This document discusses SD card standards and specifications. It describes the SD card pin definitions, speed modes, bus widths, and register maps. It also provides an overview of the Linux SD device driver stack, including the block driver, file systems, and individual driver components like the host controller and core driver. Code examples are provided for registering hardware resources and accessing register structures through readl/writel functions.

1. SD/MMC DEVICE DRIVER
1

2. 目前SD卡的標準如下
新舊版接腳相同，主要在支援的速度及指
令不同。
2
SD card規範
名稱版本最高容量
SD 1.0 4G
SDHC 2.0 32G
SDXC 3.0 2T

3. SD Physical Specification
Card 9 Pins define
<1> CD/DAT3
<2> CMD
<3><6> Ground
<4> VDD
<5> CLK
<7> DAT0
<8> DAT1
<9> DAT2

4. SD Physical Specification
Card speed mode.
<1> default:0~25Mhz, Input in clock rising edge, output in clock falling edge.
<2> high speed:0~50Mhz, Input/output in clock rising edge.
 Card bus width
<1> 1-bit
<2> 4-bit

5. SD Physical Specification
卡片的暫存器
OCR: Operation Condition about voltage and capacity.
CID: Identification about vendor, product string, date, serial number.
RCA: Relative card address, used for single/multiple card control.
DSR: Driver stage, for bus driving performance.
CSD: Card structure 1.0/2.0, TRAN_SPEED, command class,
DSR_IMP, device size, block length…
SCR: Card configuration ,SD Spec, Bus width, data after erase.
SSR: SD status, current bus width, card type, speed_class..
CSR: card status, current state, error index, auxiliary state.

6. SD Physical Specification
8 command class
0: Basic commands
2: Block-Oriented Read commands
4: Block-Oriented Write commands
5: Erase commands
6: Block-Oriented Write Protection commands
7: Lock Card commands
8: Application-specific commands
10: Switch function commands

7. SD Physical Specification
 6 responses in two length(48/136)
R1: Normal response
R1b: Normal response with busy
R2: CID,CSD register (136)
R3: OCR register
R6: Published RCA response
R7: Card interface condition

8. SD Physical Specification
Bus protocol
<1> “no response” and “no data” Operations

9. SD Physical Specification
Bus protocol
<2> Block Read Operation

10. SD Physical Specification
Bus protocol
<3> Block Write Operation

11. SD Physical Specification
Bus protocol
<4> 4-bit wide bus

12. SD Speed Class/UHS Speed Class
12

13. User Space
Kernel Space
Request Queue Request Queue
Kernel Space
Storage Media
File I/O File I/O
Virtual File System (VFS) Layer
Individual Filesystems (EXT3,EXT4,JFFS2,Reiserfs,VFAT, …)
Buffer Cache (Page Cache)
I/O Schedulers
Block Driver Block Driver
Disk
CD
Driver

14. Block Diagram of Host Controller
14

15. Kernel SD Device Driver Stack
Kernel Virtual File Manager/File system
MMC Block Device Driver
SD Device Driver
15
DMA
CPU Embedded SD controller
interrupt
interrupt

16. SD Host and the SD Card
Request
SD Command
Reply
16

17. 17
linux-2.6.x/drivers/mmc

18. 18
Source Code架構
根目錄
drivers/mmc
子目錄card
block file
system
interface
子目錄core
SD 標準協議程
式碼
子目錄host
各別硬件控制程
式碼

19. 19
SD Driver初始化流程
使用platform device
client driver的方式呼叫
platform_driver_registe
r()註冊一個platform
probe call back
function
系統呼叫platform
probe callback
function，所以在該
function中取得
resource 並初始化該元
件
呼叫mmc_alloc_host()取
得一個mmc結構的point，
之後初始化該結構，接下
來呼叫mmc_add_host()註
冊一個mmc host driver
在註冊一個mmc host
driver時會填入幾個系統
call back function，此時
系統會使用這幾個
function來scan是否有卡
插入做SD卡的初始化

20. What do Probe call back function
platform_get_resource()取得resource，並remap resource
Allocate DMA resources
若有用到work queue，則必需給予初始化
註冊一個中斷服務，並起始中斷服務
向上層MMC block註冊一個host MMC
1) mmc = mmc_alloc_host(priv_size, dev)
2) mmc_add_host(mmc)
3) mmc_priv(mmc)
* 在第一次註冊及後來插入SD卡時系統會掃描SD卡
20

21. MMC block device driver call back function
struct mmc_host_ops sd_ops = {
.request = sdhci_request,
.set_ios = sdhci_set_ios,
.get_ro = sdhci_get_ro,
}; // include/linux/mmc/host.h
request
The upper MMC block device driver will send a struct mmc_request *mrq
to this. The mrq will include what want to do. When you finish this request
you must call mmc_request_done() to note upper MMC block device
driver what it is finisned. There include command or data access.
set_ios
1) Set/disable clock
2) Power on/off to offer SD card or not
3) Set SD card bus width 1 or 4
get_ro
1) To check the SD card write protect or not
21

22. Callback function prototype
struct mmc_host_ops {
void (*request)(struct mmc_host *host, struct mmc_request *req);
/*
* Avoid calling these 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!
*
* 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
*
* Return values for the get_ro 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
*/
void (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
int (*get_ro)(struct mmc_host *host);
int (*get_cd)(struct mmc_host *host);
void (*enable_sdio_irq)(struct mmc_host *host, int enable);
};

23. Request callback function
include/linux/mmc/core.h中定義
struct mmc_request {
struct mmc_command *cmd;
struct mmc_data *data;
struct mmc_command *stop;
void *done_data; /* completion data */
void (*done)(struct mmc_request *);/* completion function */
};
由cmd中確認是否要送資料(檢查cmd->data
是否為NULL pointer)，或者只是送SD指令。
處理完該cmd之後呼叫mmc_request_done()
來回覆上層完成讓指令。
23

24. struct mmc_command
struct mmc_command {
u32 opcode;
u32 arg;
u32 resp[4];
unsigned int flags; /* expected response type
*/
unsigned int retries; /* max number of retries */
unsigned int error; /* command error */
struct mmc_data *data; /* data segment associated
with cmd */
struct mmc_request *mrq; /* associated request */
}; // include/linux/mmc/core.h

25. struct mmc_data
struct mmc_data {
unsigned int timeout_ns; /* data timeout (in ns, max 80ms) */
unsigned int timeout_clks; /* data timeout (in clocks) */
unsigned int blksz; /* data block size */
unsigned int blocks; /* number of blocks */
unsigned int error; /* data error */
unsigned int flags;
#define MMC_DATA_WRITE (1 << 8)
#define MMC_DATA_READ (1 << 9)
#define MMC_DATA_STREAM (1 << 10)
unsigned int bytes_xfered;
struct mmc_command *stop; /* stop command */
struct mmc_request *mrq; /* associated request */
unsigned int sg_len; /* size of scatter list */
struct scatterlist *sg; /* I/O scatter list */
}; // include/linux/mmc/core.h

26. scattlerlist操作
struct scatterlist {
#ifdef CONFIG_DEBUG_SG
unsigned long sg_magic;
#endif
unsigned long page_link;
unsigned int offset; /* buffer offset */
dma_addr_t dma_address; /* dma address */
unsigned int length; /* length */
};
#define sg_dma_address(sg) ((sg)->dma_address)
#define sg_dma_len(sg) ((sg)->length)
• int dma_map_sg(struct device *, struct scatterlist *, int, enum
dma_data_direction) - map a set of SG buffers for streaming mode DMA
• kmap_atomic(sg_page(sg), KM_BIO_SRC_IRQ) + sg->offset; /*virtual address */
• kunmap_atomic(buffer, KM_BIO_SRC_IRQ)
#define for_each_sg(sglist, sg, nr, __i)
for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))

27. SD card insert detecting flow chart
27
Card change interrupt
happens
Add card change work
queue on interrupt
service
Insert or remove ?
Remove all
queue
Set SD clock
Call upper MMC block driver
by mmc_detect_change()
Send many command
requests to this driver to get
information from inserted
card.
remove insert
Add a new disk to file
manager.

28. Finish all data transfer ?
28
Read/Write data
Received a request from
upper block MMC driver to
transfer data. The request
callback function is called.
1. Initial user space data
context to kernel
context.
2. Set SD chipset for data
length and timeout.
Set DMA transfer
information to DMA chipset
for fist block data.
Send start transfer data
command
Interrupt generates when a
block data is transferred.
Continue to DMA transfer
information to DMA chipset
for next block data.
Send stop transfer data
command
Call upper MMC driver
request done API
Yes
No

29. Classification of the Standard Register Map
29

30. CODING EXAMPLE
30

31. Register Structure Define
typedef struct hw_register_struct {
int rega;
int regb;
int regc;
} hw_reg_t;
static hw_reg_t *hw_reg;
static int myfunc(void)
{
……………………
readl(&hw_reg->rega);
………………………………
writel(value, &hw_reg->regb);
}
static int __init module_init(void)
{
hw_reg = (hw_reg_t *)ioremap(HW_PHYSICAL_ADDRESS, 0x100);
………………..
}
31