8. [mmc subsystem] host（第二章）——sdhci
2024-09-04 06:08:34
一、sdhci core说明
1、sdhci说明
具体参考《host（第一章）——概述》
SDHC：Secure Digital(SD) Host Controller，是指一套sd host控制器的设计标准，其寄存器偏移以及意义都有一定的规范，并且提供了对应的驱动程序，方便vendor进行host controller的开发。
vendor按照这套标准设计host controller之后，可以直接使用sdhci driver来实现host controller的使用，（qcom和samsung都使用了这套标准）。而vendor只需要实现平台相关的部分、如clock、pinctrl、power等等的部分即可。
关于这个标准，我们可以参考《SDHC_Ver3.00_Final_110225》。
注意，强调一下，这是一种mmc host controller的设计标准，其本质上还是属于mmc host。并且，其兼容mmc type card，而不是说只能使用于sd type card。
2、sdhci core
因为sdhci driver并不是某个特定host的driver，而是提供了一些接口和操作集方法给对应的host driver使用。
因此，我们将sdhci.c的代码部分称之为sdhci core用以和host driver区分。
其主要功能如下：
- 为host driver提供分配、释放sdhci_host的接口
- 为host driver提供注册、卸载sdhci_host的接口
- 实现sdhci_host和mmc_host的对接（也就是mmc core的对接）
- 实现host关于SDHCI标准的通用操作（sdhci_ops）
- 实现host的通用电源管理操作
注意，clock和pinctrl是由host driver自己管理，sdhci core并不参与。
3、代码位置
drivers/mmc/host/sdhci.c
drivers/mmc/host/sdhci.h
二、数据结构
1、struct sdhci_host
sdhci core将host抽象出struct sdhci_host来进行管理和维护。
数据结构如下：
struct sdhci_host {
/* Data set by hardware interface driver */
const char *hw_name; /* Hardware bus name */ // 名称
unsigned int quirks; /* Deviations from spec. */ // 癖好，可以理解为硬件sdhci controller和标准sdhci规范不符合的地方。
unsigned int quirks2; /* More deviations from spec. */ // 癖好2，可以理解为硬件sdhci controller和标准sdhci规范不符合的地方。
int irq; /* Device IRQ */ // sdhci的中断
void __iomem *ioaddr; /* Mapped address */ // sdhci寄存器的基地址
const struct sdhci_ops *ops; /* Low level hw interface */ // 底层硬件的操作接口
struct regulator *vmmc; /* Power regulator (vmmc) */ // sdhci core的LDO
struct regulator *vqmmc; /* Signaling regulator (vccq) */ // 给sdhci io供电的LDO
/* Internal data */
struct mmc_host *mmc; /* MMC structure */ // struct mmc_host，用于注册到mmc subsystem中
u64 dma_mask; /* custom DMA mask */
spinlock_t lock; /* Mutex */ // 自旋锁
int flags; /* Host attributes */ // sdhci的一些标识
unsigned int version; /* SDHCI spec. version */ // 当前sdhci的硬件版本
unsigned int max_clk; /* Max possible freq (MHz) */ // 该sdhci支持的最大电压
unsigned int timeout_clk; /* Timeout freq (KHz) */ // 超时频率
unsigned int clk_mul; /* Clock Muliplier value */ // 当前倍频值
unsigned int clock; /* Current clock (MHz) */ // 当前工作频率
u8 pwr; /* Current voltage */ // 当前工作电压
bool runtime_suspended; /* Host is runtime suspended */ // 是否处于runtime suspend状态
struct mmc_request *mrq; /* Current request */ // 当前正在处理的请求
struct mmc_command *cmd; /* Current command */ // 当前的命令请求
struct mmc_data *data; /* Current data request */ // 当前的数据请求
unsigned int data_early:1; /* Data finished before cmd */ // 表示在CMD处理完成前，data已经处理完成
struct sg_mapping_iter sg_miter; /* SG state for PIO */
unsigned int blocks; /* remaining PIO blocks */
int sg_count; /* Mapped sg entries */
u8 *adma_desc; /* ADMA descriptor table */
u8 *align_buffer; /* Bounce buffer */
unsigned int adma_desc_sz; /* ADMA descriptor table size */
unsigned int adma_desc_line_sz; /* ADMA descriptor line size */
unsigned int align_buf_sz; /* Bounce buffer size */
unsigned int align_bytes; /* Alignment bytes (4/8 for 32-bit/64-bit) */
unsigned int adma_max_desc; /* Max ADMA descriptos (max sg segments) */
dma_addr_t adma_addr; /* Mapped ADMA descr. table */
dma_addr_t align_addr; /* Mapped bounce buffer */
struct tasklet_struct card_tasklet; /* Tasklet structures */ // card tasklet，用于处理card的插入或者拔出事件
struct tasklet_struct finish_tasklet; // finsh tasklet，用来通知上层一个请求处理完成（包括出错的情况）
struct timer_list timer; /* Timer for timeouts */ // 超时定时器链表
u32 caps; /* Alternative CAPABILITY_0 */ // 表示该sdhci controller的属性
u32 caps1; /* Alternative CAPABILITY_1 */ // 表示该sdhci controller的属性
unsigned int ocr_avail_sdio; /* OCR bit masks */ // 在该sdhci controller上可用的sdio card的ocr值掩码（代表了其可用电压）
unsigned int ocr_avail_sd; // 在该sdhci controller上可用的sd card的ocr值掩码（代表了其可用电压）
unsigned int ocr_avail_mmc; /// 在该sdhci controller上可用的mmc card的ocr值掩码（代表了其可用电压）
/* 以下和mmc的tuning相关 */
wait_queue_head_t buf_ready_int; /* Waitqueue for Buffer Read Ready interrupt */
unsigned int tuning_done; /* Condition flag set when CMD19 succeeds */
unsigned int tuning_count; /* Timer count for re-tuning */
unsigned int tuning_mode; /* Re-tuning mode supported by host */
#define SDHCI_TUNING_MODE_1 0
struct timer_list tuning_timer; /* Timer for tuning */
/* 以下和sdhci的qos相关 */
struct sdhci_host_qos host_qos[SDHCI_QOS_MAX_POLICY];
enum sdhci_host_qos_policy last_qos_policy;
bool host_use_default_qos;
unsigned int pm_qos_timeout_us; /* timeout for PM QoS request */
struct device_attribute pm_qos_tout;
struct delayed_work pm_qos_work;
struct sdhci_next next_data;
ktime_t data_start_time;
struct mutex ios_mutex;
enum sdhci_power_policy power_policy;
bool irq_enabled; /* host irq status flag */ // 表示中断是否使能？
bool async_int_supp; /* async support to rxv int, when clks are off */
bool disable_sdio_irq_deferred; /* status of disabling sdio irq */
u32 auto_cmd_err_sts;
struct ratelimit_state dbg_dump_rs;
int reset_wa_applied; /* reset workaround status */
ktime_t reset_wa_t; /* time when the reset workaround is applied */
int reset_wa_cnt; /* total number of times workaround is used */
unsigned long private[0] ____cacheline_aligned; // 私有数据指针
};
- 癖好1（sdhci_host->quirks）各个位意义如下：
/* Controller doesn't honor resets unless we touch the clock register */
#define SDHCI_QUIRK_CLOCK_BEFORE_RESET (1<<0)
/* Controller has bad caps bits, but really supports DMA */
#define SDHCI_QUIRK_FORCE_DMA (1<<1)
/* Controller doesn't like to be reset when there is no card inserted. */
#define SDHCI_QUIRK_NO_CARD_NO_RESET (1<<2)
/* Controller doesn't like clearing the power reg before a change */
#define SDHCI_QUIRK_SINGLE_POWER_WRITE (1<<3)
/* Controller has flaky internal state so reset it on each ios change */
#define SDHCI_QUIRK_RESET_CMD_DATA_ON_IOS (1<<4)
/* Controller has an unusable DMA engine */
#define SDHCI_QUIRK_BROKEN_DMA (1<<5)
/* Controller has an unusable ADMA engine */
#define SDHCI_QUIRK_BROKEN_ADMA (1<<6)
/* Controller can only DMA from 32-bit aligned addresses */
#define SDHCI_QUIRK_32BIT_DMA_ADDR (1<<7)
/* Controller can only DMA chunk sizes that are a multiple of 32 bits */
#define SDHCI_QUIRK_32BIT_DMA_SIZE (1<<8)
/* Controller can only ADMA chunks that are a multiple of 32 bits */
#define SDHCI_QUIRK_32BIT_ADMA_SIZE (1<<9)
/* Controller needs to be reset after each request to stay stable */
#define SDHCI_QUIRK_RESET_AFTER_REQUEST (1<<10)
/* Controller needs voltage and power writes to happen separately */
#define SDHCI_QUIRK_NO_SIMULT_VDD_AND_POWER (1<<11)
/* Controller provides an incorrect timeout value for transfers */
#define SDHCI_QUIRK_BROKEN_TIMEOUT_VAL (1<<12)
/* Controller has an issue with buffer bits for small transfers */
#define SDHCI_QUIRK_BROKEN_SMALL_PIO (1<<13)
/* Controller does not provide transfer-complete interrupt when not busy */
#define SDHCI_QUIRK_NO_BUSY_IRQ (1<<14)
/* Controller has unreliable card detection */
#define SDHCI_QUIRK_BROKEN_CARD_DETECTION (1<<15)
/* Controller reports inverted write-protect state */
#define SDHCI_QUIRK_INVERTED_WRITE_PROTECT (1<<16)
/* Controller has nonstandard clock management */
#define SDHCI_QUIRK_NONSTANDARD_CLOCK (1<<17)
/* Controller does not like fast PIO transfers */
#define SDHCI_QUIRK_PIO_NEEDS_DELAY (1<<18)
/* Controller losing signal/interrupt enable states after reset */
#define SDHCI_QUIRK_RESTORE_IRQS_AFTER_RESET (1<<19)
/* Controller has to be forced to use block size of 2048 bytes */
#define SDHCI_QUIRK_FORCE_BLK_SZ_2048 (1<<20)
/* Controller cannot do multi-block transfers */
#define SDHCI_QUIRK_NO_MULTIBLOCK (1<<21)
/* Controller can only handle 1-bit data transfers */
#define SDHCI_QUIRK_FORCE_1_BIT_DATA (1<<22)
/* Controller needs 10ms delay between applying power and clock */
#define SDHCI_QUIRK_DELAY_AFTER_POWER (1<<23)
/* Controller uses SDCLK instead of TMCLK for data timeouts */
#define SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK (1<<24)
/* Controller reports wrong base clock capability */
#define SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN (1<<25)
/* Controller cannot support End Attribute in NOP ADMA descriptor */
#define SDHCI_QUIRK_NO_ENDATTR_IN_NOPDESC (1<<26)
/* Controller is missing device caps. Use caps provided by host */
#define SDHCI_QUIRK_MISSING_CAPS (1<<27)
/* Controller uses Auto CMD12 command to stop the transfer */
#define SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12 (1<<28)
/* Controller doesn't have HISPD bit field in HI-SPEED SD card */
#define SDHCI_QUIRK_NO_HISPD_BIT (1<<29)
/* Controller treats ADMA descriptors with length 0000h incorrectly */
#define SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC (1<<30)
/* The read-only detection via SDHCI_PRESENT_STATE register is unstable */
#define SDHCI_QUIRK_UNSTABLE_RO_DETECT (1<<31)
- 癖好2（sdhci_host->quirks2）各个位意义如下：
#define SDHCI_QUIRK2_HOST_OFF_CARD_ON (1<<0)
#define SDHCI_QUIRK2_HOST_NO_CMD23 (1<<1)
/* The system physically doesn't support 1.8v, even if the host does */
#define SDHCI_QUIRK2_NO_1_8_V (1<<2)
#define SDHCI_QUIRK2_PRESET_VALUE_BROKEN (1<<3)
/*
* Read Transfer Active/ Write Transfer Active may be not
* de-asserted after end of transaction. Issue reset for DAT line.
*/
#define SDHCI_QUIRK2_RDWR_TX_ACTIVE_EOT (1<<4)
/*
* Slow interrupt clearance at 400KHz may cause
* host controller driver interrupt handler to
* be called twice.
*/
#define SDHCI_QUIRK2_SLOW_INT_CLR (1<<5)
/*
* If the base clock can be scalable, then there should be no further
* clock dividing as the input clock itself will be scaled down to
* required frequency.
*/
#define SDHCI_QUIRK2_ALWAYS_USE_BASE_CLOCK (1<<6)
/*
* Dont use the max_discard_to in sdhci driver so that the maximum discard
* unit gets picked by the mmc queue. Otherwise, it takes a long time for
* secure discard kind of operations to complete.
*/
#define SDHCI_QUIRK2_USE_MAX_DISCARD_SIZE (1<<7)
/*
* Ignore data timeout error for R1B commands as there will be no
* data associated and the busy timeout value for these commands
* could be lager than the maximum timeout value that controller
* can handle.
*/
#define SDHCI_QUIRK2_IGNORE_DATATOUT_FOR_R1BCMD (1<<8)
/*
* The preset value registers are not properly initialized by
* some hardware and hence preset value must not be enabled for
* such controllers.
*/
#define SDHCI_QUIRK2_BROKEN_PRESET_VALUE (1<<9)
/*
* Some controllers define the usage of 0xF in data timeout counter
* register (0x2E) which is actually a reserved bit as per
* specification.
*/
#define SDHCI_QUIRK2_USE_RESERVED_MAX_TIMEOUT (1<<10)
/*
* This is applicable for controllers that advertize timeout clock
* value in capabilities register (bit 5-0) as just 50MHz whereas the
* base clock frequency is 200MHz. So, the controller internally
* multiplies the value in timeout control register by 4 with the
* assumption that driver always uses fixed timeout clock value from
* capabilities register to calculate the timeout. But when the driver
* uses SDHCI_QUIRK2_ALWAYS_USE_BASE_CLOCK base clock frequency is directly
* controller by driver and it's rate varies upto max. 200MHz. This new quirk
* will be used in such cases to avoid controller mulplication when timeout is
* calculated based on the base clock.
*/
#define SDHCI_QUIRK2_DIVIDE_TOUT_BY_4 (1 << 11)
/*
* Some SDHC controllers are unable to handle data-end bit error in
* 1-bit mode of SDIO.
*/
#define SDHCI_QUIRK2_IGN_DATA_END_BIT_ERROR (1<<12)
/*
* Some SDHC controllers do not require data buffers alignment, skip
* the bounce buffer logic when preparing data
*/
#define SDHCI_QUIRK2_ADMA_SKIP_DATA_ALIGNMENT (1<<13)
/* Some controllers doesn't have have any LED control */
#define SDHCI_QUIRK2_BROKEN_LED_CONTROL (1 << 14)
/* Use reset workaround in case sdhci reset timeouts */
#define SDHCI_QUIRK2_USE_RESET_WORKAROUND (1 << 15)
- sdhci host的一些标识（sdhci_host->flags）如下：
#define SDHCI_USE_SDMA (1<<0) /* Host is SDMA capable */
#define SDHCI_USE_ADMA (1<<1) /* Host is ADMA capable */
#define SDHCI_REQ_USE_DMA (1<<2) /* Use DMA for this req. */
#define SDHCI_DEVICE_DEAD (1<<3) /* Device unresponsive */
#define SDHCI_SDR50_NEEDS_TUNING (1<<4) /* SDR50 needs tuning */
#define SDHCI_NEEDS_RETUNING (1<<5) /* Host needs retuning */
#define SDHCI_AUTO_CMD12 (1<<6) /* Auto CMD12 support */
#define SDHCI_AUTO_CMD23 (1<<7) /* Auto CMD23 support */
#define SDHCI_PV_ENABLED (1<<8) /* Preset value enabled */
#define SDHCI_SDIO_IRQ_ENABLED (1<<9) /* SDIO irq enabled */
#define SDHCI_HS200_NEEDS_TUNING (1<<10) /* HS200 needs tuning */
#define SDHCI_USING_RETUNING_TIMER (1<<11) /* Host is using a retuning timer for the card */
#define SDHCI_HS400_NEEDS_TUNING (1<<12) /* HS400 needs tuning */
#define SDHCI_USE_ADMA_64BIT (1<<13)/* Host is 64-bit ADMA capable */
2、struct sdhci_ops结构体
sdhci core只是提供了一些接口和符合mmc core的操作集方法给对应的host driver使用。由于各个host的硬件有所差异，所以实际和硬件交互的驱动部分还是在host driver中实现。
所以sdhci core要求host提供标准的访问硬件的一些方法。而这些方法就被定义在了struct sdhci_ops结构体内部。
结构体如下：
struct sdhci_ops {
#ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS
// 表示host另外提供了一套访问寄存器的方法，没有定义的话，则说明使用通用的读写寄存器的方法
u32 (*read_l)(struct sdhci_host *host, int reg);
u16 (*read_w)(struct sdhci_host *host, int reg);
u8 (*read_b)(struct sdhci_host *host, int reg);
void (*write_l)(struct sdhci_host *host, u32 val, int reg);
void (*write_w)(struct sdhci_host *host, u16 val, int reg);
void (*write_b)(struct sdhci_host *host, u8 val, int reg);
#endif
void (*set_clock)(struct sdhci_host *host, unsigned int clock); // 设置时钟频率
int (*enable_dma)(struct sdhci_host *host); // 使能DMA
unsigned int (*get_max_clock)(struct sdhci_host *host); // 获取支持的最大时钟频率
unsigned int (*get_min_clock)(struct sdhci_host *host); // 获取支持的最小时钟频率
unsigned int (*get_timeout_clock)(struct sdhci_host *host);
int (*platform_bus_width)(struct sdhci_host *host, int width);
void (*platform_send_init_74_clocks)(struct sdhci_host *host,
u8 power_mode);
unsigned int (*get_ro)(struct sdhci_host *host); // 获取
void (*platform_reset_enter)(struct sdhci_host *host, u8 mask); // 进入平台复位的方法
void (*platform_reset_exit)(struct sdhci_host *host, u8 mask); // 退出平台复位的方法
int (*set_uhs_signaling)(struct sdhci_host *host, unsigned int uhs); // 设置uhs方式
void (*hw_reset)(struct sdhci_host *host); // 硬件复位的方法
void (*platform_suspend)(struct sdhci_host *host); // 平台host的suspend方法
void (*platform_resume)(struct sdhci_host *host); // 平台host的resume方法
void (*adma_workaround)(struct sdhci_host *host, u32 intmask);
void (*platform_init)(struct sdhci_host *host); // 平台host的初始化方法
void (*check_power_status)(struct sdhci_host *host, u32 req_type); // 检测总线的电源状态
#define REQ_BUS_OFF (1 << 0)
#define REQ_BUS_ON (1 << 1)
#define REQ_IO_LOW (1 << 2)
#define REQ_IO_HIGH (1 << 3)
int (*execute_tuning)(struct sdhci_host *host, u32 opcode); // 执行tuning操作的的方法
void (*toggle_cdr)(struct sdhci_host *host, bool enable);
unsigned int (*get_max_segments)(void);
void (*platform_bus_voting)(struct sdhci_host *host, u32 enable); // 平台总线投票的方法
void (*disable_data_xfer)(struct sdhci_host *host);
void (*dump_vendor_regs)(struct sdhci_host *host);
int (*config_auto_tuning_cmd)(struct sdhci_host *host,
bool enable,
u32 type);
int (*enable_controller_clock)(struct sdhci_host *host);
void (*reset_workaround)(struct sdhci_host *host, u32 enable);
};
这个结构体也就是host driver要实现的核心内容。
3、struct mmc_host_ops sdhci_ops
注意：这里的sdhci_ops是一个变量名，和上述的struct sdhci_ops不是同一个概念。搞不懂为什么这么命名，容易混淆。
sdhci core使用sdhci_ops作为sdhci host抽象出来的mmc host的操作集，所以其是一个struct mmc_host_ops结构体。
后续mmc core关于这个host的操作也都是基于这个操作集上实现的，包括使能host（enable方法）、禁用host（disable方法）、发送请求（request方法）。
具体参考《mmc core》系列。
具体实现如下，具体意义参考《mmc core（第二章）——数据结构和宏定义说明》：
static const struct mmc_host_ops sdhci_ops = {
// post_req和pre_req是为了实现异步请求处理而设置的
// 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
// 具体参考《mmc core主模块》
.pre_req = sdhci_pre_req,
.post_req = sdhci_post_req,
.request = sdhci_request, // host处理mmc请求的方法，在mmc_start_request中会调用
.set_ios = sdhci_set_ios, // 设置host的总线的io setting
.get_cd = sdhci_get_cd, // 检测host的卡槽中card的插入状态
.get_ro = sdhci_get_ro, // 获取host上的card的读写属性
.hw_reset = sdhci_hw_reset, // 硬件复位
.enable_sdio_irq = sdhci_enable_sdio_irq,
.start_signal_voltage_switch = sdhci_start_signal_voltage_switch, // 切换信号电压的方法
.execute_tuning = sdhci_execute_tuning, // 执行tuning操作，为card选择一个合适的采样点
.card_event = sdhci_card_event,
.card_busy = sdhci_card_busy, // 用于检测card是否处于busy状态
.enable = sdhci_enable, // 使能host，当host被占用时（第一次调用mmc_claim_host）调用
.disable = sdhci_disable, // 禁用host，当host被释放时（第一次调用mmc_release_host）调用
.stop_request = sdhci_stop_request, // 停止请求处理的方法
.get_xfer_remain = sdhci_get_xfer_remain,
.notify_load = sdhci_notify_load,
};
三、API总览
1、sdhci_host分配和释放相关
- sdhci_alloc_host & sdhci_free_host
由底层host driver调用。
sdhci_alloc_host为host driver分配一个sdhci_host和mmc_host，并实现其初始化，以及sdhci_host和mmc_host的关联。
sdhci_free_host则是用来释放一个sdhci_host。
原型：struct sdhci_host *sdhci_alloc_host(struct device *dev, size_t priv_size)
参数说明：struct device *dev——》对应host的device结构体
size_t priv_size——》要分配的sdhci_host的私有数据的长度，一般是平台自己定制的host的长度。
原型：void sdhci_free_host(struct sdhci_host *host)
2、sdhci_host的注册和卸载相关
- sdhci_add_host & sdhci_remove_host
由底层host driver调用。
sdhci_add_host用于向sdhci core注册一个sdhci_host。会根据sdhci的寄存器以及部分标识设置其mmc_host，最终将mmc_host注册到mmc core中。
因此，在调用sdhci_add_host之前，必须准备好sdhci的所有硬件环境。
sdhci_free_host则用于从sdhci core中卸载一个sdhci_host，对应的mmc_host也会从mmc core中被卸载。
原型：int sdhci_add_host(struct sdhci_host *host)；
原型：void sdhci_remove_host(struct sdhci_host *host, int dead)；
四、接口代码说明
1、sdhci_alloc_host
struct sdhci_host *sdhci_alloc_host(struct device *dev,
size_t priv_size)
{
struct mmc_host *mmc;
struct sdhci_host *host;
WARN_ON(dev == NULL);
/* 实现mmc_host和sdhci_host的分配 */
mmc = mmc_alloc_host(sizeof(struct sdhci_host) + priv_size, dev); // 分配一个struct mmc_host
// 分配mmc_host的同时也分配了sizeof(struct sdhci_host) + priv_size的私有数据空间，这部分就是作为sdhci_host及其私有数据使用的。
// 具体参考《mmc core——host模块说明》
if (!mmc)
return ERR_PTR(-ENOMEM);
/* 实现mmc_host和sdhci_host的关联操作 */
host = mmc_priv(mmc); // 将sdhci_host作为mmc_host的私有数据，mmc_host->private = sdhci_host
host->mmc = mmc; // 关联sdhci_host和mmc_host，sdhci_host->mmc = mmc_host
/* sdhci_host的锁的初始化工作 */
spin_lock_init(&host->lock); // 初始化sdhci_host 的占有锁
mutex_init(&host->ios_mutex); // 初始化sdhci_host 设置io setting的互斥锁
return host; // 将struct sdhci_host 返回
}
综上，
mmc_host->private = sdhci_host
sdhci_host->mmc = mmc_host
2、sdhci_add_host
（0）底层传上来的sdhci_host中应该包含什么信息
- sdhci的寄存器的映射过后的基地址（sdhci_host->ioaddr）
- sdhci的癖好quirks、quirks2（sdhci_host->quirks，sdhci_host->quirks2）
- sdhci的中断号（sdhci_host->irq）
- host提供给sdhci core用来操作硬件的操作集（sdhci_host->ops）
（1）主要完成工作如下：
- sdhci host复位
调用sdhci_reset
读取该host的sdhci的信息（从sdhci相关寄存器中读取）并设置sdhci_host相关成员
- 版本（sdhci_host->version） : 从SDHCI_HOST_VERSION寄存器中读取
- 支持的属性 : 从SDHCI_CAPABILITIES、SDHCI_CAPABILITIES_1寄存器中读取
- 标识（sdhci_host->version） : 根据sdhci_host->quirks和quirks2来设置
- 支持的最大频率和倍频（sdhci_host->max_clk & sdhci_host->clk_mul）
对应SDHCI_CAPABILITIES寄存器中的SDHCI_CLOCK_BASE_SHIFT位
对应SDHCI_CAPABILITIES寄存器中的SDHCI_CLOCK_MUL_SHIFT位 - sdhci使用的regulator（sdhci_host->vqmmc）
从节点中的命名为”vmmc”的regulator属性中获取 - card插入状态发生变化时调用的tasklet（sdhci_host->card_tasklet）
设置为sdhci_tasklet_card - 请求处理完成时调用的tasklet（sdhci_host->finish_tasklet）
设置为sdhci_tasklet_finish - 请求的处理超时定时器（sdhci_host->timer）
设置为sdhci_timeout_timer - qos处理的工作（sdhci_host->pm_qos_work）
设置为sdhci_pm_qos_remove_work
设置mmc_host的相关成员
- 操作集（mmc_host->ops）
设置为sdhci_ops，上面已经说明过了 - 最大频率（mmc_host->f_max）
用sdhci_host->max_clk的值来设置 - host的属性（mmc_host->caps & mmc_host->caps2）
通过sdhci_host->quirks和quirks2、以及SDHCI_CAPABILITIES、SDHCI_CAPABILITIES_1寄存器中的属性进行设置 - 各个电压下的最大电流值（mmc_host->max_current_330 & mmc_host->max_current_300 & mmc_host->max_current_180）
从SDHCI_MAX_CURRENT寄存器中读取 - 可用电压（mmc->ocr_avail & mmc->ocr_avail_sdio & mmc->ocr_avail_sd & mmc->ocr_avail_mmc）
从SDHCI_CAPABILITIES寄存器中的SDHCI_CAN_VDD_330、SDHCI_CAN_VDD_300、SDHCI_CAN_VDD_180位获取 - 一些块和段size的设置
- 操作集（mmc_host->ops）
中断的注册
将sdhci_host的中断处理函数注册为sdhci_irqsdhci host初始化
调用sdhci_init注册mmc_host到mmc core中
调用mmc_add_host使能card插入状态的检测
调用sdhci_enable_card_detection
（2）代码如下：
int sdhci_add_host(struct sdhci_host *host)
{
// 以下变量要注意区分
// host是指要注册的sdhci host
// mmc是指要注册到mmc subsystem的host，封装在sdhci host中
struct mmc_host *mmc;
u32 caps[2] = {0, 0};
u32 max_current_caps;
unsigned int ocr_avail;
int ret;
WARN_ON(host == NULL);
if (host == NULL)
return -EINVAL;
mmc = host->mmc; // 获取struct mmc_host
/* 执行复位操作 */
sdhci_reset(host, SDHCI_RESET_ALL);
// 执行reset操作，会调用到sdhci_host->ops->platform_reset_enter，msm并没有实现这个方法
/********************************* 获取sdhci信息并设置sdhci_host的相应成员***********************/
/* 获取sdhci controller版本号 */
host->version = sdhci_readw(host, SDHCI_HOST_VERSION);
host->version = (host->version & SDHCI_SPEC_VER_MASK) >> SDHCI_SPEC_VER_SHIFT;
// 获取sdhci host的硬件版本号
/* 获取sdhci controller支持的属性 */
caps[0] = (host->quirks & SDHCI_QUIRK_MISSING_CAPS) ? host->caps : sdhci_readl(host, SDHCI_CAPABILITIES);
// SDHCI_QUIRK_MISSING_CAPS：Controller is missing device caps. Use caps provided by host
// sdhci控制器没有devices属性的话，由底层host提供，否则，从sdhci controller的SDHCI_CAPABILITIES读取属性
if (host->version >= SDHCI_SPEC_300)
caps[1] = (host->quirks & SDHCI_QUIRK_MISSING_CAPS) ?host->caps1 : sdhci_readl(host, SDHCI_CAPABILITIES_1);
// 从sdhci controller的SDHCI_CAPABILITIES_1读取属性
/* 设置sdhci_host->flags中和DMA相关的flag */
if (host->quirks & SDHCI_QUIRK_FORCE_DMA)
host->flags |= SDHCI_USE_SDMA;
else if (!(caps[0] & SDHCI_CAN_DO_SDMA))
DBG("Controller doesn't have SDMA capability\n");
else
host->flags |= SDHCI_USE_SDMA;
// SDHCI_QUIRK_FORCE_DMA : Controller has bad caps bits, but really supports DMA
// 设置sdhci_host->flags中的SDHCI_USE_SDMA标识
//............................
if (host->flags & SDHCI_USE_ADMA) {
// sdhci_host ->adma_max_desc
// sdhci_host ->adma_desc_line_sz
// sdhci_host ->align_bytes
// sdhci_host ->adma_desc_sz
// sdhci_host ->align_buf_sz
// sdhci_host ->adma_desc
// sdhci_host ->align_buffer
}
host->next_data.cookie = 1;
/* 获取sdhci controller支持的最大频率以及倍频 */
if (host->version >= SDHCI_SPEC_300)
host->max_clk = (caps[0] & SDHCI_CLOCK_V3_BASE_MASK)
>> SDHCI_CLOCK_BASE_SHIFT; // 从sdhci controller的SDHCI_CLOCK_V3_BASE_MASK读取最大clock（单位是MHZ）
else
host->max_clk = (caps[0] & SDHCI_CLOCK_BASE_MASK)
>> SDHCI_CLOCK_BASE_SHIFT;
host->max_clk *= 1000000;（转化为hz）
// 设置sdhci_host->max_clk
sdhci_update_power_policy(host, SDHCI_PERFORMANCE_MODE_INIT);
// 设置sdhci_host->power_policy为SDHCI_PERFORMANCE_MODE_INIT
if (host->max_clk == 0 || host->quirks & SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN) {
host->max_clk = host->ops->get_max_clock(host); // 调用sdhci_host->ops->get_max_clock获得最大时钟
}
host->clk_mul = (caps[1] & SDHCI_CLOCK_MUL_MASK) >> SDHCI_CLOCK_MUL_SHIFT;
if (host->clk_mul)
host->clk_mul += 1;
// 设置sdhci_host->clk_mul，clock的倍频实行
/*************************** 以下对mmc_host和sdhci_host进行设置操作 ***************************/
/* 以下设置mmc_host，ops、f_max、f_min */
mmc->ops = &sdhci_ops; // 设置mmc_host的操作集为sdhci_ops
mmc->f_max = host->max_clk; // 设置最大时钟频率mmc_host->f_max
if (host->ops->get_min_clock)
mmc->f_min = host->ops->get_min_clock(host); // 调用sdhci_host->ops->get_min_clock获得最小时钟频率mmc_host->f_min
host->timeout_clk = (caps[0] & SDHCI_TIMEOUT_CLK_MASK) >> SDHCI_TIMEOUT_CLK_SHIFT;
// 从sdhci controller的SDHCI_TIMEOUT_CLK_MASK读取最大timeout
// 设置到sdhci_host->timeout_clk
if (host->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)
host->timeout_clk = mmc->f_max / 1000;
if (!(host->quirks2 & SDHCI_QUIRK2_USE_MAX_DISCARD_SIZE))
mmc->max_discard_to = (1 << 27) / host->timeout_clk;
// 设置mmc_host->max_discard_to
/* 设置mmc_host->caps，也就是属性 */
mmc->caps |= MMC_CAP_SDIO_IRQ | MMC_CAP_ERASE | MMC_CAP_CMD23;
if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
mmc->caps |= MMC_CAP_4_BIT_DATA;
if (host->quirks2 & SDHCI_QUIRK2_HOST_NO_CMD23)
mmc->caps &= ~MMC_CAP_CMD23;
if (caps[0] & SDHCI_CAN_DO_HISPD)
mmc->caps |= MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED;
if ((host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) &&
!(host->mmc->caps & MMC_CAP_NONREMOVABLE) &&
(mmc_gpio_get_cd(host->mmc) < 0) &&
!(host->mmc->caps2 & MMC_CAP2_NONHOTPLUG))
mmc->caps |= MMC_CAP_NEEDS_POLL;
/* 获取vqmmc regulater并使能 */
/* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
host->vqmmc = regulator_get(mmc_dev(mmc), "vqmmc");
if (IS_ERR_OR_NULL(host->vqmmc)) {
....
} else {
ret = regulator_enable(host->vqmmc);
if (!regulator_is_supported_voltage(host->vqmmc, 1700000,1950000))
caps[1] &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 | SDHCI_SUPPORT_DDR50);
}
if (host->quirks2 & SDHCI_QUIRK2_NO_1_8_V)
caps[1] &= ~(SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 | SDHCI_SUPPORT_DDR50);
/* 设置mmc_host->caps和传输模式相关的属性 */
/* Any UHS-I mode in caps implies SDR12 and SDR25 support. */
if (caps[1] & (SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_SDR50 |
SDHCI_SUPPORT_DDR50))
mmc->caps |= MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25;
/* SDR104 supports also implies SDR50 support */
if (caps[1] & SDHCI_SUPPORT_SDR104)
mmc->caps |= MMC_CAP_UHS_SDR104 | MMC_CAP_UHS_SDR50;
else if (caps[1] & SDHCI_SUPPORT_SDR50)
mmc->caps |= MMC_CAP_UHS_SDR50;
if (caps[1] & SDHCI_SUPPORT_DDR50)
mmc->caps |= MMC_CAP_UHS_DDR50;
/* 设置sdhci_host->flags中和tuning相关的flag */
/* Does the host need tuning for SDR50? */
if (caps[1] & SDHCI_USE_SDR50_TUNING)
host->flags |= SDHCI_SDR50_NEEDS_TUNING;
/* Does the host need tuning for HS200? */
if (mmc->caps2 & MMC_CAP2_HS200)
host->flags |= SDHCI_HS200_NEEDS_TUNING;
/* Does the host need tuning for HS400? */
if (mmc->caps2 & MMC_CAP2_HS400)
host->flags |= SDHCI_HS400_NEEDS_TUNING;
/* 设置mmc_host->caps和驱动类型相关的属性 */
/* Driver Type(s) (A, C, D) supported by the host */
if (caps[1] & SDHCI_DRIVER_TYPE_A)
mmc->caps |= MMC_CAP_DRIVER_TYPE_A;
if (caps[1] & SDHCI_DRIVER_TYPE_C)
mmc->caps |= MMC_CAP_DRIVER_TYPE_C;
if (caps[1] & SDHCI_DRIVER_TYPE_D)
mmc->caps |= MMC_CAP_DRIVER_TYPE_D;
/* 获取sdhci controller的tuning计数（tuning_count 、tuning_mode ）*/
host->tuning_count = (caps[1] & SDHCI_RETUNING_TIMER_COUNT_MASK) >>
SDHCI_RETUNING_TIMER_COUNT_SHIFT;
if (host->tuning_count)
host->tuning_count = 1 << (host->tuning_count - 1);
host->tuning_mode = (caps[1] & SDHCI_RETUNING_MODE_MASK) >> SDHCI_RETUNING_MODE_SHIFT;
ocr_avail = 0;
/* 获取vmmc regulater，设置caps[0]支持的电压值 */
host->vmmc = regulator_get(mmc_dev(mmc), "vmmc");
#ifdef CONFIG_REGULATOR
/*
* Voltage range check makes sense only if regulator reports
* any voltage value.
*/
if (host->vmmc && regulator_get_voltage(host->vmmc) > 0) {
ret = regulator_is_supported_voltage(host->vmmc, 2700000,
3600000);
if ((ret <= 0) || (!(caps[0] & SDHCI_CAN_VDD_330)))
caps[0] &= ~SDHCI_CAN_VDD_330;
if ((ret <= 0) || (!(caps[0] & SDHCI_CAN_VDD_300)))
caps[0] &= ~SDHCI_CAN_VDD_300;
ret = regulator_is_supported_voltage(host->vmmc, 1700000,
1950000);
if ((ret <= 0) || (!(caps[0] & SDHCI_CAN_VDD_180)))
caps[0] &= ~SDHCI_CAN_VDD_180;
}
#endif /* CONFIG_REGULATOR */
/* 设置各个电压下的最大电流值（max_current_330、max_current_330 、max_current_180 ）*/
/* 设置可用电压域 */
max_current_caps = sdhci_readl(host, SDHCI_MAX_CURRENT);
if (!max_current_caps && host->vmmc) {
u32 curr = regulator_get_current_limit(host->vmmc);
//....................
}
if (caps[0] & SDHCI_CAN_VDD_330) {
ocr_avail |= MMC_VDD_32_33 | MMC_VDD_33_34;
mmc->max_current_330 = ((max_current_caps &
SDHCI_MAX_CURRENT_330_MASK) >>
SDHCI_MAX_CURRENT_330_SHIFT) *
SDHCI_MAX_CURRENT_MULTIPLIER;
}
//.........
mmc->ocr_avail = ocr_avail;
mmc->ocr_avail_sdio = ocr_avail;
// ......
/*********************************** sdhci的初始化工作**************************************/
/* 初始化sdhci工作过程中会使用到的tasklet */
tasklet_init(&host->card_tasklet, sdhci_tasklet_card, (unsigned long)host); // host上发生card插入或者拔出时调用
tasklet_init(&host->finish_tasklet, sdhci_tasklet_finish, (unsigned long)host); // 完成一个request时调用
setup_timer(&host->timer, sdhci_timeout_timer, (unsigned long)host); // command的超时定时器
/* 初始化qos处理的工作 */
INIT_DELAYED_WORK(&host->pm_qos_work, sdhci_pm_qos_remove_work);
/* 中断注册和使能 */
ret = request_irq(host->irq, sdhci_irq, IRQF_SHARED,mmc_hostname(mmc), host);
host->irq_enabled = true;
/* 对该sdhci controller进行初始化 */
sdhci_init(host, 0);
mmiowb();
/* sdhci关于qos的请求和操作的设置 */
if (host->host_qos[SDHCI_QOS_READ_WRITE].cpu_dma_latency_us) {
// .........
}
/*********************************** 将mmc_host注册到mmc subsystem中 *******************************/
mmc_add_host(mmc);
/*********************************** 开始使能sdhci和并且开始检测card状态******************************/
sdhci_enable_card_detection(host);
return 0;
}
重点关注如下几个部分：
（1）sdhci_reset(host, SDHCI_RESET_ALL);
（2）mmc->ops = &sdhci_ops; // 设置mmc_host的操作集为sdhci_ops
（3）host->vmmc = regulator_get(mmc_dev(mmc), "vmmc");
（4）tasklet_init(&host->card_tasklet, sdhci_tasklet_card, (unsigned long)host); // host上发生card插入或者拔出时调用
（5）tasklet_init(&host->finish_tasklet, sdhci_tasklet_finish, (unsigned long)host); // 完成一个request时调用的tasklet
（6）ret = request_irq(host->irq, sdhci_irq, IRQF_SHARED,mmc_hostname(mmc), host);
（7）sdhci_init(host, 0); // 软初始化host
（8）sdhci_enable_card_detection(host); // 开始使能card插入状态的检测
五、sdhci core内部代码简单说明
1、sdhci_reset & sdhci_init & sdhci_enable_card_detection
- sdhci_reset
由sdhci core内部调用，用于复位host。 - sdhci_init
由sdhci core内部调用，用于初始化host - sdhci_enable_card_detection
由sdhci core内部调用，使能card插入状态的检测，主要是设置SDHCI_INT_ENABLE、SDHCI_SIGNAL_ENABLE寄存器
static irqreturn_t sdhci_irq(int irq, void *dev_id)
{
irqreturn_t result;
struct sdhci_host *host = dev_id;
u32 intmask, unexpected = 0;
int cardint = 0, max_loops = 16;
spin_lock(&host->lock);
/* 从SDHCI_INT_STATUS寄存器中读取中断状态 */
intmask = sdhci_readl(host, SDHCI_INT_STATUS); // 从SDHCI_INT_STATUS寄存器中读取中断状态
/* 确认是否有中断产生 */
if (!intmask || intmask == 0xffffffff) {
result = IRQ_NONE;
goto out;
}
again:
DBG("*** %s got interrupt: 0x%08x\n",
mmc_hostname(host->mmc), intmask);
/* 以下是对card插入或者拔出的中断进行处理 */
if (intmask & (SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE)) {
u32 present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
SDHCI_CARD_PRESENT;
sdhci_mask_irqs(host, present ? SDHCI_INT_CARD_INSERT :
SDHCI_INT_CARD_REMOVE);
sdhci_unmask_irqs(host, present ? SDHCI_INT_CARD_REMOVE :
SDHCI_INT_CARD_INSERT);
sdhci_writel(host, intmask & (SDHCI_INT_CARD_INSERT |
SDHCI_INT_CARD_REMOVE), SDHCI_INT_STATUS); // 重置这两个中断位
intmask &= ~(SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE);
tasklet_schedule(&host->card_tasklet); // 执行host->card_tasklet，也就是sdhci_tasklet_card进行处理，后面说明
}
/* 以下是sdhci处理命令产生的中断进行处理，不一定是出错 */
if (intmask & SDHCI_INT_CMD_MASK) {
if (intmask & SDHCI_INT_AUTO_CMD_ERR)
host->auto_cmd_err_sts = sdhci_readw(host,
SDHCI_AUTO_CMD_ERR);
sdhci_writel(host, intmask & SDHCI_INT_CMD_MASK,
SDHCI_INT_STATUS);
if ((host->quirks2 & SDHCI_QUIRK2_SLOW_INT_CLR) &&
(host->clock <= 400000))
udelay(40);
sdhci_cmd_irq(host, intmask & SDHCI_INT_CMD_MASK); // 在sdhci_cmd_irq中会执行host->finish_tasklet, 也就是sdhci_tasklet_finish来通知上层。后面说明。
}
/* 以下是sdhci处理数据产生的中断进行处理，不一定是出错 */
if (intmask & SDHCI_INT_DATA_MASK) {
sdhci_writel(host, intmask & SDHCI_INT_DATA_MASK,
SDHCI_INT_STATUS);
if ((host->quirks2 & SDHCI_QUIRK2_SLOW_INT_CLR) &&
(host->clock <= 400000))
udelay(40);
sdhci_data_irq(host, intmask & SDHCI_INT_DATA_MASK); // 在sdhci_data_irq中会执行host->finish_tasklet, 也就是sdhci_tasklet_finish来通知上层。
}
intmask &= ~(SDHCI_INT_CMD_MASK | SDHCI_INT_DATA_MASK);
intmask &= ~SDHCI_INT_ERROR;
/* 以下是对总线电源状态发生变化的中断的处理 */
if (intmask & SDHCI_INT_BUS_POWER) {
pr_err("%s: Card is consuming too much power!\n",
mmc_hostname(host->mmc));
sdhci_writel(host, SDHCI_INT_BUS_POWER, SDHCI_INT_STATUS);
}
intmask &= ~SDHCI_INT_BUS_POWER;
if (intmask & SDHCI_INT_CARD_INT)
cardint = 1;
intmask &= ~SDHCI_INT_CARD_INT;
if (intmask) {
unexpected |= intmask;
sdhci_writel(host, intmask, SDHCI_INT_STATUS);
}
result = IRQ_HANDLED;
/* 可能不止有其他事件导致中断的产生，重复检测 */
intmask = sdhci_readl(host, SDHCI_INT_STATUS);
if (intmask && --max_loops)
goto again;
out:
spin_unlock(&host->lock);
return result;
}
3、sdhci_tasklet_card
- 简单流程说明：
- 当进行卡插入或者拔出的时候，sdhci controller（硬件）会检测到其状态发生变化
- sdhci controller（硬件）会设置中断状态寄存器中SDHCI_INT_CARD_INSERT或者SDHCI_INT_CARD_REMOVE位
- sdhci controller（硬件）触发中段
- sdhci core中的中断处理函数sdhci_irq被调用（软件）
- sdhci_irq（软件）去判断出中断状态寄存器中SDHCI_INT_CARD_INSERT或者SDHCI_INT_CARD_REMOVE位被设置
- sdhci_irq执行host->card_tasklet，也就是我们这里的sdhci_tasklet_card进行相应处理。
- sdhci_tasklet_card实现如下：
static void sdhci_tasklet_card(unsigned long param)
{
struct sdhci_host *host = (struct sdhci_host*)param; // 提取sdhci_host结构体
sdhci_card_event(host->mmc); // 发送事件，如果此时有mmc_request正在处理，则会复位数据线和命令线，终止mmc_request处理
mmc_detect_change(host->mmc, msecs_to_jiffies(200));
// 调用mmc_detect_change通知mmc core卡槽状态发生了变化，剩下的就是mmc core的工作了
// mmc_detect_change实现具体参考《mmc core主模块说明》
}
4、sdhci_tasklet_finish
static void sdhci_tasklet_finish(unsigned long param)
{
//......过滤掉前面一些根据情况决定的复位操作
mmc_request_done(host->mmc, mrq);
// 调用mmc_request_done来通知mmc core 说mrq这个mmc request已经处理完成，至于处理完成的结果由上层自己解决
// mmc_request_done实现具体参考《mmc core主模块说明》
sdhci_runtime_pm_put(host);
}
5、struct mmc_host_ops sdhci_ops各个方法简单说明
static const struct mmc_host_ops sdhci_ops = {
// post_req和pre_req是为了实现异步请求处理而设置的
// 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
// 具体参考《mmc core主模块》
.pre_req = sdhci_pre_req,
.post_req = sdhci_post_req,
.request = sdhci_request, // host处理mmc请求的方法，在mmc_start_request中会调用
.set_ios = sdhci_set_ios, // 设置host的总线的io setting
.get_cd = sdhci_get_cd, // 检测host的卡槽中card的插入状态
.get_ro = sdhci_get_ro, // 获取host上的card的读写属性
.hw_reset = sdhci_hw_reset, // 硬件复位
.enable_sdio_irq = sdhci_enable_sdio_irq,
.start_signal_voltage_switch = sdhci_start_signal_voltage_switch, // 切换信号电压的方法
.execute_tuning = sdhci_execute_tuning, // 执行tuning操作，为card选择一个合适的采样点
.card_event = sdhci_card_event,
.card_busy = sdhci_card_busy, // 用于检测card是否处于busy状态
.enable = sdhci_enable, // 使能host，当host被占用时（第一次调用mmc_claim_host）调用
.disable = sdhci_disable, // 禁用host，当host被释放时（第一次调用mmc_release_host）调用
.stop_request = sdhci_stop_request, // 停止请求处理的方法
.get_xfer_remain = sdhci_get_xfer_remain,
.notify_load = sdhci_notify_load,
};
最新文章
- C# 知识特性 Attribute
- 设计模式（二）简单工厂模式（Simple Factory Pattern）
- [TCPIP] 传输控制协议 Note
- log4j写入数据库
- [Json.net]忽略不需要的字段
- xmlunit
- spring boot 初试，springboot入门，springboot helloworld例子
- Android开发规范——命名 (转）
- mysql大数据导出导入
- [Redux] Adding React Router to the Project
- 关于安装第三方模块和PILLOW
- HDU 5823 color II
- gps 经纬度 转换实际距离
- PHP7CMS 无条件前台GETSHELL
- 怎么取cxgrid某一列的合计值
- HTTPS SSL/TLS协议
- puppet 用户和组资源管理
- js闭包的作用
- Snmp学习总结(六)——linux下安装和配置SNMP
- java-nio之zero copy深入分析