块设备驱动3--sd卡驱动2(linux-3.2.36的host.h分析)

/*
 *  linux/include/linux/mmc/host.h
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  Host driver specific definitions.
 */
#ifndef LINUX_MMC_HOST_H
#define LINUX_MMC_HOST_H

#include <linux/leds.h>
#include <linux/sched.h>
#include <linux/fault-inject.h>

#include <linux/mmc/core.h>
#include <linux/mmc/pm.h>

//struct mmc_ios主要是通过mmc_set_ios()调用host->ops->set_ios()
//set_ios()由驱动提供，所以这些结构由host驱动处理，core只管用
struct mmc_ios {
	unsigned int	clock;			/* clock rate */ //时钟速度
	unsigned short	vdd; //电压

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

	unsigned char	bus_mode;		/* command output mode */
//这是io口的类型，对于我这个电气自动化学生还是懂点的，不过不细说了
#define MMC_BUSMODE_OPENDRAIN	1 //开漏
#define MMC_BUSMODE_PUSHPULL	2 //推挽

	unsigned char	chip_select;		/* SPI chip select */

#define MMC_CS_DONTCARE		0 //不关心
#define MMC_CS_HIGH		1 //高速
#define MMC_CS_LOW		2 //低速
/*
        if (mmc_host_is_spi(host))
                host->ios.chip_select = MMC_CS_HIGH;
        else
                host->ios.chip_select = MMC_CS_DONTCARE;
*/

	unsigned char	power_mode;		/* power supply mode */

#define MMC_POWER_OFF		0//关
#define MMC_POWER_UP		1//开
#define MMC_POWER_ON		2//也是开，s3c2440处理和up一样

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

#define MMC_BUS_WIDTH_1		0 //1位
#define MMC_BUS_WIDTH_4		2 //4位
#define MMC_BUS_WIDTH_8		3 //8位

	unsigned char	timing;			/* timing specification used */ //时序规范使用

#define MMC_TIMING_LEGACY	0 //旧的
#define MMC_TIMING_MMC_HS	1 //mmc
#define MMC_TIMING_SD_HS	2 //sd
//UHS：超高速版。UHS-I: 超高速版1
//UHS是一种速度标准。
//下面是UHS-I的5种模式，在SDHCI标准中有个叫Host Control 2的寄存器
//它的第0~2位就是选择UHS的模式
#define MMC_TIMING_UHS_SDR12	MMC_TIMING_LEGACY
#define MMC_TIMING_UHS_SDR25	MMC_TIMING_SD_HS
#define MMC_TIMING_UHS_SDR50	3
#define MMC_TIMING_UHS_SDR104	4
#define MMC_TIMING_UHS_DDR50	5

#define MMC_SDR_MODE		0
#define MMC_1_2V_DDR_MODE	1
#define MMC_1_8V_DDR_MODE	2

	unsigned char	signal_voltage;		/* signalling voltage (1.8V or 3.3V) */ 
//上面说信号电压(1.8v 或 3.3v),没有提到1.2v
//我看了SDHCI，还是Host Control 2的第3位 1: 1.8v 0: 3.3v
//也没提到1.2v. 不过代码中提到eMMC卡可以支持1.2v或3.3v
//eMMC:(Embedded Multi Media Card),这东西的封装是：小型的
//BGA 封装。
#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) */
//还是Host Control 2寄存器的4~5位选择，默认是B
//UHS-I卡1.8v时才有效，3.3v无效
//还有Preset Value Enable = 0时可以被主机设置
//Preset Value Enable = 1时由Preset Value寄存器决定
/*
B:默认的驱动。50欧姆传输线阻抗。支持UHS104和UHS50卡。下面的都以B为参考。
A:x1.5驱动(是50/1.5 = 33欧姆)。支持208MHz
C:x0.75。支持208MHz的最弱驱动。
D:x0.5。这个主要是速度不是要紧的，重要是低noise,低EMI。最大频率由主机设计确定。
*/
#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
};

//下面是写驱动要搞定的接口，如果你的硬件支持SDHCI。你可能看不到这个。
//已在sdhci.c统一实现。
struct mmc_host_ops {
	/*
	 * Hosts that support power saving can use the 'enable' and 'disable'
	 * methods to exit and enter power saving states. 'enable' is called
	 * when the host is claimed and 'disable' is called (or scheduled with
	 * a delay) when the host is released. The 'disable' is scheduled if
	 * the disable delay set by 'mmc_set_disable_delay()' is non-zero,
	 * otherwise 'disable' is called immediately. 'disable' may be
	 * scheduled repeatedly, to permit ever greater power saving at the
	 * expense of ever greater latency to re-enable. Rescheduling is
	 * determined by the return value of the 'disable' method. A positive
	 * value gives the delay in milliseconds.
	 *
	 * In the case where a host function (like set_ios) may be called
	 * with or without the host claimed, enabling and disabling can be
	 * done directly and will nest correctly. Call 'mmc_host_enable()' and
	 * 'mmc_host_lazy_disable()' for this purpose, but note that these
	 * functions must be paired.
	 *
	 * Alternatively, 'mmc_host_enable()' may be paired with
	 * 'mmc_host_disable()' which calls 'disable' immediately.  In this
	 * case the 'disable' method will be called with 'lazy' set to 0.
	 * This is mainly useful for error paths.
	 *
	 * Because lazy disable may be called from a work queue, the 'disable'
	 * method must claim the host when 'lazy' != 0, which will work
	 * correctly because recursion is detected and handled.
	 */
	/*
	上面解释了一大堆，自己看看。我说一下调用过程。at91_mci.c sd卡
	at91_mci_driver->at91_mci_suspend()->mmc_suspend_host()->