MMC_CAP2_NO_WRITE_PROTECT (1 << 18)	/* No physical write protect pin, assume that card is always read-write */
#define MMC_CAP2_NO_SDIO	(1 << 19)	/* Do not send SDIO commands during initialization */
#define MMC_CAP2_HS400_ES	(1 << 20)	/* Host supports enhanced strobe */
#define MMC_CAP2_NO_SD		(1 << 21)	/* Do not send SD commands during initialization */
#define MMC_CAP2_NO_MMC		(1 << 22)	/* Do not send (e)MMC commands during initialization */
#define MMC_CAP2_CQE		(1 << 23)	/* Has eMMC command queue engine */
#define MMC_CAP2_CQE_DCMD	(1 << 24)	/* CQE can issue a direct command */
#define MMC_CAP2_AVOID_3_3V	(1 << 25)	/* Host must negotiate down from 3.3V */
#define MMC_CAP2_MERGE_CAPABLE	(1 << 26)	/* Host can merge a segment over the segment size */

	int			fixed_drv_type;	/* fixed driver type for non-removable media */

	// 该host所支持的电源管理特性
	mmc_pm_flag_t		pm_caps;	/* supported pm features */

	/* host specific block data */
	unsigned int		max_seg_size;	/* see blk_queue_max_segment_size */
	unsigned short		max_segs;	/* see blk_queue_max_segments */
	unsigned short		unused;
	unsigned int		max_req_size;	/* maximum number of bytes in one req */
	unsigned int		max_blk_size;	/* maximum size of one mmc block */
	unsigned int		max_blk_count;	/* maximum number of blocks in one req */
	unsigned int		max_busy_timeout; /* max busy timeout in ms */

	/* private data */
	// 该host的bus使用的锁
	spinlock_t		lock;		/* lock for claim and bus ops */

	// 用于保存MMC bus的当前配置
	struct mmc_ios		ios;		/* current io bus settings */

	/* group bitfields together to minimize padding */
	unsigned int		use_spi_crc:1;
	unsigned int		claimed:1;	/* host exclusively claimed */	// host是否已经被占用
	unsigned int		bus_dead:1;	/* bus has been released */		// host的bus是否处于激活状态
	unsigned int		can_retune:1;	/* re-tuning can be used */
	unsigned int		doing_retune:1;	/* re-tuning in progress */
	unsigned int		retune_now:1;	/* do re-tuning at next req */
	unsigned int		retune_paused:1; /* re-tuning is temporarily disabled */
	unsigned int		use_blk_mq:1;	/* use blk-mq */
	unsigned int		retune_crc_disable:1; /* don't trigger retune upon crc */
	unsigned int		can_dma_map_merge:1; /* merging can be used */

	int			rescan_disable;	/* disable card detection */		// 禁止rescan的标识，禁止搜索card
	int			rescan_entered;	/* used with nonremovable devices */// 是否已经rescan过的标识，对应不可移除的设备只能rescan一次

	int			need_retune;	/* re-tuning is needed */
	int			hold_retune;	/* hold off re-tuning */
	unsigned int		retune_period;	/* re-tuning period in secs */
	struct timer_list	retune_timer;	/* for periodic re-tuning */

	bool			trigger_card_event; /* card_event necessary */

	struct mmc_card		*card;		/* device attached to this host */// 和该host绑定在一起的card

	wait_queue_head_t	wq;
	struct mmc_ctx		*claimer;	/* context that has host claimed */// 该host的占有者进程
	int			claim_cnt;	/* "claim" nesting count */// 占有者进程对该host的占用计数
	struct mmc_ctx		default_ctx;	/* default context */

	struct delayed_work	detect;	// 检测卡槽变化的工作
	int			detect_change;	/* card detect flag */// 需要检测卡槽变化的标识
	struct mmc_slot		slot;	// 卡槽的结构体

	const struct mmc_bus_ops *bus_ops;	/* current bus driver */ // host的mmc总线的操作集
	unsigned int		bus_refs;	/* reference counter */		 // host的mmc总线的使用计数

	unsigned int		sdio_irqs;
	struct task_struct	*sdio_irq_thread;
	struct delayed_work	sdio_irq_work;
	bool			sdio_irq_pending;
	atomic_t		sdio_irq_thread_abort;

	mmc_pm_flag_t		pm_flags;	/* requested pm features */

	struct led_trigger	*led;		/* activity led */

#ifdef CONFIG_REGULATOR
	bool			regulator_enabled; /* regulator state */ // 代表regulator（LDO）的状态
#endif
	struct mmc_supply	supply;

	struct dentry		*debugfs_root;	// 对应的debug目录结构体

	/* Ongoing data transfer that allows commands during transfer */
	struct mmc_request	*ongoing_mrq;

#ifdef CONFIG_FAIL_MMC_REQUEST
	struct fault_attr	fail_mmc_request;
#endif

	unsigned int		actual_clock;	/* Actual HC clock rate */

	unsigned int		slotno;	/* used for sdio acpi binding */

	int			dsr_req;	/* DSR value is valid */
	u32			dsr;	/* optional driver stage (DSR) value */

	/* Command Queue Engine (CQE) support */
	const struct mmc_cqe_ops *cqe_ops;
	void			*cqe_private;
	int			cqe_qdepth;
	bool			cqe_enabled;
	bool			cqe_on;

	unsigned long		private[0] ____cacheline_aligned;
};

struct mmc_host_ops

  mmc core将host需要提供的一些操作方法封装成struct mmc_host_ops。
  mmc core主模块的很多接口都是基于这里面的操作方法来实现的，通过这些方法来操作host硬件达到对应的目的。
  所以struct mmc_host_ops也是host controller driver需要实现的核心部分。

struct mmc_host_ops {
	/*
	 * It is optional for the host to implement pre_req and post_req in
	 * order to support double buffering of requests (prepare one
	 * request while another request is active).
	 * pre_req() must always be followed by a post_req().
	 * To undo a call made to pre_req(), call post_req() with
	 * a nonzero err condition.
	 */
	// post_req和pre_req是为了实现异步请求处理而设置的，是非必需的，
	// 异步请求处理就是指，当另外一个异步请求还没有处理完成的时候，
	// 可以先准备另外一个异步请求而不必等待
	void	(*post_req)(struct mmc_host *host, struct mmc_request *req,
			    int err);
	void	(*pre_req)(struct mmc_host *host, struct mmc_request *req);

	// host处理mmc请求的方法，在mmc_start_request中会调用
	void	(*request)(struct mmc_host *host, struct mmc_request *req);

	/*
	 * Avoid calling the next three functions too often or in a "fast
	 * path", since underlaying controller might implement them in an
	 * expensive and/or slow way. Also note that these functions might
	 * sleep, so don't call them in the atomic contexts!
	 */

	/*
	 * Notes to the set_ios callback:
	 * ios->clock might be 0. For some controllers, setting 0Hz
	 * as any other frequency works. However, some controllers
	 * explicitly need to disable the clock. Otherwise e.g. voltage
	 * switching might fail because the SDCLK is not really quiet.
	 */
	// 设置host的总线的io setting
	void	(*set_ios)(struct mmc_host *host, struct mmc_ios *ios);

	/*
	 * Return values for the get_ro callback should be:
	 *   0 for a read/write card
	 *   1 for a read-only card
	 *   -ENOSYS when not supported (equal to NULL callback)
	 *   or a negative errno value when something bad happened
	 */
	int	(*get_ro)(struct mmc_host *host); // 获取host上的card的读写属性

	/*
	 * Return values for the get_cd callback should be:
	 *   0 for a absent card
	 *   1 for a present card
	 *   -ENOSYS when not supported (equal to NULL callback)
	 *   or a negative errno value when something bad happened
	 */
	int	(*get_cd)(struct mmc_host *host); // 检测host的卡槽中card的插入状态

	void	(*enable_sdio_irq)(struct mmc_host *host, int enable);
	/* Mandatory callback when using MMC_CAP2_SDIO_IRQ_NOTHREAD. */
	void	(*ack_sdio_irq)(struct mmc_host *host);

	/* optional callback for HC quirks */ // 初始化card的方法
	void	(*init_card)(struct mmc_host *host, struct mmc_card *card);

	int	(*start_signal_voltage_switch)(struct mmc_host *host, struct mmc_ios *ios);

	/* Check if the card is pulling dat[0:3] low */
	int	(*card_busy)(struct mmc_host *host); // 用于检测card是否处于busy状态

	/* The tuning command opcode value is different for SD and eMMC cards */
	// 执行tuning操作，为card选择一个合适的采样点
	int	(*execute_tuning)(struct mmc_host *host, u32 opcode);

	/* Prepare HS400 target operating frequency depending host driver */
	int	(*prepare_hs400_tuning)(struct mmc_host *host, struct mmc_ios *ios);

	/* Prepare switch to DDR during the HS400 init sequence */
	int	(*hs400_prepare_ddr)(struct mmc_host *host);

	/* Prepare for switching from HS400 to HS200 */
	void	(*hs400_downgrade)(struct mmc_host *host);

	/* Complete selection of HS400 */
	void	(*hs400_complete)(struct mmc_host *host);

	/* Prepare enhanced strobe depending host driver */
	void	(*hs400_enhanced_strobe)(struct mmc_host *host,
					 struct mmc_ios *ios);
	int	(*select_drive_strength)(struct mmc_card *card,
					 unsigned int max_dtr, int host_drv,
					 int card_drv, int *drv_type);
	void	(*hw_reset)(struct mmc_host *host);		// 硬件复位
	void	(*card_event)(struct mmc_host *host);	// 硬件复位

	/*
	 * Optional callback to support controllers with HW issues for multiple
	 * I/O. Returns the number of supported blocks for the request.
	 */
	int	(*multi_io_quirk)(struct mmc_card *card,
				  unsigned int direction, int blk_size);
};

card相关

struct mmc_card

  struct mmc_card是mmc core由mmc设备抽象出来的card设备的结构体，用于代表一个mmc设备。

/*
 * MMC device
 */
struct mmc_card {
	struct mmc_host		*host;		/* the host this device belongs to */ // 该mmc_card所属host
	struct device		dev;		/* the device */ // 对应的device
	u32			ocr;		/* the current OCR setting */
	unsigned int		rca;		/* relative card address of device */
	unsigned int		type;		/* card type */ // card类型
#define MMC_TYPE_MMC		0		/* MMC card */
#define MMC_TYPE_SD		1		/* SD card */
#define MMC_TYPE_SDIO		2		/* SDIO card */
#define MMC_TYPE_SD_COMBO	3		/* SD combo (IO+mem) card */
	unsigned int		state;		/* (our) card state */ // card的当前状态
	unsigned int		quirks; 	/* card quirks */ // 该card的一些特点
	unsigned int		quirk_max_rate;	/* max rate set by quirks */
#define MMC_QUIRK_LENIENT_FN0	(1<<0)		/* allow SDIO FN0 writes outside of the VS CCCR range */
#define MMC_QUIRK_BLKSZ_FOR_BYTE_MODE (1<<1)	/* use func->cur_blksize */
						/* for byte mode */
#define MMC_QUIRK_NONSTD_SDIO	(1<<2)		/* non-standard SDIO card attached */
						/* (missing CIA registers) */
#define MMC_QUIRK_NONSTD_FUNC_IF (1<<4)		/* SDIO card has nonstd function interfaces */
#define MMC_QUIRK_DISABLE_CD	(1<<5)		/* disconnect CD/DAT[3] resistor */
#define MMC_QUIRK_INAND_CMD38	(1<<6)		/* iNAND devices have broken CMD38 */
#define MMC_QUIRK_BLK_NO_CMD23	(1<<7)		/* Avoid CMD23 for regular multiblock */
#define MMC_QUIRK_BROKEN_BYTE_MODE_512 (1<<8)	/* Avoid sending 512 bytes in */
						/* byte mode */
#define MMC_QUIRK_LONG_READ_TIME (1<<9)		/* Data read time > CSD says */
#define MMC_QUIRK_SEC_ERASE_TRIM_BROKEN (1<<10)	/* Skip secure for erase/trim */
#define MMC_QUIRK_BROKEN_IRQ_POLLING	(1<<11)	/* Polling SDIO_CCCR_INTx could create a fake interrupt */
#define MMC_QUIRK_TRIM_BROKEN	(1<<12)		/* Skip trim */
#define MMC_QUIRK_BROKEN_HPI	(1<<13)		/* Disable broken HPI support */

	bool			reenable_cmdq;	/* Re-enable Command Queue */

	unsigned int		erase_size;	/* erase size in sectors */
 	unsigned int		erase_shift;	/* if erase unit is power 2 */
 	unsigned int		pref_erase;	/* in sectors */
	unsigned int		eg_boundary;	/* don't cross erase-group boundaries */
	unsigned int		erase_arg;	/* erase / trim / discard */
 	u8			erased_byte;	/* value of erased bytes */

	u32			raw_cid[4];	/* raw card CID */ // 原始的cid寄存器的值
	u32			raw_csd[4];	/* raw card CSD */ // 原始的csd寄存器的值
	u32			raw_scr[2];	/* raw card SCR */ // 原始的scr寄存器的值
	u32			raw_ssr[16];	/* raw card SSR */ // 原始的ssr寄存器的值
	struct mmc_cid		cid;		/* card identification */ // 从cid寄存器的值解析出来的信息
	struct mmc_csd		csd;		/* card specific */ // 从csd寄存器的值解析出来的信息
	struct mmc_ext_csd	ext_csd;	/* mmc v4 extended card specific */ // 从ext_csd寄存器的值解析出来的信息
	struct sd_scr		scr;		/* extra SD information */ // 外部sd card的信息
	struct sd_ssr		ssr;		/* yet more SD information */ // 更多关于sd card的信息
	struct sd_switch_caps	sw_caps;	/* switch (CMD6) caps */  // sd的切换属性

	unsigned int		sdio_funcs;	/* number of SDIO functions */ // sdio funcs的数量
	atomic_t		sdio_funcs_probed; /* number of probed SDIO funcs */
	struct sdio_cccr	cccr;		/* common card info */
	struct sdio_cis		cis;		/* common tuple info */
	struct sdio_func	*sdio_func[SDIO_MAX_FUNCS]; /* SDIO functions (devices) */ //sdio func指针
	struct sdio_func	*sdio_single_irq; /* SDIO function when only one IRQ active */
	unsigned		num_info;	/* number of info strings */
	const char		**info;		/* info strings */
	struct sdio_func_tuple	*tuples;	/* unknown common tuples */

	unsigned int		sd_bus_speed;	/* Bus Speed Mode set for the card */
	unsigned int		mmc_avail_type;	/* supported device type by both host and card */
	unsigned int		drive_strength;	/* for UHS-I, HS200 or HS400 */

	struct dentry		*debugfs_root; // 对应debug目录的结构体
	struct mmc_part	part[MMC_NUM_PHY_PARTITION]; /* physical partitions */ // 物理分区
	unsigned int    nr_parts; // 分区数量

	unsigned int		bouncesz;	/* Bounce buffer size */
	struct workqueue_struct *complete_wq;	/* Private workqueue */
};

host的总线相关

struct mmc_bus_ops

  host的mmc总线的操作集，由host插入的card决定。
  不同类型的card对mmc总线的操作有所不同。

struct mmc_bus_ops {
	void (*remove)(struct mmc_host *); // 从软件上注销mmc总线上的card
	void (*detect)(struct mmc_host *); // 检测mmc总线上的card是否被移除
	int (*pre_suspend)(struct mmc_host *); // suspend前的准备工作
	int (*suspend)(struct mmc_host *); // 对应mmc总线的suspend操作
	int (*resume)(struct mmc_host *);  // 对应mmc总线的resume操作
	int (*runtime_suspend)(struct mmc_host *); // 对应mmc总线的runtime suspend操作
	int (*runtime_resume)(struct mmc_host *);  // 对应mmc总线的runtime resume操作
	int (*alive)(struct mmc_host *);   // 检测mmc总线上的card的激活状态
	int (*shutdown)(struct mmc_host *);// 关闭mmc总线的操作
	int (*hw_reset)(struct mmc_host *);// mmc总线上的HW 复位
	int (*sw_reset)(struct mmc_host *);// mmc总线上的SW 复位
};

struct mmc_ios

struct mmc_ios {
	unsigned int	clock;			/* clock rate */ // 当前工作频率
	unsigned short	vdd;			// 支持的电压表
	unsigned int	power_delay_ms;		/* waiting for stable power */

/* vdd stores the bit number of the selected voltage range from below. */

	unsigned char	bus_mode;		/* command output mode */ // 总线输出模式，包括开漏模式和上拉模式

#define MMC_BUSMODE_OPENDRAIN	1
#define MMC_BUSMODE_PUSHPULL	2

	unsigned char	chip_select;		/* SPI chip select */ // spi片选

#define MMC_CS_DONTCARE		0
#define MMC_CS_HIGH		1
#define MMC_CS_LOW		2

	unsigned char	power_mode;		/* power supply mode */ // 电源状态模式

#define MMC_POWER_OFF		0
#define MMC_POWER_UP		1
#define MMC_POWER_ON		2
#define MMC_POWER_UNDEFINED	3

	unsigned char	bus_width;		/* data bus width */ // 总线宽度

#define MMC_BUS_WIDTH_1		0
#define MMC_BUS_WIDTH_4		2
#define MMC_BUS_WIDTH_8		3

	unsigned char	timing;			/* timing specification used */ // 时序类型

#define MMC_TIMING_LEGACY	0
#define MMC_TIMING_MMC_HS	1
#define MMC_TIMING_SD_HS	2
#define MMC_TIMING_UHS_SDR12	3
#define MMC_TIMING_UHS_SDR25	4
#define MMC_TIMING_UHS_SDR50	5
#define MMC_TIMING_UHS_SDR104	6
#define MMC_TIMING_UHS_DDR50	7
#define MMC_TIMING_MMC_DDR52	8
#define MMC_TIMING_MMC_HS200	9
#define MMC_TIMING_MMC_HS400	10

	unsigned char	signal_voltage;		/* signalling voltage (1.8V or 3.3V) */ // 信号的工作电压

#define MMC_SIGNAL_VOLTAGE_330	0
#define MMC_SIGNAL_VOLTAGE_180	1
#define MMC_SIGNAL_VOLTAGE_120	2

	unsigned char	drv_type;		/* driver type (A, B, C, D) */ // 驱动类型

#define MMC_SET_DRIVER_TYPE_B	0
#define MMC_SET_DRIVER_TYPE_A	1
#define MMC_SET_DRIVER_TYPE_C	2
#define MMC_SET_DRIVER_TYPE_D	3

	bool enhanced_strobe;			/* hs400es selection */
};

mmc请求相关

struct mmc_command

struct mmc_command {
	u32			opcode; // 命令的操作码，如MMC_GO_IDLE_STATE、MMC_SEND_OP_COND等等
	u32			arg;    // 命令的参数
#define MMC_CMD23_ARG_REL_WR	(1 << 31)
#define MMC_CMD23_ARG_PACKED	((0 << 31) | (1 << 30))
#define MMC_CMD23_ARG_TAG_REQ	(1 << 29)
	u32			resp[4];
	unsigned int		flags;		/* expected response type */
#define MMC_RSP_PRESENT	(1 << 0)
#define MMC_RSP_136	(1 << 1)		/* 136 bit response */
#define MMC_RSP_CRC	(1 << 2)		/* expect valid crc */
#define MMC_RSP_BUSY	(1 << 3)		/* card may send busy */
#define MMC_RSP_OPCODE	(1 << 4)		/* response contains opcode */

#define MMC_CMD_MASK	(3 << 5)		/* non-SPI command type */
#define MMC_CMD_AC	(0 << 5)
#define MMC_CMD_ADTC	(1 << 5)
#define MMC_CMD_BC	(2 << 5)
#define MMC_CMD_BCR	(3 << 5)

#define MMC_RSP_SPI_S1	(1 << 7)		/* one status byte */
#define MMC_RSP_SPI_S2	(1 << 8)		/* second byte */
#define MMC_RSP_SPI_B4	(1 << 9)		/* four data bytes */
#define MMC_RSP_SPI_BUSY (1 << 10)		/* card may send busy */

/*
 * These are the native response types, and correspond to valid bit
 * patterns of the above flags.  One additional valid pattern
 * is all zeros, which means we don't expect a response.
 */
#define MMC_RSP_NONE	(0)
#define MMC_RSP_R1	(MMC_RSP_PRESENT|MMC_RSP_CRC|MMC_RSP_OPCODE)
#define MMC_RSP_R1B	(MMC_RSP_PRESENT|MMC_RSP_CRC|MMC_RSP_OPCODE|MMC_RSP_BUSY)
#define MMC_RSP_R2	(MMC_RSP_PRESENT|MMC_RSP_136|MMC_RSP_CRC)
#define MMC_RSP_R3	(MMC_RSP_PRESENT)
#define MMC_RSP_R4	(MMC_RSP_PRESENT)
#define MMC_RSP_R5	(MMC_RSP_PRESENT|MMC_RSP_CRC|MMC_RSP_OPCODE)
#define MMC_RSP_R6	(MMC_RSP_PRESENT|MMC_RSP_CRC|MMC_RSP_OPCODE)
#define MMC_RSP_R7	(MMC_RSP_PRESENT|MMC_RSP_CRC|MMC_RSP_OPCODE)

/* Can be used by core to poll after switch to MMC HS mode */
#define MMC_RSP_R1_NO_CRC	(MMC_RSP_PRESENT|MMC_RSP_OPCODE)

#define mmc_resp_type(cmd)	((cmd)->flags & (MMC_RSP_PRESENT|MMC_RSP_136|MMC_RSP_CRC|MMC_RSP_BUSY|MMC_RSP_OPCODE))

/*
 * These are the SPI response types for MMC, SD, and SDIO cards.
 * Commands return R1, with maybe more info.  Zero is an error type;
 * callers must always provide the appropriate MMC_RSP_SPI_Rx flags.
 */
#define MMC_RSP_SPI_R1	(MMC_RSP_SPI_S1)
#define MMC_RSP_SPI_R1B	(MMC_RSP_SPI_S1|MMC_RSP_SPI_BUSY)
#define MMC_RSP_SPI_R2	(MMC_RSP_SPI_S1|MMC_RSP_SPI_S2)
#define MMC_RSP_SPI_R3	(MMC_RSP_SPI_S1|MMC_RSP_SPI_B4)
#define MMC_RSP_SPI_R4	(MMC_RSP_SPI_S1|MMC_RSP_SPI_B4)
#define MMC_RSP_SPI_R5	(MMC_RSP_SPI_S1|MMC_RSP_SPI_S2)
#define MMC_RSP_SPI_R7	(MMC_RSP_SPI_S1|MMC_RSP_SPI_B4)

#define mmc_spi_resp_type(cmd)	((cmd)->flags & \
		(MMC_RSP_SPI_S1|MMC_RSP_SPI_BUSY|MMC_RSP_SPI_S2|MMC_RSP_SPI_B4))

/*
 * These are the command types.
 */
#define mmc_cmd_type(cmd)	((cmd)->flags & MMC_CMD_MASK)

	unsigned int		retries;	/* max number of retries */ // 失败时的重复尝试次数
	int			error;		/* command error */ // 命令的错误码

/*
 * Standard errno values are used for errors, but some have specific
 * meaning in the MMC layer:
 *
 * ETIMEDOUT    Card took too long to respond
 * EILSEQ       Basic format problem with the received or sent data
 *              (e.g. CRC check failed, incorrect opcode in response
 *              or bad end bit)
 * EINVAL       Request cannot be performed because of restrictions
 *              in hardware and/or the driver
 * ENOMEDIUM    Host can determine that the slot is empty and is
 *              actively failing requests
 */

	unsigned int		busy_timeout;	/* busy detect timeout in ms */
	/* Set this flag only for blocking sanitize request */
	bool			sanitize_busy;

	// 和该命令关联在一起的数据段
	struct mmc_data		*data;		/* data segment associated with cmd */
	// 该命令关联到哪个request
	struct mmc_request	*mrq;		/* associated request */
};

struct mmc_data

mmc core用struct mmc_data来表示一个命令包。

struct mmc_data {
	unsigned int		timeout_ns;	/* data timeout (in ns, max 80ms) */ // 超时时间，以ns为单位
	unsigned int		timeout_clks;	/* data timeout (in clocks) */   // 超时时间，以clock为单位
	unsigned int		blksz;		/* data block size */  // 块大小
	unsigned int		blocks;		/* number of blocks */ // 块数量
	unsigned int		blk_addr;	/* block address */    // card地址
	int			error;		/* data error */
	unsigned int		flags;      // 传输标识

#define MMC_DATA_WRITE		BIT(8)
#define MMC_DATA_READ		BIT(9)
/* Extra flags used by CQE */
#define MMC_DATA_QBR		BIT(10)		/* CQE queue barrier*/
#define MMC_DATA_PRIO		BIT(11)		/* CQE high priority */
#define MMC_DATA_REL_WR		BIT(12)		/* Reliable write */
#define MMC_DATA_DAT_TAG	BIT(13)		/* Tag request */
#define MMC_DATA_FORCED_PRG	BIT(14)		/* Forced programming */

	unsigned int		bytes_xfered;

	struct mmc_command	*stop;		/* stop command */  	// 结束传输的命令
	struct mmc_request	*mrq;		/* associated request */// 该命令关联到哪个request

	unsigned int		sg_len;		/* size of scatter list */ sg数组的size
	int			sg_count;	/* mapped sg entries */ // 通过sg map出来的实际的entry的个
	struct scatterlist	*sg;		/* I/O scatter list */ //一个struct scatterlist类型的数组
	s32			host_cookie;	/* host private data */ // host driver的私有数据
};

struct mmc_request

  struct mmc_request是mmc core向host controller发起命令请求的处理单位。其包含了要传输的命令和数据。

struct mmc_request {
	struct mmc_command	*sbc;		/* SET_BLOCK_COUNT for multiblock */ // 设置块数量的命令，怎么用的后续再补充
	struct mmc_command	*cmd;		// 要传输的命令
	struct mmc_data		*data;		// 要传输的数据
	struct mmc_command	*stop;		// 要传输的stop命令

	struct completion	completion; // 完成量
	struct completion	cmd_completion;

	// 传输结束后的回调函数
	void			(*done)(struct mmc_request *);/* completion function */
	/*
	 * Notify uppers layers (e.g. mmc block driver) that recovery is needed
	 * due to an error associated with the mmc_request. Currently used only
	 * by CQE.
	 */
	void			(*recovery_notifier)(struct mmc_request *);
	struct mmc_host		*host; // 所属host

	/* Allow other commands during this ongoing data transfer or busy wait */
	bool			cap_cmd_during_tfr;

	int			tag;
};