Linux SD/MMC Driver Stack
Champ Yen
http://champyen.blogspot.com
champ.yen@gmail.com
champ yen 1

SD/MMC Stack Architecture
 Device
BLOCK UART BlueTooth WIFI ●
Implement specific
Device (SDIO) (SDIO) (SDIO) subsystem devices(ex:
UART, WIFI) by utilizing
Core API.
Core  Core
- Diagnosing SD/MMC/SDIO
device
SDIO SD MMC
- SD/MMC/SDIO Protocol Layer
implementation
Host - Power Management Policy
 Host
- Hardware dependent interface
AIT OMAP S3C ...... - Handling requests from Core
layer.
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Host Structure
struct mmc_host {
……
const struct mmc_host_ops *ops;
/* minimum frequency */
unsigned int f_min;
/* maximum frequency */
unsigned int f_max;
/* provided voltages */
u32 ocr_avail;
unsigned long caps;
/* host specific block data */
unsigned int max_seg_size;
unsigned short max_hw_segs;
unsigned short max_phys_segs;
unsigned short unused;
unsigned int max_req_size;
unsigned int max_blk_size;
unsigned int max_blk_count;
……
};
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host allocation
struct mmc_host *mmc;
//private host data, hw dependent info is saved here.
struct foo_host *host;
//allocate mmc_host structure with private data size
//pdev is the pointer of platform_device
mmc = mmc_alloc_host(sizeof(struct foo_host), &pdev->dev);
////////////// initialization after allocation ///////////////////
////////////// private host data pointer is get as below
struct foo_host *host;
host = mmc_priv(mmc);
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Host Operations
struct mmc_host_ops {
/* request handler */
void (*request)(struct mmc_host *host, struct mmc_request *req);
/* host controller setting function */
void (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
/* read-only detection , return 1: read-only, 0: read-write */
int (*get_ro)(struct mmc_host *host);
/* card detection return 1: Card Inserted, 0: Card Not Inserted */
int (*get_cd)(struct mmc_host *host);
/* enable SDIO irq */
void (*enable_sdio_irq)(struct mmc_host *host, int enable);
};
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request
struct mmc_request {
/* command to be issued */
struct mmc_command *cmd;
/* data transmission, NULL means no transmission */
struct mmc_data *data;
/*stop command after data transmission */
struct mmc_command *stop;
/* completion data, used by core layer for sync. */
void *done_data;
/* request post processing function */
void (*done)(struct mmc_request *);
};
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request handling flow
cmd
datammc_request
stop
Y
sendcmd(req->cmd) req->data == NULL mmc_request_done
N
Y
Data Transmission req>stop == NULL
N
sendcmd(req->stop)
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Q&A
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