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[spi driver]
[Linux下spi驱动开发（1）]
Linux下SPI从设备驱动的编写
如果你需要使用spi驱动的接口，不是去修改驱动的实现代码，因为它只负责完成spi的硬件交互功能。
你使用spi功能的代码只需要用到spi.h中定义的方法就可以了，这就是linux driver layers framework的可人之处。
我们通过一个简单的例子来实际理解一下：
#include
#include
#include
#define TEST_REG 0x02
static int test_read_reg(struct spi_device *spi, int reg)
{
char buf[2];
buf[0] = reg << 2;
buf[1] = 0;
spi_write_then_read(spi, buf, 2, buf, 2);
return buf[1] << 8 | buf[0];
}
static int spi_test_probe(struct spi_device *spi)
{
printk("TEST_REG: 0x%02x\n", test_read_reg(spi, TEST_REG));
return 0;
}
static int spi_test_remove(struct spi_device *spi)
{
return 0;
}
static struct spi_driver spi_test_driver = {
.probe = spi_test_probe,
.remove = spi_test_remove,
.driver = {
.name = "testHW",
},
};
static int __init spi_test_init(void)
{
return spi_register_driver(&spi_test_driver);
}
static void __exit spi_test_exit(void)
{
spi_unregister_driver(&spi_test_driver);
}
module_init(spi_test_init);
module_exit(spi_test_exit);
MODULE_DESCRIPTION("spi device test");
MODULE_LICENSE("GPL");
在这个驱动中，你只需要用spi_register_driver向系统进行注册，就可以让系统用你指定的与 .name 相匹配的硬件交互代码
去执行你的读写请求。
几乎在所有与spi相关的函数中都会用到struct spi_device *spi这个指针，probe函数正好把这个指针传给你，保存好这个指针，你就可以在驱动的任何地方通过他去处理与spi设备相关的操作。
==============================================
四、m25p10驱动测试
目标：在华清远见的FS_S5PC100平台上编写一个简单的spi驱动模块，在probe阶段实现对m25p10的ID号探测、flash擦除、flash状态读取、flash写入、flash读取等操作。代码已经经过测试，运行于2.6.35内核。理解下面代码需要参照m25p10的芯片手册。其实下面的代码和处理器没有太大关系，这也是spi子系统的分层特点。
view plaincopy to clipboardprint?#include
#include
#include
#include
#include
#include
#include
#include // kzalloc
#include
#define FLASH_PAGE_SIZE 256
/* Flash Operating Commands */
#define CMD_READ_ID 0x9f
#define CMD_WRITE_ENABLE 0x06
#define CMD_BULK_ERASE 0xc7
#define CMD_READ_BYTES 0x03
#define CMD_PAGE_PROGRAM 0x02
#define CMD_RDSR 0x05
/* Status Register bits. */
#define SR_WIP 1 /* Write in progress */
#define SR_WEL 2 /* Write enable latch */
/* ID Numbers */
#define MANUFACTURER_ID 0x20
#define DEVICE_ID 0x1120
/* Define max times to check status register before we give up. */
#define MAX_READY_WAIT_COUNT 100000
#define CMD_SZ 4
struct m25p10a {
struct spi_device *spi;
struct mutex lock;
char erase_opcode;
char cmd[ CMD_SZ ];
};
/*
* Internal Helper functions
*/
/*
* Read the status register, returning its value in the location
* Return the status register value.
* Returns negative if error occurred.
*/
static int read_sr(struct m25p10a *flash)
{
ssize_t retval;
u8 code = CMD_RDSR;
u8 val;
retval = spi_write_then_read(flash->spi, &code, 1, &val, 1);
if (retval < 0) {
dev_err(&flash->spi->dev, "error %d reading SR\n",
(int) retval);
return retval;
}
return val;
}
/*
* Service routine to read status register until ready, or timeout occurs.
* Returns non-zero if error.
*/
static int wait_till_ready(struct m25p10a *flash)
{
int count;
int sr;
/* one chip guarantees max 5 msec wait here after page writes,
* but potentially three seconds (!) after page erase.
*/
for (count = 0; count < MAX_READY_WAIT_COUNT; count++) {
if ((sr = read_sr(flash)) < 0)
break;
else if (!(sr & SR_WIP))
return 0;
/* REVISIT sometimes sleeping would be best */
}
printk( "in (%s): count = %d\n", count );
return 1;
}
/*
* Set write enable latch with Write Enable command.
* Returns negative if error occurred.
*/
static inline int write_enable( struct m25p10a *flash )
{
flash->cmd[0] = CMD_WRITE_ENABLE;
return spi_write( flash->spi, flash->cmd, 1 );
}
/*
* Erase the whole flash memory
*
* Returns 0 if successful, non-zero otherwise.
*/
static int erase_chip( struct m25p10a *flash )
{
/* Wait until finished previous write command. */
if (wait_till_ready(flash))
return -1;
/* Send write enable, then erase commands. */
write_enable( flash );
flash->cmd[0] = CMD_BULK_ERASE;
return spi_write( flash->spi, flash->cmd, 1 );
}
/*
* Read an address range from the flash chip. The address range
* may be any size provided it is within the physical boundaries.
*/
static int m25p10a_read( struct m25p10a *flash, loff_t from,
size_t len, char *buf )
{
int r_count = 0, i;
flash->cmd[0] = CMD_READ_BYTES;
flash->cmd[1] = from >> 16;
flash->cmd[2] = from >> 8;
flash->cmd[3] = from;
#if 1
struct spi_transfer st[2];
struct spi_message msg;
spi_message_init( &msg );
memset( st, 0, sizeof(st) );
flash->cmd[0] = CMD_READ_BYTES;
flash->cmd[1] = from >> 16;
flash->cmd[2] = from >> 8;
flash->cmd[3] = from;
st[ 0 ].tx_buf = flash->cmd;
st[ 0 ].len = CMD_SZ;
spi_message_add_tail( &st[0], &msg );
st[ 1 ].rx_buf = buf;
st[ 1 ].len = len;
spi_message_add_tail( &st[1], &msg );
mutex_lock( &flash->lock );
/* Wait until finished previous write command. */
if (wait_till_ready(flash)) {
mutex_unlock( &flash->lock );
return -1;
}
spi_sync( flash->spi, &msg );
r_count = msg.actual_length - CMD_SZ;
printk( "in (%s): read %d bytes\n", __func__, r_count );
for( i = 0; i < r_count; i++ ) {
printk( "0x%02x\n", buf[ i ] );
}
mutex_unlock( &flash->lock );
#endif
return 0;
}
/*
* Write an address range to the flash chip. Data must be written in
* FLASH_PAGE_SIZE chunks. The address range may be any size provided
* it is within the physical boundaries.
*/
static int m25p10a_write( struct m25p10a *flash, loff_t to,
size_t len, const char *buf )
{
int w_count = 0, i, page_offset;
struct spi_transfer st[2];
struct spi_message msg;
#if 1
if (wait_till_ready(flash)) { //读状态，等待ready
mutex_unlock( &flash->lock );
return -1;
}
#endif
write_enable( flash ); //写使能
spi_message_init( &msg );
memset( st, 0, sizeof(st) );
flash->cmd[0] = CMD_PAGE_PROGRAM;
flash->cmd[1] = to >> 16;
flash->cmd[2] = to >> 8;
flash->cmd[3] = to;
st[ 0 ].tx_buf = flash->cmd;
st[ 0 ].len = CMD_SZ;
spi_message_add_tail( &st[0], &msg );
st[ 1 ].tx_buf = buf;
st[ 1 ].len = len;
spi_message_add_tail( &st[1], &msg );
mutex_lock( &flash->lock );
/* get offset address inside a page */
page_offset = to % FLASH_PAGE_SIZE;
/* do all the bytes fit onto one page? */
if( page_offset + len <= FLASH_PAGE_SIZE ) { // yes
st[ 1 ].len = len;
printk("%d, cmd = %d\n", st[ 1 ].len, *(char *)st[0].tx_buf);
//while(1)
{
spi_sync( flash->spi, &msg );
}
w_count = msg.actual_length - CMD_SZ;
}
else { // no
}
printk( "in (%s): write %d bytes to flash in total\n", __func__, w_count );
mutex_unlock( &flash->lock );
return 0;
}
static int check_id( struct m25p10a *flash )
{
char buf[10] = {0};
flash->cmd[0] = CMD_READ_ID;
spi_write_then_read( flash->spi, flash->cmd, 1, buf, 3 );
printk( "Manufacture ID: 0x%x\n", buf[0] );
printk( "Device ID: 0x%x\n", buf[1] | buf[2] << 8 );
return buf[2] << 16 | buf[1] << 8 | buf[0];
}
static int m25p10a_probe(struct spi_device *spi)
{
int ret = 0;
struct m25p10a *flash;
char buf[ 256 ];
printk( "%s was called\n", __func__ );
flash = kzalloc( sizeof(struct m25p10a), GFP_KERNEL );
if( !flash ) {
return -ENOMEM;
}
flash->spispi = spi;
mutex_init( &flash->lock );
/* save flash as driver's private data */
spi_set_drvdata( spi, flash );
check_id( flash ); //读取ID
#if 1
ret = erase_chip( flash ); //擦除
if( ret < 0 ) {
printk( "erase the entirely chip failed\n" );
}
printk( "erase the whole chip done\n" );
memset( buf, 0x7, 256 );
m25p10a_write( flash, 0, 20, buf); //0地址写入20个7
memset( buf, 0, 256 );
m25p10a_read( flash, 0, 25, buf ); //0地址读出25个数
#endif
return 0;
}
static int m25p10a_remove(struct spi_device *spi)
{
return 0;
}
static struct spi_driver m25p10a_driver = {
.probe = m25p10a_probe,
.remove = m25p10a_remove,
.driver = {
.name = "m25p10a",
},
};
static int __init m25p10a_init(void)
{
return spi_register_driver(&m25p10a_driver);
}
static void __exit m25p10a_exit(void)
{
spi_unregister_driver(&m25p10a_driver);
}
module_init(m25p10a_init);
module_exit(m25p10a_exit);
MODULE_DESCRIPTION("m25p10a driver for FS_S5PC100");
MODULE_LICENSE("GPL");
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